Dissection of a Small Mammal

Note:   Both safety goggles and a lab apron should be worn for this lab!

1.  Wash off the specimen if this has not been done to remove any additional preservative fluid.
2.  Place specimen in a dissection tray. Tie a piece of twine to a front and back leg. Pass the twine underneath the dissection pan to the other side and tie it to the leg on the opposite side to hold the legs apart.
3.  Identify the sex of your animal.   Link to diagram of male V. female external structures  in the fetal pig.
4.  Make incisions to open the thoracic and abdominal cavities.  This should be done  with scissors.  Use the diagram of the ventral cuts of a fetal pig dissection to assist this.
Do not use razor blades or a scalpel!. Keep the scissors parallel to the skin surface to prevent damage to the internal organs. Remove the flaps of skin to  reveal the internal organs. While most of the pig's skeleton is cartilage as it is a fetal  pig, bone development has started in the chest or thoracic area.  This means that more careful force will be required to cut through the sternum (breast bone). 
5.  Identify at least 12 major internal organs in your fetal pig.   The following fetal pig diagram link may be helpful.
Link to the fetal pig heart anatomy
The period of pregnancy or gestation for pigs is 112-115 days (3 months, 3 weeks, 3 days) and each female may produce a litter of 7-12.   As the period of development proceeds, the pig embryos get longer, so an approximate age may be calculated from the length.   (from Odlaug:  Laboratory Anatomy of the Fetal Pig, William C. Brown, 1955.)

Time from Conception	Pig Length in mm
21 days	11 mm
35 days	17 mm
49 days	28 mm
56 days	40 mm
100 days	220 mm
114 days (birth)	300 mm

Questions

All Students

1.)    Diagram the locations of the major incisions on the ventral side of the fetal pig.
2.)    How does the position of the brain and nerve cord differ in the fetal pig from that of the earthworm and grasshopper?
3.)    What is the gestation period of the pig?   How old was your pig approximately when it was delivered from the sow?  (or how would you determine an approximation of this?)
4.)    How does the growth rate of the last third of a fetal pig's development compare with that of a human embryo in the last trimester of development.
5.)    State at least one function for the listing of organs below.  Indicate the system the organ belongs to (transport, endocrine, excretory, nervous, digestive, etc.)
ex.   dorsal nerve cord -- carries nerve impulses (brain to body and vice versa) (nervous)

Organ			Function	Body System
brain medulla
brain cerebrum
brain cerebellum
heart
lungs
thymus gland
coronary arteries
diaphragm
stomach
liver
gall bladder
pyloric (stomach) sphincter valve
small intestine
esophagus
large intestine
kidneys
ureters
spleen
pancreas
testes/ovaries
	1. umbilical arteries 2. allantoic duct 3. umbilical vein 4. umbilical cord 5. scrotum 6. genital papilla (female) 7. anus 8. urogenital opening (female) 9. urogenital opening (male) 10. mammary papillae 11. tip of sternum

Next, we will go on to the respiratory system of the fetal pig.

1. thymus 2. thyroid 3. pleural membrane 4. diaphragm 5. lungs 6. bronchi 7. trachea 8. esophagus 9. larynx

THE MAJOR ARTERIES OF THE FETAL PIG

1. right subclavian 2. ductus arteriosus 3. right auricle 4. renal 5. dorsal aorta 6. umbilical 7. internal iliac 8. external iliac 9. anterior mesenteric 10. coronary 11. pulmonary 12. aortic arch 13. left subclavian 14. brachiocephalic 15. common carotid

MAJOR VEINS

1. brachiocephalic 2. ductus venosis 3. umbilical 4. renal 5. common iliac 6. superior (anterior) mesenteric 7. inferior mesenteric 8. gastric 9. hepatic portal 10. hepatic 11. posterior vena cava 12. pulmonary 13. anterior vena cava 14. left subclavian 15. external jugular 16. internal jugular

THE HEART (DORSAL VIEW)
(Please note that some of the structures are internal and are not currently viewable, but the arrows indicate their approximate location.)

1. brachiocephalic artery 2. aorta 3. pulmonary artery 4. right ventricle 5. left ventricle 6. apex 7. right auricle 8. left auricle 9. ductus arteriosus 10. left atrium 11. bicuspid valve 12. chordae tendinae 13. papillary muscle 14. tricuspid valve 15. semilunar valve

ORAL CAVITY AND PHARYNX

1. hard palate 2. soft palate 3. nasopharynx 4. esophagus 5. glottis 6. epiglottis 7. tongue

ABDOMINAL ORGANS

1. gall bladder 2. diaphragm 3. bile duct 4. duodenum 5. mesentery 6. small intestine 7. anus 8. rectum 9. cecum 10. colon 11. pancreas 12. pyloric sphincter 13. stomach 14. spleen 15. esophagus 16. retracted liver lobes 17. umbilical vein

THE REPRODUCTIVE SYSTEM (MALE)

In this section of our virtual disection, we will explore the male reproductive system.

1. adrenal gland 2. seminal vesicle 3. prostate location 4. inguinal canal 5. urinary bladder 6. urogenital opening 7. penis 8. urethra 9. bulbourethral (Cowper's) gland 10. epididymis 11. testis 12. vas deferens 13. umbilical arteries 14. genital artery 15. dorsal aorta 16. ureter 17. renal artery 18. renal vein 19. kidney

THE REPRODUCTIVE SYSTEM (FEMALE)

In this section of our virtual disection, we will explore the female reproductive system.

1. kidney 2. genital artery 3. ureter 4. umbilical arteries 5. cervix 6. urinary bladder 7. urethra 8. urogenital opening 9. urogenital sinus 10. vagina (cut open) 11. body of uterus 12. uterine horn 13. oviduct 14. ovary 15. renal artery 16. renal vein

http://mail.fkchs.sad27.k12.me.us/fkchs/vpig/EXTERNAL ANATOMY OF THE FETAL PIG

Before beginning to actually dissect your fetal pig, you should become very familiar with its external anatomy. Review ANATOMICAL TERMINOLOGY prior to starting this portion of the lab. Especially review terms that refer to relative locations or directions (click on Anatomical References at this website).

Procedure:

1. Locate each of the fetal pig's anatomical structures mentioned in the following five paragraphs.

The body is composed of head, neck, trunk, and tail. The cut umbilical cord extends from the ventral portion of the abdomen. The external opening of the large intestine, the anus, is located immediately under the tail. On the head are external ears, eyes with upper and lower lids, and a large mouth. The tongue can be seen protruding from the mouth. The nostrils lie dorsal to the mouth.

The first digit or toe of both forelimbs and hindlimbs is absent and the second and fifth digits are reduced in size. In the forelimb, the wrist (structure C) lies just above the digits. The elbow (structure D) can be felt as a bony protuberance on the posterior face of the leg close to the junction of the leg with the body. The shoulder is located well above the elbow but is not recognizable by any external feature.

In the hindlimb, the ankle (structure F) is seen as a protuberance a short distance above the digits. The knee (structure E) is located on the anterior face of the hindleg on about the same level as the elbow in the foreleg. The hip can be identified by feeling a bony mass close to the middorsal line.

Determine the sex of your specimen, and of other fetal pig specimens in the room The male is identified by a swelling, the scrotal sac (scrotum), at the caudal end of the body between the upper ends of the hindlegs and by the urogenital opening just caudal to the umbilical cord. It may also be possible to feel the penis, a long muscular tubular structure lying under the skin and proceeding caudally from the urogenital opening.

In the female, the urogenital opening is located beneath the tail immediately ventral to the anus. A small fleshy genital papilla projects from the urogenital aperture. In both males and females, there are two rows of mammary papillae on the ventral surface of the abdomen.

http://www.rit.edu/~gtfsbi/genbiol/Lab%204a.htm