In this rap you"ll dissect a fetal pig to gain a look in ~ the anatomy that a mammal. In addition, you need to study the two pre-dissected specimens available in lab.

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Objectives

Recognize the frameworks labeled on the images on this page or provided in bold in the text.

Specimens

Fetal pig that you deserve to dissect through your groupPre-dissected pig in plastic caseSagittally sliced pig sealed in plastic

Fetal pig, dissected

We have a dissected specimen in lab, kept in a plastic case. This would be a great one because that the lab exam. On the picture below, I"ve labeling some frameworks that I could potentially asking you around on the laboratory exam.

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Fetal pig sagitttal section

Here"s one more specimen available in lab.

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Dissect your own pig

The ideal online overview to fetal pig dissection is more than likely the online Fetal Pig Dissection in ~ Whitman College. I recommend utilizing that together your guide.

Here space some functions you have to look for:

Determine the sex of your pig

Before you start dissecting, study the outside of the pig and determine that is sex. Look for these features:

Males: Urogenital opened is located near the umbilicus; the cock is hidden inside. The scrotal sac might be visible as a swelling simply ventral come the anus, relying on the period of the fetus.The testes room still deep inside the body cavity; lock don"t descend right into the scrotal sac till later.Females: Look because that the urogenital papilla, situated just below the anus.

Both males and also females have nipples, simply as in humans.

Reference: Sexing your pig.

Neck region

Begin her dissection in the neck region. Try to cut as small as possible. When you open the body cavity, you will certainly generally be able to separate the various organs by just pulling them apart v your fingers, forceps, or a probe. The an ext you cut things up, the harder it will be to number out what you’re looking at. Reduced midline ~ above the ventral surface of the neck to expose the underlying muscles. Carefully separate the muscles to observe the underlying structures. Locate and also understand the features of the complying with structures:

Larynx: one enlarged framework on the trachea. If you cut it open, you deserve to see the vocal cords inside.Thymus gland: an endocrine (hormone-secreting) gland that helps manage the immune system. The a large, spongy structure extending the ventral surface of the trachea and often prolonging into the thoracic cavity adjacent to the heart.Thyroid gland: an additional endocrine gland; it’s a tiny bilobed structure simply posterior to the larynx. The thyroid secretes hormones that help regulate metabolism.Trachea: the airway; it"s reinforced v rings the cartilage so the doesn"t collapse.Esophagus: tote food indigenous mouth come stomach; soft and also muscular so it deserve to move a food bolus by peristalsis.

Thoracic cavity

Vertebrates have actually true coeloms. In mammals, the coelom is split into two main cavities: the thoracic cavity, which has the lungs, and also the ab cavity, which has the digestive system. The thoracic cavity and also the abdominal cavity are separated through the diaphragm. Keep in mind the countless membranes lining the coelom and holding the offal in place.

Look because that these structures in the thoracic cavity:

Lungs: they have actually several lobes. Keep in mind the exactly how spongy the tissue is.Diaphragm: a paper of muscle and also connective tissue that helps in breathing.

Abdominal cavity: cradle & absorption

Locate and understand the attributes of the complying with structures:

Liver: very huge and dark. It has actually several lobes. You’ll need to lift it out of the way to see the organs beneath. The gall bladder is a small organ attached come the underside that the liver; it"s typically greenish because it contains bile.Stomach:Small & big intestineRectumStomach: may be hidden beneath the liver. Keep in mind the esophagus leading into the stomach and the duodenum (first component of the tiny intestine) leading out. After passing through the huge intestine, digested chyme goes to the rectum before being removed from the body.Mesenteries: thin, transparent sheets the connective organization containing blood ship connecting the intestine and also other organs. The mesenteries space folds of the peritoneum, which is the smooth, shiny layer that lines the ab cavity.Pancreas: white and looks a small bit choose cauliflower. It secretes cradle enzymes and also buffers.

Abdominal cavity: various other organs

Locate and also understand the functions of the following structures:

Spleen. The spleen is a level organ located near the stomach. The performs several features related to producing and maturing new blood cells and also eliminating old ones. Blood overcome through open sinuses in the spleen, rather than gift confined to narrow blood vessels.Urinary bladder & urethra. The urethra is the tube the carries urine indigenous the urinary bladder to the urinary opening.Ovaries, uterus (females) or Testes (males). see the photos virtual to discover these. The size of the testes different significantly, depending upon the period of the fetal pig. The testes that males and the ovaries that females both arise indigenous the same embryonic structures; however, the testes migrate throughout fetal advance until they descend into the scrotal sac.

Circulatory system

Mammalian mind have four chambers (see Campbell, p. 42.4). Each side of the heart has actually an atrium the receives blood from somewhere else in the body and a ventricle the pumps the blood the end of the heart. The appropriate atrium receive blood native the systemic circulation and also passes it come the right ventricle, i m sorry pumps the blood come the pulmonary circuit. After the blood passes with the lung it goes come the left atrium and then into the left ventricle, which pumps the blood right into the systemic circuit. The first part that the systemic arterial circuit is the aorta, which quickly branches the end to supply assorted regions of the body.

Fetal circulation is different from adult circulation. In the fetus, blood doesn’t obtain oxygenated in the lungs; it it s okay oxygenated at the placenta. The umbilical arteries carry blood from the fetus come the placenta. The umbilical vein dead blood indigenous the placenta ago to the fetus. (Remember the in the placenta substances space exchanged between fetal and maternal blood, yet the blood chin does no mix.) Therefore, the most very oxygenated blood in the fetus is in the umbilical vein. Blood from the umbilical vein gets combined with the remainder of the systemic circulation and also returns come the best atrium. The blood beginning the right atrium is the many oxygenated blood in the fetal heart, however it’s the least oxygenated blood in the adult heart. The fetus has two vital tricks to adapt to this fact:

First, some of the blood that leaves the appropriate ventricle bypasses the lungs. In one adult, this blood demands to go to the lung to obtain oxygenated, however the fetus has actually a ductus arteriosus that short-circuits this blood flow, allowing some blood come go straight into the aorta and also then right into the systemic circulation.

Second, in the fetal heart, over there is an opening between the ideal atrium and the left atrium. This opening is dubbed the foramen ovale. The foramen ovale is beneficial in the fetus due to the fact that it allows the oxygenated blood indigenous the placenta gain circulated faster. The circulation pattern is somewhat similar to the of a frog (Campbell, p. 874). The foramen ovale usually closes up at birth, maintaining blood circulation of the two sides that the heart totally separate. In part people, the foramen ovale does not close up. This condition, called patent foramen ovale, can result in serious health problems.

Here"s a diagram of circulation in a fetal pig:

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Image courtesy the OpenWetWare.

And here"s a diagram of person fetal circulation:

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Image by OpenStax university , via Wikimedia Commons.

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Sample check questions

You need to be prepared to identify any kind of of the structures labeled ~ above the diagrams on this page or detailed in bold kind in the text of this page. You can see one of two people of the 2 specimens presented on this page, or a dissected specimen favor the one you check in lab.