Fetal Pig Dissection part I external anatomy of the fetal pig, Sus scrofa




Дата канвертавання27.04.2016
Памер17.7 Kb.
Fetal Pig Dissection
PART I-- EXTERNAL ANATOMY OF THE FETAL PIG, Sus scrofa
Before you begin the dissection look at the external anatomy of your pig and be familiar with the following termsPinna (auricle), external auditory meatus, eyelid, nictitating membrane, external nares (nostrils), elbow, wrist, knee, mammary papilla (teats), umbilical cord, umbilical vein, umbilical arteries (2), anus, genital papilla (if female), scrotum and urethra (if male).
You will notice that there is a cut already in the neck region of the piglet. This cut is made to gain access to the carotid artery, so that the blood may be withdrawn via a hypodermic needle, and a red latex rubber injected. This latex will solidify in the arteries making them visible. The procedure is repeated with the jugular vein, except that a blue latex is used. Injection of latex often breaks blood vessels in the abdomen, and one may see much coagulated blood or latex in the abdominal cavity as a result.
PART II -- THE ABDOMINAL CAVITY, PELVIC AREA, AND LOWER EXTREMITIES
A. Carefully cut the abdominal cavity so as not to damage underlying organs as demonstrated by your instructor. Make a sagittal cut along the ventral surface from the sternum to the groin, and transverse cuts posterior to the diaphragm, and anterior to the hind legs. Next unravel the intestinal tract (including the colon), so that one large loop runs from the pylorus of the stomach, to the anus--you will have to carefully cut the mesenteries to do this, and be careful not to cut the intestinal tract itself, while cutting. Structures to observe--lobes of liver, gall bladder, cystic duct, pancreas, spleen, umbilical arteries, umbilical vein, urinary bladder, esophagus, stomach (cardiac region, fundus, pylorus, greater curvature, lesser curvature), duodenum, jejuno-ileum, caecum, colon, rectum, mesenteries, visceral and parietal peritoneum (your instructor may ask you to expose and identify the hepatic duct, and common bile duct).
B. Once the intestine has been unraveled, pick away the peritoneum from the dorsal surface, so that the ureters can be traced from the kidneys to the urinary bladder. Make a coronal section of one kidney and observe the structures within. Structures to observe--kidneys, renal cortex, renal medulla, renal pelvis, ureters, urinary bladder, urethra, abdominal aorta, renal arteries and veins, posterior (inferior) vena cava, iliolumbar arteries and veins, adrenal glands, adrenolumbar arteries and veins.
C. Examine the female reproductive structures, which are located in the abdominal cavity of the pig. You should cut through the groin to trace the attachment of the uterus to the vagina--be careful not to cut major arteries or veins. Also trace the urethra from the urinary bladder to where it attaches to the vagina. Also pick away muscle tissue in the pelvis and legs so you may follow the blood vessels of the pelvis as they go into the legs. Structures to observe-

ovary, ovarian arteries and veins, horn of uterus, vagina, urethra, genital papilla, external iliac arteries, internal iliac arteries, umbilical arteries, common iliac veins, external iliac veins, internal iliac veins, femoral arteries and veins, deep femoral arteries and veins.


D. In the male, follow the testicular artery and vein through the inguinal canal to the scrotum; you will have to cut through some muscle to do this. Work carefully and do not cut the structures of importance listed below. You will also cut through the skin posterior to the urethral opening ventral to the bladder, and expose the penis. Work carefully so as not to destroy glands. One should be able to trace the sperm ducts from the testes to the penis, and follow the penis to the urethral opening. The bladder should remain intact. Also pick away muscle tissue in the pelvis and legs so you may follow the blood vessels of the pelvis as they go into the legs. Structures to observe--

testicular artery and vein, testis, epididymis, scrotum, ductus deferens (vas deferens), penis, bulbourethral glands, urethra, seminal vesicles, external iliac arteries, internal iliac arteries, umbilical arteries, common iliac veins, external iliac veins, internal iliac veins, femoral arteries and veins, deep femoral arteries and veins, sciatic nerve.



Part III-THE THORACIC CAVITY, HEAD AND THROAT.
A. Next cut around the diaphragm, circularly, so it drapes over the liver. Cut through the sternum into the thoracic cavity, but stop short of the anterior end of the heart. You may cut away as much of the rib cage as necessary to give you a good view of the heart and lungs. Then go anterior, make an incision from the papilla under the jaw, to the top of the sternum.

a. Remove the skin from the throat and shoulder regions.

b. In the throat, remove the layer of muscle that surrounds the trachea, and you will see the thymus gland. Remove the thymus anteriorly and posteriorly to expose the thyroid gland, larynx, trachea, bronchi, esophagus.

c. Pick away tissue as necessary, trace the major vessels of the neck and shoulder, back to the heart. Be careful when working at top of sternum, you will have to cut through the sternum, but avoid cutting the vessels. In the thoracic area remove the pericardium and the left lung. Recognize the following--common carotid arteries, external and internal jugular veins, anterior and posterior vena cava, aortic arch, thoracic aorta, brachiocephalic artery, left subclavian artery, ductus arteriosus, subclavian arteries and veins, axillary arteries and veins, brachial arteries and veins, azygous vein, brachiocephalic veins, mamillary arteries and veins, thyroid gland, esophagus, pleural membranes (parietal and visceral), esophagus, sympathetic (paravertebral) ganglia, .

d. Observe the heart and observe the right and left auricles. These are extensions of the right and left atria, visible on the outside. "Auricle" means ear. Also observe the ductus arteriosus, a vessel that runs from the pulmonary artery to the aorta to bypass the fetal lungs, since the blood will not be oxygenated there. Also-- apex of heart, aortic arch, brachiocephalic artery, left subclavian artery, parietal and visceral pericardium.
PART IV--ORAL CAVITY
Using the bone cutters cut the jaws on either side of the mouth following the surface of the tongue to where it meets the tracheal and esophageal openings. Follow the surface of the tongue so you do not cut into the roof of the mouth. Observe the following: hard palate, soft palate, oropharynx, nasopharynx, glottis, epiglottis, and larynx. If time permits you may be asked to expose the openings of the Eustachian tubes.

PART V--THE SHEEP BRAIN (Rust p. 97)
Each pair of students will have one and one-half sheep brains to work with. Work with another pair and make a midsagittal cut of a whole sheep brain generating two halves. Each pair of students gets half of the brain, in addition to a whole brain. Identify: Dura mater, arachnoid, pia mater, sulcus, gyrus, frontal lobe, parietal lobe, temporal lobe, occipital lobe, median longitudinal fissure, cerebrum, cerebellum, midbrain, medulla oblongata, pons (varolii), olfactory bulb (cranial nerve I), optic chiasma (cranial nerve II), oculomotor nerve (cranial nerve III), trochlear nerve (cranial nerve IV), trigeminal nerve (cranial nerve V), abducens nerve (cranial nerve VI), hypophysis, infundibulum, thalamus, hypothalamus, lateral ventricle(s), third ventricle, fourth ventricle, aqueduct of Sylvius, spinal canal, septum pellucidum, corpus callosum, corpora quadrigemina, superior colliculi, inferior colliculi, pineal body, intermediate mass, prosencephalon, mesencephalon, rhombencephalon, metencephalon, myelencephalon.

PART VII--THE SHEEP (OR COW) EYE (Rust p.99)
Make a coronal section of a sheep eye just posterior of the cornea and identify the following: conjunctiva, cornea, sclera, optic nerve, anterior cavity, anterior chamber, posterior chamber, iris, pupil, vitreous cavity, vitreous humor, choroid, retina, ciliary body, lens, optic disc
Fetal Circulation--Know the location and function of the following (the ductus venosus and foramen ovale will not be directly observed in your fetal pig dissection).


Structure

Location

Function

Ductus Arteriosus

Connects pulmonary artery and the aorta, at the aortic arch.

Allows blood to bypass pulmonary circulation (oxygenated in placenta).

Foramen ovale

Hole between the right and left atria.

Allows blood to bypass pulmonary circulation.

Umbilical vein

Connects placenta to portal vein.

Returns oxygenated, nutrified blood to fetal circulation.

Ductus venosus

Connects umbilical vein to inferior vena cava.

Bypasses hepatic circulation, ensures fully oxygenated and nutrified blood gets to heart.

Umbilical arteries

Connect internal iliac arteries to the placenta.

Takes fetal blood to placenta for gas, nutrient, and waste exchange.







База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка