Abdominal Cavity - Rat (L4)

Question 1

Xyphoid process

Answer 1

Cartilage below the sternum bone, below where the ribs meet.

Question 2

Red/blue latex

Answer 2

Red latex has been injected into arteries. Blue latex has been injected into veins.

The purpose of this is to help you observe these blood vessels.

(Also note that in our rats, yellow latex is injected into the mesenteric veins and hepatic portal vein.)

Question 3

Diaphragm

Answer 3

Domed, muscular upper border of the abdominal cavity, anterior to the liver. This muscle separates the abdominal cavity from the thoracic cavity, and powers breathing by contracting to inflate the lungs.

Question 4

Parietal peritoneum

Answer 4

A thin, transparent membrane lining the abdominal walls. Produces fluid which lubricates the organs, reducing frictional stress on constantly moving viscera.

Note that “viscera” means abdominal organs.

Question 5

Visceral peritoneum

Answer 5

AKA mesentery. Similar to the parietal peritoneum, but overlies the abdominal organs (viscera). Produces fluid which lubricates the organs, reducing frictional stress on constantly moving viscera.

Question 6

Abdominal cavity

Answer 6

Holds abdominal organs. Separated from the thoracic cavity by the diaphragm muscle.

Question 7

Thoracic cavity

Answer 7

Holds thoracic organs. Separated from the abdominal cavity by the diaphragm muscle.

Question 8

Liver

Answer 8

In the upper portion of the abdominal chamber. Large with multiple major lobes. Processes nutrient-rich blood, storing and releasing glucose (which is kept in the liver as glycogen), and detoxifies poisons. Bacteria, if present in the blood coming from the small intestines, can be killed by immigrating neutrophil white blood cells.

Note that the liver’s blood supply is peculiar among organ systems: it lies between 2 venous systems, unlike the usual artery –> organ capillary bed –> vein.

Question 9

Mesenteric veins/hepatic portal vein

Answer 9

Blood exists the small intestine via the mesenteric veins, which collect together and become the hepatic portal vein.

In our rats, yellow latex is injected into the mesenteric veins and hepatic portal vein.

Question 10

Hepatic artery

Answer 10

Supplies oxygenated blood to the liver.

Question 11

Sinusoids

Answer 11

Hepatic arterial and portal venous blood sources branch as they enter the liver. Then- small arterial and portal vessels merge to form sinusoids. Sinusoids function like specialized capillary beds in the liver.

Question 12

Hepatic vein

Answer 12

Blood exits the liver into the hepatic vein from each lobe.

Question 13

Inferior vena cava

Answer 13

The hepatic vein joins the inferior vena cava as it passes by the liver to send processed nutrients to the body.

Question 14

A major difference between rat and human liver

Answer 14

Bile drainage via ductus choledochus (also, more liver lobes).

1. In rats, bile ducts from the liver join to form a single tube, the ductus choledochus, which enters the duodenum and constantly drips bile.

In humans, the bile ducts join and enter the gall bladder– a storage place form which bile can be released to the duodenum when needed for digestion.

RATS HAVE NO GALL BLADDER!

2. Also, rats have more lobes to their liver than humans, which have only 4 liver lobes.

Question 15

Duodenum

Answer 15

First part of the small intestine.

Question 16

Stomach

Answer 16

Lift or remove the ventral lobes of the liver to see it. The stomach narrows until it becomes a tube, called the pylorus/pyloric sphincter.

Question 17

Esophagus

Answer 17

Comes through the diaphragm and enters the stomach.

Question 18

Pylorus/pyloric sphincter

Answer 18

The stomach narrows until it becomes the pylorus/pyloric sphincter, a valve at the joint between the stomach and duodenum.

Often appears as a constriction at the right, caudal end of the stomach.

Very muscular.

Functions to temporarily stop food in the stomach so it can:

1. be exposed to gastric digestive juices, and
2. be mechanically mixed by the smooth muscle of the stomach wall.

Question 19

Parts of the small intestine

Answer 19

Duodenum, then short section called jejunum, then the ileum, which is convoluted.

The ileum is a fan-like array connected by mesentery and mesenteric blood vessels to a central artery and hepatic portal vein.

It is difficult to distinguish these 3 sections– use microscopic analysis to see differences in the simple columnar epithelial cells that make up the linings.

Question 20

Function of the small intestine

Answer 20

Digest and absorb proteins, carbohydrates, and fatty acids

Question 21

Cecum

Answer 21

At the end of the ileum is the ileocecal valve, followed by a large, floppy sac called the cecum– the beginning of the large intestine.

Contains microflora that can ferment foods and break down cellulose.

Some vitamin, carbohydrate, and protein absorption also occurs here.

Question 22

Colon

Answer 22

The cecum opens onto this next section of the GI tract– the colon.

Ascends cranially, making a twisting loop across the back of the cavity then proceeding caudally.

Colon sections: ascending, transverse, descending, sigmoid colon.

Note that the colon is stiffer than the small intestines due to the large amount of smooth muscle in it’s walls, which moves chyme then feces through the intestines via peristalsis.

Question 23

Rectum

Answer 23

The sigmoid colon joins the rectum.

Question 24

Anus

Answer 24

Rectum terminates in the anus. Has dual sphincters which control defecation.

Question 25

Spleen

Answer 25

A dark, sickle-shaped organ, lateral and to the left of the stomach.

An antigen encounter site for white blood cells to recognize foreign microbes and begin an immune response.

Also the “graveyard” for senescent red blood cells.

(“Senescent” means deteriorated.)

Question 26

Pancreas

Answer 26

Diffuse, granular organ loosely attached to the caudal part curve of the stomach. Can be easily confused with fat but is darker- grey or pink, instead of off-white or yellow like fat.

Packets of pancreatic tissue are bound in mesentary and stretch from the pyloric sphincter to the spleen.

The pancreas is involved in carbohydrate metabolism.

Produces insulin, a hormone secreted into the blood stream.

Also produces digestive enzymes, including amylase, trypsin, and chymotrypsin, which are secreted into the duodenum of the SI.

Question 27

Bladder

Answer 27

Surprisingly small. Connected to the kidney by the ureters.

Note that the bladder and ureters are lined with transitional epithelium.

Question 28

Kidneys

Answer 28

Connected to the bladder by the ureters. Produce urine.

Contains simple squamous and simple cuboidal epithelium. Behind the shiny layer of the parietal peritoneum (not actually contained within the abdominal cavity.)

Gets its arterial blood supply from the abdominal aorta.

Question 29

Urethra

Answer 29

The bladder is connected to the urethra, which excretes urine.

Question 30

Why is the colon stiffer than the small intestine?

Answer 30

Note that the colon is stiffer than the small intestines due to the large amount of smooth muscle in it’s walls, which moves chyme then feces through the intestines via peristalsis.

Question 31

Types of cells: kidney, bladder + ureters, small intestine

Answer 31

Kidney: Contains simple squamous and simple cuboidal epithelium.

Bladder + Ureters: Lined with transitional epithelium.

Small intestine: It is difficult to distinguish the 3 sections of the small intestine– use microscopic analysis to see differences in the simple columnar epithelial cells that make up the linings.