Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Gastrointestinal system > Overview of GI function > Flashcards

Overview of GI function Flashcards

1
Q

Functions of GI system

A
  • Digestion - chemical and mechanical breakdown of large particles into those small enough to be absorbed
  • Absorption: movement of organic substrates, electrolytes, vitamins and water across digestive epithelium into blood/lymph
  • Motility: smooth muscle contractions - movement and mixing
  • Motility can be peristalsis (oesophagus and stomach), segmentation contractions (small intestine), migrating motility complex (small intestine whilst fasting), haustral contractions (large intestine) and mass movements (large intestine)
  • Gastrocolic reflex: 30 mins after meal - promote removal of material from large intestine to rectum
  • Secretion: water, mucus, acids, enzymes, buffers and salts
  • Excretion: waste material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the mesentery?

A

Attaches to posterior abdominal wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Gastrocolic reflex

A

30 mins after meal - promote removal of material from large intestine to rectum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

GI tract wall

A
  • Mucosa: mucous membrane (epithelial layer), lamina propria (connective tissue and GALT), muscularis mucosa (smooth muscle)
  • Submucosa: connective tissue containing nerves, blood vessels and glands
  • Muscularis externa: circular and longitudinal layers of smooth muscle, nerves
  • Serosa: lubricating outer layer of connective tissue connected to mesentery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are lymphocytes found?

A

Appendix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Enteric nervous system

A

Myenteric and submucosal plexus + input from autonomic, sympathetic and parasympathetic nervous system (VAGUS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Functions of oral cavity

A
  • Salivary secretions
  • Salivary glands: parotid glands (ear), sublingual (below tongue), submandibular (mandible) - main is submandibular
  • Moistens and lubricates food
  • Dissolves food
  • Initiates digestion of polysaccharides (amylase) and lipids (lipase)
  • Forms bolus (compact ball of food)
    antibacterial actions (IgA and lysozyme)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the three pairs of salivary glands?

A

Parotid, sublingual and submandibular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Function of stomach

A

Stores ingested food, secretes (intrinsic factor, HCL, pepsinogen, mucus) to form gastric juice, mechanical breakdown of food = chyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Key regions of stomach

A

cardiac system, cardia, fundus (pacemaker cells), body (oxyntic glands), antrum (pyloric glands), pyloric sphincter, rugae (deep folds to increase volume) = receptive relaxation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is vit B12 broken down?

A

Intrinsic factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Function of small intestine

A

Digestion and absorption of nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Three sections of small intestines

A

Duodenum, jejunum and ileum (vit B12 ingested here)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Function of duodenum

A
  • Receives secretions from liver, gall bladder and pancreas
  • Sphincter of Oddi stops bile entering duodenum
  • Precipitation of bile = gall bladder stones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Function of sphincter of oddi

A

Stops bile entering duodenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Function of pancreas

A

Release of digestive enzymes and alkaline fluid into duodenum

  • Enzymes and bicarbonate secretion
  • Bile: bile salts (cholesterol), lecithin (phospholipid), alkaline secretions and metabolic wastes including bilirubin (from RBCs break down in liver)
  • Bile emulsifies and forms micelles
  • Majority of bile salts recycled back to liver via hepatic portal system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Function of hepatocytes

A

Synthesise bile into bile duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is bile?

A

bile salts (cholesterol), lecithin (phospholipid), alkaline secretions and metabolic wastes including bilirubin (from RBCs break down in liver)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Substrates of trypsin

A

Proteins (attack different peptide bonds) -> small peptides and amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Substrates of lipase

A

Triglycerides -> monoglycerides and fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Substrates of amylase

A

Starch (amylose and amylopectin) -> maltose and a-limit dextrin

22
Q

Areas of large intestine

A

Cecum (and appendix), ascending, transverse, descending and sigmoid colon and rectum

23
Q

Functions of large intestine

A

reabsorb water and salt from chyme, stores and compacts faecal matter prior to defecation

24
Q

Defecation reflex

A

mass movement of faeces - stretch of rectum - internal anal sphincter relaxes and contraction of rectum and sigmoid colon. Defecation occurs when external anal sphincter relaxed

25
Q

Function of haustra

A

Moves material down

26
Q

Gut microbiome functions

A
  • Ferment dietary fibre: fatty acids for absorption and gas
  • Synthesise vitamin B12, folate and K
  • Protects gut from invasion by pathogens and educate your immune system
27
Q

Helicobacter pylori

A
  • Helicobacter pylori survives acidic environment by secreting ammonia
  • Helicobacter pylori causes stomach ulcers
28
Q

Nervous innervation of stomach movement

A

Vagus nerve and myenteric plexus (enteric N/S)

29
Q

Out of stomach

A

steady flow of partially digested liquid chyme, largely sterile

30
Q

Function of oxyntic glands

A

Oxyntic glands release acid by parietal cells

31
Q

Function of pyloric glands

A

Pyloric glands contain regulatory G and D cells

32
Q

Mucous secreting pits

A

At neck of pits are mucous secreting cells - parietal cells (HCl acid and intrinsic factor) - chief cell (pepsinogen) - G and D cells (gastrin and somatosensin)

33
Q

Function of gastrin

A

stimulates gastric acid secretion and motility and is released into mucosal blood vessels

34
Q

Intrinsic factor and vit B12

A
  • Released from parietal cells
  • Vit B12 is water-soluble vitamin and must be bound to intrinsic factor to be absorbed which facilitates absorption into terminal ileum
  • B12 transported by transcobalamin
  • Pernicious anaemia: loss of parietal cells due to auto-immune attack of stomach = no intrinsic factor
35
Q

Gastric acid production

A
  • Produced by parietal cells
  • CO2 enters parietal cell
  • CO2 combines with water to form carbonic acid (carbonic anhydrase)
  • Carbonic anhydrase dissociates into bicarbonate and hydrogen ions
  • H+ enters stomach anterior through proton pump
  • H+ in means K+ out (electroneutral exchange of ions)
  • Antiporter system: HCO3- out and Cl- in - passive
  • After meal, fluid leaving stomach is alkaline
  • Cl- that enters in proton pump enters stomach lumen and combines with H+ to form HCl
36
Q

Gastric acid function

A
  • Kills ingested bacteria
  • Denatures proteins - particle breakdown
  • Facilitates gastric lipase
  • Converts pepsinogen to pepsin for protein digestion
  • Proton pump inhibitors and H2 receptor antagonists used as treatment for acid
37
Q

Gastric acid complications

A
  • Stomach mjucosa protected from gastric acid by gastric-mucosal barrier
  • A layer of bicarbonate-rich mucus
  • Luminal membranes impermeable to H+ ions
  • Tight junctions between mucosal cells
  • Replacement of mucosal cells every 3 days
  • Peptic ulcers arise by breaking down of stomach lining and acid reflex into oesophagus and excess acid entering duodenum
  • Treat using antibiotics (helicobacter pylori), PPIs and H2 histamine receptor antagonists
38
Q

Neuronal regulation - intrinsic nerve plexus

A
  • Enteric nervous system
  • Myenteric plexus: smooth muscle contraction and tone
  • Submucosal plexus: controls GI secretions and blood flow
  • Short reflexes: stimulus - nerve plexus - response
  • ACh and NO increase motility
39
Q

Neuronal regulation - external nerve plexus

A
  • P/S vagus nerve and sympathetic influence on motility and secretions
  • Long reflexes: stimulus - CNS - nerve plexus - response
40
Q

Smooth muscle pacemaker

A

GI tract has basic electrical rhythm generated by pacemaker cells in muscularis extern

41
Q

Gastric secretions and stomach emptying

A
  • Cephalic: initiated by smell/taste, involved higher brain centres, Ghrelin hormone, initiates gastric secretions and motility
  • Gastric: initiated in stomach, mediated by enteric and P/S nervous system and gastrin - increased gastric secretions and motility
  • Intestinal: initiated in duodenum, mediated by inhibitory hormones, slows gastric emptying to optimise digestion and absorption within small intestine, enterogastric reflex
42
Q

Cephalic phase

A
  • Sight, smell, taste or thoughts of food
  • CNS - parasympathetic (vagus)
  • Submucosal plexus
  • Mucous cells secrete mucus, chief cells secrete pepsinogen and parietal cells secrete HCl
  • Ghrelin - released from flaccid stomach, acts on hypothalamus to stimulate appetite
  • Ghrelin levels increase after weight loss, lower in people with obesity, higher in anorexia nervosa, higher in Prader-Willi syndrome
43
Q

gastric phase

A
  • Arrival of food in stomach = secretions and contractility
  • Stretch receptors - submucosal and myenteric plecus
  • Mucus cells - mucus, chief cells - pepsinogen, parietal cells - HCl, G cells - gastrin
  • CNS (parasympathetic vagus)
  • Histamine stimulates parietal cells to release HCl
  • Gastrin released when pH falls - increases secretions and motility
44
Q

Inhibiting stomach emptying

A
  • Duodenal distension
  • Irritation of duodenum mucosa
  • Increase in fats and proteins
  • Increase in acidity
  • Increase in osmolarity
  • Act on receptors in duodenum to trigger enterogastric reflex
45
Q

Function of leptin in fat

A

Maintains fat stores

46
Q

Intestinal phase

A
  • Enterogastrones inhibit gastric acid secretions and gastric emptying
  • Stretch and chemoreceptors - myenteric plexus (negative feedback)
  • Stretch and chemoreceptors - CCK, secretin and somatosensin
  • Negative feedback on chief cells (decreased pepsinogen) and parietal cells (decreased HCl)
  • CCK: released by L cells in small intestine, stimulates pancreatic secretions and gall bladder contraction
  • Secretin: released by S cells in response to low pH, stimulates pancreatic and bile secretions
  • Somatostatin: released by D cells, inhibits everything
47
Q

Function of leptin

A

Maintains fat store - released from adipose tissue and acts on hypothalamus to suppress appetite

48
Q

How to inhibit stomach emptying

A
  • Duodenal distension
  • Irritation of duodenum mucosa
  • Increase in fats and proteins
  • Increase in acidity
  • Increase in osmolarity
  • Act on receptors in duodenum to trigger enterogastric reflex
49
Q

Function of somatosensin

A

Released by D cells, inhibits everything

50
Q

Function of secretin

A

Released by S cells, in response to low pH - stimulates pancreas and bile secretions

51
Q

Function of cholecystokinin

A

Released by I cells in small intestine, stimulates pancreatic secretion and gall bladder contraction

Gastrointestinal system (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions