Large Intestine Structure and Function

Question 1

What muscular layer of the large intestine is complete?

Answer 1

The circular muscle layer

Question 2

What muscle layer of the large intestine is incomplete and how does it appear on the large intestine?

Answer 2

The longitudinal muscle layer - 3 strips of longitudinal muscle run along the entire length of the outside of the colon

Question 3

What are the 3 strips of longitudinal muscle running along the outside of the large intestine known as?

Answer 3

Teniae coli

Question 4

The contractions of the teniae coli cause

Answer 4

the haustra - puckered appearance of the colon

Question 5

What epithelium is the mucosa of the large intestine composed of?

Answer 5

Simple columnar epithelium

Question 6

What cells provide the lubrication needed in the large intestine for the movement of faeces?

Answer 6

Goblet cells

Question 7

What nerve is the main innervation from the parasympathetic system to the GI tract?

Answer 7

Vagus nerve

Question 8

What nerve is the main innervation from the sympathetic system to the GI tract?

Answer 8

Splanchnic nerve

Question 9

What effect do the parasympathetic and sympathetic systems have on the GI tract, respectively?

Answer 9

Parasympathetic - stimulatory

Sympathetic - inhibitory

Question 10

What functions does the pancreas have?

Answer 10

Exocrine and endocrine

Question 11

What are the functions of the large intestine?

Answer 11

It actively transports sodium from the lumen into the blood causing the osmotic absorption of water and dehydration of the chyme to produce solid faeces

Question 12

What are the main components of the large intestine?

Answer 12

Caecum 
Ascending colon 
Transvers colon 
Descending colon 
Sigmoid colon

Question 13

What is the ileocaecal valve?

Answer 13

Where the ileum and the large intestine join

Question 14

What essential vitamin is obtained from the bacterial fermentation of undigested carbohydrates in the intestines?

Answer 14

Vitamin K

Question 15

Why is vitamin K essential?

Answer 15

It is essential for the clotting of blood

Question 16

What can be obtained from the bacterial flora in the intestines that acts as an energy source?

Answer 16

Short chain fatty acids

Question 17

The bacterial flora in the colon protects against

Answer 17

pathogenic bacteria in the colon

Question 18

What is the rectum?

Answer 18

Straight, muscular tube between the end of the sigmoid colon and the anal canal

Question 19

What is the epithelium type of the mucosa of the rectum?

Answer 19

Simple columnar epithelium

Question 20

How does the muscularis externa of the rectum compare to elsewhere in the alimental canal?

Answer 20

It is thicker in the rectum

Question 21

Is the muscularis externa of the anal canal thicker or thinner than that of the rectum?

Answer 21

Thicker

Question 22

What muscle type is the external anal sphincter formed from?

Answer 22

Skeletal muscle

Question 23

How does the epithelium of the anal canal change as you move down the canal?

Answer 23

Epithelium changes from simple columnar to stratified squamous

Question 24

Normally the anus is closed by the

Answer 24

internal anal sphincter

Question 25

What muscle type is the internal anal sphincter formed from?

Answer 25

Smooth muscle

Question 26

Which anal sphincter is under autonomic control and which is under voluntary control?

Answer 26

Autonomic - internal | Voluntary - external

Question 27

The rectal wall distends as a result of

Answer 27

the mass movement of faecal material into the rectum

Question 28

The distension of the rectal wall triggers the

Answer 28

mechanoreceptors responsible for the defaecation reflex which stimulates the urge to defaecate

Question 29

Is the defaecation reflex under sympathetic or parasympathetic control?

Answer 29

Parasympathetic via the pelvic splanchnic nerves

Question 30

What is caused by the defaecation reflex?

Answer 30

Contraction of rectum Relaxation of internal anal sphincter Contraction of external anal sphincter

Question 31

What is the defaecation reflex?

Answer 31

Increased peristaltic activity in the colon increasing the pressure on the external anal sphincter which relaxes under voluntary control and allows the expulsion of faeces

Question 32

What is diarrhoea?

Answer 32

The too-frequent passage of faeces which are too liquid

Question 33

What are the common causes of diarrhoea?

Answer 33

``` Pathogenic bacteria Protozoans Viruses Toxins Food ```

Question 34

Enterotoxigenic bacteria produce protein enterotoxins which

Answer 34

maximally turn on intestinal chloride secretion from the crypt cells, causing increased water secretion

Question 35

Increased water secretion swamps the

Answer 35

absorptive capacity of the villi

Question 36

What solutions can be given to drive water reabsorption and cause rehydration?

Answer 36

Sodium or glucose solutions