functions and secretion of alimentary tract part 2

Question 1

Types of alimentary tract glands

Answer 1

a. single-cell mucous glands/ goblet cells that secrete mucus in response to irritation in the epithelial surface.

B. crypts of Lieberkühn specialized secretory cells( acts as stem cells)

c. tubular glands- secret HCL and pepsinogen.

d. salivary glands

e. pancreatic glands

f.liver.

Question 2

basic mechanism of stimulation of the alimentary tract glands:

Answer 2

begins as the local stimulation of the epithelial lining to activate the enteric nervous system of the gut by?

a. tactile stimulation
b. chemical irritation
c. distention

which results in the stimulation of gut mucus cells and deep gland secretion.

Question 3

Parasympathetic stimulation

Answer 3

increase GIT glandular (salivary, pancreatic, oesophageal, gastric &
Brunner’s glands) secretion rate.

and parasympathetic is innervated by glossopharyngeal and vagus parasymp nerves

Question 4

Sympathetic stimulation has a dual effect on GIT glandular secretion rate

Answer 4

a. Sympathetic nerve stimulation→ GIT→ increase (slight—moderate) local glandular secretion
(however, if parasymp or hormones increase secretions, then sympathy will reduce them)
b) Sympathetic nerve stimulation→ constriction of glandular blood vessel

Question 5

Secretion of Organic Substances:

Answer 5

Transportation of nutrients (through blood to gland)→ mitochondria inside glandular cells form ATP
→ ATP + Nutrient substrate→ form organic secretory substance
(in ER & Golgi complex)→ transported through ER tubules→ to vesicles of Golgi complex→
modification→ into secretory vesicles→ stored in secretory cells apical ends→ nervous/hormonal
signal stimulation→ cause vesicular contents release (through calcium effect “exocytosis”).

Question 6

water and eletrolyte secretion:

Answer 6

nervous stimulation-salivary secretion manly water + salt through glandular cells

Question 7

Lubricating & Protective Properties of Mucus in GIT: mucus:

Answer 7

Adherent qualities (for food & other)
b) Coats gut wall.
c) Low resistance for slippage.
d) Adheres faecal materials= faeces.
e) Resistant to digestion (by gut enzymes).
f) Buffer small amounts of acids or alkalies.
g) Contain bicarbonate (small amounts).

Question 8

name salivary glands

Answer 8

a) Parotid: serous secretion
b) Submandibular: mucus + serous secretions
c) Sublingual: mucus + serous secretions
Additionally, buccal glands: mucus only

Question 9

average daily secretion in mL and pH

Answer 9

800-15000 (1000)mL
pH 6-7

Question 10

2 Major types of Salivary Protein Secretion:

Answer 10

serous secretion= ptyalin
mucus secretion= mucin

Question 11

submandibular gland secretion:

Answer 11

) Acini: primary secretion= Ptyalin,
mucin, ECF
b) Salivary ducts: Na+ actively
reabsorbed (drops in saliva)→ K+
actively secreted (in exchange for Na+)
(increase in saliva)→Cl- reabsorbed
passively (drop in saliva)→ HCO3-
secreted.

Question 12

Nervous Regulation of Salivary Secretion:

Answer 12

Parasympathetic NS from Superior + Inferior salivatory nuclei (in brain stem)→increase salivation
Salivation stimuli= taste, tactile from tongue—mouth—pharynx
Salivation by stomach + upper small intestine reflexes (irritating foods, nausea)
Parasymp→ vasodilation (also due to kallikrein) of salivary glands blood vessels→ increase nutrient
supply

Sympathetic NS→ slightly increase salivation (thick)

Question 13

oesophageal secretion

Answer 13

mainly mucus for lubrication
the upper portion of the esophagus has compound mucus glands = prevent excoriation from entering foods.

middle portion= of simple mucus glands for lubrication during swallowing

the lower portion (esophagogastric junction)= prevents digestion of oesophageal wall by gastric juices
(reflux)= peptic ulcer

Question 14

peptic cells

Answer 14

secrete pepsinogen that is stimulated by ACh from the parasympathetic system.

Question 15

parietal cell

Answer 15

secret HCL that will convert pepsinogen to pepsin =a protein for digestion.

vitamin B12 absorption in ileum=achlorhydria
pernicious anaemia when parietal cells are destroyed.

Question 16

pancreatic Acini

Answer 16

secretes pancreatic digestive enzymes.
sodium bicarbonate by ductules

insulin -secreted by islets of Langerhans.

Question 17

name the protein digestive pancreatic enzymes.

Answer 17

trypsin, chymotrypsin, carboxypolypeptidase.

Question 18

carbohydrates digestive enzyme

Answer 18

Amylase

Question 19

Fat digestive pancreatic enzymes

Answer 19

pancreatic lipase, cholesterol esterase and phospholipase

Question 20

secretion of bile

Answer 20

In The Liver
about 600-100 mL OF BILE IS secreted for fat digestion (emulsification) and absorption, waste excretion from food.

Question 21

flow of bile from the liver to intestines

Answer 21

hepatocytes secrete bile into bile canaliculi to the terminal bile duct, larger ducts, hepatic ducts then common bile ducts either duodenum or gall bladder through cystic duct..

Question 22

storage of bile

Answer 22

gall bladder about 30 -60 mL

Question 23

Functions of Bile Salts in Fat Digestion & Absorption:

Answer 23

FAT digestion-emulsification of fat

absorption using micelles cells-fatty acids,monoglyceride cholesterol or other lipids

Question 24

Secretion of Mucus by Brunner’s Glands in The Duodenum

Answer 24

Brunner’s glands located→ between pylorus & papilla of Vater→ secrete alkaline mucus→ due to
irritation/tactile stimuli duodenum + vagal stimulation + gastrointestinal hormones (secretin)
→mucus secreted → protect duodenal wall from acids
Inhibition of Brunner’s glands→ sympathetic SN (can cause peptic ulcer in this region

Question 25

secretion of crypts of lierkuhn

Answer 25

located over surface of small intestine= crypts of lieberkuhn.