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Dentistry Biological Science > Histology of GI tract > Flashcards

Histology of GI tract Flashcards

1
Q

What are the two points on the GI tract?

A
  • Long muscular tube lined by mucous membrane

- Concerned with the intake, digestion and absorption of climatic waste

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2
Q

What is the organisation of the GI tract?

4 layers

A
  • Mucosa
    Epithelium
    Lamina propria
    Muscularis mucosae
  • Submucosa
  • Muscularis externa
    Inner circular layer
    Outer longitudinal layer
  • Adventia/serosa
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3
Q

What are the three types of epithelium as you go down the GI tract?

A

protective
secretory
absorptive

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4
Q

Oesophagus:
What is the type of epithelium?
What glands does it have and why?
What is the muscle present?

A

Stratified squamous epithelium
Submucosal glands for lubrication of food
Voluntary top 1/3, voluntary and smooth middle 1/3 and last 1/3 is smooth.

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5
Q

What change of epithelium occurs at the gastro-oesophageal junction?

A

Stratified squamous epithelium becomes simple epithelium.

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6
Q

What are the 3 layers of the stomach and their function?

A

Fundus - turn the material that arrives in the stomach into an acidic form. Saliva enzymes is alkaline so the first thing tot stomach needs to do is neutralise and acidify this to function.
Body - production of stomach enzymes
Pylorus - food being prepared to enter small intestine. Many cells here are mucus producing cells.

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7
Q

What are the 3 layers of smooth muscles in the stomach called?

A

Oblique, circular and longitudinal.

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8
Q

What are the internal large folds in the muscle called?

A

Rugae which catch material and move them around to create a more efficient mix.

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9
Q

What are the secretory parts of the stomach?

A

Gastric pits and glands

Mucus 
Pepsin
HCl
Intrinsic factor (Vit B12)
Gastrin
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10
Q

How do we stop the GI tract from producing enzymes constantly?

A

Endocrine cells secrete hormones that signal to the next region that food is on its way.

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11
Q

What are the layers of the gastric glands?

A

1) Surface mucous cells
2) Isthmus (Parietal cells)
3) Neck (neck mucous and stem cells)
4) Base of gland

2-4 is gastric gland and 1 is gastric pit.

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12
Q

What do parietal cells produce?

A

Produce HCl

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13
Q

Where are all the mucous secreting cells in the gastric glands?

A

Nearly all mucous secreting cells.

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14
Q

Why does the stomach not digest itself?

A

Surface epithelial cells secrete bicarbonate ions to establish a neutral pH in the mucus layer adjacent to the cells.

Below pH4, low viscosity HCL penetrates the mucus layer like a finger, without mixing.

Above pH4, HCl can’t penetrate mucus at all.

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15
Q

Give some anatomical features of the duodenum in the small intestine

A

Where digestion and absorption occurs.

Brunner’s glands: large glands that project out. Produce alkaline mucus (HCO3-) to neutralise the acidic contents of stomach.
Villi

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16
Q

What are the 4 adaptations for the small intestine for absorption?

A
  1. Pilcae circulares (begins in duodenum, most prominent in jejunum and become further apart in ileum
  2. Villi (richly vascularised to take food away, has lacteals which are lymphatics which take away fats in chylomicrons which Jonis the lymphatic system)
  3. Microvilli (brush-border)
  4. Peyer’s patches (lots of typhoid tissue grouped together, found in ileum - mainly formed of B&T lymphocytes)
17
Q

What are the 4 cells of the small intestine epithelium?

A
  1. Enterocytes (absorption)
  2. Goblet cells (mucus)
  3. Crypts (stem cells)
  4. Paneth cells (lysosome)
18
Q

What is the colon function and explain the features of this?

A

Function = water recovery

No villi, just glands.
Glands actively pump water across and produce mucus.
They form a bolus which is expelled from the body.
Mucus producing cells lubricate the passage of thus.

Very thick muscularis extend, 3 bands of smooth muscles which spiral to wring food out.

Cell types in epithelium:
Enterocytes with microvilli and goblet cells.

19
Q

What is the change in epithelium at the ano-rectal junction?

A

Transition from glandular structure of colon to a stratified squamous epithelium.

Begins as non keratinising cells and become keratinising.

20
Q

What are the 3 main salivary glands in the face and what is the job of saliva?

A
  1. Parotid
  2. Submandibular
  3. Sublingual

Lubricates, moistens, begins digestion, antiseptic

21
Q

Is the submandibular or the sublingual gland closer to the oral cavity?

A

Sublingual (under the cavity)

22
Q

Why is a salivary gland merocrine and what type of structure does it have

A

A cell is classified as merocrine if the secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and then onto a bodily surface or into the lumen.

Branched acinar structure.

23
Q

What are the two types of salivary secretion?

What does each salivary gland in the face secrete?

A

1) Serous (thin, watery)
2) Mucous (thick, viscous)

Parotid gland = serous
Submandibular = mixed
Sublingual = mucous

Thicker ones have less distance to travel .

24
Q

When a acinus has both the secretory cell types in the gland, how are they arranged?

A

As a serous demilune.

25
Q

Explain the concept of the myoepithelial cells in the acinus

A

Very similar to a fibroblast with some features of a muscle cell.

26
Q

What three tubes does the secretion travel through before it enters the body cavity?

A

Intercalated duct and then into striated duct (decreases tonicity) and then into the large excretory duct.

27
Q

What is the purpose of the name striated duct?

What happens at this site?

A

They have infoldings of the basal plasma membrane with vertically aligned mitochondria.

This is the site of the Na+ pumps which reabsorb Na+ and Cl-, replace then with K+ and HCO3-, so the saliva become hypotonic.

28
Q

Functions of the tongue (a muscular organ covered by oral mucosa)

A
  • Manipulation of food
  • General sensory reception (heat and pain)
  • Special sensory reception (taste)
  • Speech
29
Q

Why does the body of the tongue have bundles of skeletal muscles in all orientations?

A

Permits movement in all directions.

has minor salivary glands

30
Q

Give the anatomical features of the anterior 2/3 of the tongue

A

Dorsal surface covered with papillae.

  • Filiform (keratinised spikes)
  • Fungiform (scattered, ricchi vascularised, taste buds)
  • Circumvallate (along sulcus terminals, taste buds)
31
Q

Where are the filiform and fungiform papillae found?

Which way around do they sit?

A

Most anterior part of tongue. They give the roughness of the tongue.

Fungiform ones sit behind the filiform.

32
Q

Give the two things found in the circumvallate papillae

A
  • Taste buds

- Salivary glands (Glands of Von Edner)

33
Q

Give the anatomical features found in the posterior third of the tongue

A

Relatively smooth oral epithelium overlying abundant lymphoid tissue.

Dentistry Biological Science (88 decks)

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