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Digestion & excretion physiology > L1 & L2 RECAP - GIT : oesophagus, swallowing and stomach histology > Flashcards

L1 & L2 RECAP - GIT : oesophagus, swallowing and stomach histology Flashcards

This deck covers the topics in lecture 1 & 2

1
Q

What are the main digestive organs?

A
  • oral cavity
  • pharynx
  • oesophagus
  • stomach
  • large and small intestine
  • anus
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2
Q

what are the accessory digestive organs?

A
  • salivary gland
  • liver
  • gallbladder
  • pancreas
  • not part of the tract but secrete substances into it via connecting ducts
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3
Q

What are the main layers in the tubular part of the GIT?

A
  1. Lumen - hollow center of the tube
  2. mucosa
  3. underneath is the submucosa - whitish layer
  4. muscularis - externa & propia
  5. adventitia
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4
Q

What are the 3 layers of the mucosa?

A
  • epithelium E - endocrine, exocrine and mucous cells
  • lamina propia LP ( middle layer)
  • muscularis mucosa MM ( outermost layer - contains smooth muscle cells & elastin)
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5
Q

What is the lamina propia?

A
  • a thin layer of connective tissue that forms the mucous membranes / mucosa
  • separates the layer of epithelial cells from the muscularis mucosa
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6
Q

What is the submucosal plexus & the myenteric plexus?

A
  • plexus = network of nerves or vessels in the body
  • forms the enteric nervous system in the GIT
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7
Q

What does the submucosa layer contain?

A

major blood and lymphatic vessels#

submucosal plexus

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8
Q

What does the muscularis externa contain?

A
  • circular muscle - prevents food moving backwards
  • myenteric plexus
  • longitudinal muscle - shortens the tract
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9
Q

What are alternative names for the submucosa plexus & myenteric plexus?

A
  • submucosa - meissner’s
  • myenteric - auerbach’s
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10
Q

What does the control of the GIT (in terms of contraction etc) require?

A
  • local control - ie the enteric NS
  • external influence - ANS -
  • the parasympathetic NS through the vagus nerve & pelvic nerve - generally excitatory Ach which increases motility and secretion
  • the sympathetic NS - generally inhibitory which will decrease mobility and secretion
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11
Q

Which of the 3 main pairs of salivary glands would you most associate with a watery secretion?

A
  • parotid - mostly serous
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12
Q

What are sphincter muscles?

A
  • circular muscles that open and close certain parts of the body
  • eg allowing food to enter the stomach, or for digestive enzymes to go from one part of body to another
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13
Q

What are the main steps in the first part of digestion (mouth to stomach) digestion?

A
  1. mastication - ie chewing food
  2. bolus preparation - ball like structure that forms in the mouth during the process of chewing
  3. enzymatic digestion
  4. food content sensing
  5. delivering of appropriately sized bolus to the stomach
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14
Q

what is the CPG? What is it involved in?

A

CPG is a group of neurons in the CNS that can automatically execute a complex motor act without the need for continous sensory input

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15
Q

What are the 3 phases of mastication?

A
  • mouth opening
  • mouth closing
  • intercuspal phase (occlusion)
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16
Q

What are salivary glands - where are they located & the 3 main pairs?

A
  • exocrine glands that produce saliva through a system of ducts located in the mouth
  • we have 3 paired major salivary glands - parotid, submandibular & sublingual
  • note there are also many minor glands present in mouth to assist
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17
Q

What are the 3 pairs of salivary glands?

A
  1. parotid
  2. submandibular
  3. sublingual
18
Q

What is saliva? - composition & function

A
  • extracellular fluid produced by salivary glands
  • comp : water and bicarb, enzymes eg amylase, immunoglobins etc
  • functions : lubrication, PH control, digestion, prevention of desiccation ( drying out)
19
Q

How is salivary production controlled?

A
  • NEURAL - not hormonal
  • stimulated by taste, smell and even thought of food
  • parasym and symp innervation
20
Q

Explain the difference between serous and mucous cells

A
  • serous cells - produce a watery secretion that contains a lot of proteins
  • mucous cells - produce mucous
21
Q

Which of the 3 main pairs of salivary glands would you most associate with the production of a mucous rich secretion?

A
  • sublingual glands - contain mostly mucous cells
22
Q

What is swallowing?

A
  • process that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis
23
Q

What is ‘aspiration’?

A
  • a situation when food travels down the trachea and can cause choking
24
Q

What are the 2 types of innervations of the GIT?

A
  • intrinsic - enteric NS - the myenteric and the submucosa plexus
  • extrinsic - the ANS - sympathetic and parasympathetic NS
25
Q

What 2 types of cell would you expect to find in a mixed salivary gland?

A
  • seramucous = mixed
  • serous
  • mucous cells
26
Q

what are the sequence of events that occur during swallowing?

A
  • tongue pushes food bolus to the back of the pharynx
  • soft palate elevates to prevent food to enter the nasal passages
  • epiglottis covers the glottis to prevent aspiration
  • upper oseophagus sphincter relaxes and opens
  • pharyngeal muscles contract behind the bolus
  • food descends into the epiglottis
  • NOTE: apnoea - epiglottis flips over trachea - blocking of breathing
27
Q

What is peristalsis? - what muscles does it involve?

A
  • wave like contractions promoting motility in the GIT, squeezes material down the GIT away from the mouth
  • involves inner circular muscle & outer longitudinal muscle
28
Q

describe oesophagus histology

A
  • stratified squamous epithelial cells on the mucosa layer
  • lamina propia
  • connective tissue papillae
  • muscularis
  • blood vessels at the submucosa area
  • note circular & longitudinal muscle
  • serosa/ adventitia
29
Q

What is the function of stratified squamous epithelium?

A
  • protection
30
Q

What is ‘non-keratinized’ epithelium?

A
  • does not have keratinous tissue
31
Q

What is the gastro-oseophagal junction?

A
  • junction between the distal ( away from the centre of the body) oesophagus and the proximal ( near the centre body) stomach (cardia)
32
Q

What are the functions of the stomach?

A
  • saclike organ that functions to store, dissolve & partially digest the macro molecules found in food and also to regulate the rate at which this food is emptied into the small intestine
33
Q

What is chyme?

A
  • chyme= the mixture of food particles and gastric secretions
34
Q

What are the 4 main anatomical parts of the stomach?

A
  • Cardia ( junction )
  • Fundus
  • Body
  • Pylorus
35
Q

What are the 3 main functions of the stomach?

A
  • storage
  • mixing - gastric motility
  • digestion - gastric motility and gastric acid production
36
Q

What is the difference between adventitia and serosa?

A
  • the adventitia is the outermost layer when the tissue is outside the peritoneum ( eg upper oesophagus)
  • the serosa is the outermost layer when the tissue is within the peritoneum ( eg stomach) - has lubrication functions
37
Q

What is the function of the fundus part of the stomach?

A
  • production of gastric acid
  • mixing
38
Q

What are the main functions of the pylorus?

A
  • muscle
  • prevents food from going back into the stomach once it has moved into the small intestine
39
Q

Describe the histology of the fundus

A

remember main function: gastric acid

large mucosal region

  • 3 cells types : surface mucosal cells, parietal cells (HCL production )& chief (purple) cells
  • presence of rugae (folds)
  • gastric glands
40
Q

What are the key muscle cell types?

A
  • surface mucous cell - thick mucous, high in bicarb
  • mucous neck cell - less columnar, rounded nuclei
  • parietal cell - secretes HCL and instrinsic factor
  • Chief cell - produces pepsinogen & gastric lipase
  • enteroendocrine cells - lamina propia of fundus, gastrin producing cells
41
Q

What group of neurons is mastication controlled by?

A
  • CPG - central pattern generator
  • they don’t need continuous sensory input
42
Q

How do acinar cells and ductal cells make saliva?

A
  • They make the salvia hypotonic - less Na+ and Cl-

Digestion & excretion physiology (24 decks)

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