GI and renal system

Question 1

What are the three glands that produce saliva and where are they?

Answer 1

Partoid: near ear—> have serous cells which produce enzyme amylase as they have Zymogen granules.
Submandibular: near mandible—> mainly serous
Sublingual: under tongue—> mainly mucous cells

Question 2

What are the two ways saliva is produced?

Answer 2

1. Chemoreceptors or pressure sensors send a signal to the medulla.
2. Cerebral cortex send message to medulla when they see food. This is learnt.

Question 3

What are the layers in the digestive tract wall?

Answer 3

Mucosa, submucosa, muscularis externa, serosa.

Question 4

GI tract works with — and —?

Answer 4

nervous system
endocrine system

Question 5

What cells in the stomach produce what?

Answer 5

Chief cells: pepsinogen—> pepsin—> breaks proteins down
Parietal cells: intrinsic factor+ HCL —> breaks proteins down

Question 6

What are the segments in small intestine? and what do the contractions in each segment depend on?

Answer 6

Duodenum—> jejunum—> ileum
Contractions depend on: Basal Electrical Rhythm (BER), from pacemaker cells.
It is controlled by gastrin: chyme is secreted into the small intestine lumen exposing all chyme absorptive surfaces of small intestine mucosa.

Question 7

Tubular reabsorption hormones??

Answer 7

RAAS- renin angiotensin aldosterone system
NaCl, ECF volume and arterial bp decreases, juxtaglomerular cells secrete renin into blood, renin turns angiotensin into angiotensinI, Angiotensin I turns into Angiotensin II by angiotensin converting enzyme.
Angiotensin II is a stimulus for the secretion of hormone aldosterone.

Question 8

What does aldosterone do?

Answer 8

Aldosterone either increases Na+ reabsorption and H20 reabsorption or allows vasoconstriction. Either way, the bp increases. It can increase Na+ reabsorption or increase tubular secretion of K+.

Question 9

How is salivary seretion mainly controlled?

Answer 9

Mainly controlled by the sympathetic nervous system.

Question 10

What does GCBP do?

Answer 10

Glomerular capillary BP: Hydrostatic pressure exerted by blood.
Affected by heat, resistance etc.

Question 11

What is plasma colloid pressure?

Answer 11

Caused by unequal distribution of plasma proteins across the glomerular membrane. It opposes filtration.

Question 12

What does the bowmans capsule hydrostatic pressure do?

Answer 12

Opposes filtration

Question 13

What is the process for absorption of monosaccharides in the digestive tract?

Answer 13

1. Glucose and galactose are absorbed into epithelial cells by NA+ and energy dependent secondary active transport. This is done by the symporter SGLT at the luminal membrane.
2. Fructose: passive faciliitated diffusion via GLUT-5.
3. Glucose, galactose and fructose exit GLUT-2 by the luminal membrane.
4. Monosaccharides enter blood by simple diffusion.

Question 14

How are amino acids absorbed into the Digestive tract?

Answer 14

1. Na+ energy dependant secondary transport via symporter.

Question 15

How are lipids digested into the digestive tract?

Answer 15

Triglycerides are mixed with bile salts to emulsify them. They are further broken down by pancreatic lipase.

Question 16

How does swallowing work?

Answer 16

When pressure receptors in the mouth are disturbed, the swallowing centre (medulla) is told, the medulla innervates the muscles in the pharynx. Peristalsis (regular contractions) occur which lasts for 9 seconds. The lower oesophageal sphincter opens, food passes into the stomach.