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BMS13 > Gastrointestinal Histology > Flashcards

Gastrointestinal Histology Flashcards

1
Q

What is the basic organisation of the GI tract?

A

Mucosa - epithelium, lamina propria, muscularis mucosae

Submucosa - connective tissue

Muscularis externa - inner circular and outer longitudinal

Adventitia/serosa

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2
Q

What is the muscularis mucosae?

A

Very thin layer of muscle involved in fine movement

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3
Q

What is found in the submucosa?

A

Fibroblasts and collagen

Some areas have glands

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4
Q

What is the difference between an adventitia and a serosa?

A

Adventitia - merges with other connective tissue, no clear ending

Serosa - defined outer surface, thin, always surrounded by a thin layer of squamous epithelial cells

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5
Q

What are the three main types of epithelium found in the GI tract?

A

Protective

Secretory

Absorptive

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6
Q

Describe the epithelium of the oesophagus.

A

Non-keratinised, stratified, squamous epithelium

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7
Q

Describe the muscularis externa of the oesophagus.

A

Upper third - voluntary

Middle third - mixed

Lower third - smooth

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8
Q

What is the function of the submucosal glands in the oesophagus?

A

Produce mucus for lubrication

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9
Q

What are the three regions of the stomach?

A

Funduc/cardiac

Body/corpus

Pylorus

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10
Q

What is the main function of the fundus region?

A

HCl secretion

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11
Q

What is the main function of the body of the stomach?

A

Enzyme delivery and digestion

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12
Q

What is the main function of the pylorus?

A

Prepare party digested food for movement into duodenum - mucus secretion

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13
Q

How is the surface area increased in the stomach?

A

Rugae

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14
Q

What are the layers of the muscularis externa of the stomach?

A

Oblique layer

Inner circular layer

Outer longitudinal layer

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15
Q

What type of epithelium is in the stomach?

A

Secretory

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16
Q

What is secreted in the stomach?

A

Mucus

Pepsin

HCl

Intrinsic factor

Gastrin

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17
Q

What is another name for a gastric pit?

A

Foveolus

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18
Q

What are the regions of the gastric glands?

A

(Pit)

Isthmus

Neck

Base

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19
Q

What cells are found at the isthmus of a gastric gland?

A

Parietal cells

Mucous cells

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20
Q

What concentration of HCl is produced by the gastric glands?

A

0.1M

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21
Q

What cells are found at the neck of a gastric gland?

A

Stem cells

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22
Q

What cells are found at the base of a gastric gland?

A

Peptic cells

Neuroendocrine cells

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23
Q

What do parietal cells produce?

A

HCl

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24
Q

What do peptic cells produce?

A

Enzymes such as pepsinogen

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25
Q

What do the neuroendocrine cells of the gastric glands produce?

A

Gastrin

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26
Q

What do the neuroendocrine cells do in the GI tract?

A

Control local movement

Prepare duodenum and pancreas for arrival of food

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27
Q

What do parietal cells look like histologically?

A

Fried eggs

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28
Q

How do the gastric glands vary in the different regions of the stomach?

A

Fundus - lots of parietal cells (to acidify quickly)

Body - lots of peptic and parietal cells

Pylorus - mucous cells (lubricate)

29
Q

Why doesn’t the stomach self-digest?

A

Surface epithelial cells secrete HCO3- to establish a neutral pH in mucus layer adjacent to cells

Enzymes are not active in mucus

30
Q

Why don’t the gastric glands get burned by the acid?

A

Parietal cells secrete into the centre of the gastric gland

Below pH 4 - viscous fingering of HCl in mucus

31
Q

What are the submucosal glands found in the duodenum called?

A

Brunner’s glands

32
Q

What do Brunner’s glands do?

A

Produce mucus which is alkaline to neutralise stomach acid

33
Q

What are two differences between the duodenum and the rest of the small intestine?

A

Shorter villi in duodenum

No submucosal glands in jejunum and ileum

34
Q

What are the villi mounted on in the jejunum and ileum?

A

Plicae circulares

35
Q

What are the specialisations for absorption in the jejunum and ileum?

A

Plicae circulares (most prominent in jejunum)

Villi with goblet cells

Microvilli

Blood supply

Lacteals

36
Q

What are the epithelial cells of the small intestine?

A

Enterocytes

Goblet cells

Paneth cells

Stem cells

37
Q

What are Paneth cells?

A

Neuroendocrine cells of small intestine

38
Q

Where are the Paneth and stem cells found?

A

Crypts at base of villi in mucosa

39
Q

What are Peyer’s patches?

A

Lymphoid tissue grouped together for surveillance

Most prominent in ileum

40
Q

Describe the material leaving the ileum.

A

Loose and watery

41
Q

Describe the colon’s wall.

A

No villi

Tubular glands within mucosa

Enterocytes with microvilli and goblet cells

Thick muscularis externa with discontinuous outer layer

42
Q

What is the function of the enterocytes in the colon?

A

Sodium pumps help water absorption by osmosis

43
Q

What is the function of the goblet cells in the colon?

A

Lubricate bolus

44
Q

How does the epithelium change at the ano-rectal junction?

A

Sudden switch to stratified, squamous epithelium

Still lots of glands

45
Q

What are the functions of saliva?

A

Lubricate, moisten

Begin digestion (α-amylase, lipase)

Antiseptic (IgA, lysozyme)

46
Q

Where are the three main salivary glands located?

A

Parotid - just below ear lobe

Submandibular - below tongue and mostly below sublingual

Sublingual - below tongue

47
Q

What type of secretion occurs at salivary glands?

A

Merocrine

48
Q

What type of structure do salivary glands have?

A

Branched acinar

49
Q

What is a serous demilune?

A

Artefact of fixation when an acinus has both serous and mucous cells

50
Q

Describe the acini of the three main salivary glands.

A

Parotid - almost all serous

Submandibular - mixed

Sublingual - almost all mucous

51
Q

What are myoepithelial cells?

A

Cells found outside acini which have processes to contract to release saliva on stimulation by the ANS

52
Q

What is the tonicity of the primary salivary secretion in relation to plasma?

A

Hypertonic

53
Q

What is the order of ducts which saliva flows through?

A

Intercalated –> striated –> excretory

54
Q

How can you tell the difference between the salivary ducts histologically?

A

Intercalated = smallest with indistinguishable lumen

Striated = obvious lumen, striated simple layer of cells

Excretory = found outside acini/in connective tissue

55
Q

What is the function of the striated salivary ducts?

A

Reabsorb Na+ and Cl- and replace them with K+ and HCO3- so saliva becomes hypotonic and alkaline

56
Q

What are the functions of the tongue?

A

Manipulation of food

General sensory reception (touch, pressure, heat)

Special sensory reception (taste)

Speech

57
Q

Why is the muscle in the tongue orientated the way it is?

A

Bundles of skeletal muscle arranged in all orientations to allow movement in all directions

58
Q

Describe the epithelium of the tongue.

A

Partly keratinised, stratified, squamous epithelium

59
Q

What are the three types of tongue papillae?

A

Fungiform

Filiform

Circumvallate

60
Q

Describe filiform papillae.

A

Small keratinised spikes present at front of tongue

Catch and manipulate food

Most common

61
Q

Describe fungiform papillae.

A

Thin keratinisation

Scattered

Richly vascularised core

Taste buds

Ducts from glands of Von Ebner open into base

62
Q

Describe circumvallate papillae.

A

Chef hat-shaped

6-14 along sulcus terminalis

Taste buds

Ducts from glands of Von Ebner open into base

63
Q

What are taste buds?

A

Pale-staining structures at base of fungiform and inner wall of circumvallate papillae

Associated with supporting cells and a nerve ending

64
Q

Why are taste buds found at the base of papillae?

A

Prevent damage by food

65
Q

What are glands of Von Ebner?

A

Large salivary glands

66
Q

Where are the papillae of the tongue found?

A

Anterior two-thirds

67
Q

Describe the posterior third of the tongue.

A

Relatively smooth oral epithelium - stratified, squamous, non-keratinised

Abundant lymphoid tissue associated with lingual tonsil

68
Q

What does Waldeyer’s ring comprise of?

A

Lingual tonsil

Palatine tonsil

Adenoids

BMS13 (7 decks)

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