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Tissue Biology > GI Tract (W3) > Flashcards

GI Tract (W3) Flashcards

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1
Q

Explain the process of digestion through the GI tract

A
  • mouth
  • osesophagus
  • stomach
  • small intetsine
  • large intestine
  • anus
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2
Q

What 2 mechanism propel food down the GI tract

A
  1. voluntary muscle acrion in oral cavity, pharynx and upper third of oesphagus
  2. Peristalsis - involuntary wave of smooth mucle contraction
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3
Q

How is the ANS involved in the mechanisms

A

modulates the 2 mechanims and also secretes a variety of neuorendocine hormones

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4
Q

Name the 4 layers that make up the GI tract

A

Mucosa
- made up of 3 layers (epithelium , lamina propria & muscularis muscosae
Submucosa
- collagenous collective tissue
- contains larger BVs, lymphatic and nerves
Muscularis propria
- smooth muscle usally arranged as an inner circular layer and longitudinal layer
Adentitia
- outer layer loose supporitn tissue
- conducts major vesssl nerves
- contains adipose tissue

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5
Q

What types of epithelial cell make up the GI tract

A
  • stratified squamos epithelium
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6
Q

What are the basic muscosal forms in the GI tract

A
  • protective
  • absorptive
  • secretory
  • absorptove/protective
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7
Q

Describe the structure of the oesophagus

A
  • lined with non-keratinsed squamos epithelium epithelium
  • in submucosa there are groups of small mucos -secreting glands (oesphageal glands) for lubrication and protection
  • conatins a basal layer (stem cells)
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8
Q

What is the difference in tissue type between the oesophagus and the oesophagus gland

A

the gland is columnar not squamous

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9
Q

What is the function of the oesophagus

A
  • transport of food and water to the stomach
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10
Q

What is the gastro oesophageal sphincter in humans and what is its function

A

where the oesophagus and stomach meet
- the muscles constrict the opening at the stomach and orevent the escape of acid/pepsin and food back into the oesophagus

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11
Q

What happens to the cells at the gastro oesophageal junction

A

junction where the oesophagus and stomach meet and the mucosa abruptly change to glangular secretory phenotype

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12
Q

What is the most proximal area of the stomach

A

the cardia

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13
Q

stomach

Describe the sturcture of the gastric cardia

A
  • narrow circular band
  • mucosa conatins simple or branched cardiac glands coiled with large lumens
  • most of the glands produce muscis and lysozymes
  • few parietal cells
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14
Q

Describe the sturcture of the fundus and body of the stomach

A
  • fundus is above the body
  • mucuosa coinatins numerous gastric glands (secrete acid and pepsin)
  • distrubution of epithelium cells aren’t uniform
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15
Q

Describe the gastric glands and where are they located

A
  • straight tubular glands that synthesis and screte gastric jucie
  • hydrolyse proteins into polypeptide fragments
  • mucosa layer
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16
Q

What stops the stomach from self digestion by gastric glands

A

thick surface covering of mucos

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17
Q

Where are the gastric glands stem cells located

A

isthmus/ neck region immediately below the pit

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18
Q

Nmae the cells which are in the gastric glands and at what level

A
  1. fovela - surface mucos cells
  2. parietal cells - isthmus
  3. neck, stem and parietal cells - neck
    4.peptic, parietal, neuroendocrine cells - base of gland
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19
Q

What are the foveolar cells

A
  • sometimes called pit cells
  • secrete protective mucins
  • MUC5AC (resistant to degrdation)
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20
Q

What is the role of stem cells in the gastric glands

A
  • high proliferation rate
  • move upwards to replace muscous cells (4-7day turnover)
  • some migrate downwards to differentiate into parietal,cheif and endocrine cells
21
Q

What are parietal (oxyntic) cells

A
  • secret hydrocholric acid
22
Q

Describe the shape of parietal cells and how do we know they are active

A
  1. large round cells (‘fried egg shape’) with eosinophilic cytoplasm
  2. prescence of numerous mitochondria and intracellular canaliculi
23
Q

What ions are involved in the secretion of HCl by parietal cells

A

H+, K+, Cl-

24
Q

What are chief (zymogenic) cells

A

secret pepsinogen (inactive enzyme)
- it rapidly converts into the active from pepsin in the prescene of acid
- also secretes lipase

25
Q

What are neuroendocrine cells

A

hormne secretng cells of the glands

26
Q

What are the gastric hormones and their functions

A
  1. Gastric (from G cells)
    - activates parietal cells to secret acid
    - parasympathetic stimulation , AAs and stomach disentions directly stimulate G cells to secret gastrin
  2. Somatostatin (from D cells)
    - inhibits the relase of gastrin
    - stimulated by HCl and counterbalances acid secretion
27
Q

What is pylorus and its function

A

final part after the antrum beofre the small intestine
- secretes mucos and lysozymes

28
Q

What cells line the small intestine

A

simple columnar epithelium

29
Q

What cells are in the small intestine

A
  1. enterocytes
  2. goblet cells
  3. paneth cells
  4. neuroendocrine cells
  5. stem cells
30
Q

How does the small intestine structire aid in the function

A

Mutiple villi and microvilli to increase SA for absorption

31
Q

What are enterocytes and their function

A
  • most sbundnat cell in the villus
  • absorptove cell of the intestine
  • APC
32
Q

What are glycocalyx

A

filament network convoluted into villi projections that serve to increase the absorptive muscosal surface area

33
Q

What does the glycocalyx consist of

A

acidic mucopolysaccharodes and glycoproteins

34
Q

What is the small intestine crypt

A

pocket at the base of villus where stem cells produce transmit amplyfying cells which are commited to produce mature cell lineages

35
Q

Describe goblet cells

A
  • secrete mucos
  • contian dense secretory granules which provide a protective gel barrier
36
Q

What are paneth cells

A
  • function to keep the crypt sterile
  • produce lysozome
37
Q

What are Brunner glands

A
  • specific to duodenum
  • produce alkaline mucus to neutrlaize the acid content entering the duodenum from the stomach
38
Q

Describe the structure of Brunners glands

A
  • compound tubular mucous glands located in the submucosa duodenum
39
Q

What are pilcae circulares

A

lining of small intestine that consists of permenant spiral or ciruclar folds to amplify the organs SA

40
Q

What arer Peyers patches

A
  • unique to small intestine
  • provide immune surveillance of small intestine
41
Q

What is the ileocaecal valve

A

where food from the small intestine passes to the large intestine

42
Q

Describe the transition of the ileum to the colon

A
  • from villous mucosal surface of ilum to flat mucosa of large intestine
  • change of villi to crypt
43
Q

What is the appendix

A
  • blind-ended tubular sac attached to caecum
  • masses of lymphoid tissue in submucosa
  • glands spaced more widely then elsewhere in large intestine
44
Q

What is the function of the colon

A
  • recovery of water,peistalsis of faecal material
45
Q

Describe the structure of the colon

A
  • thick muscular wall
  • absorptive cells and mucus-secreting cells
  • commensal bacterisa
46
Q

What happens to the cells at the recto-anal junction

A

abrupt transition to stratfired squamo epithelium

47
Q

What is Meissners plexus

A

network of unmyelinated nerve fibres (generally inconspicuous)
- also called submucoal plexus
- considered part of the ANS

48
Q

What is Auerbachs plexus

A

a group of ganglia that run throughout the entire GI tract and innervate its multiple layers of smooth muscle.
- circulr and longitudinal muscles

Tissue Biology (6 decks)

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