Brainscape's Knowledge GenomeTM

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


See full index

Introduction to medicine (Year 1) > Introduction to the function and control of the alimentary tract > Flashcards

Introduction to the function and control of the alimentary tract Flashcards

1
Q

How does the ANS enable the storage of food in the stomach?

A
  • ANS allows for accommodation of food
  • Does this through receptive relaxation of the fundus and body, which is coordinated by the ANS, not voluntarily controlled
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the fundus and what does it do?

A
  • Bulbous dome-shaped gastric region, stores undigested food + gases released during chemical digestion process
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe receptive relaxation of the fundus and body

A
  • Refers to muscle relaxation in stomach that occurs before entry of food through oesophagus
  • Gastric motility is first movement of digestive system, activated when food present or absent in stomach
  • With entry of food as liquid or bolus, stomach wall receptors are stimulated to relax to take up and store food that is swallowed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the process of digestion

A
  • Fundus and body of stomach (thinner muscle tone) relaxes, allowing larger volume (1.5L) of food storage
  • Vagal reflex inhibits smooth muscle tone - mechanoreceptors → fundic relaxation
    • Vasoactive intestinal peptide (VIP) and NO
  • Antral region mixes/grinds food with gastric secretions - digestion
  • Colon/rectum- storage of indigestive residues and faecal matter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is receptive relaxation considered a vagovagal reflex?

A

As it is both excited and inhibited by the vagus nerve

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

What happens after receptive relaxation?

A
  • Peristaltic movements that mix the food, and various changes convert the food into chyme
  • After chyme is formed, the contents of the stomach empty into the duodenum, in a process called gastric emptying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What branch of the ANS enables accommodation?

A

Peripheral - vagus inhibitory fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How much can a full stomach accommodate?

A

1.5 L

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

What branch of the nervous system allows the movement of food into the duodenum?

A

Autonomic

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

Explain the mechanism of the peritalsic wave and how food is mixed and transported into duodenum

A
  • Ripples of contraction move food to antrum and pyloric sphincter closed upon arrival of peristaltic wave
  • Repulsion of chyme causes pyloric sphincter to open and small partially digested material is squired through pyloric sphincter into duodenum
  • Repulsion of astral contents back into body allows mixing/grinding
  • Sieving effect - viscous and solid matter are retained in the stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are paracrine secretions and name an example and its function?

A
  • Secreted from cells in mucosa
  • Act on adjacent cells via interstitial fluid
  • Somatostatin- inhibits gastrin release in stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where are exocrine secretions secreted from?

A

Secreted from numerous glands with ducts

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

What are the generic functions of exocrines?

A
  • Digestion
  • Lubrication
  • Protection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name salivary exocrine secretions and their function

A

Mucus for lubrication for mastication and speech

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Name gastric gland exocrine secretions

A

Secrete HCL, pepsin, and mucus

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

Name pancreas exocrine secretions

A

Bicarbonate ion and enzymes- amylase, lipase, carboxypeptidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Name liver exocrine secretions and their function

A

Bile acids - emulsification of fats

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

Name the different types of gastric secretions and describe their functions

What cells are they secreted from?

A
  • Mucus -(secreted by goblet cells + mucus neck cells) - acts as lubricant by acting as a barrier that prevents the stomach and colon especially from gastric acid (prevents trauma)
  • Lipase - Converts triglycerides to fatty acids + glycerol
  • Pepsin - Secreted by chief cells or peptic cells as pespinogen. Protein digestion
  • Intrinsic factor - Secreted by parietal cells for vitamin B12 absorption
  • HCL - Secreted by parietal cells. Important in defence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are endocrine secretions?

A

Hormone secretions - synthesised by ductless glands, enter blood stream, travel to target and bind to specific receptor

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

Name examples of endocrine secretions, where are they found?

A
  • Gastrin - released by G cells in antrum
  • Secretin - duodenal mucosa
  • Pancreoxymin-cholecystokinin- duodenal mucosa
  • Insulin - secreted from Beta cells of pancreas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are G cells?

A
  • Neuroendocrine cells responsible for the synthesis and secretion of gastrin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is gastric juice stored in the stomach composed of

A
  • Mucus
  • Lipase
  • Pepsin
  • HCL
  • Intrinsic factor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the role of mucus in the GI system

A

Mucus (secreted by goblet cells + mucus neck cells) - acts as lubricant by acting as a barrier that prevents the stomach and colon especially from gastric acid (prevents trauma)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe the role of lipase in the GI system

A

Converts triglycerides to fatty acids + glycerol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the role of pepsin in the GI system

A

Secreted by chief cells or peptic cells as pespinogen

Protein digestion

26
Q

Describe the role of HCL in the GI system

A

Secreted by parietal cells

Important in defence

27
Q

Describe the role of intrinsic factors in the GI system

A

Secreted by parietal cells

For vitamin B12 absorption

28
Q

What are the digestive functions of the stomach?

A
  • Accommodation & storage
  • Mechanical and enzymatic breakdown
  • Slow delivery of chyme to duodenum
29
Q

Describe the role of absorption in the alimentary tract

A
  • Nutrients from digestion transported across intestinal epithelium into blood or lymph (via lacteals - fats/lipids)
  • Absorption occurs mainly in small intestine
  • Absorption of fluid occurs in small intestine + colon
  • Colon absorbs 90% of water, reducing volume to 200ml semi-solid faecal matter
  • Disorders of fluid secretion + absorption important (together with motility) in pathogenesis of diarrhoea
30
Q

Describe the role of motility in the alimentary tract

A
  • Motility = movements of muscular wall
  • Allows:
    • Movement from one region to another part of gut; mass evacuation
    • Mechanical degradation, e.g. gastric antrum
    • Mixing lumen contents, e.g. small intestine
    • Transport of nutrients, water and of urea and electrolytes
    • Digestion
    • Absorption
31
Q

Describe the role of excretion in the alimentary tract

A
  • Drugs + some products of normal metabolism may leave body in:
    • Saliva
    • Bile
    • Faeces
    • Vomit
  • Indigestible food residues (e.g. tomato skin) leave body in faeces
32
Q

Describe the role of defence in the alimentary tract

A
  • Gut epithelium = interface that is exposed to external environment
  • Intestine is largest mucosal surface in body, all the largest lymphoepithelial organ
  • If there’s a breach in the barrier, toxins enter the blood to destroy microorganisms
33
Q

What are the defence mechanisms of the alimentary tract?

A
  • Sight, smell, taste alerts us to harmful food substances
  • Vomit reflex
  • Acid in stomach (HCL) kills most harmful bacteria
  • Muscus secretions
  • Natural bacterial flora, prevents colonisation of harmful bacteria
  • Aggregation of lymphoid tissue (e.g. Peyer’s patches) able to most a response to food-borne antigens - analyse and respond to pathogenic microbes
  • Peyer’s patches- Located in laminate propria layer of mucosa and extending into submucosa of ileum
34
Q

How is mucosal repair and integrity maintained?

A

Growth factors (e.g. epidermal growth factor, insulin-like growth factor I) and prostaglandins

35
Q

What 2 nerve fibres are intrinsic to the gut and what do they control?

A
  • Myenteric/ Auerbach;s plexus - control motor functions
  • Submucosal/ Meissner’s plexus - control intestinal secretions
36
Q

What is unique about the enteric nervous system?

A
  • These fibres regulate GI function in wall of gut
  • Connected to CNS but can function on own and mediated entirely by ENS
37
Q

What are some neurotransmitters of the ENS?

A
  • Noradrenaline
  • Ach
  • 5-HT
  • GABA
  • ATP
  • NO
38
Q

Where are the two nerve fibres that are part of the ENS found?

A
  • Auerbach’s - most prominent between longitudinal and circular muscle
  • Meissner’s - surrounds the submucosa under circular
39
Q

Describe the innervations of the gut

A
  • Brain/ spinal cord send efferent signals to ENS, acts on gut muscle + mucosa
  • Afferent vagus nerve sends gut signals to brain
  • Efferent vagus nerve can mediate signal between brain/ ENS
  • Afferent splanchnic nerves sends gut signals to spinal cord
  • Efferent splanchnic nerve sends signals to ENS
40
Q

What is the colo-colonic reflex?

A
  • Plexuses found in wall of colon innervated by ANS
  • Parasympathetic nervous system increases colon contraction and sympathetic nervous system decreases colon contraction = colo-colonic reflex
41
Q

What is the role of cholinergic transmission in the GI tract?

A

Increases motility + secretions

42
Q

What is the role of adrenergic transmission in the GI tract?

A

Decreases motility + secretions

43
Q

What is the role of adrenergic transmission in the GI tract?

A

Decreases motility + secretions

44
Q

What are hormones produced by the gut called?

A

Peptides

45
Q

What hormones controls gastric HCL secretion?

A
  • Gastrin - peptide hormone primarily responsible for enhancing gastric mucosal growth, gastric motility, and secretion of HCL into the stomach
46
Q

Where does gastrin primarily act?

A
  • Body of stomach
47
Q

Describe how gastrin mediated effects are stimulated

A
  • G cells stimulated by neurone, releasing GRP (gastrin releasing peptide) causing gastrin release
  • Gastrin travels in blood and bind to enterochromaffin- like cells (ECL) in gastric glands of gastric mucosa
  • ECL cells release histamine acting on parietal cells
  • This causes HCL release, which can also occur through:
    • Gastrin also directly acting on parietal cells
    • ECL also acted upon by Ach, causes release of histamine which acts on parietal cells then causing HCL release by parietal cells
    • Ach also directly acting on parietal cells
48
Q

What are the roles of paracrine factors in the regulation of gastric HCL secretion?

A

H+ from HCL bind to D cells which release somatostatin which binds to G cells inhibiting gastrin release = less gastrin = less acid secreted by parietal cells

49
Q

What do D cells in the GI do?

A
  • Endocrine cell that releases hormone somatostatin, which binds to G cells inhibiting the synthesis and secretion of gastrin, and therefore preventing the secretion of HCL
50
Q

What are the roles of nerves in regulation of gastric HCL secretion?

A
  • Vagus nerve afferents innervate lower oesophagus, fundic region and duodenal region
  • Vago-vagal reflex:
    • Used to relax stomach allowing swallowed food to enter + be stored
    • Vagal afferents from gut enter into medulla and synapse/terminate at nucleus tracts solitaries (NTS)
    • Info processed and vagal efferents originate and leave medulla at dorsal motor vagal nucleus (DMVN)
    • Vagal efferents then release Ach at target tissue of gut = affects secretion and motility of gut
51
Q

How long does food stay stored in the stomach?

A
  • 1 hr
52
Q

How does the stomach accommodate for larger volumes?

A
  • Fundus and body of stomach allows for larger volume of storage
53
Q

What is the mechanism which allows for the stomach to relax and increase its volume?

A

Vagal reflex inhibits smooth muscle - allows fundic relaxation (via mechanoreceptors in lower oesophagus and fundic area)

VIP (vasoactive intestinal peptide) and NO involved in this.

54
Q

What is the role of the astral region of the stomach?

A

Antral region of stomach mixes/grinds food with gastric secretions and expels food down the pyloric sphincter - a sieve allowing food of certain site through

55
Q

What is the role of the colon/rectum?

A

Storage of digestive residues and faeces

56
Q

What does motility allow for?

A
  • Allows:
    • Movement from one region to another part of gut; mass evacuation
    • Mechanical degradation, e.g. gastric antrum
    • Mixing lumen contents, e.g. small intestine
    • Transport of nutrients, water and of urea and electrolytes
    • Digestion
    • Absorption
57
Q

Describe the parasympathetic innervation of the GI tract

A
  • Vagus nerve
  • Pelvic splanchnic nerves
    • 2 nerves provide parasympathetic innervation of GI tract
    • Ganglia are in myenteric and submucosal plexuses - regulate GI motility and secretion respectively
58
Q

Describe the sympathetic innervation of the GI tract

A
  • Celiac ganglion - This is where the greater splanchnic nerve terminates
  • Superior mesenteric ganglion - This is where the lesser splanchnic nerve terminates
  • Inferior mesenteric ganglion - This is where the lumbar splanchnic nerve terminates
  • Hypogastric ganglion
    • The preganglionic neurones synapse outside the GI tract in the 4 ganglia
59
Q

Describe the metabolic control of the GI system?

A
  • Rate of gastric emptying dependent on ability of material to be absorbed:
  • Carbohydrates emptied quickly into duodenum
  • Proteins - slow emptying
  • Fatty food - even slower emptying
  • Fatty acids in dudodenum - decrease in gastric emptying by increasing the contractility of the pyloric sphincter
60
Q

What parasympathetic nerve innervates the hindgut?

A

Pelvic sphlanchnic nerves

Introduction to medicine (Year 1) (59 decks)

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