Fwfrul Filg ffilssww$frron mBecause much can be learned from dissecting embalmed fetal

pig specimens, they are frequently utilized in anatomy laboratories.Fetal pigs are purchased from biological supply houses and are spe-cially prepared for dissection. Excess embalming fluid should bedrained from the packaged specimen prior to dissection.

Examine your specimen and identify the umbilical cordattached to the ventral sudace of the abdomen. Locate the r'rvorows of teats that extend the length of the abdomen. Determinethe sex of your specimen. A male has a scrotal sac in the pelvicregion ofthe body benveen the hind legs and a urogenital open-ing just caudal to the umbilical cord.The penis can be palpated asa muscular tubular structure just underneath the skin along themidline proceeding caudally from the urogenital opening.A femalehas a small fleshy genital papilla projecting from the urogenitalopening, which is located immediately ventral to the anal open-mg.

Before the muscles and viscera of a fetal pig can be studied, thespecimeni skin has to be removed according to the following sug-gested guidelines.

Figure 20.1A ventral view of the suface anatomy of the fetal pig.

1. Nose 5. Scrotum

Place your specimen on a dissecting tray ventral side up.Using a sharp scalpel, make a shallow incision through theskin extending from the chin caudally to the umbilicalcord. Carefully continue your cut around one side of theumbilical cord. If vour soecimen is a male. make adiagonal cut from'the umbilical cord to the scrotum. If afemale, continue a midventral incision from the umbilicalcord to the genital papilla. Make an incision around thegenitalia and tail.

From the midventral incision, extend an incision downthe medial surfaces of the forelegs to the hoofs and thendo the same for the skin of the hindlegs. Make circularincisions around each of the hoofs. Following the ventralborders of the lower jaws, make extended cuts from thechin dorsolaterally to just below the ears.

Grasp the cut edge of the skin and carefully remove itfrom your specimen. If the skin is difiicult to remove,grasp the cut edge of the skin with one hand and push onthe muscle with the thumb of the other hand.

After the specimen is skinned, the muscles can be seenmore easily if the moisture on them is sponged away witha paper towel. The muscles of a fetal pig are extremelydelicate and as you proceed to dissect your specimen,make certain that you separate the muscles along theirnatural boundaries.When transection of a muscle isnecessary, carefully isolate the muscle from its attachedconnective tissue and make a clean cut across the belly ofthe muscle, leaving the origin and insertion intact.

At the end of the laboratory period, wrap your specimenin muslin cloth and store it in a tight, healry-dury plasticbag. Discard the skin that was removed from your speci-men, and the plastic shipment bag.Wet your specimenfrom time to time with a preservative solution (usually2-3% phenol). Caution is necessary when using a phenolwetting solution as it is caustic and poisonous if misusedor used in a concentrated form.

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10. Umbilical cord1 1. Knee12. Ankle

3. Elbow4. Teats

7. Nostril8. Tongue

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Flgure 20.3Ventral view of superficial muscles of neck and upper torso.

1. Mylohyoid m.2. Digastric m.3. Srylohyoid m.4. Omohyoid m.5. Sternohyoid m.6. Thymus7. Sternomastoid m.

9. Pectoralis profundus m.10. Masseter m.11. Thyrohyoid m.12. Mandibular gland13. Larynx14. Sternothyroid m.15. Mandibular lymph nodes

6. Gluteus medius m.7. tnsor fasciae latae m.8. Biceps femoris m.9. Peroneus longus m.

1. Axillary artery andvein, brachial plexus

2. Biceps brachii m.3. Exterxor carpi radialis m.4. Flexor carpi radialis m.5. Flexor digitorum

profundus m.

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Qateral head)9. Triceps brachii m.

(long head)8. Pectoralis superficialis m. 16. Brachiocephalic m.

Figure 20.5A lateral view ofthe superficial thigh and leg.

Medial muscles of thigh and leg.1. External aMominal oblique m.2. Psoas major m.3. Iliacus m.4. Tensor fasciae latae m.5. Sartorius m.6. Rectus femoris m.7. Vastus medialis m.8. Pectineus m.9. Adductor m.

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1. Gluteus superficialis m.2. Semitendinosus m.3. Semimembranosus m.4. Gastrocnemius m.

11. Semimembranosus m.12. Semitendinosus m.13. Tibialis anterior m.14. Linea alba15. Rectus femoris m.16. Vastus medialis m.17. Sartorius m.18. Gracilis m. (cut)19. Gracilis m.5. Extensor digitorum quarti 10. Peroneus tertius m.

Figure 20.4Superficial medial muscles of the forelimb.

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and quinti mm. 11. Tibialis anterior m. 10. Aponeurosis of gracilis (cut) 20. Semitendinosus m.

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Flgure 20.12Thorax and neck regions ofthe fetal pig.

1. Larynx 5. Heart2. Thymus 6. Lung3. Lung4. Liver (cut)

7. Spleen (cut)

Figure 20.13A ventral view of the abdominal caviry of a fetal pig.1. Diaphragm2. Liver3. Gallbladder4. Umbilical vein

Figure 20.14Abdominal organs of the fetal pig.

1. Liver (cut)2. Small intestine3. Umbilical arteries4. Stomach (reflected)5. Spleen6. Pancreas

5. Small intestine6. Undescended testis7. Umbilical artery8. Urinary bladder

7. Kidney8. Large intestine9. (Jreter

10. Ductus (vas) deferens11. Urinary bladder

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Chapter 20 - Fetal Pig Dissection,.

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Figure 20.17Urogenital systen.r of the fetal pig.1. Kidney2. Caudal (inferior) vena cava

3. (Jreter

4. Rectum (cut)5. Partially dissected testis

Renal veinDescending aortaDuctus deferensUrinary bladderUmbilical arteryEpididymis

Figure 20.18Urogenital system of the fetal pig.1. Umbilical cord 6.2. Right kidney 7.3. Ureter 8.4. Umbilical artery 9.5. Urinary bladder 10

PenisVas (ductus) deferensSpermatic cordRight testisEpididymis

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Figure 20.19General structures of the fetalpig brain. Because the cerebrumis less deEned in pigs, the regionsare not known as lobes as theyare in humans.

1. Occipital region of cerebrum2. Cerebellum3. Medulla oblongata4. Spinal cord5. External acoustic meatus6. Longitudinal fissure7. Parietal region ofcerebrum8. Frontal region ofcerebrum9. Temporal region of cerebrum

10. Eye

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