lecture 25 - secretion

Question 1

what are exocrine secretions

Answer 1

produced by epithelia - move into the lumen

Question 2

what are endocrine “secretions”

Answer 2

move into the body = meaning they aren’t secreted as such

Question 3

what are the components and functions of exocrine secretions

Answer 3

mucus = protection + absorption, also aids mechanical digestion

electrolyte solution = dilutes food and provides optimal pH, essential for chemical digestion

digestive enzymes = essential for chemical digestions, aids absorption

Question 4

how much fluid do salivary glands produce per day

Answer 4

1.5 L

Question 5

composition of salivary secretion

Answer 5

mucus
dilute solution of NaHCO3/NaCl
digetive enzymes

Question 6

what do the salivary glands aid with

Answer 6

talking, chewing and swallowing

Question 7

what are the two forms of salivary gland regulation

Answer 7

nervous = thought, smell and sight
autonomic nervous system = parasympathetic and sympathetic

Question 8

how much gastric secretions do we produce daily

Answer 8

2-3L

Question 9

what are the functions of intrinsic factor in gastric secretions

Answer 9

stabilises vitamin B12 and facilitates its absorption in small intestine

Question 10

what are the functions of pepsinogen in the gastric secretions

Answer 10

inactive form of pepsin (converted by acid) that starts digesting proteins

Question 11

what is the function of gastric acid in gastric secretions

Answer 11

• dilutes food
• denatures protein
• activates pepsinogen to pepsin
• creates optimum pH for pepsin action
• protection

Question 12

what are the three phases of gastric secretions and what controls them

Answer 12

• cephalic phase = head controls secretion
• gastric phase = stomach controls secretion
• intestinal phase = intestine controls secretion

Question 13

what is happening the cephalic phase of gastric secretion

Answer 13

preparation of arrival of food

Question 14

what is the stimuli of the cephalic phase of gastric secretion

Answer 14

• higher centres (CNS) = thought, smell and sight of food
• chewing action, taste

Question 15

what happens in response to stimuli of the cephalic phase of gastric secretions

Answer 15

extrinsic parasympathetic nervous system response
- stimulates parietal cells, chief cells and goblet cells
- stimulate secretion of hormone gastrin

Question 16

what is happening the gastric phase of gastric secretion

Answer 16

ensures sufficient secretion to handle ingested food

Question 17

what is the stimuli in stomach of the gastric phase of gastric secretion

Answer 17

• stretch of stomach wall
• products of digestion stomach lumen
• elevated pH

Question 18

what happens in response to stimuli of the gastric phase of gastric secretions

Answer 18

• local nervous reflex = enteric nervous system
• external (long) nervous reflex = parasympathetic nervous system

both stimulate secretion from gastric glands and motility

Question 19

what is happening the intestinal phase of gastric secretion

Answer 19

controls delivery to small intestine

Question 20

what is the stimuli of the intestinal phase of gastric secretion

Answer 20

• distension of duodenum
• arrival of acid chyme, lipids and carbohydrates into the duodenum

Question 21

what happens in response to stimuli of the intestinal phase of gastric secretions

Answer 21

• hormones = GIP, CCK, secretin (responding to nutrients +acid, increase enzymes that respond)
• nerves = enterogastric reflex (long reflex duodenum to brain to stomach)

both inhibit secretion and motility

Question 22

what are the two components of pancreatic secretions

Answer 22

enzymes = acinar cells, chemical digestion of food
alkaline fluid = duct cells, neutralize acid

Question 23

what do pancreatic enzymes act on

Answer 23

all classes of foods

Question 24

what are proteolytic enzymes

Answer 24

secreted as inactive precursors and activated to active enzyme in the duodenum

Question 25

what are the functions of biliary secretions

Answer 25

• bile salts = fat digestion
• HCO3 rich fluid = neutralizes acid
• bile pigments = excretion

Question 26

what does the hormone cholecystokinin (CCK) do and when is it produced

Answer 26

produced in response to products of digestion in duodenum
- contraction of gallbladder
- relaxation of hepatopancreatic ampulla