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HIstology CAM202 > 3. Intestines > Flashcards

3. Intestines Flashcards

1
Q

Name the Layers of the GIT

A
  1. Tunica Mucosa
  2. Tunica Submucosa
  3. Tunica Muscularis
  4. Tunica Serosa or Adventitia
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2
Q

What does the Tunica Mucosa Consist of

A

a) epithelium
b) Lamina propria
c) Muscularis mucosa

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3
Q

What does the Tunica Submucosa Consist of

A

connective tissue

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4
Q

What does the Tunica Muscularis Consist of

A

Inner Circular

Outer longitudinal

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5
Q

What does the Tunica Serosa or Adventitia Consist of

A

Simple Squamous Epithelium (mesothelium) and/or CT.

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6
Q

Name the three regions of the small intestine

A

Duodenum
Jejjunum
Ileum

*Can be distinguished histologically because one of the major functions of the SI is the absorption of digested food there are various structural mechanisms for increasing efficiency by increasing the surface area. This also means we can have a smaller intestine in terms of length

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7
Q

Name some of the structures which aid absorption

A
  1. Plicae circulares- fold of submucosa and mucosa. (similar folds are found in the colon (non permanent) and stomach (rugae)
  2. Villi
  3. Crypts of Lieberkuhn
  4. Microvilli
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8
Q

What is another function of the Villi?

A

INCREASE THE SURFACE AREA- villi are finger -like projections of the mucosa- they have a core of lamina propria covered by epithelium. Between the villi are glands which extend into the lamina propria as far as the muscarlaris mucosa. These are called:
Intestinal glands or Crypts of Lieberkuhn.

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9
Q

What type of glands are the Crypts of Lieberkuhn?

A

Simple Coiled Tubular glands - won’t see full section arrows shows opening of intestinal glands

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10
Q

What epithelium lines the villus?

A

Simple columnar epithelium

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11
Q

What is the function of microvilli?

A

Increase surface area- these are finger like projections of the cell membrane from the luminal surface of the lining epithelium. there are literally thousands per cell. Each microvilli has a core of cytoplasm containing many actin filaments.
Some evidence of a glycocalyx may be seen on the surface of the microvilli- describe the presence of microvilli as a BRUSH BORDER or STRIATED BORDER

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12
Q

How much does the combination of the plicae circulareas, villi and microvilli increase the SA by?

A

600 times . this is then further increased by the filamentous nature of the glycocalyx

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13
Q

What is glycocalyx

A

Glycocalyx are glycoproteins and intramembranous enzymes.
The broad digestion brought about by gastric and pancreatic enzymes is continued by enzymes on the microvilli
-eg. peptidases, glycosidases, oligosaccharides
These + actin filamentous core = ACIDOPHILIA

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14
Q

What type of epithelium lines the MUCOSA?

What are the cells in the mucosal epithelium?

A

SIMPLE COLUMNAR EPITHELIUM

  1. Columnar absorptive cells (enterocytes) with microvilli
  2. Goblet Cells- mucous secreting
  3. Enteroendocrine cells - secreting hormones such as CCK and secretin
  4. Paneth cells- secrete antimicrobial peptides and enzymes such as lysozyme, defensins and phospholipase A2 (ONLY found at the base of crypts of leuberkein)
  5. Stem cells to replace the other cell types which have a rapid turnover- 7 days.
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15
Q

What is an Enterocytes

A

Intestinal absorptive cells-
Lifespan of 5-6 days
Lost from villus tip and replaced by stem cells in the base of the crypts of leiberkuhn
Fats are broken down by pancreatic lipases, mix with bile salts (gall bladder/liver) and form micelles. These are hen absorbed, reconstituted into triglycerides, combined with proteins to form chylomicrons and released into the lateral intercellular space.
These then pass into lacteals of the lamina propria and re enter the bloodstream

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16
Q

Goblet Cells

A

Wine goblet shape
Basally located RER. Pale staining MUCIN granules (glycoprotein- lots of sugars)- eosin cant stain because goblet cell is like a christmas tree- can’t touch the glycoprotein. The glycoprotein is the stem of the tree surrounded by branches of mucin.
Goblet cells have 1-2 secretory cycles in a lifespan of 2-4 days
Use compound exocytosis with random fusion of secretory vesicles before exocytosis.

17
Q

Enteroendocrine cells- what hormones do they secrete?

A

In the small intestine enteroendocrine cells secrete hormones that include CCK, SECRETIN, and GIP (gastric inhibitory peptide)

18
Q

Describe the Crypts of Lieberkuhn

A

These are mucosal glands (not sub-mucosal). They are simple coiled tubular glands.
They are similar to gastric glands of the stomach and to the glands of the large intestine
The glands open into the lumen of the small intestine at the base of, and between, the villi.
Enzymes on the surface of the cells of these glands complement the secretions of the pancreas and liver and are important in the digestion ofproteins, carbohydrates and lipids
Between the glands is the loose connective tissue of the lamina propria

19
Q

WHERE are Brunners glands found?

A 
ONLY found in the duodenum- extensive, mucous secreting.
Compound tubular glands that secrete mucous that helps to neutralise the incoming acidic chyme from the stomach- in order for secretions to reach the surface the glands must bypass the muscarlaris mucosa
Mucosal glands (crypts of Lieberkuhn) are still present in the lamina propria
20
Q

Pyloro-duodenal junction

A

There is a massive thickening of the tunica muscalaris (smooth muscle layer)- there is a change in epithelial composition and thickening.
GOBLET CELLS ARENT PRESENT IN THE STOMACH
Pyloric glands change to goblet cells.. Look for BRUNERS GLANDS

21
Q

Ileum

A

Can be distinguished from the other regions of the SI by the presence of PEYERS PATCHES- in the submucosa.

PP- are part of the MALT (mucosa associated lymphatic tissue) that can be seen throughout the GIT. They are permanent aggregations of lymphatic nodules (similar to the appendix)
Goblet cells are also most numerous in the ileum of the three regions of the SI.- *increasing numbers of goblet cells as you move from the duodenum to the large intestine!

22
Q

LARGE INTESTINE- parts?

differences?

A

Includes the appendix, caecum, colon and rectum.

  1. Longitudinal muscle of the tunica muscularis is arranged as three bands called taenia coli.
  2. Large numbers of goblet cells which increase in number as we move towards the rectum.
  3. NO VILLI
  4. Crypts are STRAIGHT TUBULAR GLANDS
  5. May be confused histologically with the STOMACH
  6. Major function is the reabsorption of water and the provision of sufficient mucous to lubricate the faeces.
23
Q

Features to NOTE in the LARGE INTESTINE

A
  1. No villi
  2. Glands are simple, straight, and unbranched
  3. Gands extend from the surface to the muscularis mucosa
  4. Large numbers of GOBLET CELLS
  5. Taenia coli very obvious in human specimens
24
Q

What are the names of the anal sphincters and what muscles are they composed of?

A

Internal anal sphincter = smooth muscle

External anal sphincter = skeletal muscle

HIstology CAM202 (2 decks)

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