57. GI Physiology part 2

Question 1

What produces gastric peristaltic waves?

Answer 1

Peristaltic rhythms generated by pacemenaker cells

slow wave rhythm is produced by the basal electric rhythm

Question 2

What are the two regions on the pancreas

Answer 2

Endocrine region- pancreatic islets of langerhan

Exocrine region- acinar cells and lobules

Question 3

What do duct cells do in the pancreas?

What do acinar cells do in the pancreas?

Answer 3

Bicarbonate is secreted by duct cells

Digestive enzymes are secreted by acinar cells

Question 4

What enzymes are produced from the pancreas?

Answer 4

Proteases- cleaves peptide bonds

Nucleases- hydrolyses DNA

Elastases- collagen digestion

Phospholipids- phospholipids to fatty acids

Lipases-tricglycerides into fa and glycerol

A-amylase- starch into maltose and glucose

ALL STORED AS ZYMOGENS

Question 5

What controls pacreatic enzyme secretion

Answer 5

Bicarbonate secreted by secretin (acid in duodenum)

Zymogen secretion dye to cck (fat/amino acids in duodenum)

Vagal measures

Question 6

What is the role of hepatocytes?

Answer 6

Bile synthesis
Nutrient storage
Glycogen, fat, vitamin, copper and iron storage
Nutrient interconversion
Detoxification (puts bad stuff in bile)

Question 7

What are the components of bile

Answer 7

Bile acids
Lecithin
Cholesterol (all synthesised in liver)

Bile pigments- bilirubin (from heamoglobin)
Toxic metals- detoxed
Bicarbonate- duct cells

Question 8

How does bilirubin provide colour for different areas in the body?

Answer 8

Makes bile yellow
Makes poo brown
Makes urine yellow

Question 9

How are bile acids stored?

Answer 9

Synthesised from the liver at a rate of 0.5g/day

Reabsorbed within the small intestine

Question 10

How is bile released into the small intestine?

Answer 10

Controlled by the sphincter of oddi

sphincter is relaxed in response to CCK

Question 11

Summarise the effects of secretin and cholecystokinin

Answer 11

Secretin- neutralisation (stops stomach emptying, causes bicarbonate release)

CCK- Digestion (stops stomach emptying and causes enzyme and bile release)

Question 12

How does the small intestine increase absorption due to its large surface area

Answer 12

Its a cylinder
The cylinder has folds
The folds are made up of tiny cells (villi)
Which have projections on top of them (microvilli)

Question 13

Explain the makeup of a villus cell?

Answer 13

Made up of columnar epithelium with a capillary network and a lacteal inside each. They are surrounded by goblet cells and crypts of liberkuhn

Question 14

What functions does the 1500ml of water secreted daily by the intestines possess?

Answer 14

Maintains luminal contents in liquid state
Promotes mixing of nutrients with digestive enzymes
Aids nutrient presentation to absorbing surface
Dilutes and washes away potentially injurious surfaces

Question 15

How is water secreted in such volumes by the intestines?

Answer 15

Chloride moves out via the CFTR channel and drags water with it through the crypt cells.

Question 16

What are the two types of intestinal motility?

Answer 16

Segmentation- sloshes chyme about and brings it in contact with basal surfaces

Peristalsis- Movement of food down from mouth to anus.This is called the migrating motility complex. It is controlled by motilin

Question 17

What is the gastroileal relfex?

Answer 17

Gastric emptying causes incresaign segmentation activity in ileum

Question 18

Explain the histology in the large intestine
Rectum
Anal canal

Answer 18

Large intestine- simple columnar epithelium
Rectum-Simple columnar epithelium
Anal canal - simple columnar to stratified squamous

Question 19

What vitamins does the large intestine reabsorb?

Answer 19

Vitamins that are produced by colonic bacteria such as vitamin K.

Question 20

How do enterotoxigenic bacteria e.g. vibrio cholerae and e.coli cause diorrhea?

Answer 20

Produces protein enterotoxins which cause chloride secretion from crypt cells

cAMP, cGMP and calcium causes mass H20 secretion

Question 21

How do you treat secretory diarrhoea?

Answer 21

Give sodium/glucose solution.

Drives reabsorbtion of water