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Body Logistics > Session 9: Digestive System > Flashcards

Session 9: Digestive System Flashcards

1
Q

The alimentary canal consists of what?

A

Mouth, tongue, pharynx, esophagus, stomach, small intestine, colon of the large intestine, appendix, rectum, anus

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2
Q

What are the accessory organs of the digestive system?

A

Salivary glands, Liver, Gall bladder, Pancreas

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3
Q

What is the mesentery?

A

The double fold of the peritoneum that attaches the intestines to the wall of the abdomen

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4
Q

What are the four layers of the gut wall?

A 
The mucosa (innermost)
The submucosa 
The external muscle layers (muscularis externae) 
The serosa (outermost)
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5
Q

The mucosa of the gut wall lines the lumen and is made up of what three layers?

A

Epithelium
Lamina propria
Muscularis mucosae

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6
Q

What structures are often present in the lamina propria of the gut mucosa?

A

Peyer’s patches

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7
Q

The submucosa of the gut contains what important features?

A 
Layer of connective tissue 
Glands
Arteries 
Veins 
Nerves
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8
Q

The external muscle layers of the gut wall contain what?

How are these seen histologically?

A

2 layers of smooth muscle:

1) Outer longitudinal layer (cells with cigar-shaped nuclei)
2) Inner circular layer (cells with central nuclei)

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9
Q

Which layer of the gut wall is responsible for the successive peristaltic waves required to move luminal contents along the gut?

A

Muscularis externa (External muscle layers)

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10
Q

The outermost layer of the gut wall is known as what?

A

The serosa (a serous membrane)

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11
Q

The serosa of the gut wall is made up of what layers?

A

Connective tissue

Mesothelium (simple squamous epithelium)

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12
Q

The mesentery contains what?

A

Arteries
Veins
Nerves

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13
Q

List some of the major functions of the GI tract

A 
Port of entry for food into the body
Mechanically disrupt food 
Temporarily store food 
Chemically digest food 
Kill pathogens
Move food along the tract 
Absorb nutrients from the resultant solution 
Eliminate residual waste
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14
Q

What is digestion?

A

The conversion of what we eat, by physical and chemical disruption into a solution from which we can absorb our nutrients

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15
Q

The solution brought about by chemical and physical disruption from which we absorb our nutrients is relatively _________, _______ in pH and __________

A

sterile
neutral
isotonic

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16
Q

Saliva starts digestion with the aid of which enzymes?

A

Amylase and lipase

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17
Q

What two features of saliva are bacteriostatic?

A

IgA

Lysozyme

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18
Q

What features of saliva helps to protect our teeth?

A

High in calcium

Alkaline

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19
Q

How does the digestive system contribute to physical disruption of food?

A

By the action of teeth, tongue and muscles of mastication (chewing)

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20
Q

During mastication, the mouth forms a _____ which enters the oesophagus

A

bolus

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21
Q

Which section of the oesophagus is under voluntary control?

A

Upper third

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22
Q

The lower section of the oesophagus is under ___________ control

A

involuntary

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23
Q

The upper end of the oesophagus contains some ________ _______ muscle as well as smooth muscle

A

Striated skeletal

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24
Q

The lower end of the oesophagus contains only which types of muscle?

A

Smooth

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25
Q

What mechanism is used to transport bolus to the stomach?

A

Rapid peristaltic transport

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26
Q

How long does it take for the bolus to travel from the mouth to the stomach?

A

8-9 seconds

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27
Q

Where does the fastest of the GI transport take place?

A 
On entry (oesophagus) 
On exit (rectum/acus)
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28
Q

The oesophagus is made up of what four layers?

It is lacking what layer that is found in the gut wall?

A 
Mucosa 
Submucosa 
Muscularis externa 
Adventitia 
There is no serosa, not intraperetaneal
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29
Q

What are the name of the two major nerve centres of the digestive system?

A

Myenteric plexus

Submucosal plexus

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30
Q

The stomach undergoes receptive relaxation, what is meant by this?

A

The walls relax so that pressure in the stomach does not increase as it swells (up to a point)

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31
Q

The stomach secretes what to break down tissues and disinfect?

A

Acid and proteolytic enzymes

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32
Q

How does the stomach protect its epithelium?

A

By secreting mucus onto its surface

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33
Q

The stomach produces hypertonic chyme, what is meant by hypertonic in this case?

A

The osmotic pressure of chyme increases and it therefore wants to draw in fluid from the rest of the body

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34
Q

What is chyme?

A

Broken down, partially digested stomach contents

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35
Q

Where is the chyme delivered to?

A

The duodenum

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36
Q

The stomach is lined with simple columnar epithelium with openings to various what?

A

Gastric pits

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37
Q

What extend down into the gastric pits?

A

Long, straight tubular gastric glands

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38
Q

Shallow gastric pits are lined with what cells?

Where are these cells infrequently found?

A

Surface mucous cells

Tubular gastric glands

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39
Q

The mucous secreted by gastric pits is released in response to what?

A

Distention
Stomach contents
Acid secretion from gastric glands

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40
Q

Secreted mucus is resistant to what?

A

Pepsin

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41
Q

What can cause damage to the mucous cells?

How are these damaged cells replaced?

A

Alcohol and aspirin

By mitosis in deeper cells in the neck of the gastric pit

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42
Q

Secreted mucus contains what which neutralises the effect of H+ ions?

A

Bicarbonate ions (HCO3-)

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43
Q

What is the isthmus?

A

The region of the gastric gland in which stem cells divide to populate the gland by upward or downward migration

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44
Q

What do parietal cells secrete?

A

H+ ions into the lumen

HCO3- ions into nearby capillaries which move it to surface mucous cells

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45
Q

What do chief cells secrete?

A

Pepsinogens which are converted into pepsins which partly hydrolyse proteins

46
Q

Enteroendocrine cells include _____ cells which secrete what?

A

G cells

Gastrin

47
Q

What does gastrin secretion by G cells cause in the wider gastric mucosa?

A

Causes the gastric mucosa to secrete acid

48
Q

What is the name given to the proximal part of the small intestine?

A

Duodenum

49
Q

What shape is the duodenum?

How long is the duodenum?

A

C-shaped

20-25cm

50
Q

The walls of the duodenum contain ___________ _______ which secrete what?
Why?

A

Brunner’s glands
Bicarbonate
To neutralise acidic chyme

51
Q

Which two organs connect with the duodenum?

A

Liver

Pancreas

52
Q

__________ and __________ enter the duodenum at from ampulla of Vater?

A

Bile

Pancreatic juice

53
Q

What is the ampulla of Vater?

A

The joining of the pancreatic duct and the common bile duct

54
Q

_____ is drawn in from the ECF to render the hypertonic chyme _________.

A

Water

Isotonic

55
Q

The liver releases a substance called _______, generally via what organ?

A

Bile

Gall bladder

56
Q

What does bile contain?

A

Water
Alkali
Bile salts

57
Q

What is the function of bile salts?

A

To emulsify fat

58
Q

The _______ and ________ secrete alkali to neutralise acidic chyme, this is precisely controlled

A

Liver

Pancreas

59
Q

Which organs secrete specific enzymes that come to lie in an “unstirred layer” and complete digestion

A

Liver
Pancreas
Intestine

60
Q

What are the roles of enzymes secreted from the pancreas and intestine?

A

Cleave peptides into amino acids
Cleave polysaccharides to monosaccharides
Break down and re-form lipids
Break down nucleic acids

61
Q

True or false: Absorption is a passive process

A

FALSE, it is an active process as it requires energy

62
Q

Is absorption a slow or fast process?

A

Slow

63
Q

How does the small intestine achieve such a large surface area for absorption?

A

Many folds

Villi and micro-villi on simple columnar cells

64
Q

True or false: The intestine has a good blood supply/drainage system?

A

TRUE TRUE TRUE

65
Q

How is blood drained from the small intestine and colon?

A

Via the hepatic portal vein

66
Q

Blood containing products of digestion is drained from the gut and passes through the ________ before entering venous circulation

A

Liver

67
Q

The entire small intestine is how long?

A

22 feet (7 metres)

68
Q

With its length along with the folds and villi/micro-villi, the small intestine has a surface area of what?

A

> 25cm^2

69
Q

The duodenum absorbs what mineral?

A

Iron

70
Q

What is absorbed by the jejunum?

A

Most of sugars, amino acids and fatty acids

71
Q

What is absorbed by the ileum?

A

Vitamin B12, bile acids and remaining nutrients

72
Q

By the terminal ileum, ________ have been absorbed, but ________ still needs to be absorbed

A

Nutrients

Water (Lots of it)

73
Q

The large intestine is made up of what?

A 
Caecum 
Ascending colon
Transverse colon 
Decending colon 
Sigmoid colon
74
Q

The whole colon is approximately how long and how wide?

A

1.2m long

6-9cm wide

75
Q

The large intestine is made up of what three layers?

A

Mucosa
Submucosa
Muscularis externa

76
Q

The surface epithelial cells of the large intestine are responsible for what vital function?

A

Absorption of water and electrolytes

77
Q

Which cells are responsible for the production of mucus and for supplying cells to the surface of the crypts?

A

The simple columnar epithelium of the crypts

78
Q

Intestinal glands of the colon are known as what?

A

Crypts of Lieberkuhn

79
Q

The large intestine continues a water recovery over a ______ hour transit

A

20

80
Q

By the end of the large intestine the contents are in what state?

A

Semi-solid

81
Q

Where do the semi-solid contents of the large intestine await expulsion?

A

In the colon, NOT the rectum

82
Q

What happens if higher centre control overrides the reflex to defaecate?

A

Reverse peristalsis

83
Q

Which part of the GI tract contains the most bacteria?

A

The colon

84
Q

Of the bacteria contained in the colon, most are anaerobic or aerobic?

A

Anaerobic

85
Q

True or false: Most of the bacteria of the GI tract are lost in faeces

A

True

86
Q

Bacteria in the large intestine are important for what processes?

A

Synthesis of vitamins K, B12, thiamine and riboflavine
Breakdown of primary to secondary bile acids
Conversion of bilirubin to non-pigmented metabolites

87
Q

Decreased absorption or increased secretion of fluid in the gut can result in what?

A

Life threatening dehydration

Life threatening electrolyte imbalance

88
Q

How is motility and secretion in the gut kept under precise control?

A

Overlapping neural, paracine and endocrine mechanisms

89
Q

The digestive system is under what kinds of neural control?

A

Somatic for ingestion (mouth, first 1/3 oesophagus) and excretion (last sphincter of anus)
Autonomic NS for rest

90
Q

The somatic nervous system innervates what type of muscle in the digestive system?

A

Striated

91
Q

_____ ___________ neurones form plexuses as part of the autonomic nervous system for the control of resting digestion

A

Post ganglionic

92
Q

Where are plexuses of post ganglionic neurones found in the digestive system?
What are the names given to these plexuses?

A

One between circular and longitudinal muscle of the gut wall (Auerbach’s “Myenteric” plexus)
One between submucosa and muscularis externa (Plexus of Meissner)

93
Q

True of false: The “gut nervous system” develops with the rest of the nervous system during development?

A

False, it develops separately and connects up

94
Q

Which substances contribute to the paracrine control of the digestive system?

A

Histamine which controls production of acid in the stomach

Vasoactive substances which affect blood flow in the gut

95
Q

Do substances that are released in a paracrine fashion in the gut act locally or systemically?

A

Locally

96
Q

What aspects of digestion are under endocrine (hormonal) control?

A

Secretion of stomach acid
Alkali secretion from the liver and pancreas
Enzyme secretion

97
Q

Generally the gut is controlled by hormones that it makes itself or elsewhere?

A

Makes itself

98
Q

What hormone is responsible for the promotion of HCl production by parietal cells?

A

Gastrin

99
Q

What cells are responsible for secreting Gastrin?

Where are they found?

A

G cells

Pyloric antrum of the stomach

100
Q

Gastrin is released by..?

A

G cells of stomach
Pancreas
Duodenum

101
Q

What is the role of secretin?

A

Promotes bicarbonate secretion from duct cells of the pancreas
Promotes bile production by the liver
Inhibits secretion of acid by parietal cells of the stomach

102
Q

Where is cholecystokinin (CKK) synthesised and secreted from?

A

Enteroendocrine cells of the duodenum

103
Q

What is the role of CKK?

A

Promotes release of digestive enzymes from the pancreas

Promotes release of bile from gall bladder (stimulates it to contract)

104
Q

True of false: CKK causes hunger

A

FALSE, it is a hunger supressant

105
Q

What are the three phases of swallowing?

A

1) Oral
2) Pharyngeal
3) Oesophageal

106
Q

What happens during swallowing to prevent the solids/fluids from entering the trachea?

A

The epiglottis goes down and sits over the trachea to stop it from moving into the airway

107
Q

What happens during swallowing to prevent the solids/fluids from entering the nose?

A

The soft palette moves up when we swallow to protect the nose

108
Q

True or false: the main mechanism that moves food/liquid down our oesophagus is gravity

A

False!!! The main mechanism is peristalsis, gravity only plays a small part

109
Q

What mechanisms do we have to prevent the stomach from digesting itself?

A

Mucus production
Bicarbonate production
Both act as a buffer to neutralise acid
Zymogens are not activated until acid is present in response to food

110
Q

Without bile we would not be able to do what?

A

Absorb fats and therefore fat soluble vitamins: A,D,E and K

111
Q

Does the small intestine normally contain bacteria?

A

No, not normally

112
Q

What mechanisms are in place to prevent the bacteria in the colon from invading the colonic wall and underlying tissues?

A 
Peyer's patches
Mucus 
Tight junctions 
IgA
High turnover of cells

Body Logistics (16 decks)

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