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Human Physiology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the four main functions of the GI tract?

A
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
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2
Q

What three parts make up the small intestine?

A
  1. Duodenum
  2. Jejunum
  3. Ileum
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3
Q

What is the function of the GI tract concerning motility?

A
  1. Smooth muscle maintains constant low-level contraction (tone)
  2. Propulsion to move contents forward (peristalsis)
  3. Mixing of contents with digestive juices
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4
Q

What is the function of the GI tract concerning secretions?

A
  1. The GI tract secretes water, electrolytes, enzymes, and buffers
  2. Secretions used for neural and hormonal control
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5
Q

What is the function of the GI tract concerning digestion?

A

Biochemical breakdown of food by enzymes

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6
Q

What is the function of the GI tract concerning absorption?

A

Absorption of nutrients into the blood or lymph

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7
Q

What is the function of the mouth in the digestive system?

A
  1. Mastication
  2. Initial stages of carbohydrate digestion
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8
Q

What is the function of the stomach in the digestive system?

A
  1. Stores food
  2. Initial stages of protein digestion
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9
Q

What is the function of the small intestine in the digestive system?

A
  1. Digestion of proteins, carbs, fats, and nucleic acids
  2. Main nutrient absorption site
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10
Q

What is the function of the large intestine in the digestive system?

A
  1. Final digestion and nutrient absorption
  2. Water absorption
  3. Waste concentration
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11
Q

From the inside to the outside, what are the layers of the GI tract?

A
  1. Lumen
  2. Mucosal layers/mucosa
  3. Submucosa
  4. Muscular externa
  5. Serosa
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12
Q

What is the function and the structure of the mucosa?

A
  1. Highly folded and modified for secretion & absorption
  2. Secretes digestive juices & blood-borne hormones
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13
Q

What is the structure and function of the submucosa?

A
  1. Connective tissue for elasticity
  2. Contains nerve network - submucosal plexus (sensory & secretory)
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14
Q

What is the function of the serosa?

A
  1. Lubricating
  2. Prevents friction between organs - supporting role
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15
Q

What is the structure and function of the muscular external?

A
  1. Smooth muscle for contraction - propulsion & mixing
  2. Myenteric plexus nerve network lies between the two layers (motor)
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16
Q

Which of the myenteric plexus or submucosa plexus stimulates increased tone in GI tract smooth muscle?

A

Myenteric plexus

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17
Q

What part of the nervous system controls the autonomous behaviour of the digestive system?

A

Enteric nervous system

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18
Q

What nerve network of the GI tract is associated with mechano- and chemo- receptors in the mucosa?

A

Submucosal nerve plexus

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19
Q

What nerve network of the GI tract controls the endocrine and exocrine secretion of the mucosa?

A

Submucosal nerve plexus

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20
Q

What nerve network of the GI tract controls contraction & relaxation of smooth muscle?

A

Myenteric nerve plexus

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21
Q

What is the mechanism for saliva production?

A
  1. Chemoreceptors & mechanoreceptors respond to food presence
  2. Afferent impulses go to salivary centre in brainstem
  3. PNS stimulates saliva secretion
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22
Q

What GI tract secretion contains amylase and bicarbonate to moisten food and form a food bolus?

A

Saliva

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23
Q

What is the swallowing reflex?

A
  1. The bolus stimulates stretch receptors which cause widening ahead (relaxation) and narrowing behind (contraction)
  2. Peristalsis in response to stretching
  3. Inhibitory neurons cause area of receptive relaxation ahead of bolus
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24
Q

One role of the stomach is to store food. What does the stomach secrete for digestion?

A
  1. Intrinsic factor
  2. Mucus
  3. Pepsinogen
  4. Acid
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25
Q

Peristaltic contractions of the stomach start in ‘pacemaker’ region and sweep towards what part of the stomach?

A

Antrum and pyloric sphincter

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26
Q

Contraction of the pyloric sphincter of the stomach causes what to happen?

A

Gastric mixing

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27
Q

What is gastrin and what does it do?

A

Gastrin is a hormone that causes the release of gastric secretions

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28
Q

What three places/phases is gastrin released in?

A
  1. Cephalic (head) phase
  2. Gastric phase
  3. Intestinal phase
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29
Q

What stimulates gastrin release in the cephalic phase?

A
  1. Food presence in the mouth
  2. Thinking about, smelling, tasting, chewing, or seeing food
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30
Q

What stimulates gastrin release in the gastric phase?

A
  1. Food is in the stomach
  2. Stretch of the stomach
  3. Presence of proteins
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31
Q

What stimulates gastrin release in the intestinal phase?

A

Food in the small intestine

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32
Q

When chyme leaves the stomach, where does it enter next?

A

Duodenum of small intestine

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33
Q

What is the state of the food/fluid mixture in the duodenum? Name all components.

A
  1. Carbs - partial disaccharides by salivary amylase
  2. Proteins - small peptides due to pepsin & HCl action
  3. Fats - mainly triglycerides
  4. Acidic environment
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34
Q

Acid in the duodenum stimulates the secretion of what hormone?

A

Secretin

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35
Q

What is the function of secretin?

A
  1. Increases bicarbonate secretion by stimulating liver to produce bicarb rich bile
  2. Stimulates bile generation
  3. Increases gall bladder contraction
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36
Q

What is the function of bicarbonate in the GI tract?

A

To neutralise acid in the intestines/places other than stomach

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37
Q

How long is the gall bladder and what is its capacity?

A

9cm long with 50ml capacity

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38
Q

What is secreted by hepatocytes and transported down the bile duct to the gall bladder?

A
  1. Bile salts
  2. Bilirubin
  3. Cholesterol
  4. Phospholipids
  5. Proteins
  6. Electrolytes
  7. Water
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39
Q

What is the function of the gall bladder?

A

Store bile before emptying it into the duodenum

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40
Q

How much bile (approximately) does the liver produce per day?

A

1000ml

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41
Q

In the duodenum, the presence of fats and proteins stimulates the release of what hormone?

A

Cholecystokinin (CCK)

42
Q

What is the function of cholecystokinin (CCK)?

A
  1. Stimulate pancreatic release of proteolytic enzymes, lipases, amylases, disaccharidases, and nucleases
  2. Increase motility of SI and colon
  3. Cause gall bladder contraction
43
Q

Explain where mechanical digestion occurs.

A
  1. Begins in the mouth with mastication
  2. Continues in the stomach where food is churned through stomach smooth muscle contractions
44
Q

Explain the four functions of stomach acid (HCl).

A
  1. Antimicrobial activity
  2. Aids in breakdown of connective tissue and muscle fibres
  3. Denatures proteins to expose more of the peptide bonds for enzymatic attack
  4. Activates pepsin from inactive pepsinogen
45
Q

Vitamin B12 is required for the synthesis of what cell type?

A

Red blood cell

46
Q

What is pernicious anaemia and how is it treated?

A
  1. Autoimmune disorder that causes diminished vitamin B12
  2. Treatment involved vitamin B12 shots
47
Q

Intrinsic factor and vitamin B12 combine to form a complex that is resistant to digestion by GI juices. Where is then absorbed?

A

The terminal ileum

48
Q

Where is intrinsic factor secreted to combine with vitamin B12?

A

The stomach

49
Q

The stomach does not absorb food. What can it absorb and why?

A
  1. Can absorb alcohol and aspirin
  2. They are lipid soluble and can diffuse through the stomach mucosa plasma membrane
50
Q

Pancreatic enzymes are released into where when stimulated by CCK?

A

Duodenum

51
Q

What three enzymes do pancreatic cells secrete for digestion in the duodenum?

A
  1. Pancreatic amylase
  2. Pancreatic lipase
  3. Proteolytic enzymes
52
Q

Peptidases hydrolyse peptide fragments into what?

A

Individual amino acids

53
Q

Amylase breaks down glucose polymers such as starch and glycogen into what?

A

Maltose, sucrose and lactose

54
Q

Maltase breaks down maltose into what constituents?

A

2 glucose molecules

55
Q

Sucrase breaks down sucrose into what components?

A

1 glucose and 1 fructose

56
Q

Lactase breaks down lactose into what constituents?

A

1 glucose and 1 galactose

57
Q

Pancreatic lipases break down triglycerides into what?

A
  1. Monoglycerides
  2. Free fatty acids
58
Q

Intestinal movements break up large fat droplets into smaller ones. These would quickly re-coalesce if not for what?

A

Bile salts

59
Q

Bile salts act as detergents, converting large fat globules into a lipid emulsion. The resulting larger surface area allows attack by what enzyme?

A

Pancreatic lipase

60
Q

What percentage of vitamin B12 ingested is absorbed passively and without the need for intrinsic factor?

A

1%

61
Q

The exocrine tissue of the pancreas secretes alkaline secretions such as bicarbonate and enzymes. What does the endocrine tissue do?

A

Release hormones

62
Q

90% of absorption occurs in the small intestine. What is absorbed here?

A
  1. Monosaccharides
  2. Amino acids
  3. Fatty acids and monoglycerides
  4. Electrolytes
  5. Vitamins
  6. Water
63
Q

Everything in the small intestine is absorbed fully regardless of the body’s needs. What are the two exceptions?

A
  1. Calcium
  2. Iron
64
Q

What parts of the small intestine does absorption most occur?

A

Duodenum and jejunum

65
Q

Explain the adaptations the small intestine has for efficient absorption.

A
  1. Microvilli increase surface area
  2. Microvilli contain enzymes and transport proteins for nutrient absorption
  3. Capillary network drains into hepatic portal system for nutrient processing
  4. Lacteals for fat absorption
66
Q

Explain the mechanism by which glucose and galactose are absorbed into epithelial cells.

A
  1. Na+/K+ pump uses ATP to pump Na+ out of cell into interstitium against conc gradient, reducing cytoplasmic Na+
  2. Na+ and glucose are symported from lumen into cell by SGLT transporter protein, using energy of Na+ gradient
  3. Glucose leaves the cell down its conc gradient and moves into interstitium via GLUT2
67
Q

Pancreatic lipases hydrolyse triglycerides to fatty acids and monoglycerides. These form small droplets called what?

A

Micelles

68
Q

What do micelles contain?

A
  1. Digested triglycerides (fatty acids & monoglycerides)
  2. Cholesterol
  3. Fat-soluble vitamins
69
Q

Micelles are coated with a layer of lipoprotein when inside cells. This forms what?

A

Chylomicrons

70
Q

Chylomicrons are water soluble with a hydrophobic core. What system do they enter?

A

Lymphatic system

71
Q

Chylomicrons travel via the lymphatic system and are returned to the venous system near the heart. Where do they deliver their lipid components to and why?

A
  1. Delivers to adipose, cardiac and skeletal muscle
  2. Use and storage
72
Q

Excess chylomicrons are taken up by what organ to be packages into VLDL and LDLs?

A

Liver

73
Q

VLDL delivers triglycerides to what tissues/muscles?

A

Skeletal muscle and adipose tissue

74
Q

LDL delivers what to peripheral tissues to be used in processes such as steroid hormone synthesis?

A

Cholesterol

75
Q

Excess LDL can lead to LDL plaques in blood vessels, which can lead to what?

A

Atherosclerosis

76
Q

HDL picks up excess cholesterol in the blood and takes it to the liver for removal in what substance?

A

Bile

77
Q

Does a high HDL:LDL ratio reduce or increase the risk of a heart attack?

A

Reduce

78
Q

Where do intestinal gases come from?

A
  1. Bacterial fermentation in colon
  2. Swallowed air
79
Q

At what structure does the small intestine join the colon?

A

Caecum

80
Q

What valve in the caecum opens when contents from the small intestine push forward?

A

Ileocaecal valve

81
Q

How much chyme does the large intestine receive each day?

A

500ml

82
Q

What is the chyme coming into the large intestine made up of?

A
  1. Indigestible food residue
  2. Bile components
  3. Water
83
Q

What does the colon absorb?

A

Water and electrolytes

84
Q

Bacterial flora ferment cellulose and undigested carbs to produce gas. What else do they do?

A

Synthesise B vitamins & vitamin K which are absorbed by the colon

85
Q

What is the difference between absorptive properties of the large and small intestine?

A
  1. Luminal surface is smoother in colon
  2. Less absorptive surface area in colon
86
Q

Mass movements in the large intestine propel faeces forwards as the ascending & transverse colon contract simultaneously. How many times a day does this happen?

A

3-4 times

87
Q

What is the gastro-ileal reflex?

A

Moving food from small intestine into the colon

88
Q

The internal anal sphincter is made from smooth muscle. What neurons is it innervated by?

A

Enteric neurons

89
Q

The external anal sphincter is made from skeletal muscle. What neurons innervate it?

A

Somatic efferent neurons

90
Q

What is the percentage composition of faeces?

A
  1. 67% water
  2. 33% solids, of which 11% is bacteria
91
Q

Describe the mechanism of the defaection reflex.

A
  1. Resulting distension of the rectum stimulates stretch receptors of rectal wall
  2. Internal anal sphincter relaxes; colon contracts vigorously
  3. If external anal sphincter is relaxed, defaection occurs
92
Q

Defaecation is assisted by the simultaneous voluntary contraction of what muscles?

A

Abdominal muscles

93
Q

What are some age-related changes that affect digestion and absorption?

A
  1. Epithelial stem cell division rate decreases
  2. Smooth muscle tone decreases
  3. Loss of teeth due to dental cavities/gingivitis
  4. Toxins lead to liver cirrhosis and cancer
94
Q

Where are bile salts made and stored, and when are they released?

A
  1. Made in liver
  2. Stored in gallbladder
  3. Released when food enters duodenum
95
Q

What are chylomicrons composed of?

A
  1. Lipoproteins (surface)
  2. Cholesterol (core)
  3. Triglycerides (core)
  4. Fat-soluble vitamins (core)
96
Q

The appendix is made up of what type of tissue?

A

Lymphoid tissue

97
Q

What is the consequence of decreases GI motility & contraction strength due to age?

A

Constipation

98
Q

What is the gastro-colic reflex?

A

Movement within the colon

99
Q

What is the consequence of decreased muscle tone & straining due to old age?

A

Haemorrhoids

100
Q

What is the consequence of weakening sphincters due to aging?

A

Reflux and heart burn

Human Physiology (6 decks)

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