Download Dissection Guide – Male Section A: Mouth structures 1. To expose

Dissection Guide – Male
Section A: Mouth structures
1. To expose structures in the mouth cavity, use sharp-pointed scissors.
Label all structures in BOLD on your specimen.
Place your fetal pig in the dissecting pan ventral side up. Use string to "hog-tie" your pig so
that the legs are spread eagle and not in your way
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Cut at the corners of the mouth along the line of the tongue.
Continue to cut until the lower jaw can be lowered, being careful not to cut into the
tissues in the roof of the mouth cavity.
Continue to cut, pulling down on the lower jaw until your cuts reach the muscle and
tissue at the back of the mouth.
Cut through this muscle until lowering the jaw exposes the back of the mouth cavity.
Open the pig's mouth and locate the hard and soft palate on the roof of the mouth.
Find the taste buds (also known as sensory papillae) on the side of the tongue.
Locate the esophagus at the back of the mouth.
Feel the edge of the mouth for teeth.
Locate the epiglottis, a cone-shaped structure at the back of the mouth, a flap of
skin helps to close this opening when a pig swallows.
The pharynx is the cavity in the back of the mouth - it is the junction for food
(esophagus) and air (trachea).
Section B: Internal Structures
To expose internal structures, use a sharp scalpel and scissors.
• Cut 1: Make a shallow mid-ventral incision from the base of the throat to the
umbilical cord.
• Cut 2: Cut around the umbilical cord to the medial surface of each leg.
• Cut 3: Cut through the body wall laterally
just posterior to the diaphragm.
• Cut 4: Cut laterally at the posterior margin
of the abdominal cavity.
• After completing the cuts, locate the
umbilical vein that leads from the umbilical
cord to the liver. You will need to cut this
vein in order to open up the abdominal
cavity.
• Pin the skin and muscle to the side so that
the internal organs are visible.
• Your pig may be filled with water and
preservative, drain over the sink if
necessary and rinse organs.
Locate and label each of the following organs below.
1. Diaphragm. This muscle divides the thoracic and abdominal cavity and is located
near the ribcage.
2. Liver. This structure is lobed and is the largest organ in the body.
3. Gall bladder. This greenish organ is located underneath the liver; the bile duct
attaches the gall bladder to the duodenum.
4. Stomach. A pouch shaped organ that rests just underneath and to the pig's left. At
the top of the stomach, you'll find the esophagus.
5. The stomach leads to the small intestine, which is composed of the duodenum
(straight portion just after the stomach) and the ileum (curly part). The ileum is
held together by mesentery. In the small intestine, further digestion occurs and
nutrients are absorbed through the arteries in the mesentery.
6. Pancreas: a bumpy organ located along the underside of the stomach, a pancreatic
duct leads to the duodenum.
7. Spleen: a flattened organ that lies across the stomach and toward the extreme left
side of the pig. The spleen is a large lymph node that removes old red blood cells and
houses many immune system cells.
8. At the end of the ileum, where it widens to become the large intestine, a "dead-end"
branch is visible. This is the cecum. The cecum helps the pig digest plant material.
9. The Colon or large intestine can be traced to the rectum. The rectum lies toward
the back of the pig and will not be moveable. The rectum opens to the outside of the
pig, or the anus.
10. Lying on either side of the spine are two bean shaped organs: the kidneys. The
kidneys are responsible for removing harmful substances from the blood; these
substances are excreted as urine.
11. Two umbilical artery and vein can be seen in the umbilical cord, and the flattened
urinary bladder lies between them.
Show Mr. J your labeled dissection before proceeding.
Section C: The stomach
1. Carefully remove the stomach and open it
up.
2. Locate and label the cardiac and pyloric
sphincters.
3. Locate and label the esophagus and
duodenum.
4. Locate and label the folds of the inner
lining of the stomach called gastric rugae.
Show Mr. J your labeled dissection before proceeding.
Section D: The Thoracic cavity
• Begin the dissection by opening the thoracic cavity, which houses the heart and
lungs, and making an incision that extends to the jaw.
• Use scissors to deepen the superficial incision previously made anterior to the
abdominal cavity, and continue deepening this incision to the base of the lower jaw
• Cut through the body wall in the region of the thorax, clipping through the ribs
slightly to the right or left of the sternum (the flat bone lying mid-ventrally to
which ribs attach)
• Continue the incision past the rib cage to the base of the lower jaw
• Using the blunt probe to separate tissues, carefully remove the skin and muscles in
the neck region.
Locate and label each of the following organs below.
1. Expose the thymus gland on each side of the neck. The thymus is critical to the
development of the immune system cells called T-cells.
2. The Thyroid gland produces a hormone called thyroxin which regulates metabolic
rate.
3. Larynx or voice box on top of the trachea.
4. Lobes of either right or left lung.
5. Diaphragm
Show Mr. J your labeled dissection before proceeding.
Section E: The Heart
• Expose the heart lying in the pericardial cavity between the two pleural cavities.
• Gently push open the rib cage, using scissors and a probe to cut through muscle and
connective tissue.
• Another lobe of the thymus gland will be seen lying over the pericardial sac housing
the heart.
• Cut into and push aside the pericardial sac. Carefully dissect away membranes
adhering to the heart until you can identify the four chambers of the heart
Locate
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and label each of the following structures below.
Right and left atria
Right and left ventricles
Superior and inferior vena cava – bringing blood back to the right atrium
Pulmonary trunk – taking blood to the lungs
Aorta – taking blood to the body and head
Coronary artery and vein – supply blood to the cardiac muscle
Ductus arteriosis or arterial duct – allows blood to bypass the lungs in the fetal
heart
Show Mr. J your labeled dissection before proceeding.
Use a scalpel and scissors to open the heart
8. Find the oval opening or foramen ovale – allows blood to pass between the right and
left atria and therefore bypass the lungs.
Section F: The Kidneys
Locate and label each of the following structures below.
1. Descending aorta – brings blood to the body
2. Renal artery – takes blood to the kidney
3. Renal vein – takes blood from the kidney
4. Inferior vena cava – brings blood back to heart
5. Kidney – filters blood
6. Ureter – takes urine from kidney to urinary bladder
7. Urinary bladder – temporarily stores urine
8. Urethra – takes urine from urinary bladder out of body
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Locate
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Carefully take one kidney out and dissect it down the midline of the kidney.
and label each of the following structures below.
Renal cortex – outer layer of kidney
Renal medulla – middle layer of kidney
Renal pelvis – inner region of kidney
Adrenal gland – sits on top of kidney
and produces adrenalin.
Show Mr. J your labeled dissection before proceeding.
Section G: Reproductive and Urinary Systems
Male
Locate and label each of the following structures below.
1. Find the scrotal sacs at the posterior end of the pig; testes are located in each sac.
2. Open the scrotal sac to locate the testes.
3. On each teste, find the coiled epididymis. Sperm cells produces in the teste pass
through the epididymis and into a tube called the vas deferens (in humans, a
vasectomy involves cutting this tube).
4. The vas deferens crosses over the ureter and enters the urethra, which leads to
the penis.
5. The penis will be located in the flap that has the umbilical cord. Cut away the skin to
reveal the penis.
Show Mr. J your labeled dissection. Congratulations you are done.
Make sure you do a thorough clean up and dissection tools and your desk.
Dispose of fetal pig tissue in the proper bio-bag.