LAB #3: Digestive/Circulatory/Respiratory Systems

PART I: DIGESTIVE SYSTEM

The digestive system of the cat begins at the mouth and terminates at the anus. While passing through this system, food is sectioned and subdivided physically by the teeth and jaws; chemically reduced by digestive enzymes; transported through the tract by contractions of the muscular wall; and absorbed through the intestinal wall. After absorption the substances are carried back to the liver for further treatment or storage.

A. Oral Cavity:

Cut through the muscles and skin at both corners of the mouth in a

posterior direction, then press down the lower jaws with your fingers.

1. Tongue --- large muscular structure lies upon floor of mouth. It is connected to

the floor by the frenulum. The surface of the tongue is covered by

projections known as papillae with microscopic taste buds.

2. Palate --- forms the roof of the mouth; separates oral and nasal cavities. The

anterior portion is supported by bone known as the hard palate. A

muscular structure called the soft palate continues posteriorly.

3. Epiglottis – cone-shaped flap of cartilage located at top of larynx (voice box)

near base of tongue. During swallowing/eating, it prevents food from

entering the trachea.

4. Trachea --- commonly called the windpipe. It is kept open by cartilage rings.

5. Esophagus – muscular tube located dorsal to the trachea. Food is pushed down

to the stomach by rhythmic contractions known as peristalsis.

B. Abdominal Cavity:

1. Diaphragm --- dome-shaped muscular wall separates the thoracic from theabdominal cavity.

It is an important muscle for breathing.

2. Liver --- large dark brown organ that dominates the upper abdomen. It is the largest gland in the

cat (and human)! It consists of 5 lobes. Bile is drained from liver cells to the small

intestines to aide in fat digestion. In addition, the liver functions in storing glycogen (the storage form of sugar).

3. Gallbladder --- small, sac-like pouch tucked in a depression within the liver lobes. Its function is

to store bile. Bile is transported by the cysticduct from the gallbladder; then joins the hepatic duct from the liver to form the common bile duct which enters the duodenum.

* Almost all of the organs below the liver are covered by a sheet/net/apron-like membrane known

as the greater omentum. Carefully cut it away to the side to reveal the lower abdominal organs.

4. Stomach --- muscular pouch lies on the left side in the upper abdomen. Carefully open it with

your scissors along the upper left side. Note the cardiac sphincter which controls the

entrance of food in the stomach from the esophagus. The pyloric sphincter at the

posterior end regulates the release of partially digested food (chyme) into the duodenum.

Note the rugae (folds) lining the inner walls; they help in churn/mixing the food with

digestive juices.

5. Small Intestine --- the first portion is the duodenum; it is a short “U” shaped tube about 4 inches

long. The second section is the jejunum, which makes up about half its length. The ileum

is the final section. The coils of the small intestine are held in place by a fine, transparent

membrane called the mesentery. Cutting it will unravel the small intestine.

6. Large Intestine --- the first segment is called the cecum. At the junction of the small and large

intestines is a valve called the ileocolic valve (the appendix which extends from the

cecum of man is ABSENT in cats). The remaining segments consist of the: ascending

colon, transverse colon, descending colon, rectum, and anus.

7. Pancreas --- flat, elongated gland which lies between the duodenum and the spleen and

underneath the stomach. It’s an accessory organ that secretes pancreatic juice into the

duodenum. It also serves as an endocrine gland to secrete the hormones insulin &

glucagons into the bloodstream.

8. Spleen --- large, dark (possibly reddish) organ lies to the left of the stomach. It actually is part

of the CIRCULATORY system! It’s a “junkyard” for old red blood cells.

PART II: RESPIRATORY SYSTEM

Cut into the thoracic cavity (rib cage) by making an incision

with your scissors at the base of the rib cage about a half inch

to the right or left of mid-ventral line (this will avoid hitting

the bony sternum and you will cut across softer costal cartilage.

Spread the rib cage. Locate the following structures below:

C. Thoracic Cavity:

  1. Lungs --- the right lung has 4 lobes; the left has 3. It should

feel spongy. They are positioned laterally to the heart.

Alveoli are the tiny air sacs for gas exchange with the

circulatory system.

  1. Trachea --- windpipe; lies ventral to the esophagus.
  2. Larynx --- “voice box”. Located on top of trachea.

PART III : CIRCULATORY SYSTEM (HEART & BLOOD VESSELS):

1. Heart --- surrounded by a thin pericardial sac (tissue); the upper two chambers are the atria

and the two lower chambers are called the ventricles. The largest artery in the body, the

aorta, located on the anterior side, carries oxygenated blood away from the heart.

2. Blood Vessels (Arteries = RED & Veins = BLUE):

  1. Carotid Arteries -- rise cranially & lie parallel to each other on either side of trachea.
  2. Coronary Arteries – supply the heart with blood.
  3. Jugular Vein --- lie along each side of the neck.
  4. Femoral Artery & Vein ---lie within the thigh.
  5. Renal Artery & Vein --- vessels that lead to/from the kidneys. Remove the fat

surrounding the kidneys with your fingers (DON’T USE YOUR SCALPEL!).

POST-LAB #3: SUMMARY SHEET Name ______

Period _____Date______

Label the structure/organs of the GI tract:

Fig 1: Digestive System

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Fig 1

Label the structures of the heart:

Fig 2: Cardiovascular System

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Fig 2

Completion. Fill in the blanks with the BEST term.

1. The flap of cartilage that prevents food from entering the trachea while swallowing is the ______.

2. The esophagus is located ______to the trachea. (HINT: use a directional term)

3. The appendix attaches itself to which part of the GI tract? ______

4. The vessels that supply the heart with blood are the ______arteries.

5. Name the organ that serves as both a digestive AND endocrine organ: ______.