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Semester 1-Body Logistics > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the four layers of the gut wall, starting from the innermost?

A

Mucosa
Submucosa
External muscle layers (muscularis externae)
Serosa

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2
Q

What does the submucosa contain?

A

Layer of CT bearing glands, arteries, veins and nerves

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3
Q

How many layers of smooth muscle does the muscularis externa contain and what are they?

A

2
Outer longitudinal layer
Inner circular layer

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4
Q

What does the muscularis externa do?

A

Creates successive peristaltic waves to move luminal contents along the gut

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5
Q

What makes up the serosa? (2)

A

Simple squamous epithelium (mesothelium)

Connective tissue

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6
Q

What are the major functions of the GI tract? (8)

A
  1. Port of entry for food into body
  2. Mechanically disrupt food
  3. Temporarily store food
  4. Chemically digest food
  5. Kill pathogens in food
  6. Move food along tract
  7. Absorb nutrients from resultant solution
  8. Eliminate residual waste
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7
Q

Complete the sentence:

Digestion is the conversion of what we eat by ________ and ________ disruption into a solution (relatively sterile, _______ in pH and _______) from which we can absorb our nutrients.

A

Physical
Chemical
Neutral
Isotonic

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8
Q

Which enzymes in saliva start digestion?

A

Amylase

Lipase

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9
Q

Saliva is bacteriostatic, what does this mean?

A

Prevents bacteria multiplying without destroying them

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10
Q

Why does saliva have a high calcium content?

A

Protects teeth

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11
Q

Complete the sentence:

Physical disruption starts in the mouth by the action of _____, ______ and muscles of _____________.

A

Teeth
Tongue
Mastication

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12
Q

True or false: the fastest GI transport is on entry and exit

A

TRUE

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13
Q

Complete the sentence:

The mouth forms a _____ which enters the oesophagus and is transported to the stomach.

A

Bolus

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14
Q

True or false: the upper end of the oesophagus is solely smooth muscle so involuntary control

A

FALSE - lower end, upper end has some striated skeletal muscle so control is voluntary

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15
Q

Which type of epithelium is found in the oesophagus?

A

Stratified squamous non-keratinised (withstands abrasion)

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16
Q

What does the lamina propria of the oesophageal mucosa contain?

A

Loose CT with blood and lymph vessels, some smooth muscle cells and many immune cells

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17
Q

Complete the sentence:

Physical disruption continues in the stomach by _______ (_ muscle layers and ________ ______)

A

Churning
3
Mucosal rugae

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18
Q

What is receptive relaxation?

A

Stomach wall relaxes so pressure doesn’t rise

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19
Q

Why does the stomach secrete acid and proteolytic enzymes?

A

To break down tissues and disinfect

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20
Q

How does the stomach protect its epithelium?

A

By secreting mucus

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21
Q

Complete the sentence:

The stomach produces hypertonic ______ by combined action of acid, ________ and agitation

A

Chyme

Enzymes

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22
Q

What is chyme?

A

Partially digested stomach content

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23
Q

What are the layers of smooth stomach muscle?

A

Oblique
Circular
Longitudinal

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24
Q

What are rugae?

A

Fold of gastric mucosa forming longitudinal ridges in the empty stomach

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25
True or false: surface mucous cells are abundant in the gastric pits but infrequent in the tubular gastric glands below
TRUE
26
Mucus is released by surface mucous cells in the stomach in response to what? (3)
Distension Stomach content Acid secretion by gastric glands
27
What can damage the surface mucous cells of the stomach?
Alcohol or aspirin
28
How is the stomach lining protected?
Mucus secreted by surface mucous cells in the stomach contain HCO3- ions which neutralise the effect of H+ ions and thereby protect the stomach lining
29
What is the isthmus?
Region in which stem cells divide to populate a gland by upward or downward migration
30
What do chief cells do?
Secrete pepsinogens which are converted into pepsin which partly hydrolyse proteins
31
What do enteroendocrine cells do?
Include G cells which secrete gastrin
32
How long is the duodenum?
20-25cm
33
True or false: the duodenum is the shortest and most proximal portion of the small intestine
TRUE
34
What do the walls of the duodenum contain?
Brunner's glands which secrete bicarbonate-rich mucus to neutralise acidic chyme
35
What does bile contain?
Water Bile salts (to emulsify fats) Alkali
36
True or false: pancreas and liver secrete alkali to neutralise acidic chyme
TRUE
37
What do the enzymes from the pancreas and intestine do? (4)
1. Cleave peptides to AA 2. Cleave polysaccharides to monosaccharides 3. Break down and re-form lipids 4. Break down nucleic acids
38
What does absorption require?
Lots of energy Large surface area Good blood supply/drainage
39
Drainage during absorption occurs via which vessel?
Hepatic portal vein
40
What is a lacteal?
Dilated lymphatic capillary vessel
41
What are the three parts of the small intestine called?
Duodenum Jejunum Ileum
42
What does the duodenum absorb?
Iron
43
What does the jejunum absorb?
Most sugars AAs Fatty acids
44
What does the ileum absorb?
Vitamin B12 Bile acids Remaining nutrients
45
What are the different parts of the large intestine, going in a clockwise motion and ending with the rectum?
``` Caecum Ascending colon Transverse colon Descending colon Sigmoid colon ```
46
True or false: colon contains most of the GI tract's bacteria
TRUE
47
What are the bacteria in the colon involved in? (3)
1. Synthesis of vitamins K, B12, thiamine and riboflavine 2. Breakdown of primary to secondary bile acids 3. Conversion of bilirubin to non-pigmented metabolites
48
Decreased absorption or increased secretion can result in what?
Life threatening dehydration | Life threatening electrolyte imbalance
49
Motility and secretion need precise control and this is achieved by what three types of overlapping mechanisms?
Neural Paracrine Endocrine
50
What are the two types of neural control?
Somatic | Autonomic
51
Which two processes are involved in somatic control?
Ingestion | Excretion (last sphincter of anus)
52
What do post ganglionic neurones form?
Plexuses
53
Name two locations of plexuses
Between muscle layers of gut wall (myenteric plexus) | Between submucosa and muscularis externa (submucosal plexus)
54
What are two types of paracrine control and what do they do?
Histamine - controls production of acid in stomach | Vasoactive substances - affect blood flow in gut
55
What do the range of endocrine hormones involved control?
Secretion of stomach acid Alkali secretion from liver and pancreas Enzyme secretion
56
What does secretin promote? (2)
HCO3- secretion from duct cells of the pancreas | Bile production by the liver
57
What does secretin inhibit?
Secretion of acid by parietal cells of the stomach
58
What does CCK stand for?
Cholecystokinin
59
What does CCK do? (3)
Promotes release of digestive enzymes from pancreas. Promotes release of bile from gall bladder (stimulates it to contract). Hunger suppressant.
60
Where is CCK made?
Enteroendocrine cells of duodenum
61
Where is gastrin released? (3)
1. G cells of pyloric antrum of stomach 2. Pancreas 3. Duodenum
62
What does gastrin do?
Promotes the production of HCl (gastric acid) by parietal cells of the stomach
63
What are the overall roles of the gut? (3)
Secretion Movement Absorption

Semester 1-Body Logistics (20 decks)

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