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ABDOMEN AND GI TRACT > histology of GI tract > Flashcards

histology of GI tract Flashcards

1
Q

Four main layers of the gut tube from lumen to outside

A

mucous membrane- mucosa

submucosa

muscularis externa

adventitia/serosa

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2
Q

three layers of the mucosa + what is present in each

A

surface epithelium, lying on basal lamina

lamina propria - supporting tissue with abundant neurovasculature and cells of the immune system

muscularis mucosae- thin double layer of smooth muscle

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3
Q

submucosa structure and components

A

formed of fibroelastic loose connective tissue with vessels and nerves of the submucosal plexus (Meissner’s), wandering lymphocytes and large quantities of fat

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4
Q

muscularis externa structure

A

two thick layers of smooth muscle

inner layer is circular

outer layer formed of longitudinal fibres

between the muscle layers the myenteric nerve plexus (Auerbach’s) is located

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5
Q

adventitia definition

A

thin outer layer of loose connective tissue that is continuous with the adjacent organ or tissue

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6
Q

structure of adventitia if gut wall is free and mobile

A

covered in mesothelium and connective tissue forming the serosa which is joined to the mesentery

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7
Q

serosa definition

A

smooth membrane consisting of a mesothelium and connective tissue layer containing neurovasculature

line and enclose several body cavities and secretre a lubricating fluid to reduce friction

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8
Q

difference between adventitia and serosa

A

adventitia is a connective tissue layer which binds together structures rather than reducing friction between them

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9
Q

mesentery definition

A

fold of peritoneum that attaches the small intestine, stomach, pancreas, spleen and other organs to the posterior abdominal wall

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10
Q

two identifiable features of the oesophagus

A

non-keratinised stratified squamous epithelium

folded mucosa

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11
Q

explain function of the adaptations

A

non-keratinised, as the epithelium must withstand a large amount of abrasion from food

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12
Q

more structural features of oesophagus + functions

A

small amount of mucous glands in submucosa- secrete mucus that lubricates surface epithelium for passage of food

nerve plexuses- coordinate peristalsis of food bolus

Langerhans cells- antigen presentation, helps immune response

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13
Q

which region is what type of muscle?

A

upper 1/3rd is skeletal

bottom 2/3rds is smooth

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14
Q

function of stomach

A

mix and churn food into chyme

preliminary digestion via secretion of digestive enzymes

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15
Q

structure present throughout the stomach + fuction

A

ruggae- longitudinal folds of mucosa and submucosa

allow the stomach to distend when food enters

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16
Q

what epithelium lines the internal stomach?

A

simple columnar surface epithelium

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17
Q

what does the surface epithelium form?

A

small invaginations called gastric pits (foveolae)

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18
Q

what do the gastric pits connect to?

A

various glands of the stomach

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19
Q

three histologically different regions of the stomach

A

fundus, cardia and pyloris

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20
Q

three different stomach glands + locations and functions

A

principal gastric - present in the fundus and body, produce gastric acid

cardiac- cardiac region, produce mucus

pyloric - pyloris, produce mucus

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21
Q

association between gastric gland and pit

A

gastric pit opens up into the gland

same type of cells

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22
Q

different cells in the gastric gland and pit

A

surface lining cells

mucus neck cells

parietal cells

chief cells

DNES cells

stem cells

23
Q

organisation of cells

A

top of the pit is lined with surface lining cells

neck of pit lined with mucus neck cells

stem cells concentrated in neck

gland is formed of a mix of the other cells

24
Q

surfacing lining cell function

A

produces mucus, to lubricate the surface epithelium and protect cells from the acidic and enzymatic properties of gastric juices

25
Q

mucous neck cell function

A

secretes mucus, however less alkaline than that produced of surfacing lining cells

26
Q

parietal cell synonym

A

oxyntic cell

27
Q

oxyntic cell structure + function

A

large round or pyrimidal cells

secrete intrinsic factor and HCL

28
Q

chief cell synonym

A

zygomatic cells

29
Q

zygomatic cell function

A

secrete pepsinogen and gastric lipase

30
Q

stem cell function + location benefit

A

replace damaged cells

able to move up to replace pit cells or down to replace gland cells

31
Q

turnover of pit cells

A

5-7 days

32
Q

explain relative turnover of pit vs gland

A

pit exposed to HCL, so more damaged, higher turnover compared to gland

33
Q

what does DNES stand for?

A

diffuse neuroendocrine cells

34
Q

DNES function

A

secrete endocrine, paracrine and neurocrine hormones

secrete gastrin

35
Q

difference in gastric pits in different histological regions

A

principal glands in fundus and body- have the greatest proportion of oxyntic and zygomatic cells

cardiac glands- short, coiled and branched

pyloric region- deeper gastric pit, with mainly mucous type cells

36
Q

three anatomical segments of the small intestine

A

duodenum, jejunum and ileum

37
Q

common histological features to all regions of the small intestine

A

inner lining forms transverse ridges called plicae circulares

tall fingerlike projections- villi

tubular glands, crypts of Lieberkuhn extend to or beyond the muscularis mucosae

mucosal epithelium is simple columnar type covered in microvilli

38
Q

what does the microvilli form?

A

brush border

39
Q

microvilli function

A

increase SA, facilitating absorption and secretion

40
Q

two main cell types in small intestine

A

enterocytes- absorptive cells

goblet cells- mucous secreting

41
Q

where are the crypts of Lieberkuhn located?

A

in the epithelial lining between villi

42
Q

crypts of Lieberkuhn structure

A

contain stem cells, enteroendocrine cells, Paneth cells and Peyer’s patches (only in ileum)

43
Q

function of enteroendocrine cells

A

synthesise and secrete hormones

44
Q

function of Paneth cells

A

secrete defensive enzymes such as defensins and lysozymes

45
Q

differences in structure in small intestine

A

duodenum- contains submucosal Brunner glands that secrete alkaline mucoid secretion into crypts to neutralise stomach acid

jejunum- tallest villi

ileum- Peyer’s patches in crypts

46
Q

what are peyer’s patches?

A

contain mucosal- associated lymphoid tissue (MALT) which houses white blood cells and lymphocytes

located in the submucosa

47
Q

villi structure

A

epithelialy covered finger like protrusions of the lamina propria

contain core capillary loops

blindly ending lymphatic channel, the lacteal

48
Q

lacteal structure

A

forms core of villi

49
Q

how are the epithelial cells replaced?

A

division, migration and differentiation of stem cells

50
Q

structure of colon

A

smooth surface bu appearance of infoldings due to contractions

numerous crypts

many goblet cells, outnumbered by absorptive enterocytes

51
Q

colon function

A

supply mucus to the bowel contents, facilitating passage

extract water and electrolytes

52
Q

what is the outer muscularis externa transformed into?

A

three longitudinal strops of smooth muscle called the teniae colae

53
Q

function of teniae coloae

A

allow the different segments of the colon to contract independently

promotes faecal compaction and general peristalsis

54
Q

are villi present in the large intestine?

A

no

ABDOMEN AND GI TRACT (6 decks)

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