Intestines

Question 1

What are the two methods of absorption via specific transport proteins in the small intestine?

Answer 1

1) diffusion down their concentration gradient

2) secondary active transport

Question 2

Why can up to 50% of SI can be resected without hindering digestion / absorption?

Answer 2

it has a very large reserve capacity

Question 3

Compare luminal and membranous digestion

Answer 3

Luminal = enzymes secreted by salivary glands/pancreas
Membranous = enzymes attached to epithelial surface of intestinal cells

Question 4

What are the 3 parts of the small intestine?

Answer 4

Duodenum
Jejunum
Ileum

Question 5

What increases the surface area in the small intestine?

Answer 5

Mucosal folds
Villi
Microvilli

Question 6

What are the 4 types of interstitial epithelial cell?

Which one makes up the majority of cells?

Answer 6

Goblet cells
Enteroendocrine cells
Paneth cells
Enterocytes - majority

Question 7

What helps small intestine emptying into the colon?

Answer 7

1) Circular muscle at ileo-colic junction well developed

2) “Gastro-ileal reflex” – long reflex arc

Question 8

What is the main type of contraction when digestion is occurring?

Answer 8

Segmental contractions

Question 9

What is the main type of contraction when digestion / absorption complete?

Answer 9

Peristaltic contractions

Question 10

How is peristalsis propagated?

Answer 10

Motor neurones of enteric NS release ACh which stimulates smooth muscle to contract

Question 11

Name the pacemaker cells that regulate motility in the small intestine

Answer 11

interstitial cells of Cajal

Question 12

Which type of carbohydrate is indigestible by mammalian enzymes and why?

Answer 12

Cellulose - β-glycosidic bonds

Requires microbial fermentation

Question 13

How do disaccharidase enzyme levels change with age?

Answer 13

Neonate - high lactase/low maltase
Adult - low lactase/high maltase
Ruminants - NO sucrase

Question 14

How are glucose and galactose absorbed in the SI?

Answer 14

By sodium-glucose co-transporter SGLT1

- secondary active transport

Question 15

What are the 2 passive transporters and what do they absorb?

Answer 15

GLUT5
GLUT2
Fructose

Question 16

As most animals mature they lack the enzyme lactase, what happens when lactose accumulates in the gut lumen?

Answer 16

• osmotic force -> decreased water absorption
• fermented in LI
• causes pH to decline
• gas products cause distention

Question 17

How does the ruminant small intestine receive a lot of protein despite being herbivores?

Answer 17

microbial protein passing from the rumen

Question 18

Where does protein digestion occur?

Answer 18

Initiated in the stomach and continues in the SI with pancreatic proteases

Question 19

What is enables in neonates to allow absorption of intact antibodies?

Answer 19

• Epithelial cells of intestine are permeable to intact protein
• Stomach produces negligible amounts of HCl
• Pancreatic enzyme secretion is low
• Colostrum contains trypsin inhibitors

Question 20

What are the two types of fat present in animal tissue?

Answer 20

Cholesterol esters

Phospholipids

Question 21

Which enzyme breaks down fats? What are they broken down into?

Answer 21

Lipase

• mono-glycerides
• free fatty acids

Question 22

What is secreted by the liver that is required for fat digestion? How does this support digestion?

Answer 22

Bile salts

Reduce large droplets to a smaller size increasing the SA

Question 23

What would happen to fat droplets in the absence of bile?

Answer 23

They would re-coalesce into larger droplets

Question 24

What is a micelle and what is their function?

Answer 24

• Bile salts that have aggregated together

- when they come into contact with emulsified fat droplets they absorb mono-glycerides and FFA’s

Question 25

Where do mono-glycerides / FFAs re-esterified to form tri-glycerides?

Answer 25

Endoplasmic reticulum

Question 26

What is formed when tri-glycerides coalesce with cholesterol & phospholipids?

Answer 26

Chylomicrons

Question 27

What enables a chylomicron to be transported in lymph and blood?

Answer 27

A protein coat - lipoprotein

Question 28

What are the two main routes of water transport?

Answer 28

Para-cellular = across tight junctions between epithelial cells
Trans-cellular = across cell membrane via transporter proteins

Question 29

What is secreted in digestive juices that must be re-absorbed to prevent metabolic acidosis?

Answer 29

HCO3-

Question 30

What increases the passive transport of Ca2+?

Answer 30

high dietary Ca2+

Question 31

Where are no digestive enzymes present?

Answer 31

Large intestine

Question 32

How is the ascending colon adapted in the following:

1) horses
2) carnivores
3) ruminants/omnivores

Answer 32

1) extensive
2) simple
3) moderate

Question 33

what are the two major cell types in the large intestine and what are their functions?

Answer 33

1) colonocytes - absorptive function

2) goblet cells - secrete mucous and HCO3-

Question 34

What occurs in the large intestine that leads to the production of a large energy source?

Answer 34

Fermentation of structural carbohydrate (fibre) into VFA’s

Question 35

By what process is propinoate fermented? What is the end product?

Answer 35

Gluconeogenesis

Glucose

Question 36

Diarrhoea is when water is lost in faeces through:

1) ?
2) ?

Answer 36

1 = increased secretion
2 = decreased absorption

Question 37

What are the 3 main causes of diarrhoea?

Answer 37

• Nutritional (microbial imbalance)
• Infections
• Stress

Question 38

Which muscles contract/relax to allow defaecation?

Answer 38

• Terminal colon and rectum contract
• Inner anal sphincter muscle relaxes
• Outer anal sphincter muscle under conscious control
• contraction of abdominal muscles