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PHYS 150: physiology > digestive physiology > Flashcards

digestive physiology Flashcards

1
Q

Label:

Organs of the digestive system

in order

A
  1. oral cavity
  2. pharynx
  3. esophagus
  4. stomach
  5. small intestine: duodenum, jejunum, ileum
  6. large intestine: ascending colon, transverse colon, descending, sigmoid
  7. rectum
  8. anus
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2
Q

Label:

Accessory organs of the digestive system

in order

A
  1. teeth = mechanical breakdown
  2. tongue = concerts to bolus
  3. Salivary glands
  4. liver
  5. gall bladder
  6. pancreas
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3
Q

What is the aim of control of the digestive system?

A

motility & secretion

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4
Q

How is the digestive system controlled?

A
  1. neural mechanisms
  2. hormonal mechanisms
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5
Q

What does the neuroendocrine control?

A
  1. salivary secretion
  2. gastric function (stomach)
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6
Q

Describe:

Control of salivary secretion

A

controlled by ANS (PNS)

activated by:
* thought, sight, smell of feed
* stimuli associated with food (sitting at the dining table)
* food in the mouth

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7
Q

Name:

The salivary glands

A
  1. Parotid
  2. Sublingual
  3. Submandibular
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8
Q

Name:

Phases of gastric stimulation

A
  1. Cephalic Phase
  2. Gastric Phase
  3. Intestinal Phase
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9
Q

In what phase is gastric juice released before food is in the stomach?

A

Cephalic phase

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10
Q

What triggers the cephalic phase?

explain what happens after

A

triggered by: sight, smell, taste, or thought of food

  1. olfactory & taste centres send message to hypothalmus
  2. hypothalamus sends message to brainstem/medulla
  3. medulla stimulates gastrin release (from stomach) into blood vessels via vagus nerve
  4. gastrin stimulates stomach to release gastric juices into the lumen of the stomach

purpose = prepare stoamch for incoming food

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11
Q

What makes up gastric juices?

A
  1. HCl
  2. enzymes: pepsinogen, mucus (protects lining)
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12
Q

In what phase is food in the stomach?

A

gastric phase

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13
Q

Describe:

Receptors in the stomach wall

gastric phase

A

Chemoreceptors = stimulated by chemicals in the food

Stretch receptors = stimulated by distention of the stoamch wall

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14
Q

What stimulates chemoreceptors?

A
  • proteins
  • low acidity of stomach (low H+ ions)
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15
Q

What happens in the:

Gastric phase

2 effects

A

direct local effect = secretion of gastric juices into the lumen of the stomach

indirect effect = via hypothalmus –> medulla –> vagus nerve
* secretion of gastrin into blood –> stimulates more secretion of gastric juices into lumen of the stomach

purpose = maintain digestion

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16
Q

In what phase does food enter the duodenum?

A

Intestinal phase

17
Q

What are the 2 phases of the intestinal phase?

A

Excitatory phase = stimulates release of increase of digestive enzymes

Inhibitory phase = when too much digestion is occuring, it slows down digestion (negative feedback)

18
Q

How does chyme stimulate the duodenum?

A
  1. chemical (partially digested food)
  2. pH (Acid)
  3. stretch
19
Q

What happens in the:

Intestinal phase

A

Part 1: positive feedback
* stimulates gastric secretion and motility –> release intestinal gastrin (via vagus neve)
* stimulates pyloric sphincter relaxation

Part 2: negative feedback
* increases acid (low pH) and stretch of duodenum decreases gastric secretion & slow down motility
* chemicals initiate secretion of some hormones

20
Q

How is gastric function inhibited?

two mechanisms

A
  1. neural = enterogastric reflex
  2. hormonal = enterogastrones
21
Q

Describe:

enterogastric reflex

A

activated by: distension of duodenum & low pH

effects: slow down!
* inhibits gastric motility
* inhibit secretion
* constricts pyloric sphincter

22
Q

Describe:

Enterogastrones

hormones? functions?

A

hormonal regulation

hormones: GIP, CCK, secretin

functions:
* inhibit secretion and motility
* cause contractions of accessory organs –> stimulate pancreatic juice and bile into intestines

23
Q

Describe:

gastric inhibitory peptide (GIP)

trigger? effects?

A

released by: presence of fats or glucose in chyme in duodenum

effects: inhibits gastric phase of gastric function
* decreases motility and secretion in stomach

24
Q

Describe

cholecystokinin (CKK)

trigger? effects?

A

released by: presence of fatty chyme in duodenum

effects:
* stomach: inhbits gastric secretion and motility
* pancreas: increase secretion
* gall bladder: stimulate contraction to eject bile into duodenum

25
Q

Describe:

secretin

trigger? effects?

A

released by: low pH or partially digested foods in duodenum

effects:
* stomach: inhibit secretion and motility
* pancreas: increases bicarbonate ion secretion
* liver: increase bile production

26
Q

Functions of the liver

A
  • storage of nutrients –> glucose
  • detoxification –> via hepatic portal vein
  • synthesis of plasma proteins (albumin, fibrinogen, prothrombin)
  • *bile production** –> digestive function
27
Q

What is:

Bile

what is it? where is it stored? composition

A

greenish yellow, bitter solution
* produced in the liver
* stored in gall bladder

composition:
* 97% water
* 3% electrolytes & organic compounds: bilirubin from RBCs (pigment), bile salts, cholesterol, phospholipids

28
Q

What part of bile does the work?

explain

A

bile salts
* from cholesterol
* active agents in the emulsification of fats –> separates the lipid into smaller sections of fat –> can be broken down and absorbed easier

29
Q

What do bile salts aid in the absorption of?

A
  • fatty acids
  • cholesterol
  • fat-soluble vitamins (A,D,E,K)
30
Q

What happens after bile salts do their job?

A
  • reabsorbed by the ileum
  • returned to liver
  • recycled in bile
31
Q

What are:

bile pigments

what is it? how is it excreted?

A

mostly bilirubin (from RBC breakdown)
* excreted in feces

32
Q

Describe the:

Organization of the liver

A

4 lobes

lobes are divided into lobules
* **hexagon-shaped **areas with lots of hepatocytes in it
* at the centre = central vein (CV)
* Triad = hepatic portal vein (HPV), hepatic artery (HA), bile duct (BD)
* triad is found at every corner of the hexagon

PHYS 150: physiology (7 decks)

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