2.2: Pre-Lab 2: External Anatomy - Biology

Name: ________________________________

General Anatomy

Label the body axes on the following diagrams with the most appropriate of the the following terms: anterior, posterior, dorsal, ventral, medial, and lateral.

External Morphology: On the cockroach below, label the Antennae, head, T1, T2, T3, Abdomen segments 1 to terminus (9), cerci, legs, forewing, hindwing, lateral margin, anterior, posterior, costal wing margin, jugal lobe, and the prothoracic shield.

Beyond the general arthropod bauplan, there are many adaptations that allow the organisms to enhance its survival strategy by specific exploitation of habitat conditions, resources or even social interactions. Many of the physiological adaptations are easily seen externally, and allow a viewer to hypothesize ecological roles, life history, etc. Two of the simplest examples are modifications to the antennae and the legs.

What is the function of antennae? ________________________________________________________

Find two examples of modifications to antennae for a specific purpose. In the space provided, draw the antennal structure, give the name for the antennae type, an example of an insect with this antennal type, and describe the need for the adaptation based on the insect life history.

Draw (and label) the Coxa, Trochanter, Femur, Tibia, Tarsus, and Pre-Tarsus (claw) leg segments on an unmodified, typical insect leg (i.e. a cockroach or grasshopper foreleg).

As with the antennae above, find two examples of modifications to leg structures for a specific purpose. In the space provided on the next page, draw the leg structure for each, naming for the leg type and showing the segment modified, then give an example of an insect with this leg type, and describe the need for the adaptation based on the insect life history.

2.2: Pre-Lab 2

Fill in the table with the appropriate terms. For the remaining illustrations, label the structures indicated.

Name of a structure is directional term to Name of the second structure
radius is proximal to ulna
femur is superior to
is inferior to thoracic vertebrae
patella is anterior to
is distal to metacarpals
tibia is medial to
is lateral to sternum

Label the cranial structures and bones. (0.5 points)

Label the cranial bones and special features. (0.5 points)

Label the distinctive parts of the vertebra. (0.5 points)

Label the features of the scapula. (0.5 point)

Label the features of the humerus. (0.5 points)

Label the features of the radius and ulna. (0.5 point)

Label the features of the femur. (0.5 points)

Label the features of the tibia and fibula. (0.5 points)

Online Prerequisites: Course Offerings

This is a complete list of prerequisite courses and labs for the health professions offered throughout the year at the MGH Institute. Go to the registration page for courses currently open for registration. Courses are offered in the following subjects:

Offered: Fall, Spring
Prerequisite: General Chemistry I for the Health Sciences or permission of the instructor. The topics in General Chemistry for the Health Science II course are also explained and discussed in context with simple clinical applications to different health professions such as, pharmacy etc. The course includes topics from intermolecular forces, properties of solutions, chemical kinetics, chemical equilibrium, acid-base and aqueous equilibrium, thermodynamics, electrochemistry and nuclear chemistry. The lab for this course provides on a hands-on experience using a lab kit purchased from eScience Labs. You will perform each experiment, record your notes, obtain results and respond to pre and post experiment questions write a final lab report including Introduction, Objectives, Methods and Materials, Procedure, and Results. Syllabus overview.

Fetal Pig Dissection and Fetal Pig Anatomy

Mammals are vertebrates having hair on their body and mammary glands to nourish their young. The majority are placental mammals in which the developing young, or fetus, grows inside the female’s uterus while attached to a membrane called the placenta. The placenta is the source of food and oxygen for the fetus, and it also serves to get rid of fetal wastes. The dissection of the fetal pig in the laboratory is important because pigs and humans have the same level of metabolism and have similar organs and systems. Also, fetal pigs are a byproduct of the pork food industry so they aren’t raised for dissection purposes, and they are relatively inexpensive.

Objectives of fetal pig dissection:

  • Identify important external structures of the fetal pig anatomy.
  • Identify major structures associated with a fetal pig’s digestive, respiratory, circulatory, urogenital, & nervous systems.
  • Compare the functions of certain organs in a fetal mammal with those of an adult mammal.

preserved fetal pig, dissecting pan, dissecting kit, dissecting pins, string, plastic bag, metric ruler, paper towels

Before observing internal or external structures of the fetal pig, use your dissection manual, textbook, and dissection notebook to answer the pre-lab questions on the fetal pig. You may have to refer to more than one dissection manual to answer all the questions so trade and share with other dissection groups.

***Wear your lab apron and eye cover at all times. Watch your time and be sure to clean up all equipment and working area each day before leaving.

  1. Obtain a fetal pig and rinse off the excess preservative by holding it under running water. Lay the pig on its side in the dissecting pan and locate dorsal, ventral,& lateral surfaces. Also locate the anterior and posterior ends.
  2. A fetal pig has not been born yet, but its approximate age since conception can be estimated by measuring its length. Measure your pig’s length from the tip of its snout to the base of its tail and record this on your hand-in. Use the length/age chart on this sheet or the inside cover of your dissection manual to determine the age of your fetal pig & record this.
  3. Examine the pig’s head. Locate the eyelids and the external ears or pinnae. Find the external nostrils.
  4. Study the pig’s appendages and examine the pig’s toes. Count and record the number of toes and the type of hoof the pig has.
  5. Locate the umbilical cord. With scissors, cut across the cord about 1 cm from the body. Examine the 3 openings in the umbilical cord. The largest is the umbilical vein, which carries blood from the placenta to the fetus. The two smaller openings are the umbilical arteries which carry blood from the fetus to the placenta.
  6. Lift the pig’s tail to find the anus. Study the ventral surface of the pig and note the tiny bumps called mammary papillary. These are present in both sexes. In the female these structures connect to the mammary glands.
  7. Determine the sex of your pig by locating the urogenital opening through which liquid wastes and reproductive cells pass. In the male, the opening is on the ventral surface of the pig just posterior to the umbilical cord. In the female, the opening is ventral to the anus. Record the sex of your pig.
  8. Carefully lay the pig on one side in your dissecting pan and cut away the skin from the side of the face and upper neck to expose the masseter muscle that works the jaw, lymph nodes, and salivary glands. Label these on your hand-in.
  9. With scissors, make a 3-cm incision in each corner of the pig’s mouth. Your incision should extend posteriorly through the jaw.
  10. Spread the jaws open and examine the tongue.
  11. Observe the palate on the roof of the mouth. The anterior part of the palate is the hard palate, while the posterior part is the soft palate.
  12. Locate the epiglottis, a cone-shaped structure at the back of the mouth. Above the epiglottis, find the round opening of the nasopharynx. This cavity carries air from the nostrils to the trachea, a large tube in the thoracic which supplies air to the lungs.
  13. Dorsal to the glottis, find the opening to the esophagus. Examine the tongue and note tiny projections called sensory papillae.
  14. Examine the teeth of the pig. Canine teeth are longer for tearing food, while incisor are shorter and used for biting. Pigs are omnivores, eating plants and animals.
  15. Label the drawing of the inside of the pig’s mouth.
  16. Clean up your materials and work area. Wrap the pig in damp paper towels and put it in a zip-lock plastic bag. Obtain a piece of masking tape and label your bag with your names. Return your lab equipment and pig to the supply cart and then thoroughly wash your hands with soap.

Day 2 Part A: The Incision

  1. Be sure to wear your lab apron and eye cover. Obtain your dissecting equipment and pig from the supply cart.
  2. Place the fetal pig ventral side up in the dissecting tray.
  3. Tie a string securely around a front limb. Run the string under the tray, pull it tight, and tie it to the other front limb. Repeat this procedure with the hind limbs to hold the legs apart so you can examine internal structures.
  4. Study the diagram below. The dashed lines numbered 1-5 show the first set of incisions that you will make. To find the exact location for the incision marked 2, press along the thorax with your fingers to find the lower edge of the ribs. This is where you will make incision 2.
  5. With scissors, make the incisions in order, beginning with 1. Be sure to keep the tips of your scissors pointed upward because a deep cut will destroy the organs below. Also, remember to cut away from yourself.
  6. After you have made your incisions through the body wall, you will see the peritoneum, a thin layer of tissue that lines the body cavity. Cut through the peritoneum along the incision lines.
  7. Spread the flaps of the body wall apart. Cut the umbilical vein which extends through the liver.
  8. Once the vein is cut, carefully pull the flap of skin, including the end of the umbilical cord between the hind legs. Your are now able to see the organs of the abdominal cavity.

If time remains continue with part B, the digestive tract. Otherwise, clean up and return your materials and pig as you did on day 1.

  1. Be sure you are wearing your lab apron and eye cover.
  2. Locate the diaphragm, a sheet of muscle that separates the abdominal cavity from the thoracic cavity. Find the most obvious structure in the abdominal cavity, the brownish-colored liver. Count the number of lobes.
  3. Find the tube-like esophagus which joins the mouth and the stomach. Food moves down the esophagus by muscular contractions after being softened by saliva in the mouth. Follow the esophagus and locate the soft, sac-like stomach beneath the liver.
  4. With scissors, cut along the outer curve of the stomach. Open the stomach and note the texture of its inner walls. These ridges inside the stomach are called rugae and increase the area for the release of digestive enzymes. The stomach may not be empty because fetal pigs swallow amniotic fluid.
  5. The pig has a digestive system which is classified as monogastric or nonruminant. Humans also have this type of digestive system. They have one stomach (mono=one, gastric=stomach). Locate the entrance to the stomach or esophageal area, the cardiac region which is largest, and the pyloricregion where the stomach narrows to join to the small intestine.
  6. At the end of the stomach, there is a sphincter, or ring-shaped muscle to control food leaving the stomach and entering the duodenum. Locate the cardiac sphincter at the junction of the stomach and esophagus, and the pyloric sphincter at the junction of the stomach and small intestine. Fetal pigs receive their nourishment from their mother through the umbilical cord.
  7. Identify the first part of the small intestine, the U-shaped duodenum, which connects to the lower end of the stomach. Pancreatic juice, made by the pancreas, and bile, made by the liver and stored in the gall bladder, are add to food here to continue digestion.
  8. Study the rest of the small intestine. Notice that it is a coiled, narrow tube, held together by tissue called mesentery. The soupy, partly digested food that enters the small intestine from the stomach is called chyme.
  9. Carefully cut through the mesentery and uncoil the small intestine. Note and record its length in centimeters. The mid-section is called the jejunum, while the last section is called the ileum.
  10. With scissors, remove a 3-cm piece of the lower small intestine. Cut it open and rinse it out.
  11. Observe the inner surface of the small intestine. Run your finger along it and note its texture. Using a magnifying glass, examine the villi, the tiny projections that line the small intestine and increase the surface area for absorption.
  12. Follow the small intestine until it reaches the wider, looped large intestine. Cut the mesentery and unwind the large intestine or colon. Measure and record its length.
  13. At the junction of the large and small intestine, locate a blind pouch called the caecum. The caecum has no known function in the pig.
  14. Notice that the large intestine leads into the rectum, a tube that runs posteriorly along the dorsal body wall. The rectum carries wastes to the opening called the anus where they are eliminated.
  15. Locate the thin, white pancreas beneath the stomach and duodenum. Pancreatic juice flows through pancreatic ducts to the duodenum.
  16. Between the lobes of the liver, find the small, greenish-brown gall bladder. Locate the hepatic duct which carries bile from the liver to the gall bladder.
  17. Find the spleen, a long, reddish-brown organ wrapped around the stomach. The spleen filters out old red blood cells and produces new ones for the fetus.
  18. On the diagram on the back of day 2 hand-in, label the pig’s body organs.

Clean up your materials and work area. Wrap the pig in damp paper towels and put it in a zip-lock plastic bag. Return your lab equipment and pig to the supply cart and then thoroughly wash your hands with soap.

  1. Be sure to wear your lab apron and eye cover.
  2. Examine the diaphragm, a sheet of muscle that stretches across the abdominal cavity and separates it from the thoracic cavity where the lungs are located. The diaphragm isn’t used by the fetal pig because gas exchange occurs through the umbilical cord. The diaphragm in adult pigs moves up and down changing air pressure in the chest cavity causing air to move into and out of the lungs.
  3. In order to see the upper part of the respiratory system, you will need to extend cut #1 up under the pig’s throat and make to more lateral incisions in order to fold back the flaps of shin covering the throat.
  4. In the thoracic cavity, carefully separate the pericardium or sac surrounding the heart and the diaphragm from the body wall.
  5. Locate the two, spongy lungs that surround the heart. The tissue that covers and protects the lungs is called pleura. The lungs haven’t been used by the fetus so they have never contained air.
  6. Find the trachea, a large air tube that lies anterior to the lungs. The trachea is easy to identify because of the cartilaginous rings that help keep it form collapsing as the animal inhales and exhales.
  7. Notice that the trachea branches into each lung. These two tubes are called bronchial tubes. Inside the lungs these branch into smaller bronchioles that end with a grape-like cluster of air sacs or alveoli where oxygen and carbon dioxide are exchanged with capillaries.
  8. Lying ventral to the trachea or windpipe, locate the pinkish-brown, V-shaped structure called the thyroid gland. This gland secretes hormones that control metabolism.
  9. At the top, anterior end of the trachea, find the hard, light-colored larynx or voice box. This organ contains the vocal cords that enable the animal to produce sound.
  10. Locate the epiglottis at the top of the trachea. This flap of skin closes over the trachea whenever you swallow. Find the area called the pharynx at the back of the nasal cavity. Air enters an adult pig through the mouth or nose before passing through the pharynx and down the trachea to the lungs.
  11. Label the diagram of the respiratory system on your day 3 hand-in.

Clean up your materials and work area. Wrap the pig in damp paper towels and put it in a zip-lock plastic bag. Return your lab equipment and pig to the supply cart and then thoroughly wash your hands with soap.

Perch Dissection 2

The fish in the class Osteichthyes have bony skeletons. There are three groups of the bony fish — ray-finned fish, lobe-finned fish, and the lung fish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage &/or bone to support them. Fins help the perch to move quickly through the water and steer without rolling. The perch also has a streamline body shape that makes it well adapted for movement in the water. All ray-finned fish have a swim bladder that gives the fish buoyancy allowing them to sink or rise in the water. The swim bladder also regulates the concentration of gases in the blood of the fish. Perch have powerful jaws and strong teeth for catching and eating prey. Yellow perch are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the hundreds.

The scientific name for the yellow perch, most often used in dissection, is Perca flavescens (Perca means “dusky” flavescens means “becoming gold colored”). The sides of the yellow perch are golden yellow to brassy green with six to eight dark vertical saddles and a white to yellow belly. Yellow perch have many small teeth, but no large canines. Yellow perch spawn from mid-April to early May by depositing their eggs over vegetation or the water bottom, with no care given. The eggs are laid in large gelatinous adhesive masses.

Preserved perch, dissecting pan, scalpel, scissors, forceps, magnifying glass, dissecting pins, apron, gloves, eye cover, tape measure

Program Requirements

Each student is required to complete the core program, plus all of the requirements in the selective program.

A. Core Program

1. Lower Division Courses (26 units)

2. Upper Division Courses (18 units)

3. Mathematics Requirement

All Biology B.A. students are required to demonstrate proficiency in mathematics equivalent to a passing grade in MATH 105, MATH 106 (or MATH 102 and MATH 104). They may do this by receiving a passing score on the Mathematics Placement Test sufficient for admission to MATH 255A.

B. Selective Program (20 units)

Students must take a minimum of 20 units of specialized coursework in addition to the core. With the approval of a faculty advisor and the concurrence of the department curriculum committee, students may create their own program. Approval for such individualized programs must be obtained before enrollment in the last 12 units of Biology courses. By appropriate choice of courses, students may obtain the equivalent of a traditional degree in Botany or Zoology.

1. Molecular, Cellular and Physiological Biology

Take at least 7 units from the following, including at least one course that has a bench lab designated by an “L” and at least one course that is at the 400-level or above:

This requirement ensures that the student will study two examples of the molecular and functional mechanisms that occur within individual organisms.

2. Systematics and Comparative Biology

Choose one from the following list. Either the course chosen here in List 2 (Systematics and Comparative Biology) or the one chosen in List 3 (Ecology and Environmental Biology) must have a field studies component, as designated by an asterisk (*).

BIOL 312/L/BIOL 392F Vertebrate Biology and Lab/Field Studies (2/1/1)*
BIOL 313/L/BIOL 392B Invertebrate Zoology and Lab/Field Studies (2/1/1)*
BIOL 403/L Plant Morphology and Lab (2/2)
BIOL 404/L/BIOL 492Y Phycology and Lab/Field Studies (2/1/1)*
BIOL 406/L/BIOL 492K Flowering Plant Systematics and Lab/Field Studies (2/1/1)*
BIOL 409/L/BIOL 492J Non-Flowering Plants and Lab/Field Studies (2/1/1)*
BIOL 410/L Medical Microbiology and Lab (2/2)
BIOL 412/L/BIOL 492E Herpetology and Lab/Field Studies (2/1/1)*
BIOL 413/L/BIOL 492AA Entomology and Lab/Field Studies (2/1/1)*
BIOL 415/L/BIOL 492M Mammalogy and Lab/Field Studies (2/1/1)*
BIOL 418/L Bacterial Diversity (2/2)
BIOL 430/L/BIOL 492BB Ichthyology and Lab/Field Studies (2/1/1)*
BIOL 432/L Comparative Anatomy and Lab (2/2)
BIOL 433/L Biology of Marine Tetrapods and Lab (2/1)
BIOL 435/L Parasitology and Lab (2/2)
BIOL 437/L/BIOL 492V Biology of Fungi and Lab/Field Studies (2/1/1)*
BIOL 438/L/BIOL 492R Tropical Botany and Lab/Field Studies (2/1/2)*
BIOL 446/L/BIOL 492T Biology of Tropical Vertebrates and Lab/Field Studies (2/1/2)*
BIOL 448/BIOL 492U Tropical Biodiversity/Field Studies (2/1)*
BIOL 452/L Molecular Markers in Evolutionary Studies and Lab (2/2)

This requirement ensures that the student will have the opportunity to study biodiversity closely in one group of organisms from the points of view of adaptive diversification, phylogeny, biogeography and classification.

3. Ecology and Environmental Biology

Choose one from the following list. Either the course chosen here in List 3 (Ecology and Environmental Biology) or the one chosen in List 2 (Systematics and Comparative Biology) must have a field studies component, as designated by an asterisk (*).

BIOL 407/L/BIOL 492N Plant Ecology and Lab/Field Studies (2/1/1)*
BIOL 414/L/BIOL 492A Avian Ecology and Lab/Field Studies (2/1/1)*
BIOL 419/L/BIOL 492C Microbial Ecology and Lab/Field Studies (2/1/1)*
BIOL 421/L/BIOL 492B Marine Biology and Lab/Field Studies (2/1/1)*
BIOL 422/L Physiological Ecology and Lab (2/2)
BIOL 423/BIOL 492F Field Ecology/Field Studies (2/2)*
BIOL 424/L/BIOL 492G Ecological Modeling and Lab/Field Studies (2/1/1)
BIOL 425/BIOL 492D Animal Behavior/Field Studies (3/1)*
BIOL 426/L/BIOL 492P Biology of Deserts and Lab/Field Studies (2/1/1)*
BIOL 427/L/BIOL 492H Principles of Ecology and Lab/Field Studies (2/1/1)*
BIOL 427A/AL/BIOL 492L Biology of Pelagic Organisms and Lab/Field Studies (2/1/1)*
BIOL 428/L/BIOL 492W Wildlife Ecology and Management and Lab/Field Studies (2/1/1)
BIOL 429/L/BIOL 492I Marine Ecology and Lab/Field Studies (2/1/1)*
BIOL 434/L/BIOL 492Q Ecology of Marine Fishes and Lab/Field Studies (2/1/1)*
BIOL 439/L/BIOL 492S Tropical Ecology and Conservation and Lab/Field Studies (2/1/2)*
BIOL 451/BIOL 326 Tropical Biology/Regional Excursions (3/1)*
BIOL 453/L/BIOL 492Z Behavioral Ecology and Lab/Field Studies (2/1/1)*
BIOL 456/BIOL 492O Conservation Biology/Field Studies (3/1)*

This requirement ensures that the student will study some aspect of the interactions between organisms and their environment.

4. Elective Requirement

Electives should be taken to bring the total beyond the core courses to 20 units, including at least 17 units at the upper division level. No more than 3 units of BIOL 490, BIOL 495, BIOL 499 and BIOL 526 combined may be used, and they may not be used to satisfy either lab or field requirements. Electives may include any upper division Biology course (except those explicitly excluded in their description) or the following:

This requirement gives additional opportunity for student choices in the program, while guaranteeing that students are exposed to biological concepts and practices.

C. General Education (48 units)

Undergraduate students must complete 48 units of General Education as described in this Catalog, including 3 units of coursework meeting the Ethnic Studies (ES) graduation requirement.

12 units are satisfied by the following courses in the major: CHEM 101 satisfies B1 Physical Science BIOL 106 satisfies B2 Life Science BIOL 106L satisfies B3 Science Laboratory Activity MATH 105 satisfies Basic Skills B4 Mathematics/Quantitative Reasoning and BIOL 360 satisfies B5 Scientific Inquiry and Quantitative Reasoning.

Urinary and Reproductive Systems (Urogenital)

1. Locate the kidneys which are bean shaped structures lying toward the back of the abdomen.
2. The ureters are tubes carry urine to the urinary bladder. To find these, you may need to wiggle the kidneys.
3. The urinary bladder is located between the umbilical vessels and stores urine.
4. Lift the bladder to locate the urethra, the tube that carries urine out of the body.
5. Note the vessels that attach to the kidney – these are the renal vessels.

6. Find the scrotal sacs at the posterior end of the pig (between the legs), testes are located in each sac. Open the scrotal sac to locate the testes. ( Testes is plural, testis is singular.)

7. Coiled around the testis is the epididymis. Sperm cells produced in the testes pass through the epididymis and into a tube called the vas deferens (in humans, a vasectomy involves cutting this tube).

8. The penis can be located by cutting away the skin on the flap near the umbilical cord. This tube-like structure eventually exits out the urogenital opening, also known as the urethra.

9. Use the bold structures above to label the diagram:

10. Why does a vasectomy not affect urine flow? (Be specific with your answer using anatomical terms)

11. In the female pig, locate a bean shaped ovary located near the kidneys and connect to the curly oviducts. The pig has a left and right ovary.

12. The curled oviducts are also referred to as uterine horns, which eventually merges at the uterus and then becomes the vagina. Piglets develop in the uterine horns, where a female can produce 12 or more piglets.

13. The urethra exits near the anus at the urogenital opening at the urogenital papilla.

14. Use the bold structures above to label the diagram:

15. What structures can be found in both the male and female urogenital systems?

16. In humans, eggs form in the ovary and then travel into the Fallopian tube where they are fertilized. The egg eventually implants into the uterus. What part of the pig anatomy is comparable to the Fallopian tube in humans?

17. Compare the location of the urogenital opening in female pigs to the urogenital opening in male pigs.

16. Consider a pig that has only one fully formed ovary. How would this affect the pig&rsquos future reproduction?

Dissection of the Thoracic Cavity

You may need to cut through the pig's sternum and expose the chest cavity (thoracic cavity) to view. Identify each of the following organs.

1. Find the diaphragm again. Remember that the diaphragm separates the abdominal cavity from the thoracic cavity and it aids in breathing. Above the diaphragm is the heart and lungs.
2. Remove the pericardium, which is a thin membrane that surrounds the heart .
3. The structures visible on the heart are the two atria (12,13), ventricles (14).
4. The most obvious vessel on the front of the heart is the pulmonary trunk (1) . It curves upward and joins the aorta (2) - a vessel which arches from the heart and curves around to go to the lower part of the body -where it is called the abdominal (dorsal) aorta (9). The aorta supplies the body with blood.
5. The aorta has two branches above the heart- the right brachiocephalic (3) and the left subclavian (5)
6. The right brachiocephalic then branches into arteries - the common carotid (4) and the right subclavian (10) The subclavians supply blood to the arms and follow the clavicle bone

7. The common carotid (4), branches into the left (7) and right carotid arteries (8). The carotid arteries supply blood to the head and neck.
8. Locate the coronary vessels (6) on the outside of the heart - these vessels supply blood to the muscle of the heart.
9. Easy arteries to find are the ones that run near the ribs. These are the intercostal arteries (11).

10. Lift the heart to look on its dorsal side (toward the back), you should be able to see the anterior and posterior vena cava, which brings blood from the body back to the heart.

11. Find the left and right jugular veins. in the neck near the carotid arteries. These drain blood from the head.

12. Locate two spongy lungs located to the left and right side of the heart.

13. The trachea is the airway to the lungs and is easy to identify due to the cartilage rings, which keeps it from collapsing. The trachea should be located in the neck area.
13. Lying atop the trachea, locate the pinkish-brown, V shaped structure called the thyroid gland. This gland secretes hormones that control growth and metabolism.
14. At the anterior (toward head) of the trachea, you can find the larynx (or voice box). The larynx allows the pig to produce sounds - grunts and oinks.

Identify by number:

Aorta ____ Dorsal Aorta ____ Pulmonary Trunk ___
Common carotid ____ Left & Right Carotid ____
Coronary vessels ___ Left Subclavian_____
Right Subclavian _____ Right Brachiocephalic _____
Right Atrium _____ Left Atrium _____
Intercostal _____ Ventricle _____

Identify the structure.

1. _________________________________ Membrane over the heart.
2. _________________________________ Airway from mouth to lungs
3. _________________________________ Blood supply to head and neck
4. _________________________________ Lower heart chambers
5. _________________________________ Blood supply to lower body
6. _________________________________ Large veins that return blood to the heart
7. _________________________________ Vessel that leaves the heart and joins aorta
8. _________________________________ Used to make noises (voicebox)
9. ________________________________ Arteries on heart surface.
10. ________________________________ Supplies blood to the arms
11. ________________________________ Drains blood from the head and brain (returns to the heart)
12. ________________________________ Splits into the left and right carotid arteries
13. _________________________________ Muscle to aid breathing (separates abdominal and thoracic cavity)
14. _________________________________ Gland that secretes hormones


Elements of the human body by mass. Trace elements are less than 1% combined (and each less than 0.1%).
Element Symbol percent mass percent atoms
Oxygen O 65.0 24.0
Carbon C 18.5 12.0
Hydrogen H 9.5 62.0
Nitrogen N 3.2 1.1
Calcium Ca 1.5 0.22
Phosphorus P 1.0 0.22
Potassium K 0.4 0.03
Sulfur S 0.3 0.038
Sodium Na 0.2 0.037
Chlorine Cl 0.2 0.024
Magnesium Mg 0.1 0.015
Trace elements < 0.1 < 0.3

The human body is composed of elements including hydrogen, oxygen, carbon, calcium and phosphorus. [1] These elements reside in trillions of cells and non-cellular components of the body.

The adult male body is about 60% water for a total water content of some 42 litres (9.2 imp gal 11 US gal). This is made up of about 19 litres (4.2 imp gal 5.0 US gal) of extracellular fluid including about 3.2 litres (0.70 imp gal 0.85 US gal) of blood plasma and about 8.4 litres (1.8 imp gal 2.2 US gal) of interstitial fluid, and about 23 litres (5.1 imp gal 6.1 US gal) of fluid inside cells. [2] The content, acidity and composition of the water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride, whereas within cells it is potassium and other phosphates. [3]

Cells Edit

The body contains trillions of cells, the fundamental unit of life. [4] At maturity, there are roughly 30 [5] –37 [6] trillion cells in the body, an estimate arrived at by totaling the cell numbers of all the organs of the body and cell types. The body is also host to about the same number of non-human cells [5] as well as multicellular organisms which reside in the gastrointestinal tract and on the skin. [7] Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen, surrounded by extracellular fluids. Of the 70 kg (150 lb) weight of an average human body, nearly 25 kg (55 lb) is non-human cells or non-cellular material such as bone and connective tissue.

Genome Edit

Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA. [8] The RNA is then used to create proteins which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. [9] However, not all cells have DNA some cells such as mature red blood cells lose their nucleus as they mature.

Tissues Edit

The body consists of many different types of tissue, defined as cells that act with a specialised function. [10] The study of tissues is called histology and often occurs with a microscope. The body consists of four main types of tissues. These are lining cells (epithelia), connective tissue, nerve tissue and muscle tissue. [11]

Cells that lie on surfaces exposed to the outside world or gastrointestinal tract (epithelia) or internal cavities (endothelium) come in numerous shapes and forms – from single layers of flat cells, to cells with small beating hair-like cilia in the lungs, to column-like cells that line the stomach. Endothelial cells are cells that line internal cavities including blood vessels and glands. Lining cells regulate what can and can't pass through them, protect internal structures, and function as sensory surfaces. [11]

Organs Edit

Organs, structured collections of cells with a specific function, [12] mostly sit within the body, with the exception of skin. Examples include the heart, lungs and liver. Many organs reside within cavities within the body. These cavities include the abdomen (which contains the stomach, for example) and pleura, which contains the lungs.

Systems Edit

Circulatory system Edit

The circulatory system consists of the heart and blood vessels (arteries, veins and capillaries). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen, fuel, nutrients, waste products, immune cells and signalling molecules (i.e. hormones) from one part of the body to another. Paths of blood circulation within the human body can be divided into two circuits: the pulmonary circuit, which pumps blood to the lungs to receive oxygen and leave carbon dioxide, and the systemic circuit, which carries blood from the heart off to the rest of the body. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as the spleen and bone marrow. [13] [14] [15] [16]

Digestive system Edit

The digestive system consists of the mouth including the tongue and teeth, esophagus, stomach, (gastrointestinal tract, small and large intestines, and rectum), as well as the liver, pancreas, gallbladder, and salivary glands. It converts food into small, nutritional, non-toxic molecules for distribution and absorption into the body. These molecules take the form of proteins (which are broken down into amino acids), fats, vitamins and minerals (the last of which are mainly ionic rather than molecular). After being swallowed, food moves through the gastrointestinal tract by means of peristalsis: the systematic expansion and contraction of muscles to push food from one area to the next. [17] [18]

Digestion begins in the mouth, which chews food into smaller pieces for easier digestion. Then it is swallowed, and moves through the esophagus to the stomach. In the stomach, food is mixed with gastric acids to allow the extraction of nutrients. What is left is called chyme this then moves into the small intestine, which absorbs the nutrients and water from the chyme. What remains passes on to the large intestine, where it is dried to form feces these are then stored in the rectum until they are expelled through the anus. [18]

Endocrine system Edit

The endocrine system consists of the principal endocrine glands: the pituitary, thyroid, adrenals, pancreas, parathyroids, and gonads, but nearly all organs and tissues produce specific endocrine hormones as well. The endocrine hormones serve as signals from one body system to another regarding an enormous array of conditions, and resulting in variety of changes of function. [19]

Immune system Edit

The immune system consists of the white blood cells, the thymus, lymph nodes and lymph channels, which are also part of the lymphatic system. The immune system provides a mechanism for the body to distinguish its own cells and tissues from outside cells and substances and to neutralize or destroy the latter by using specialized proteins such as antibodies, cytokines, and toll-like receptors, among many others. [20]

Integumentary system Edit

The integumentary system consists of the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands. The skin provides containment, structure, and protection for other organs, and serves as a major sensory interface with the outside world. [21] [22]

Lymphatic system Edit

The lymphatic system extracts, transports and metabolizes lymph, the fluid found in between cells. The lymphatic system is similar to the circulatory system in terms of both its structure and its most basic function, to carry a body fluid. [23]

Musculoskeletal system Edit

The musculoskeletal system consists of the human skeleton (which includes bones, ligaments, tendons, and cartilage) and attached muscles. It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in the body contain bone marrow, the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate. This system can be split up into the muscular system and the skeletal system. [24]

Nervous system Edit

The nervous system consists of the body's neurons and glial cells, which together form the nerves, ganglia and gray matter which in turn form the brain and related structures. The brain is the organ of thought, emotion, memory, and sensory processing it serves many aspects of communication and controls various systems and functions. The special senses consist of vision, hearing, taste, and smell. The eyes, ears, tongue, and nose gather information about the body's environment. [25]

From a structural perspective, the nervous system is typically subdivided into two component parts: the central nervous system (CNS), composed of the brain and the spinal cord and the peripheral nervous system (PNS), composed of the nerves and ganglia outside the brain and spinal cord. The CNS is mostly responsible for organizing motion, processing sensory information, thought, memory, cognition and other such functions. [26] It remains a matter of some debate whether the CNS directly gives rise to consciousness. [27] The peripheral nervous system (PNS) is mostly responsible for gathering information with sensory neurons and directing body movements with motor neurons. [26]

From a functional perspective, the nervous system is again typically divided into two component parts: the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS is involved in voluntary functions like speaking and sensory processes. The ANS is involved in involuntary processes, such as digestion and regulating blood pressure. [28]

The nervous system is subject to many different diseases. In epilepsy, abnormal electrical activity in the brain can cause seizures. In multiple sclerosis, the immune system attacks the nerve linings, damaging the nerves' ability to transmit signals. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a motor neuron disease which gradually reduces movement in patients. There are also many other diseases of the nervous system. [26]

Reproductive system Edit

The reproductive system consists of the gonads and the internal and external sex organs. The reproductive system produces gametes in each sex, a mechanism for their combination, and in the female a nurturing environment for the first 9 months of development of the infant. [29]

Respiratory system Edit

The respiratory system consists of the nose, nasopharynx, trachea, and lungs. It brings oxygen from the air and excretes carbon dioxide and water back into the air. First, air is pulled through the trachea into the lungs by the diaphragm pushing down, which creates a vacuum. Air is briefly stored inside small sacs known as alveoli (sing.: alveolus) before being expelled from the lungs when the diaphragm contracts again. Each alveolus is surrounded by capillaries carrying deoxygenated blood, which absorbs oxygen out of the air and into the bloodstream. [30] [31]

For the respiratory system to function properly, there need to be as few impediments as possible to the movement of air within the lungs. Inflammation of the lungs and excess mucus are common sources of breathing difficulties. [31] In asthma, the respiratory system is persistently inflamed, causing wheezing and/or shortness of breath. Pneumonia occurs through infection of the alveoli, and may be caused by tuberculosis. Emphysema, commonly a result of smoking, is caused by damage to connections between the alveoli. [32]

Urinary system Edit

The urinary system consists of the kidneys, ureters, bladder, and urethra. It removes toxic materials from the blood to produce urine, which carries a variety of waste molecules and excess ions and water out of the body. [33]

Human anatomy is the study of the shape and form of the human body. The human body has four limbs (two arms and two legs), a head and a neck which connect to the torso. The body's shape is determined by a strong skeleton made of bone and cartilage, surrounded by fat, muscle, connective tissue, organs, and other structures. The spine at the back of the skeleton contains the flexible vertebral column which surrounds the spinal cord, which is a collection of nerve fibres connecting the brain to the rest of the body. Nerves connect the spinal cord and brain to the rest of the body. All major bones, muscles, and nerves in the body are named, with the exception of anatomical variations such as sesamoid bones and accessory muscles.

Blood vessels carry blood throughout the body, which moves because of the beating of the heart. Venules and veins collect blood low in oxygen from tissues throughout the body. These collect in progressively larger veins until they reach the body's two largest veins, the superior and inferior vena cava, which drain blood into the right side of the heart. From here, the blood is pumped into the lungs where it receives oxygen and drains back into the left side of the heart. From here, it is pumped into the body's largest artery, the aorta, and then progressively smaller arteries and arterioles until it reaches tissue. Here blood passes from small arteries into capillaries, then small veins and the process begins again. Blood carries oxygen, waste products, and hormones from one place in the body to another. Blood is filtered at the kidneys and liver.

The body consists of a number of body cavities, separated areas which house different organ systems. The brain and central nervous system reside in an area protected from the rest of the body by the blood brain barrier. The lungs sit in the pleural cavity. The intestines, liver, and spleen sit in the abdominal cavity.

Height, weight, shape and other body proportions vary individually and with age and sex. Body shape is influenced by the distribution of bones , muscle and fat tissue. [34]

Human physiology is the study of how the human body functions. This includes the mechanical, physical, bioelectrical, and biochemical functions of humans in good health, from organs to the cells of which they are composed. The human body consists of many interacting systems of organs. These interact to maintain homeostasis, keeping the body in a stable state with safe levels of substances such as sugar and oxygen in the blood. [35]

Each system contributes to homeostasis, of itself, other systems, and the entire body. Some combined systems are referred to by joint names. For example, the nervous system and the endocrine system operate together as the neuroendocrine system. The nervous system receives information from the body, and transmits this to the brain via nerve impulses and neurotransmitters. At the same time, the endocrine system releases hormones, such as to help regulate blood pressure and volume. Together, these systems regulate the internal environment of the body, maintaining blood flow, posture, energy supply, temperature, and acid balance (pH). [35]

Development of the human body is the process of growth to maturity. The process begins with fertilisation, where an egg released from the ovary of a female is penetrated by sperm. The egg then lodges in the uterus, where an embryo and later fetus develop until birth. Growth and development occur after birth, and include both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. Development and growth continue throughout life, through childhood, adolescence, and through adulthood to old age, and are referred to as the process of aging.

Professional study Edit

Health professionals learn about the human body from illustrations, models, and demonstrations. Medical and dental students in addition gain practical experience, for example by dissection of cadavers. Human anatomy, physiology, and biochemistry are basic medical sciences, generally taught to medical students in their first year at medical school. [36] [37] [38]

Depiction Edit

Anatomy has served the visual arts since Ancient Greek times, when the 5th century BC sculptor Polykleitos wrote his Canon on the ideal proportions of the male nude. [39] In the Italian Renaissance, artists from Piero della Francesca (c. 1415–1492) onwards, including Leonardo da Vinci (1452–1519) and his collaborator Luca Pacioli (c. 1447–1517), learnt and wrote about the rules of art, including visual perspective and the proportions of the human body. [40]

History of anatomy Edit

In Ancient Greece, the Hippocratic Corpus described the anatomy of the skeleton and muscles. [41] The 2nd century physician Galen of Pergamum compiled classical knowledge of anatomy into a text that was used throughout the Middle Ages. [42] In the Renaissance, Andreas Vesalius (1514–1564) pioneered the modern study of human anatomy by dissection, writing the influential book De humani corporis fabrica. [43] [44] Anatomy advanced further with the invention of the microscope and the study of the cellular structure of tissues and organs. [45] Modern anatomy uses techniques such as magnetic resonance imaging, computed tomography, fluoroscopy and ultrasound imaging to study the body in unprecedented detail. [46]

History of physiology Edit

The study of human physiology began with Hippocrates in Ancient Greece, around 420 BCE, and with Aristotle (384–322 BCE) who applied critical thinking and emphasis on the relationship between structure and function. Galen (ca. 126–199) was the first to use experiments to probe the body's functions. [47] The term physiology was introduced by the French physician Jean Fernel (1497–1558). [48] In the 17th century, William Harvey (1578–1657) described the circulatory system, pioneering the combination of close observation with careful experiment. [49] In the 19th century, physiological knowledge began to accumulate at a rapid rate with the cell theory of Matthias Schleiden and Theodor Schwann in 1838, that organisms are made up of cells. [48] Claude Bernard (1813–1878) created the concept of the milieu interieur (internal environment), which Walter Cannon (1871–1945) later said was regulated to a steady state in homeostasis. In the 20th century, the physiologists Knut Schmidt-Nielsen and George Bartholomew extended their studies to comparative physiology and ecophysiology. [50] Most recently, evolutionary physiology has become a distinct subdiscipline. [51]

Virtual Rat Dissection

Step 1: In the biology lab, you will be working with specimens that have been preserved in chemicals and you will be working with sharp instruments.

Before you start, obtain safety goggles, and nitrile gloves. Nitrile gloves come in different sizes, most women will wear a medium and most men will wear a large. This can vary though. Try not to waste gloves by choosing the correct size.

Check to see if your station has the equipment you will need to dissect the rat. This includes a dissecting pan, scalpel, scissors, probes, and pins.

Rats are ordered from biological supply companies. They come stored in a preserving fluid, either in bags or in a bucket. Always use latex or nitrile gloves when handling your rat and safety goggles are required to protect your eye from chemical splattering or debris.

The rats do have fur, though they can vary in color. Many lab rats are white, but this does not mean they are albino. Some rats are white with a black stripe, sometimes called "hooded rats." Other rats are dark brown or gray.

These rats are stored in "carosafe" a chemical that keeps them preserved. Over time, rats stored in buckets become bloated with the chemical, use caution when opening the body cavity of these rats as the chemical is prone to spray and splatter. Once an incision is made, the rats can be drained of fluid.

Place your rat in a dissecting tray and examine the external features. The rat (and all vertebrates) has anatomical regions to help locate structures.

cranial region – head | cervical region – neck
pectoral region - area where front legs attach
thoracic region - chest area | abdomen - belly
pelvic region - area where the back legs attach


A typical sea anemone is a sessile polyp attached at the base to the surface beneath it by an adhesive foot, called a basal or pedal disc, with a column-shaped body topped by an oral disc. Most are from 1 to 5 cm (0.4 to 2.0 in) in diameter and 1.5 to 10 cm (0.6 to 3.9 in) in length, but they are inflatable and vary greatly in dimensions. Some are very large Urticina columbiana and Stichodactyla mertensii can both exceed a metre in diameter and Metridium farcimen a metre in length. [1] Some species burrow in soft sediment and lack a basal disc, having instead a bulbous lower end, the physa, which anchors them in place. [1]

The column or trunk is generally more or less cylindrical and may be plain and smooth or may bear specialist structures these include solid papillae (fleshy protuberances), adhesive papillae, cinclides (slits) and small protruding vesicles. In some species the part immediately below the oral disc is constricted and is known as the capitulum. When the animal contracts, the oral disc, tentacles and capitulum fold inside the pharynx and are held in place by a strong sphincter muscle part way up the column. There may be a fold in the body wall, known as a parapet, at this point, and this parapet covers and protects the anemone when it is retracted. [1]

The oral disc has a central mouth, usually slit-shaped, surrounded by one or more whorls of tentacles. The ends of the slit lead to grooves in the wall of the pharynx known as siphonoglyphs there are usually two of these grooves, but some groups have a single one. The tentacles are generally tapered and often tipped by a pore, but in some species they are branched, club-tipped, or reduced to low knobs. [1] The tentacles are armed with many cnidocytes, cells that are both defensive and used to capture prey. Cnidocytes contain stinging nematocysts, capsule-like organelles capable of everting suddenly, giving the phylum Cnidaria its name. [2] Each nematocyst contains a small venom vesicle filled with actinotoxins, an inner filament, and an external sensory hair. A touch to the hair mechanically triggers a cell explosion, which launches a harpoon-like structure that attaches to the organism that triggered it, and injects a dose of venom in the flesh of the aggressor or prey. [3] At the base of the tentacles in some species lie acrorhagi, elongated inflatable tentacle-like organs armed with cnidocytes, that can flail around and fend off other encroaching anemones one or both anemones can be driven off or suffer injury in such battles. [1]

The venom is a mix of toxins, including neurotoxins, that paralyzes the prey so the anemone can move it to the mouth for digestion inside the gastrovascular cavity. Actinotoxins are highly toxic to prey species of fish and crustaceans. However, Amphiprioninae (clownfish), small banded fish in various colours, are not affected by their host anemone's sting and shelter themselves from predators among its tentacles. [4] Several other species have similar adaptions and are also unaffected (see Mutualistic relationships). Most sea anemones are harmless to humans, but a few highly toxic species (notably Actinodendron arboreum, Phyllodiscus semoni and Stichodactyla spp.) have caused severe injuries and are potentially lethal. [5]

Digestive system Edit

Sea anemones have what can be described as an incomplete gut the gastrovascular cavity functions as a stomach and possesses a single opening to the outside, which operates as both a mouth and anus. Waste and undigested matter is excreted through this opening. The mouth is typically slit-like in shape, and bears a groove at one or both ends. The groove, termed a siphonoglyph, is ciliated, and helps to move food particles inwards and circulate water through the gastrovascular cavity. [6]

The mouth opens into a flattened pharynx. This consists of an in-folding of the body wall, and is therefore lined by the animal's epidermis. The pharynx typically runs for about one third the length of the body before opening into the gastrovascular cavity that occupies the remainder of the body. [1]

The gastrovascular cavity itself is divided into a number of chambers by mesenteries radiating inwards from the body wall. Some of the mesenteries form complete partitions with a free edge at the base of the pharynx, where they connect, but others reach only partway across. The mesenteries are usually found in multiples of twelve, and are symmetrically arranged around the central lumen. They have stomach lining on both sides, separated by a thin layer of mesoglea, and include filaments of tissue specialised for secreting digestive enzymes. In some species, these filaments extend below the lower margin of the mesentery, hanging free in the gastrovascular cavity as thread-like acontial filaments. These acontia are armed with nematocysts and can be extruded through cinclides, blister-like holes in the wall of the column, for use in defence. [6]

Musculature and nervous system Edit

A primitive nervous system, without centralization, coordinates the processes involved in maintaining homeostasis, as well as biochemical and physical responses to various stimuli. There are two nerve nets, one in the epidermis and one in the gastrodermis these unite at the pharynx, the junctions of the septa with the oral disc and the pedal disc, and across the mesogloea. No specialized sense organs are present but sensory cells include nematocytes and chemoreceptors. [1]

The muscles and nerves are much simpler than those of most other animals, although more specialised than in other cnidarians, such as corals. Cells in the outer layer (epidermis) and the inner layer (gastrodermis) have microfilaments that group into contractile fibers. These fibers are not true muscles because they are not freely suspended in the body cavity as they are in more developed animals. Longitudinal fibres are found in the tentacles and oral disc, and also within the mesenteries, where they can contract the whole length of the body. Circular fibers are found in the body wall and, in some species, around the oral disc, allowing the animal to retract its tentacles into a protective sphincter. [6]

Since the anemone lacks a rigid skeleton, the contractile cells pull against the fluid in the gastrovascular cavity, forming a hydrostatic skeleton. The anemone stabilizes itself by flattening its pharynx which acts as a valve, keeping the gastrovascular cavity at a constant volume and making it rigid. When the longitudinal muscles relax, the pharynx opens and the cilia lining the siphonoglyphs beat, wafting water inwards and refilling the gastrovascular cavity. In general, the sea anemone inflates its body to extend its tentacles and feed, and deflates it when resting or disturbed. The inflated body is also used to anchor the animal inside a crevice, burrow or tube. [1]

Unlike other cnidarians, anemones (and other anthozoans) entirely lack the free-swimming medusal stage of their lifecycle [7] the polyp produces eggs and sperm, and the fertilized egg develops into a planula larva which develops directly into another polyp. Both sexual and asexual reproduction can occur. [1]

The sexes in sea anemones are separate in some species, while other species are sequential hermaphrodites, changing sex at some stage in their life. The gonads are strips of tissue within the mesenteries. [1] In sexual reproduction, males may release sperm to stimulate females to release eggs, and fertilization occurs, either internally in the gastrovascular cavity or in the water column. The eggs and sperm, or the larvae, are ejected through the mouth. In many species the eggs and sperm rise to the surface where fertilisation occurs. The fertilized egg develops into a planula larva, which drifts for a while before sinking to the seabed and undergoing metamorphosis into a juvenile sea anemone. Some larvae preferentially settle onto certain suitable substrates, The mottled anemone (Urticina crassicornis) for example, settles onto green algae, perhaps attracted by a biofilm on the surface. [8]

The brooding anemone (Epiactis prolifera) is gynodioecious, starting life as a female and later becoming hermaphroditic, so that populations consist of females and hermaphrodites. [9] As a female, the eggs can develop parthenogenetically into female offspring without fertilisation, and as a hermaphrodite, the eggs are routinely self-fertilised. [8] The larvae emerge from the anemone's mouth and tumble down the column, lodging in a fold near the pedal disc. Here they develop and grow, remaining for about three months before crawling off to start independent lives. [8]

Sea anemones have great powers of regeneration and can reproduce asexually, by budding, fragmentation, or by longitudinal or transverse binary fission. Some species such as certain Anthopleura divide longitudinally, pulling themselves apart, resulting in groups of individuals with identical colouring and markings. [10] Transverse fission is less common, but occurs in Anthopleura stellula and Gonactinia prolifera, with a rudimentary band of tentacles appearing halfway up the column before it splits horizontally. [11] Some species can also reproduce by pedal laceration. In this process, a ring of material may break off from the pedal disc at the base of the column which then fragments, the pieces regenerating into new clonal individuals. [12] Alternatively, fragments detach separately as the animal creeps across a surface. In Metridium dianthus, fragmentation rates were higher in individuals living among live mussels than among dead shells, and all the new individuals had tentacles within three weeks. [13]

The sea anemone Aiptasia diaphana displays sexual plasticity. Thus asexually produced clones derived from a single founder individual can contain both male and female individuals (ramets). When eggs and sperm (gametes) are formed, they can produce zygotes derived from "selfing" (within the founding clone) or out-crossing, that then develop into swimming planula larvae. [14] Anemones tend to grow and reproduce relatively slowly. The magnificent sea anemone (Heteractis magnifica) for example, may live for decades, with one individual surviving in captivity for eighty years. [15]

Movement Edit

A sea anemone is capable of changing its shape dramatically. The column and tentacles have longitudinal, transverse and diagonal sheets of muscle and can lengthen and contract, as well as bend and twist. The gullet and mesenteries can evert (turn inside out), or the oral disc and tentacles can retract inside the gullet, with the sphincter closing the aperture during this process, the gullet folds transversely and water is discharged through the mouth. [16]

Locomotion Edit

Although some species of sea anemone burrow in soft sediment, the majority are mainly sessile, attaching to a hard surface with their pedal disc, and tend to stay in the same spot for weeks or months at a time. They can move however, being able to creep around on their bases this gliding can be seen with time-lapse photography but the motion is so slow as to be almost imperceptible to the naked eye. [17] The process resembles the locomotion of a gastropod mollusc, a wave of contraction moving from the functionally posterior portion of the foot towards the front edge, which detaches and moves forwards. [18] Sea anemones can also cast themselves loose from the substrate and drift to a new location. [17] Gonactinia prolifera is unusual in that it can both walk and swim walking is by making a series of short, looping steps, rather like a caterpillar, attaching its tentacles to the substrate and drawing its base closer swimming is done by rapid movements of the tentacles beating synchronously like oar strokes. [19] Stomphia coccinea can swim by flexing its column, and the sea onion anemone inflates and casts itself loose, adopting a spherical shape and allowing itself to be rolled about by the waves and currents. [1] There are no truly pelagic sea anemones, but some stages in the life cycle post-metamorphosis are able, in response to certain environmental factors, to cast themselves off and have a free-living stage that aids in their dispersal. [20]

The sea onion Paranthus rapiformis lives on subtidal mud flats and burrows into the sediment, holding itself in place by expanding its basal disc to form an anchor. If it gets washed out of its burrow by strong currents, it contracts into a pearly glistening ball which rolls about. [21] Tube-dwelling anemones which live in parchment-like tubes, are in the anthozoan subclass Ceriantharia, and are only distantly related to sea anemones. [22]

Feeding and diet Edit

Sea anemones are typically predators, ensnaring prey of suitable size that comes within reach of their tentacles and immobilizing it with the aid of their nematocysts. [23] The prey is then transported to the mouth and thrust into the pharynx. The lips can stretch to aid in prey capture and can accommodate larger items such as crabs, dislodged molluscs and even small fish. [1] Stichodactyla helianthus is reported to trap sea urchins by enfolding them in its carpet-like oral disc. [1] A few species are parasitic on other marine organisms. [23] One of these is Peachia quinquecapitata, the larvae of which develop inside the medusae of jellyfish, feeding on their gonads and other tissues, before being liberated into the sea as free-living, juvenile anemones. [24]

Mutualistic relationships Edit

Although not plants and therefore incapable of photosynthesis themselves, many sea anemones form an important facultative mutualistic relationship with certain single-celled algae species that reside in the animals' gastrodermal cells, especially in the tentacles and oral disc. These algae may be either zooxanthellae, zoochlorellae or both. The sea anemone benefits from the products of the algae's photosynthesis, namely oxygen and food in the form of glycerol, glucose and alanine the algae in turn are assured a reliable exposure to sunlight and protection from micro-feeders, which the sea anemones actively maintain. The algae also benefit by being protected by the sea anemone's stinging cells, reducing the likelihood of being eaten by herbivores. In the aggregating anemone (Anthopleura elegantissima), the colour of the anemone is largely dependent on the proportions and identities of the zooxanthellae and zoochlorellae present. [1] The hidden anemone (Lebrunia coralligens) has a whorl of seaweed-like pseudotentacles, rich in zooxanthellae, and an inner whorl of tentacles. A daily rhythm sees the pseudotentacles spread widely in the daytime for photosynthesis, but they are retracted at night, at which time the tentacles expand to search for prey. [25]

Several species of fish and invertebrates live in symbiotic or mutualistic relationships with sea anemones, most famously the clownfish. The symbiont receives the protection from predators provided by the anemone's stinging cells, and the anemone utilises the nutrients present in its faeces. [26] Other animals that associate with sea anemones include cardinalfish (such as Banggai cardinalfish), juvenile threespot dascyllus, [27] incognito (or anemone) goby, [28] juvenile painted greenling, [29] various crabs (such as Inachus phalangium, Mithraculus cinctimanus and Neopetrolisthes), shrimp (such as certain Alpheus, Lebbeus, Periclimenes and Thor), [30] opossum shrimp (such as Heteromysis and Leptomysis), [31] and various marine snails. [32] [33] [34]

Two of the more unusual relationships are those between certain anemones (such as Adamsia, Calliactis and Neoaiptasia) and hermit crabs or snails, and Bundeopsis or Triactis anemones and Lybia boxing crabs. In the former, the anemones live on the shell of the hermit crab or snail. [30] [32] [33] [34] In the latter, the small anemones are carried in the claws of the boxing crab. [30] [35]

Habitats Edit

Sea anemones are found in both deep oceans and shallow coastal waters worldwide. The greatest diversity is in the tropics although there are many species adapted to relatively cold waters. The majority of species cling on to rocks, shells or submerged timber, often hiding in cracks or under seaweed, but some burrow into sand and mud, and a few are pelagic. [1]

Sea anemones and their attendant anemone fish can make attractive aquarium exhibits and both are often harvested from the wild as adults or juveniles. [36] These fishing activities significantly impact the populations of anemones and anemone fish by drastically reducing the densities of each in exploited areas. [36] Besides their collection from the wild for use in reef aquaria, sea anemones are also threatened by alterations to their environment. Those living in shallow water coastal locations are affected directly by pollution and siltation, and indirectly by the effect these have on their photosynthetic symbionts and the prey on which they feed. [37]

In southwestern Spain and Sardinia, the snakelocks anemone (Anemonia viridis) is consumed as a delicacy. The whole animal is marinated in vinegar, then coated in a batter similar to that used to make calamari and deep-fried in olive oil. [38] Anemones are also a source of food for fisherman communities in the east coast of Sabah, Borneo [39] and the Thousand Islands (as rambu-rambu) [40] in Southeast Asia.

Most Actiniaria do not form hard parts that can be recognized as fossils, but a few fossils of sea anemones do exist Mackenzia, from the Middle Cambrian Burgess Shale of Canada, is the oldest fossil identified as a sea anemone. [41]

Sea anemones, order Actiniaria, are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. [42] Rodriguez et al. proposed a new classification for the Actiniaria based on extensive DNA results. [43]

Suborders and Superfamilies included in Actiniaria are:

  • Suborder Anenthemonae
    • Superfamily Edwardsioidea
    • Superfamily Actinernoidea
    • Superfamily Actinostoloidea
    • Superfamily Actinioidea
    • Superfamily Metridioidea

    External relationships Edit

    Anthozoa contains three subclasses: Hexacorallia, which contains the Actiniaria Octocorallia and Ceriantharia. These are monophyletic, but the relationships within the subclasses remain unresolved. [44]

    Actiniaria (Sea anemones)

    Internal relationships Edit

    The relationships of higher-level taxa in Carlgren's [45] classification are re-interpreted as follows: [43]