Lecture 20: BASIC STRUCTURE OF THE GI SYSTEM Flashcards

1
Q

What is the primary function of the GI system?

A

Bring nutrients into the internal environment (blood) so that they can be used for growth and energy. Waste is excreted

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2
Q

What functions is the GI system specialised for?

A

Motility, secretion, digestion and absorption

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3
Q

What are the key structures of the GI system?

A

Long tube with outgrowths, closed off at both ends, lined by epithelium

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4
Q

How is the GI system closed off at both ends?

A

Sphincters - thickened regions of circular smooth muscle

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5
Q

Why is the GI system lined by epithelium?

A

Because it is exposed to the outside

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6
Q

Where in the GI system is there stratified squamous epithelium?

A

Mouth/oral cavity, oesophagus, anal canal

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7
Q

What is the purpose of stratified squamous epithelium?

A

Protection from abrasion

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8
Q

Where in the GI system is there simple columnar epithelium?

A

Stomach, small intestine and large intestine

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9
Q

What is the purpose of simple columnar epithelium?

A

Secretion and absorption

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10
Q

What are unicellular glands?

A

Goblet cells

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11
Q

What is the shape of goblet cells?

A

Columnar, goblet

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12
Q

What is on the apical side of goblet cells?

A

Mucous granules

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13
Q

What is on the basal side of goblet cells?

A

Nucleus and other organelles because the mucous granules push them down

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14
Q

What can the epithelium do?

A

Invaginate to form glands

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15
Q

What are the types of multicellular glands?

A

Simple and compound

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16
Q

What are simple glands?

A

Gland with a single duct

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17
Q

What are compound glands?

A

Gland with two or more ducts, have more surface area for secretion

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18
Q

What are the layers of the gut (from inner to outer)?

A

Mucosa, submucosa, muscular (externa/proper) and adventitia

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19
Q

What is in the mucosa?

A

Epithelium, lamina propria (FCT), muscularis mucosa and sometimes glands

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20
Q

What is between the epithelium and lamina propria?

A

Basement membrane

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21
Q

What does the lamina propria of the mucosa contain?

A

Blood vessels and lymphatics

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22
Q

What is the muscular mucosa?

A

Thin layer of smooth muscle

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23
Q

What is in the submucosa?

A

Glands and blood vessels

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24
Q

How is secretion in the submucosa regulated?

A

By the submucosal nerve plexus which is part of the enteric nervous system (ENS)

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25
Q

What is the ENS?

A

The nervous system of the gut which can work independently of the CNS

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26
Q

What does the muscularis made of?

A

Smooth muscle under involuntary control and the myenteric plexus

27
Q

What are the layers of smooth muscle in the muscularis?

A

Inner circular and outer longitudinal

28
Q

What is the myenteric plexus part of?

A

ENS

29
Q

Where is the myenteric plexus found?

A

In between the muscle layers of the muscularis

30
Q

What does the myenteric plexus do?

A

Regulate motility

31
Q

What is the outermost layer of the gut tube?

A

Adventitia

32
Q

What do organs have when in the peritoneal cavity?

A

An additional covering called the serosa which is not considered to be one of the four layers

33
Q

What is the peritoneum?

A

A serous membrane

34
Q

What does the parietal layer of the peritoneum line?

A

The body wall

35
Q

What does the visceral layer of the peritoneum line?

A

The organs

36
Q

What is between the visceral and parietal peritoneum?

A

A fluid filled space (peritoneal space/cavity)

37
Q

What does retroperitoneal mean?

A

Posterior to the peritoneum

38
Q

What is retroperitoneal?

A

Organs which don’t move when functioning - these organs still have visceral peritoneum

39
Q

What are mesenteries?

A

Double layers of visceral peritoneum that connect the organ to the body wall

40
Q

What are omentas?

A

Double layers fo visceral peritoneum that connect organ to another organ

41
Q

Where is food ingested?

A

At the mouth/oral cavity

42
Q

What happens in the moth?

A

Digestion begins (mechanical and chemical - requires enzymes) and lubrication

43
Q

Where does the food go from the mouth?

A

Through fauces, into oropharynx, then into esophagus

44
Q

How many pairs of salivary glands are there?

A

3 which are connected to the oral cavity via ducts

45
Q

What are the 3 salivary glands?

A

Parotid, sublingual and submandibular

46
Q

What is secreted by the parotid glands?

A

serous fluid with amylase

47
Q

What is secreted by the sublingual glands?

A

Mucous only

48
Q

What is secreted by the submandibular glands?

A

Mix of serous fluid with amylase and mucous

49
Q

What is the total volume of salivary secretions?

A

1L per day

50
Q

What type of glands are salivary glands?

A

Compound secretory

51
Q

What are cells in clusters?

A

Acinus

52
Q

What do acinar cells do?

A

Secrete enzymes (amylase)

53
Q

What do duct cells do?

A

Secrete bicarbonate (buffering)

54
Q

How long is the oesophagus?

A

Approximately 25 cm

55
Q

Where is the oesophagus located?

A

Posterior to the trachea and extends from the pharynx to the stomach

56
Q

What is the oesophagus?

A

A basic tube modified to pass food

57
Q

What is within the oesophagus?

A

Highly folded submucosa and mucosa with the capacity to expand

58
Q

What is the mucosa of the oesophagus?

A

Stratified squamous epithelium

59
Q

What does the muscularis in the oesophagus do?

A

Move food

60
Q

What is the first third of the muscularis of the oesophagus?

A

Skeletal muscle

61
Q

What is the second third of the muscularis of the oesophagus?

A

mixture of smooth and skeletal muscle

62
Q

What is the last third of the muscularis of the oesophagus?

A

Smooth muscle

63
Q

What is mucous needed for in the oesophagus?

A

Lubrication and protection

64
Q

How is the mucous in the oesophagus made?

A

No goblet cells, instead have glands with ducts to the surface