Lecture 23: Large Intestine and Comments on the Liver

Question 1

what are the parts of the large intestine?

Answer 1

cecum
colon (divides into more parts)
rectum

Question 2

what are the parts of the colon?

Answer 2

• ascending colon
• transverse colon
• descending colon
• sigmoid colon

Question 3

what part of the large intestine is retroperitoneal?

Answer 3

ascending and descending colon

Question 4

what part of the large intestine is intraperitoneal?

Answer 4

transverse and sigmoidal colon

Question 5

what is the ileocecal valve?

Answer 5

between the ileum and cecum
- regulates the passage of material into the cecum

Question 6

what are the features of the appendix?

Answer 6

• has a reserve of bacteria
• variety of locations
• inflammation is called appendicitis

Question 7

what is a barium enema?

Answer 7

enables x-ray image to be taken of large intestine to assess function

Question 8

what structures does the large intestine have?

Answer 8

• teniae coli
• haustra
• omental appendices

Question 9

what are teniae coli?

Answer 9

• modification of muscularis layer
• three bands of longitudinal smooth muscle
• help with stronger contraction

Question 10

what are haustra?

Answer 10

series of pouches in the wall of colon

Question 11

what are omental appendices?

Answer 11

sacs of fat

Question 12

how are the villi in the large intestine?

Answer 12

lack of villi in large intestine

Question 13

what does the mucosa do in the large intestine?

Answer 13

invaginates to form intestinal glands

Question 14

what is the function of the mucosa of the colon?

Answer 14

water and salt absorption
goblet cells in the mucosa produce mucus (protection and lubrication)

Question 15

what is the epithelia like in the rectum and anus?

Answer 15

anal columns mark boundary where epithelium changes

• before the anal columns it is simple columnar epithelium
• the anal canal has stratified squamous epithelium

Question 16

what are the sphincters of the anus?

Answer 16

internal anal sphincter
- smooth muscle (involuntary)

external anal sphincter
- skeletal muscle (voluntary)

Question 17

what is the defacation reflex?

Answer 17

• movement of faeces into the rectum stimulates stretch receptors
• the internal anal sphincter relaxes (involuntary)
• after conscious decision to defecate is made, external anal sphincter relaxes

Question 18

where is the liver located?

Answer 18

superior right quadrant of abdominopelvic cavity

Question 19

what is the function of the liver

Answer 19

produce lots of bile
- stored in gall bladder

Question 20

what is the blood supply of the liver?

Answer 20

• liver receives 25% of cardiac output
• 1/3 of blood supply is from hepatic artery
• the rest is venous blood from hepatic portal vein
• the mesenteric veins contain nutrient rich deoxygenated blood from the small intestine which is processed by hepatocytes

Question 21

how is the lesser omentum involved in liver blood supply?

Answer 21

hepatic portal vein, hepatic artery and bile duct travel within the lesser omentum

Question 22

what is the structure of the liver?

Answer 22

• made of functional units called lobules
• rows of hepatocytes produce bile
• liver sinusoids are between rows
• bile canaliculi between cells
• portal triad

Question 23

what is a portal triad?

Answer 23

• branch of hepatic artery
• branch of hepatic portal vein
• a bile duct

Question 24

what is blood flow and bile flow like in the liver?

Answer 24

• blood flows towards the central vein
• processed by hepatocytes, which produces bile
• bile is secreted into canaliculi and travels to bile duct

Question 25

what is the venous drainage in the liver?

Answer 25

central veins drain into the hepatic vein, which drains into inferior vena cava

*note that hepatic vein is different to hepatic portal vein

Question 26

what does bile do in the liver?

Answer 26

• bile travels to the gall bladder where it is stored and concentrated
• the bile duct joins the pancreatic duct and the hepatopancreatic ampulla