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1Principles of Biomedicine - MD1 > 101 - Gastrointestinal Tract > Flashcards

101 - Gastrointestinal Tract Flashcards

1
Q 
Functions of the GIT
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A

1) Digestion
2) Absorption
3) Movement
4) Protection

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2
Q 
Layers of GIT wall
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A

– Mucosa
– Submucosa
– Muscularis externa
– Serosa

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3
Q

Length of GIT

A

~9M

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4
Q

Layers of muscularis externa

A

Inner circular layer

Outer longitudinal layer

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5
Q 
Mucosa
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A

1) Innermost layer, closest to the lumen
2) Columnar or stratified squamous epithelium, depending on location
3) Supported by a connective tissue layer (lamina propria) that contains nerves, vessels
4) Thin layer of smooth muscle (muscularis mucosae) forms boundary of mucosa

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6
Q

Structure of mucosa

A

Can be thick due to folding of the surface or presence of glands

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7
Q

Blood vessels in lamina propria

A

Blood vessels in lamina propria are small (capillaries and lymphatics)

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8
Q

Composition of submucosa

A

Dense, fibrous connective tissue (rich in collagen, elastin)
Sometimes glands present.
Blood vessels, nerves present.

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9
Q

Role of submucosa

A

Provides strength and elasticity

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10
Q

Thickness of muscularis externa

A

Usually two layers of smooth muscle (circumferential and longitudinal layers)

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11
Q

What is responsible for peristalsis?

A

Muscularis externa

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12
Q

What co-ordiantes movement of muscularis externa?

A

Autonomic nervous system

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13
Q

ROle of serosa

A

Provides non-stick surface of gut

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14
Q

What is the serosa?

A

Layer of connective tissue binding GIT to surrounding structures or an epithelial structure in the free gut (peritoneal cavity)

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15
Q

Cell type of serosa

A

Simple squamous

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16
Q

Components of autonomic NS

A

Sympathetic, parasympathetic, enteric

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17
Q

Locations of enteric NS plexuses
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1

A

1) Myenteric plexus lies between longitudinal and circular muscle layers
2) Submucous lies in the submucosa

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18
Q

Epithelium in oesophagus

A 
Stratified squamous (non-keratinising)
Has submucosal glands for lubrication
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19
Q

Unusual aspect of composition of oesophagus muscularis externa

A

Half smooth muscle and half skeletal muscle

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20
Q

Muscle distribution in the oesophagus (of muscularis externa)

A

Top third is skeletal muscle.
Middle third is mixed.
Lower third is smooth muscle.

21
Q

Macronutrients that stomach is best at breaking down

A

Proteins (not as good at digesting carbohydrates or fats)

22
Q

Name for material partially digested by stomach

A

Chyme

23
Q

Epithelium of etomach

A

Simple columnar

24
Q 
Structure of stomach wall
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A

1) Simple columnar epithelium
2) Prominent muscularis mucosae
3) Thick submucosa
4) Thick muscularis externa (with a third, oblique layer in parts)

25
Q

Role of rugae

A

To allow expansion of stomach

26
Q

Surface of stomach wall

A

Contains many holes (gastric pits) which lead to gastric glands.

27
Q

Structure of gastric pits

A

Each gastric pit splits into 3-5 gastric glands.
These are simple tubular glands that penetrate into lamina propria.
Organisation varies across stomach

28
Q 
Structure of gastric glands (top to bottom)
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A

Made up of many cell type, arranged in particular areas from top to bottom.

1) Top cells are gastric surface cells and neck cells (produce mucus)
2) Regenerative (stem) cells in neck of gland.
3) Mucous neck cells
4) Parietal cell produce hydrochloric acid
5) Chief cells release pepsinogen at the base of the gland

29
Q

Pepsinogen

A

Inert form of pepsin, which breaks down proteins

30
Q

Pepsin activation
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A

1) Pepsinogen is released from chief cells.

2) Acidic environment activates some pepsinogen to pepsin, which then cleaves and activates more pepsinogen

31
Q

Protection of the stomach from pepsin and low pH

A

1-2mm layer of mucus released constantly from gastric glands

32
Q

Structure of epithelium of small intestine

A

Simple columnar epithelium (with microvili)
Vili form prominent extensions of epithelium
Vili are present on transverse folds (plica circulares)
Base of vili give rise to tubular glands (Crypts of Lieberkuhn)

33
Q

Microvili distribution

A

All columnar epithelial cells in small intestine have microvili except goblet cells.
Form brush border

34
Q

Arrangement of vili to maximise surface area

A

Plica circulares increase surface area by 2-3.

Vili increase surface area by a factor of 10.

35
Q 
Crypts of Liberkuhn
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A

Penetrate into lamina propria from base of vili.
Secrete fluid and mucus
Mucus secreted from goblet cells on vili (in both vili and crypts)
Contain stem cells for renewal of epithelium

36
Q

Where do many of the cancers of the GIT form?

A

From stem cells in the crypts (intestinal cancers), gastric pits (gastric cancers)

37
Q

Arrangement of lamina propria in a vilus

A

Extends into the core of each vilus

38
Q

Contents of lamina propria in the small intestine

A

Contain smooth muscle (muscularis mucosa), blood vessels, lymphatics and immune cells

39
Q

Role of muscularis mucosa in the vili of the small intestine

A

Move vili to prevent any areas where vili can’t absorb nutrients from fluid

40
Q 
Features of surface of duodenum
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A

1) Short (25cm)
2) Has only low plica circulares
3) Fewer goblet cells
4) Receeves secretions from gall bladder and pancreas (bile for digestion of fat

41
Q

Duodenal functions
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A

1) Receives acidic chyme with active pepsin from stomach
2) Has glands in submucosa (Brunner’s glands) that release alkaline mucus
3) The pH is raised to ~7.3, which inactivates pepsin

42
Q

Features of surface of jejunum and ileum
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A

1) More plica, shorter vili
2) Lots of goblet cells (increase in number in ileum)
3) Ileum has a lot of Peyer’s patches

43
Q

Amount of fluid absorbed by small intestine each day

A

~8.5L

44
Q

Role of large intestine

A

Compacts faeces, recovers water and electrolytes

45
Q

Structure of the colon

A 
Smooth surface (no vili)
Many tubular glands (Crypts of Liberkuhn, mainly producing mucus)
46
Q

Composition of faeces

A

Water, roughage, bacteria, fat, inorganic material, bile pigment.
Stuck together with mucus

47
Q

Problem with bacteria living in small and large intestine

A

Produce acid. HCO3 released from crypts to neutralise this acid

48
Q

Amount of water lost each day in faeces

A

~50-100mL

1Principles of Biomedicine - MD1 (157 decks)

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