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Digestive System > Intestinal microanatomy > Flashcards

Intestinal microanatomy Flashcards

1
Q

Things that increase SA of the small intestine?

A

Plicae, villi, crypts of lieberkuhn and microvilli

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2
Q

Purpose of blood vessels to the small intestines?

A

They carry Oxygen-rich blood to the SI, allowing metabolic activity

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3
Q

Purpose of the venous system of the SI

A

Carries away nutrient-rich blood to the liver for processing and redistribution (Hepatic Portal Vein)

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4
Q

Purpose of lacteal lymphatic vessels and the SI

A

transport lipids

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5
Q

What is in the core of a villus

A

Blood vessels and lacteals, embedded in CT support. muscle fibres extend in from muscularis mucosae

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6
Q

What is the purpose of the smooth muscle fibres in the lamina propria?

A

Help milk and squeeze the lacteals

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7
Q

Another name for intestinal glands? What is their purpose?

A

Crypts of Lieberkuhn. To increase SA

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8
Q

What is an issue that can happen to the elderly around blood supply.

A

Sometimes, especially in elderly, blood supply and circulation can decrease.
> less absorption taking blood away from gut > malabsorption and malnutrition

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9
Q

What is studded in the lipid bilayers?

A

1000’s of digestive enzymes eg) glycosidase breaks down carbs

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10
Q

What are the cells of the SI

A 
columnar absorptive cells (enterocytes)
Goblet cells
Enteroendocrine cells
undifferentiated cells
Paneth cells
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11
Q

Microvilli are

A

projections of membrane filled with cytoplasm. Have a core of actin filaments. Found at the apical surface of columnar absorptive cells. (enterocytes)

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12
Q

Why do microvilli have a core of actin filaments

A

Bc the actin filaments are connected to the cytoskeleton network
SM in LP contract > BM of epi. cells move > Cells atop BM move > Microvilli atop epi cells move

This creates localised, homogenous mixing of contents, via ‘microwhisks’.

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13
Q

What is the glycocalyx?

A

a slippery biological film made of glycoproteins and acidic mucopolysaccharides. Sits atop and coats microvilli

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14
Q

Function of the glycocalyx?

A

Selective gate keeper, attracts desirable contents and blocks unwanted.

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15
Q

Goblet cells

A
  • no microvilli on apical surface
  • secrete mucus for lubrication
  • theories that mucus contributes to glycocalyx
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16
Q

Undifferentiated cells are?

A

Stem cells that can divide and migrate to replace epithelium.

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17
Q

What stimulates enteroendocrine cells, and what do they release?

A

Stimulus: acidic chyme, FA, amino acids

Release: Cholecystokinin, serotonin, secretin and somatostatin.

18
Q

Purpose of Cholecystokinin

A

1) + gall bladder to contract (bile released into duodenum)

2) + pancreas to increase enzyme production and secretion

19
Q

Purpose of secretin

A

1) + pancreas to produce bicarbonate (from ductule cells)

2) - acid production by stomach

20
Q

Purpose of serotonin

A

1) + peristalsis

2) + intestinal secretion (goblet, paneth etc)

21
Q

Purpose of somatostatin

A

1) Reduce gastrin
2) Facilitates SM contraction
3) enhances absorption

22
Q

Paneth cells around found? what are they for? What do they produce

A

Found at bottom of crypts

important for antimicrobial and antibacterial purposes

produce TNF-alpa, lysozymes, defensins

23
Q

acidic chyme, amino acids and FAs from the stomach stimulate?

A

pancreas and gallbladder > release digestive enzymes, HCO3- and bile into the duodenum

24
Q

How does the pH of the duodenum change and how does this occur?

A

from acidic pH 1-2 to eventual 7-8 (neutral).
This is due to submucosal ‘Brunners glands’ (as well as bile)
that secrete an alkaline mucus that counteracts the acidic chyme.
(lots initially, less distally)

25
Q

Length of the Duodenum, jejunum and ileum

A

D: 25cm
J: 2.5m
I: 3.5m

26
Q

Purpose of the pyloric sphincter

A

To control the volume and frequency of chyme into the duodenum

27
Q

Features of the jejunum?

A

Heavily twisted
suspended with mesentery
increased plicae

28
Q

Identifying feature of the ileum? What is this for?

A

Macroscopically visible lymphatic aggregates “Peyers Patches”
These have a B cell core, and a M cell outer (antigen presenting/sensing cells for sampling)
This is for defence against the large amount of bacteria in the LI

29
Q

What is in the lamina propria

A

BVs, lacteals, SM, lymphocytes, fibroblasts

30
Q

Muscle type of the anal sphincters

A

Internal sphincter = smooth muscle

external sphincter = skeletal muscle

31
Q

The rectum and anal canal has different types of epithelium. What are these?

A

Rectum: Simple columnar enterocytes + goblet cells
Superior half: simple columnar epithelium
Inferior half: Stratified squamous epithelium

32
Q

Purpose of the SS epithelium in the anal canal?

A

protects against the friction of faecal matter leaving

33
Q

How does the frequency of goblet cells change throughout the colon and why?

A

Start of colon: Watery substances, few goblet cells

Water is absorbed

End of colon: viscous, dry, dehydrated, many goblet cells

34
Q

Features of the colon mucosa?

A

smooth with no plicae or villi
Numerous crypts of lieberkuhn
Main two cells:
1) Columnar absorptive cells (absorb, water, electrolytes and vitamins B&K)
2) Goblet cells (secrete mucus for lubrication)

also have enteroendocrine cells (not visible by light microscope)
undifferentiated cells: at base of glands (migrate upwards

35
Q

Features of the colons lamina propria

A

Lots of lymphatics

dense layer of collagen immediately beneath the surface epithelium

36
Q

Features of the colons muscularis externa.

A

Still has inner circular and outer longitundinal muscle layers

But outer longitudinal forms three strips ‘teniae coli’ that run along the colon

  • this allows segments of the colon to contract independently
  • contraction pulls colon into sac like pockets ‘haustraccoli’
37
Q

is the colon covered in serosa or adventitia?

A

Posterior surface = adventitia

elsewhere = serosa

38
Q

Describe the purpose of the rectum/ anus

A

temporary storage of faecal material (movement of material into leads to the urge to defecate

39
Q

What are the sections of the rectum/anus

A

final portion = anal canal (mucosa has anal columns)
distal margin = pectinate line (transverse folds)
anal sphincters = internal and external
end of anal canal = anus

40
Q

What is the general trend around cell replacement rates

A

surface/ SF cells: high replacement rate (days)
Deeper cells: replaced every few months

Deeper cells are more specialised, require more energy to replace.

41
Q

What are some common GI effects of chemo

A

diarrhoea, nausea.

This is due to the mitotically targeting anticancer drugs affecting the highly replaced surface cells

Digestive System (27 decks)

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