Histology - GI tract Flashcards by Lucas Findlay

Describe the epithelium of the:

oral cavity
oropharynx
laryngopharynx

stratified squamous epithelium

usually non-keratinised

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Describe the epithelium of the tongue

stratified squamous epithelium

Anterior 2/3rds:

ventral surface = thin
dorsal surface = thick

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Describe the papillae found on the tongue

Anterior 2/3rds:

fungiform
foliate
filiform

Posterior 1/3rd:

Circumvallate

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Does the posterior 1/3rd of the tongue have substantial lymphoid aggregates?

yes, in its submucosa

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Describe the types of papillae

Have Taste Buds:

fungiform - anterior 2/3

fusiform - anterior 2/3

circumvallate - posterior 1/3

No Taste Buds:

filiform - no taste buds, lots on dorsal surface

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Describe the tissue that composes the tonsils

lymphoid tissue

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Give the layers of the digestive tract

including the stomach

Mucosa:

epithelium
basal lamina
lamina propria
muscularis mucosae

Submucosa

Muscularis Externa:

circular layer (inner)
longitudinal layer (outer)

Serosa or Adventitia

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Describe the muscularis mucosae

thin layer of smooth muscle in the mucosa of the GI tract

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Describe the muscularis externa

Layer of smooth muscle

2 layers:

circular layer (inner)
longitudinal layer (outer)

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Describe the gastroesophageal junction

Z line

The change from the epithelium of the oesophagus to that of the cardia of the stomach

stratified squamous (oesophagus)
-->
simple columnar (cardia)

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Describe the mucosa of the stomach

simple columnar epithelium

gastric pits –> gastric glands

muscularis mucosae

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Describe the gastric pits and glands found in the stomach

In the gastric mucosa

Gastric pit
–>
multiple gastric glands

Secrete enzymes and HCl

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Describe a gastric pit

lined by surface mucus cells

It leads into the gastric glands

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Describe surface mucous cells

secrete protective mucus

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List the regions of the gastric gland

Isthmus (top part, joins to gastric pit)

Neck

Fundus (base)

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Describe the distribution of cells in the gastric glands

Isthmus:

parietal cells
stem cells

Neck:

parietal cells
mucous cells

Fundus:

chief cells
enteroendocrine cells
(very few parietal cells)

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Describe a chief cell

Secretes digestive enzymes

Mainly in the fundus of the gastric gland

Describe a parietal cell

Secretes HCl

Mainly in the top of the gastric gland (Isthmus and neck)

Describe the prominence of stem cells in the gastric glands

there are lots of them due to the destructive nature of the chemicals being produced

Describe an enteroendocrine cell

neuroendocrine cell

secrete hormones

contributes to control of secretion and motility

Describe how the mucosa differs in different regions of the stomach

Cardia:

deep gastric pits
loosely packed tortuous gastric glands

Body:

shallow gastric pits
long straight gastric glands

Pylorus:

Deep gastric pits
branched, coiled gastric glands

Describe the muscularis externa of the stomach

Layers?

Function?

It has an extra layer of smooth muscle that is oblique to the circular and longitudinal layers

The extra layer helps with churning

3 layers:

oblique layer (inner)
circular layer (middle)
longitudinal layer (outer)

Describe the gastroduodenal junctional

The abrupt change from gastric mucosa to duodenal mucosa

Occurs at the pyloric sphincter

Describe the pyloric sphincter (pylorus)

sphincter at the gastroduodenal junction

it is a thickened circular layer of the muscularis externa

Describe the mucosa of the small intestine

- Villi - crypts of Lieberkuhn Epithelium: - enterocytes - goblet cell - paneth cells - enteroendocrine cells - stem cells

Compare the histology of the different regions of the small intestine

Duodenum: - Brunner's glands in the submucosa Jejunum: - Tall villi - circular folds in mucosa and submucosa (Plicae circulares) Ileum: - short villi - lymphoid follicles

Describe an enterocyte

tall simple columnar epithelium with microvilli main absorptive cells of the small intestine

Describe goblet cells

Mucinous cells that protect the epithelium and lubricate the passage of material

Describe paneth cells

Found at the base of the crypts of Lieberkuhn Roles: - regulate bacterial flora - secrete lysosomes and defensins

Describe villi

projections of the mucosa into the intestinal lumen Layers in cross section: - epithelium (enterocytes) - basal lamina - lamina propria - lacteal (the muscularis mucosae doesn't enter the villi, instead it runs below it)

describe crypts of lieberkuhn

Exists between the bases of villi Extend down into the mucosa Has panth cells at its base

Describe a lacteal

the core of a villi is lymphatic absorbs fats and fatty acids

What is meant by a cell with a brush border?

It has microvilli

describe Brunner's glands

Found in the duodenum In the submucosa Secrete alkaline mucus in response to acidic chyme from the stomach Mucus neutralises acidic chyme

Describe the plicae circularis

circular folds in mucosa and submucosa Found in the jejunum

Describe Peyer's patches

aggregations of lymphoid tissue ileum

Describe the mucosa of the large intestine

2 main cell types: - absorptive cells - goblet cells Lots of crypts (straight tubes) extend into the mucosa

Describe the teniae coli

The discrete stripes of longitudinal muscle in the muscularis externa (i.e. the longitudinal layer of the muscularis externa isn't circumferential, instead it exists in discrete strips)

Describe the histology of the appendix

Similar to the rest of the colon Less crypts Lots of lymphoid tissue in the submucosa and lamina propria

Describe the rectoanal junction

Change from: simple columnar epithelium (rectum) --> non-keratinized stratified squamous epithelium (anal canal)

Name the 2 plexuses of the enteric nervous system Location? Function?

Submucosal: - in the submucosa - regulates secretions and muscularis mucosae Myenteric: - between the layers of the muscularis externa - controls gut motility

Summarise the mucosa of each main region of the GI tract

Oral cavity --> oesophagus: - non-keratinized simple squamous epithelium Stomach: - Simple columnar epithelium - Gastric pits and glands Small intestine: - simple columnar epithelium - villi and crypts of Lieberkuhn Large intestine: - simple columnar epithelium - crypts