Digestion Flashcards

1
Q

Omnivore digestion is more similar to…

A

Carnivores

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2
Q

Give the types of herbivore

A
  • Monogastric
  • Ruminants
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3
Q

Microbial digestion in monogastric herbivores occurs…

A

In the distal section of the gastrointestinal canal

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4
Q

In the rabbit, microbial digestion primarily occurs in the…

A

Caecum

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5
Q

In the rabbit, microbial vitamins and proteins are not entirely lost, this is due to…

A

Pseudo-faeces intake

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6
Q

Which grouping is considered to have the highest level of evolution in terms of digestive physiology

A

Ruminants

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7
Q

Which composites of food are absorbed in the abomasum + small intestines of ruminants?

A
  • Volatile fatty acids
  • Proteins of microflora origin
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8
Q

Describe pseudocopraphagia

A
  • At night
  • Rabbits expel soft-faeces
  • Faeces are then eaten
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9
Q

Microbial digestion in ruminants occurs in the…

A

Forestomachs

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10
Q

Microbial digestion in monogastric herbivores occurs in…

A
  • Caecum
  • Colon
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11
Q

Give the body length: Digestive canal ratio: Horse

A

1:12

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12
Q

Give the body length: Digestive canal ratio: Cattle

A

1:20

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13
Q

Give the body length: Digestive canal ratio: Pig

A

1:14

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14
Q

Give the body length: Digestive canal ratio: Dog

A

1:6

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15
Q

Give the capacity of the digestive tract in horse

A

211 L

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16
Q

Give the capacity of the digestive tract in cattle

A

356 L

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17
Q

Give the capacity of the digestive tract in pigs

A

27.5 L

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18
Q

Give the capacity of the digestive tract in dogs

A

7 L

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19
Q

The average length of the GI tract in Horse

A

30m

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20
Q

The average length of the GI tract in cattle

A

57m

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21
Q

The average length of the GI tract in pigs

A

23.5m

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22
Q

The average length of the GI tract in dogs

A

4.8m

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23
Q

Passage time in: Horse

A

1 Day

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24
Q

Passage time in: Cattle

A

1-2 days

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25
Q

Passage time in: Sheep

A

14-19 hours

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26
Q

Passage time in: Pig

A

11-13 hours

Peaking at 12-24 hours

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27
Q

Passage time in: Dog

A

12-15 hours

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28
Q

The point where the animal changes from milk to dry food

A

Ablactation

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29
Q

Volume of the rumen in the first 3 weeks of life

A

0.7L

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30
Q

The volume of the fundus in the first 3 weeks of life

A

1.5L

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31
Q

Rumen and reticulum originate from the…

A

Fundus (Next to the cardia)

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32
Q

Omasum originates from…

A

The terminal part of the fundus

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33
Q

How many phases of postnatal forestomach development are there?

A

3

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34
Q

Postnatal forestomachs development: Phase 1

A
  • Ruminoreticulum doesn’t function
  • Animal lives on mother’s milk
  • Carbohydrate metabolism is similar to a monogastric animal
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35
Q

Postnatal forestomach development: Phase 2

A
  • Early ruminous stadium
  • From 3-8 weeks since birth
  • Increased volume of rumen + reticulum
  • Animal interested in rougher fodder
  • Decreased blood glucose
  • Volatile fatty acids increase
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36
Q

Postnatal forestomach development: Phase 3

A
  • Forestomachs completely developed
  • Rumen at largest volume
  • Food enters rumen via the cardia
  • Growth and thyroid gland hormones may play a role
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37
Q

Formation of the reticular groove is a result of…

A
  • Reflex mechanism
  • Stimulation of pharyngeal receptors:
    • From milk
    • From suckling mechanism
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38
Q

How can the reticular groove reflex be performed experimentally?

A

Copper-salt CuSO4 solution orally

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39
Q

Give the effect of curdled milk in the abomasum

A
  1. Antrum becomes slightly stretched
  2. Fundus region becomes relaxed (Vagovagal reflex)
  3. Antrum becomes relaxed by an adrenergic effect
  4. Inhibits motility of the abomasum
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40
Q

Enzymes in the digestive system are produced by…

A
  • Accessory glands related to the alimentary canal
  • Epithelial cells
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41
Q

Why is the catabolism of amylase practically negligible in newborn pigs?

A
  • Its secretion is low
  • Increasing with age and then decreasing after 2-3 weeks
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42
Q

Give the enzyme activity of lactase from birth

A
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43
Q

Give the enzyme activity of pepsin from birth

A
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44
Q

Why is pepsin at such low levels in the first 2 weeks from birth?

A

So as to not degrade the immunoglobulin content of the colostrum

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45
Q

Give the enzyme activity of trypsin from birth

A
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46
Q

Explain the prevalence of trypsin from birth

A
  • Increased enzyme secretion from the pancreas
  • Change in feedstuff components
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47
Q

Give the enzyme activity of chymotrypsin from birth

A
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48
Q

Explain the decrease in lactase activity from birth

A

Young require milk less and less in the transition from milk → solid food

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49
Q

How can immunity be transferred to offspring?

A

Via:

  • Colostrum
  • Fetal circulation
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50
Q

When would immunity by colostrum be found?

A

When the species has a multi-layered placenta

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51
Q

Maternal immunity is split into…

A
  • Group I
  • Group II
  • Group III
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52
Q

Group I maternal immunity

A
  • Primates + Rabbits
  • Immunoglobulins (IgG) from the placenta reach the fetus
  • Mothers milk:
    • Low IgG
    • High IgA
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53
Q

Group II maternal immunity

A
  • Rodents, dog, cat
  • Immunoglobulins from the placenta and colostrum
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54
Q

Group III maternal immunity

A
  • Most domestic farm animals
  • IgG immunoglobulins from the colostrum
  • Immunoglobulins absorbed into the small intestine only within the first 2 hours of life
  • Important that colostrum is supplied quickly after birth
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55
Q

How are immunoglobulins absorbed into the body in young?

A
  • Specific cell structures
  • Transport through enterocytes to the lymphatic pathways
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56
Q
A

Villi

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57
Q
A

Lymph node

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58
Q

Give the components of the small intestine wall

from inside to outside

A
  1. Mucosa
  2. Submucosa
  3. Stratum ciliare
  4. Stratum longitudinale
  5. Serosa
  6. Smooth muscle layer
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59
Q

Which layer of the intestinal wall contains lymph nodes

A

Submucosa (interstitial tissue)

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60
Q

Lymph nodes of the digestive tract take part in both…

A

Immune responses

  • Local cellular
  • Humoral
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61
Q

Location of lymphatic vessels in the villi

A

In the centre

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62
Q

What is shown?

A

Electric activity of gastrointestinal smooth muscle cells

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63
Q
A

Slow waves

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64
Q
A

Spike potential

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65
Q
A

Slow waves

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66
Q
A

Spikes

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67
Q
A

Depolarisation

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68
Q
A

Resting potential

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69
Q
A

Hyperpolarisation

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70
Q
A

Tonus contraction of the GI smooth muscle cells

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71
Q

The sum of the electric activity generated by the slow waves is known as the

A

Basic electrical rhythm

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72
Q

Basic electrical rhythm waves are not considered to be…

A

Action potentials

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73
Q

The value of potential changes formed in slow waves ranges between…

A

5-15mV

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74
Q

The frequency of slow waves along the GI tract fluctuates between which values?

A

3-12 waves per minute

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75
Q

Spike potential

A

Action potential of the gastrointestinal smooth muscle cells.

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76
Q

Give the steps towards spike potential stimulation?

A
  1. Resting potential becomes positive (due to slow waves)
  2. Hyperpolarisation reaches threshold level (40mV)
  3. Spike potential stimulation
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77
Q

The more the extent with which the potential overshoots 40 mV…

A

…the higher the frequency of the “onbuilt” spikes

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78
Q

The frequency of spike potential ranges between…

A

1-10 per second

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79
Q

Slow spike potentials are generated by…

A

Slow Ca2+ influx

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80
Q

Action potentials of nerve fibres are generated by…

A

Fast Na+ influx

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81
Q

Why are muscle contractions not generated by slow waves?

A

Slow waves → Na+ migration

Spike potentials → Ca2+ migration

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82
Q

Give the resting potential of the muscle cells

A

50-60mV

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83
Q

Depolarisation of the cell membrane can be initiated by which factors?

A
  • Stretching of muscle cell
  • Acetylcholine
  • Parasympathomimetics
  • GI hormones
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84
Q

Hyperpolarisation of the cell membrane can be initiated by…

A
  • Adrenaline
  • Noradrenaline
  • GI hormones
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85
Q

What are the suspected reasons for tonus contraction on GI SM cells?

A
  • GI Hormones
  • The permanent influx of Ca2+ with no change in membrane potential
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86
Q

The nervous and hormonal system of the alimentary canal synchronises…

A
  • Motor function
  • Digestive function
  • Absorptive function
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87
Q

The initial and terminal tract is under control by…

A

The CNS

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88
Q

The GI tract from the stomach to the rectum is under control by…

A

Local regulation

Influenced by the CNS

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89
Q
A

Amygdala + Prefrontal cortex

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90
Q
A

Hypothalamus

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91
Q
A

Lateral nucleus

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92
Q
A

Ventromedial nucleus

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93
Q
A

Brain stem

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94
Q
A

The mechanics of food intake

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95
Q

Give the physiological function of ventromedial nucleus stimulation/lesion

A
  • Stimulation → Aphagia
  • Lesion → Hyperphagia
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96
Q

Appetite

A

Hunger complex directing food selection

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97
Q

Give the theories of hunger

A
  • Nutritional regulatory signals (Slow regulation)
  • Effects arising from the gastrointestinal canal (Fast regulation)
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98
Q

Give the effects acting as nutritional regulatory signals

A
  • Glucostatic effect
  • Aminostatic effect
  • Volatile fatty acid effect
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99
Q

Give the effects rising from the gastro-intestinal canal

A
  • Gastric and intestinal filling
  • Hormonal factors
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100
Q

Give the ‘other’ hunger theories

A
  • Temperature
  • Estrogens
  • Volemia
  • Density of population
  • Hierarchy
  • Night-day cycle
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101
Q

What can cause a decrease/stop of fodder intake in the rumen

A

A large amount of indigestible polypropylene fibres

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102
Q

Food intake is influenced by hormones by which mechanism?

A

By changing the glucose uptake of the hypothalamic cells

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103
Q

List the mediators which decrease food intake

A
  • Serotonin
  • Cholecystokinin
  • Glucagon
  • Somatostatin
  • VIP
  • Neurotensin
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104
Q

List the major endocrine factors that increase food intake

A
  • Hypothalamic neuropeptide Y
  • Opioid peptides
  • GABA
  • Dopamine
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105
Q

Give the effect of increasing/decreasing blood temperature on the digestive system

A

Stimulation/blocking of satiety centres

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106
Q

Increase of environmental temperature causes…

A

Decrease of food intake

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107
Q

High oestrogen causes…

A

Hunger decrease

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108
Q

Dehydration of the GI causes…

A

Decreased food uptake

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109
Q

Leptin is produced by…

A

Adipocytes

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110
Q

Function of leptin

A

Reduces food intake when enough reserves have already been formed

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111
Q

1

A
  • Feed intake increases insulin secretion
  • Increasing LPL
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112
Q

2

A

Decreasing HSL

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113
Q

3

A

Activity of adipose cells

  • Triglyceride uptake increase
  • Fat synthesis increase
  • Adipocytes grow
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114
Q

4

A

Adipocyte growth

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115
Q

5

A

Adipocyte division

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116
Q

6

A

More leptin produced

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117
Q

7

A
  • Leptin enters hypothalamus (via blood)
  • Increases local GLP-1 production
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118
Q

8

A
  • Depression of the effect of feed uptake
  • NPY stimulation
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119
Q

9

A
  • An increasing amount of adipose tissue signals back
  • Decreased feed intake
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120
Q

The most probable factor inducing obesity is…

A

Insensitivity of the hypothalamus towards leptin

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121
Q

Although, the gastrointestinal nervous system works independently, what can influence its activity

A
  • Sympathetic nervous system
  • Parasympathetic nervous system

Extrinsic regulation

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122
Q

Increase in the tone of the sympathetic nervous system causes…

A

Inhibition of the intestinal tract

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123
Q

What are the ways noradrenaline affects the intestinal tract

A
  • Hyperpolarises the smooth muscle
  • Decreases RMP of enteral plexus

Inhibits the passing of intestinal content

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124
Q

Location of postganglionic parasympathetic nerve cells

A

Enteral plexus

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125
Q

The increase of parasympathetic tone causes…

A
  1. Hyperpolarisation of almost all enteral nerve cells
  2. Increasing GI activities
  3. Increasing motility and secretion
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126
Q

Afferent nerves of the stomach/intestine are stimulated by…

A
  1. Excitation of the mucous membrane
  2. Vigorous dilation of the intestines
  3. Presence of specific substances
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127
Q

What is shown?

A

The enteral nervous system

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128
Q
A

Longitudinal muscle tract

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129
Q
A

Circular muscle tract

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130
Q
A

Plexus myentericus

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131
Q
A

Plexus submucosus

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132
Q

Functioning of the enteral nervous system is known as…

A

Intrinsic regulation

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133
Q

Which neurotransmitter excites intrinsic neural regulation?

A

Acetylcholine

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134
Q

Which neurotransmitters inhibit intrinsic neural regulation?

A
  • Vasoactive intestinal peptide (VIP)
  • Opoid peptides
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135
Q

Efferent neurones are located in the…

A

Plexus myentericus

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136
Q

Increased activity of the plexus myentericus causes…

A
  • Increase in tone contraction
  • Raise the intensity and frequency of rhythmic contractions
  • Increase the spreading speed of the stimulus
  • Increase speed of peristaltic waves
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137
Q

What is found in the plexus submucosus?

A

Receptors and afferent fibres of the local reflex arcs

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138
Q

The function of the receptors and afferent fibres of the local reflex arcs

A

Regulation of peristaltic movements

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139
Q

Plexus submucous regulates…

A
  • Local circulation
  • Secretion of GI juices
  • Absorption
  • Submucosa muscles defining the haustrum
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140
Q

List the GI reflexes:

Intestines - prevertebral ganglion - intestines

A
  • Gastric-colon reflex
  • Colon-gastric reflex
  • Colon-ileum reflex
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141
Q

List the GI reflexes:

  • Intestines-spinal cord
  • Brainstem-Intestines
A
  • Reflexes influencing gastric functions
  • Nociceptive reflexes
  • Defecation reflex
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142
Q

Give the groups of reflexes regulating the GI canal

A
  • Autonomous (intrinsic)
  • Prevertebral sympathetic ganglia reflexes
  • Spinal cord and brain stem reflexes
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143
Q

Gastric-colon reflex

A

Colon empties by the effect of the fullness of the stomach

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144
Q

Colon-gastric reflex

A

Termination of:

  • Colon dilation
  • Gastric motor activity
  • Secretion
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145
Q

Colon-ileum reflex

A

Fullness of the colon inhibits the emptying of the ileum towards the colon

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146
Q

Nociceptive reflexes cause

A

Paresis of the GI tract

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147
Q

Defecation reflex

A

Vigorous contractions of the colon, rectum and abdominal muscles

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148
Q

The body’s largest endocrine gland

A

The GI canal

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149
Q

Endocrine cells of the GI canal are known as…

A

Amine precursor uptake and decarboxylation (APUD) cells

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150
Q

The function of APUD cells

A

Synthesis of peptides and amines that are transmitted by adequate stimulus

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151
Q

Effects of GI peptides

A
  • Hormonal effect (mainly)
  • Local effects
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152
Q

List the peptides released from nerve terminals in the GI canal

A
  • Substance-P
  • Somatostatin
  • Vasoactive intestinal peptide (VIP)
  • Endorphins
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153
Q

Give the hormone groups: By location of synthesis

A
  • Sympathetic nervous system
  • Parasympathetic nervous system
  • Enteral nervous system
    • APUD cells
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154
Q

Give the hormone groups: By action

A
  • Paracrine
  • Endocrine
    • Gastrin
    • Secretin
    • CCK
    • Pancreatic polypeptide
    • GIP
    • Motilin
    • Enteroglucagon
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155
Q

Give the hormone groups: By chemical structure

A
  • Gastrin (+CCK)
    • Stimulate (Gastrin)
    • Inhibit (CCK)
  • Secretin, VIP, GIP, Enteroglucagon
    • Inhibit
    • Stimulate
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156
Q

The stimulating functions of gastrin

A
  • Motility
  • Intestinal mucosa growth
  • Secrete:
    • Gastric Juices
    • Enzyme
    • Pancreatic juice
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157
Q

The inhibiting functions of CCK

A
  • Gastric emptying
  • Gastric motility
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158
Q

List the hormones involved in gastric juice secretion

A
  • Secretin
  • VIP
  • GIP
  • Enteroglucagon
  • Gastrin
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159
Q

Give the two basic movements found in the digestive canal

A
  • Passing movement
  • Mixing movement
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160
Q

Give the steps of the passing movement

A
  1. Dilation of the intestines
  2. Peristaltic contraction
  3. Receptive relaxation
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161
Q

Bolus

A

The content of the intestines

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162
Q

Describe ‘dilation of the intestines’

A
  1. Bolus influences stretch receptors
  2. Intestinal wall narrows orally
  3. Intestinal wall dilates aborally
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163
Q

Describe ‘peristaltic contraction’

A
  1. Serotoninergic interneurons excite
  2. Cholinergic motor neurons excite
  3. Circular muscle layer contracts before the bolus
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164
Q

Describe ‘receptive relaxation’

A
  • Circular muscles released from inhibition
  • Become inhibited towards progression
  • Dilation formed, pressing intestinal content aborally
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165
Q

Mixing movements

A
  • Segmentation of bolus
  • Causes mingling
  • Detaches the content
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166
Q

Describe the ‘own movements of the villi’

A
  • Carried out by the muscle layer of their mucosa
  • Secures direct contact between epithelium and intestinal content
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167
Q

What is the fundamental condition of optimal digestion?

A
  • Intestinal canal lets food in proper timing to each of the digesting sections
  • Mixing it properly with enzymes
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168
Q

Give the feeding habits of: Canine

A
  • Quick ingestion
  • Great amounts
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169
Q

Give the feeding habits of: Feline

A
  • Regular eating
  • Smaller portions
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170
Q

Give the feeding habits of: Equine

A
  • Encircle rough food with their sensitive lips
  • Food is then bitten off with their corner teeth
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171
Q

Give the feeding habits of: Ruminants

A
  • Pull rough food into their mouth with their tongue twisted round it
  • Press food between their lower incisor teeth and their upper edentate edge and tear
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172
Q

Give the feeding habits of: Swine

A
  • Nuzzle up to the ground with their nose ring
  • Using their extended lower lip, place food inside mouth
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173
Q
A

Bolus

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174
Q
A

Mechanical sensation

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175
Q
A

Brain Stem:

Reflex inhibition

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176
Q
A

Relaxation of the chewing muscles

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177
Q
A

Mouth opens

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178
Q
A

Stretching of the stretch receptors

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179
Q
A

Brain stem:

Stretch reflex

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180
Q
A

Contraction

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181
Q

Bolus: Next step

A

Mechanical sensation

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182
Q

Mechanical sensation: Next step

A

Reflex inhibition

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183
Q

Reflex inhibition: Next step

A

Relaxation of the chewing muscles

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184
Q

The mouth opens: Next step

A

Stretching of the stretch receptors

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185
Q

Stretching of the stretch receptors: Next step

A

Stretch reflex

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186
Q

Stretch reflex: next step

A

Contraction

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187
Q

Chewing in the case of an intact nervous system

A
  • Initiated consensually by the cortex
  • Controls reflex motions
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188
Q

What regulates the contraction and relaxation of the tongue and cheek muscles?

A

Afferent stimuli arising from the mechanoreceptors

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189
Q

What method is used to study the order of swallowing?

A
  • Radioscopy
  • Pressure conditions are examined with the balloon technique
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190
Q

Give the phases of swallowing

A
  1. Bolus: Oral cavity → Pharynx
  2. Bolus: Pharynx → Oesophagus
  3. Bolus is passed in the oesophagus
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191
Q

Describe step I of swallowing

A
  1. Tongue forms boluses
  2. Placed between the tongue and hard palate
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192
Q

Describe step 2 of swallowing

A
  1. Soft palate rises
  2. Dorsal opening of the nasopharynx closes
  3. Breathing inhibited
  4. Larynx rises, glottis closes
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193
Q

Describe step 3 of swallowing

A
  1. Pressure from tongue movements presses bolus into the pharynx
  2. Bolus presses epiglottis backwards
  3. Entrance to pharynx closes
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194
Q

Describe phase 4 of swallowing

A
  1. The pressure in the pharynx increases
  2. Pharyngoesophageal sphincter relaxes
  3. Pharyngoesophageal sphincter contracts tightly
  4. Bolus can no longer re-enter the pharynx
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195
Q

Describe step 5 of swallowing

A
  1. The pressure in the pharynx increases
  2. Pharyngoesophageal sphincter relaxes
  3. Pharyngoesophageal sphincter contracts tightly
  4. The bolus can no longer re-enter the pharynx
  5. Contraction of muscles in the oesophagus
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196
Q

Describe the final phase (III) of swallowing

A
  1. Peristaltic wave pushes bolus toward the stomach
  2. Pressure is larger in the sub-diaphragmatic region of the oesophagus than the stomach
  3. Bolus arrives at the cardia
  4. The tone of cardia decreases
  5. Peristaltic wave passes
  6. Cardia pressure doubles (Preventing regurgitation)
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197
Q

Give the motor tasks of the stomach

A
  • Store ingested food until it’s passed to the duodenum
  • Mixing food with gastric secretions to form the pulpy chyme
  • Chyme passed to ileum in a proper rhythm to secure digestion + absorption
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198
Q
A

Proximal stomach

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199
Q
A

Distal stomach

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200
Q

Muscle elements in the stomach wall act as a…

A

Syncytium

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201
Q

Where are the areas of strongest and weakest gastric wall contraction

A
  • Weakest = Fundus + Pylorus
  • Strongest = Antrum
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202
Q

As the stomach fills, pressure…

A
  • Doesn’t increase
  • This is known as adaptive relaxation
  • Independent from gastric innervation
  • Accounted for by the law of laplace
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203
Q

Law of Laplace in relation to the stomach

A
  • The increase of stomach content causes:
  • The proportional increase in the stretching of the wall
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204
Q

Ptyalin digests for how long?

A

30 minutes

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205
Q

The content of the stomach after mingling is called…

A

Chyme

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206
Q

Which nerve reflexively decreases pressure in the stomach?

A

Vagus nerve

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207
Q

Law of Laplace formula

A

p = 2T/R

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208
Q

Describe the process of vomiting

A
  1. Repeated inhalation with a closed glottis
  2. Thoracic section of oesophagus fills with stomach content
  3. Up and down movements of stomach content
  4. Due to abd. pressure, stomach content moves orally
  5. Intrathoracic pressure repeatedly increases suddenly
  6. Stomach content pushed to the oral cavity
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209
Q

Step 1 of the stomach motions

A
  1. Circular retraction (rolling mixing tonic contraction)
  2. Moving food toward the antrum
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210
Q

Step 2 of the stomach motions

A

Circular contraction in the middle of the corpus

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211
Q

Step 3 of the stomach motions

A
  1. Peristalsis starts from the corpus
  2. Increases with the process of digestion
  3. Contraction rings become tighter
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212
Q

Step 4 of the stomach motions

A
  • Chyme whirls through the contraction ring
  • Then back towards the oral part of the stomach
  • Mixing
  • Increase in tone of proximal part presses chyme aborally
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213
Q

Step 5 of stomach motions

A
  • The more diluted the gastric content, the more is pressed through into the intestines
  • Dependent on pressure conditions
  • Strengthened by the pre-pyloric activity of antrum
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214
Q

What directly controls the peristaltic and other contractions of the stomach?

A
  • Plexus myentericus
  • Plexus submucosus
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215
Q

The effect of gastrin on the motions of the stomach

A
  • Gastrin facilitates gastric motility
  • Facilitates:
    • Physiological gastrooesophageal tone
    • Amplitude and velocity of BER
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216
Q

Enterogastric reflex

A
  • Decreases the motions of the stomach
  • Decreases tone of the pylorus
    • Increasing physicochemical effects in the duodenum
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217
Q

Enterogastrone affecting gastric motions

A
  • The inhibitory effect on gastric motility
  • Caused by hormones
  • Caused by low pH/High lipid content of the duodenum
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218
Q

Secretin affecting gastric motions

A
  • Inhibitory effect of gastric motility
  • Produced in small intestines
  • Due to low pH in the small intestines
  • Opposite effect of gastrin
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219
Q

Cholecystokinin (CCK) is stimulated by

A

High lipid content

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220
Q

Give the movement types in the ileum

A
  • Mingling movements
  • Processing movements
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221
Q

Give the groups of ileum function

A
  • Mingling action - degrading protein, lipid and carbohydrate
  • Absorption of nutritive materials
  • Forwarding content to the colon
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222
Q

Which evacuates bolus faster?

  • Ileum
  • Jejunum
A

Jejunum

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223
Q

What is the function of the mingling movements of the ileum?

A
  • Increase the emulsification of content
  • Achieve increased degree of contact with nutritive material
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224
Q

Which mingling movements are included in the ileum?

A
  • Segmental movements
  • Movements of the villi
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225
Q

Movements of the villi

A
  • Muscle fibres pull the villi toward their basal part
  • The content of lymphatic and blood vessels are pumped in their drainage vessels
  • Responsible by the hormone villiquinine
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226
Q

What causes the release of villiquinine?

A

HCl

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227
Q

What are the types of ilial-peristalsis?

A
  • Slow peristalsis
  • Accession peristalsis
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228
Q

Speed of slow peristalsis

A

0.5-2 cm/sec

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229
Q

Speed of accession peristalsis

A

10 cm/sec

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230
Q

What is the primary role of the ileocaecal valve?

A

Prevention of regurgitation of colon contents

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231
Q

How does the ileocaecal valve prevent content moving orally?

A

By gently contracting the ileocaecal sphincter

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232
Q

What secondary role occurs due to the ileocaecal valve?

A
  1. Chyme remains longer in the ileum
  2. Greater absorption in the ileum
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233
Q

The ileocaecal sphincter opens simultaneously to…

A

The filling of the stomach

(Gastroilial reflex)

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234
Q

The gastroilial reflex allows…

A

Makes possible the quick passing of the piled up ilial conten towrd the colon

  • Secured by:
    • Enteral reflex
    • Effect of gastrin
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235
Q

Intestinal movements are regulated by…

A
  • BER
  • Nervous control
  • Reflexes
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236
Q

Nervous control of bowel movements

A

Influenced by

  • Sympathetic splanchnic nerve (Inhibition)
  • Parasympathetic vagus nerve (Excitation)
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237
Q

Give the primary pacemaker activity in the duodenum for dogs

A

17-18/minute

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238
Q

Give the primary pacemaker activity in the duodenum for horses

A

14-15/minute

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239
Q

During ileogastric reflex, the ilial contraction…

A

Lowers gastric motility

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240
Q

Gastrointestinal reflex

A
  • Stomach activity ↑ → Ileum activity ↑
  • Therefore chyme passes through the ileocaecal sphincter speeds up
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241
Q

Give the roles of the colon

A
  • Microbial digestion
  • Water + electrolyte reabsorption
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242
Q

Give the pathway of bolus in the colon in ruminants

A
  1. Small intestine
  2. Colon
  3. Retrograde flow
  4. Colon
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243
Q

Retrograde flow

A
  • Some content of the colon returns to the caecum for microbial digestion
  • This slows down the flow intestinal content
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244
Q

Give the pathway of bolus in the colon in horse

A
  1. Basal part of caecum
  2. Cupola of caecum
  3. Caecum presses part of the content to colon
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245
Q

Type-I contraction in the horse

A
  1. Small intestine content pressed into the basal part and cupola of the caecum
  2. Cupola becomes segregated, part of it’s content is pressed into the colon
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246
Q

Type-II contraction in the horse

A
  • Gas removal
  • Contraction of the basal caecum presses gasses into the cupola, dilating it
  • The liquid content of the cupola sinks
  • Gases enter the colon
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247
Q

Type-III contraction in horse

A
  • Constant contraction appearing in haustra
  • Creates continuous mixing which contracts during peristalsis
  • Inhibits the passing of intestinal content
  • Backward whirling is formed
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248
Q

Movement of colon content is faster in…

A

Carnivores

  • Caused by aboral mass-peristalsis
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249
Q

The tone of the intestinal wall…aborally…

A

Decreases

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250
Q

Give the main activity of the rectum

A

Regulation of the storage and evacuation of the faeces

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251
Q

In few species such as dog, voluntary defecation is under the what control?

A

Hypothalmic and cortical control

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252
Q

What forms the internal sphincter muscle?

A
  • Thickening of the circular muscles in the rectum
  • Smooth muscle
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253
Q

What forms the external sphincter muscle?

A
  • Striped-striated muscle
  • Circularly thickened part of the perineum
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254
Q

Sympathetic innervation of the rectum arises from…

A

L1-L3

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255
Q

The effect of efferent stimuli on the rectum

A
  • Relaxation of the muscle wall of the rectum
  • Raise the tone of the inner sphincter
  • Relaxation of the inner sphincter
  • Increased peristalsis in the colon
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256
Q

Parasympathetic innervation of the rectum arises from the…

A

Sacral segments

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257
Q

The outer sphincter is innervated by…

A

Motor fibres from the brain cortex

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258
Q

Under physiological conditions:

  • The rectum is…
  • Faeces are stored in the…
A
  • The rectum is empty
  • Faeces are stored in the colon
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259
Q

Faeces evacuation can be caused if…

A

15-20 Hgmm pressure is exerted on the wall of the rectum

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260
Q

Describe faeces entering the rectum

A
  • Faeces evacuation reflex
  • Receptors sensitive to rectal wall stretching
  • Afferent nerves travel to S1-S4
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261
Q

Describe faeces evacuation reflex

A
  1. Increases contraction of the rectum + peristalsis
  2. Relaxes tone of the inner sphincter
  3. Longitudinal muscles contract
  4. Rectum shortens
  5. Faecal evacuation
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262
Q

Give the characteristics of the motions of the colon

A
  1. Slow waves
  2. Transmitters in the autonomic nervous system
  3. Stimulation from pacemaker areas
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263
Q

Slow waves of the colon

A
  • Arise from the circular muscle layer
  • Spread to the longitudinal fibres
  • (Stomach - ileum)
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264
Q

Mediator effect of the autonomic nervous system is stronger than…

A

The slow waves of the colon

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265
Q

The stimuli from the pacemakers areas spread to…

A

Both directions

  • Peristalsis
  • Antiperistalsis

= Mixing

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266
Q

Aboral mass peristalsis is present in…

A

Dog and cat

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267
Q

Aboral mass peristalsis

A
  • Secondary signal sequence produced by pacemaker cells
  • AP is retained for a long time
  • Generates an elongated and strong contraction of the circular muscle layer
  • Causes evacuation of the majority of colic content
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268
Q

What are the functions of the secretory glands in the intestinal tract?

A
  • Digestive enzyme secretion
  • Mucin-rich fluid for chemical protection of mucosa
  • Secretions contribute to the optimal pH for digestive enzymes
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269
Q

How many salivary glands are there in the oral mucosa?

A

3 pairs

  • Parotid
  • Mandibular
  • Sublingual
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270
Q

Functions of saliva

A
  • Digestion - initiation and maintenance of chewing
  • Buffer capacity
  • Protection
  • Taste sensation
  • Mouth hygiene
  • Thermoregulation in carnivores
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271
Q

What gland type produces saliva?

A

Serous and mucinous salivary glands

272
Q

The function of the buccal + labial glands in: Bo/Su

A
  • Serous secretion
  • Mucinous secretion
273
Q

The function of the buccal + labial glands in: Ca/Fe

A

Mucinous secretion only

274
Q

Serous saliva contains which enzyme…

A

Ptyalin (a-amylase)

275
Q

Ptyalin cleaves…

A

1, 4 glycosidic bond of carbohydrates

276
Q

Mucinous saliva contains…

A

Mucin

  • Protects the mouth
  • Forms the bolus
277
Q

Lipase is found in

A

Saliva of the calf

278
Q

Function of lipase

A

Hydrolysis of triglycerides

279
Q

In ruminants, saliva contains a large quantity of…

A

Urea

(For microbial homeostasis in the forestomachs)

280
Q

What is the antifoaming mechanism of saliva?

A

In ruminants

  • Inhibits formation of gas bubbles
  • These wouldn’t be emptied from the forestomachs by eructation
281
Q

Rile of saliva in mouth hygiene

A
  • Moisten
  • Mashing off bacteria
  • Antibodies
  • Bacteriolytic enzymes: Lysozyme
282
Q

Give the similarities between the nephron and the salivary glands

A
  • Filtration
  • Secretion
  • Reabsorption
  • Double capillarisation
283
Q

Primary secretion occurs in the…

A

Acini

284
Q

Primary secretion

A
  • Na+, Cl-, Phosphate, bicarbonate transported to primary saliva by active secretion
  • Produced by diffusion + secretion
  • Isotonic with the plasma
  • Acini cells produce ptyalin mucin
285
Q

Double capillarisation

A
  1. Capillarisation occurs first around the tubules
  2. Then around the acini

Primary saliva flows through the tubules where secretory reabsorptive processes influence it’s composition

286
Q

Secondary secretion of saliva

A
  • Electrolyte composition change of primary saliva
    • Na+ and Cl- are partly absorbed
    • K+ and HCO3- is secreted
  • Partial water reabsorption
  • Hypotonic in monogastric animals
287
Q

Saliva in monogastric animals

  • Ion composition
  • pH
A

pH of saliva = pH of the blood (pH 7.4)

288
Q

Saliva in ruminants

A
  • Always isotonic
  • Slightly alkaline (8.2)
  • High in: HCO3- and HPO42-
  • Buffer capacity caused by their secretion
289
Q
A

60-180

290
Q
A

8-16

291
Q
A

40

292
Q
A

12-15

293
Q
A

10-12 ml

294
Q
A

1.5-2

295
Q

When dry food is consumed

A

A large amount of saliva is released

296
Q

Saliva of carnivores is rich in….

A

Mucin

297
Q

Which species has constant salivary secretion

A

Ruminants

298
Q

Regulation of quantity and composition of saliva is controlled by…

A
  • Neural reflexes
  • (Hormonal effects)
299
Q

Afferentiation of the salivary secretion reflex is by…

A
  • Chemical stimuli:
    • Taste buds
    • Mechanoreceptors of the olfactory epithelium
300
Q

Salivary secretion is observed after…

A

Activation of the salivary centre in the mesencephalon

301
Q

Innervation of the salivary glands is carried out via…

A
  • Parasympathetic (cholinergic) efferentation
  • Sympathetic (adrenergic) efferentation
302
Q

During salivary excretion, parasympathetic fibres are found…

A

Running inside the:

  • Collateral of the glossopharyngeal nerve (parotid)
  • Facial nerve (mandibular/ sublingual)
303
Q

During salivary excretion, sympathetic fibres are found…

A
  • Arising from the upper thoracic segments of the spinal cord
  • Then to the cranial cervical ganglion
  • Then to the glands through different plexuses
304
Q

What is shown in the figure?

A

Regulation of salivary excretion

305
Q
A

Acinar cell

306
Q
A

Kallikrein

307
Q
A

Bradykinin

308
Q
A

Vasodilation

309
Q

The parasympathetic release of saliva can be blocked by…

A

Atropine

310
Q

Acetylcholine released from the parasympathetic nerve fibres has its effect via…

A

The IP3 activating system of the acini cells

311
Q

There is a significant dilation of blood vessels during salivation which is resistant to atropine, what causes this effect?

A

Vasodilators

  • VIP
  • Bradykinin
312
Q
  • The Na+ absorption of the tubules is significantly modified by…
A

Aldosterone conc. of blood

313
Q

Regulation of salivary secretion in the acini is controlled by…

A
  • Parasympathetic + sympathetic nervous systems
314
Q

Give the process of parasympathetic saliva release

A
  1. Parasympathetic fibres release acetylcholine
  2. This binds to muscarine type Acetyl choline-receptors via IP3 system
  3. This increases Ca2+ in the cells
  4. Increases Na+ + Cl- secretion toward the lumen
  5. Higher enzyme secretion due to DAG + protein kinase C mechanism activation
315
Q

Give the process of sympathetic saliva release

A
  • Sympathetic innervation initiates cAMP system
  • Small volume of saliva
  • Rich in mucin (high viscosity)
316
Q

Na+ absorption of the tubules is significantly modified by…

A

Aldosterone conc. in the blood

317
Q

Tubular glands of the corpus and fundus contain…

A

Chief cells

  • Producing pepsinogen

Parietal cells

  • Producing HCl → gastric juice
318
Q

Gastric mucosa produces ‘intrinsic factor’ which has a role in…

A

Cobalamin (Vitamin B12) absorption

319
Q

Which part of the stomach produces gastrin?

A

Pylorus

320
Q

List the regions of the gastric mucosa

A
  • Aglandular region
  • Cardia
  • Fundus
  • Pylorus
321
Q

Aglandular region function

A

Microbial digestion (ruminants)

322
Q

Cardia function

A

Mucin production

  • Protection of the gastric mucosa
323
Q

Fundus function

A

HCl + pepsinogen synthesis

324
Q

The pylorus produces…

A
  • Mucin
  • Pepsinogen
  • Gastrin
325
Q

HCl is produced by…

A

Parietal cells

326
Q

Where does microbial digestion occur in the stomach of the horse?

A

The blind sac

327
Q

Where does microbial digestion occur in the stomach of the pig

A

The diverticulum

328
Q

Pepsinogen is produced by…

A

Chief cells

329
Q

The fundus produces…

A

HCl + Pepsinogen

330
Q

The antrum produces…

A

Mucin

331
Q

Why is the blood flowing off the stomach slightly alkaline?

A

HCO3- ions are transported to the interstitium during HCl secretion

332
Q

Which part of the parietal cell secretes HCl?

A

The canaliculi

333
Q

Describe HCl production in parietal cells

A
  • H+/K+ pump moves H+ into the lumen and K+ into the cell
  • K+ flows out of the cell via K+ channel
  • Cl- channel into the lumen
334
Q

Describe the formation of H+ in parietal cells

A
  • Water dissociation
  • H2O → OH- + H+
335
Q

Give the fate of the OH- molecules produced by the dissociation reaction in parietal cells

A

OH- + CO2 → HCO3

Carbonic anhydrase enzyme

336
Q

The HCO3- by-product of parietal cells is released via…

A

Anion-exchange pump

in the basal membrane

337
Q

Where is pepsinogen stored?

A

In the granules of the chief cells

338
Q

Pepsinogen is degraded to pepsin at what pH?

A

2

339
Q

Role of pepsin

A
  • Autocatalytically activates other pepsinogens
  • If pH= 1.8-3.8​ hydrolysis of peptide bonds in:
    • Phe
    • Tyr
    • His
340
Q

Pepsin can degrade proteins better if…

A

The proteins are denatured by HCl/heat

341
Q

Causes of pepsinogen release

A
  • Vagus nerve stimulation
  • Low blood sugar level (induced by insulin)
  • Histamine → HCl secretion → Pepsinogen release
342
Q

Describe cells producing mucin

A
  • Epithelial cells of the gastric mucosa
    • Release mucin + bicarbonate on the luminal surface
  • pH of mucosa is therefore neutral
343
Q

Regulation of parietal cells is divided into which phases?

A
  1. Cephalic phase
  2. Gastric phase
  3. Intestinal phase
344
Q

How are pepsinogen-producing cells regulated?

A
  • Indirect HCl production by parietal cells
  • Higher [HCl] in the stomach → Higher pepsinogen release
345
Q

HCl production in parietal cells is influenced mainly by…

A

Neuronal + endocrine regulation

  1. Acetylcholine (released from paras. vagus nerve)
  2. Gastrin (released from G-cells
  3. Histamine (produced by H-cells)
346
Q

Cephalic phase

A

Proceeded through the nervous system

  1. Food stimulates taste buds
  2. Stimulus → CNS
  3. Efferentation (via vagus) stimulating chief and parietal cells*
  4. Indirect stimulation of gastrin-producing cells*
  5. 3+ 4 cause gastric secretion

*These steps occur in parallel

347
Q

Gastric phase (Acetylcholine effect)

A
  1. Gastric stretch + chemoreceptors stimulated by bolus
  2. Chief + parietal cells stimulated
348
Q

Gastric phase (gastrin effect)

A
  1. G-cell activation → Gastrin secretion
  2. Gastric secretion until pH=3
349
Q

Gastric phase (histamine effect)

A
  1. Gastrin stimulated H-cells → Histamine production
  2. Parietal cells have an H-receptor → Increased HCl
350
Q

If the pH of the stomach is less than 3…

A

Gastrin secretion of G-cells is blocked

351
Q

The effect of histamine in the presence of gastrin is…

A

Multiplied

352
Q

The effects of histamine can only be blocked by antihistamines blocking…

A

H2 receptors

Most antihistamines block H1-receptors only

353
Q

Histamine receptors of the parietal cells belong to the…

A

H2-receptor family

and not the widespread H1 receptor family

354
Q

Give the regulatory effect during the gastric phase

A
  1. Acetylcholine released (acts as a mediator)
  2. Acetylcholine binds to muscarine-type receptors on:
    1. G-cells
    2. H-cells
    3. Parietal cells
  3. The effect is mediated by the increase of IC Ca2+
355
Q

Describe the secretion of gastrin from G-cells

A
  1. Gastrin-synthesising G-cells are found in the pylorus
  2. Gastrin is secreted into the blood upon:
    1. Vagal effect
    2. Chemical stimulus
356
Q

Which receptors are found on parietal cells?

A
  • m-ACh receptor (Acetylcholine)
  • Gastrin receptor
  • H2 type receptor
357
Q

Summarise the intestinal phase

A

Substances entering the duodenum which induce gastrin secretion cause gastric juice secretion

Same effect if jejunum is mechanically expanded

358
Q

Intestinal phase:

In the case of hyperosmotic, strongly acidic or lipid-rich chyme…

A

Motor and secretory activity is inhibited

359
Q

Describe the process of the intestinal phase

A
  1. Chemical + mechanical effects of the chyme induce secretion of:
    1. Secretin
    2. CCK
    3. GIP
    4. V|P
  2. These effects inhibit HCl production + gastric motility
360
Q

Describe Vitamin B12 absorption

A
  • Stomach mucosa produces intrinsic factor
  • This absorbs Vitamin B12 into the ileum
361
Q

Deficiency of Vitamin B12

A
  • Anaemia develops
  • Caused by lack of absorption
    • Caused by absence of transcorrin
362
Q

Source of Vitamin B12

A

Synthesised by microorganisms

363
Q

Cobalamin

A
  • Bound to a complex
  • Released in the stomach, binding to R-protein (salivary origin)
364
Q

In the duodenum, trypsin digests…

A

R-protein

Releasing vitamin B12

365
Q

Describe the specialised receptors on the epithelial cells in the ileum

A
  • Selectively bind B12-IF complex taking them to the cell if:
    • pH > 5.6
    • Ca2+ are present
366
Q

Cobalamin entering the blood plasma may bind which transporting proteins?

A
  • Transcobalamin 1 (TC1)
  • Transcobalamin 2 (TC2)
  • Transcobalamin 3 (TC3)
367
Q

TC1 function

A

Stores cobalamin in the plasma

368
Q

TC3 function

A

Transfers cobalamin to the liver

where it is stored and excreted

369
Q

TC2 function

A

Passes cobalamin to almost all mitotically dividing cells

370
Q

The exocrine product of the pancreas

A

Pancreatic juice

371
Q

Roles of pancreatic juice

A
  • Neutralise contents of the duodenum and colon (Buffer)
  • Enzyme activity - digesting:
    • ​​Proteins
    • Fats
    • Carbohydrates
372
Q

What regulates the secretion of pancreatic juice?

A

Composition and amount chyme in the initial segment of the ileum

373
Q

Describe pancreatic juice production

A
  • Exocrine cells organised into acinar cells
    • Containing zymogen granules
  • Drainage tubules
    • Produce bicarbonate
374
Q

Describe the primary pancreatic secretion

A
  • Produced by acinar cells
  • Isotonic
  • Contains pancreatic enzymes + proenzymes
  • Highly concentrated
375
Q

Describe pancreatic juice secretion

A
  1. Primary secretion
  2. Ions secreted into the intralobular duct
  3. HCO3- is secreted influenced by secretin
  4. Ion pump secretes bicarbonate and takes up Cl-
376
Q

Effect of flow rate on pancreatic juice composition

A
  • Anion conc. independent of flow rate
  • Low enzyme conc.
  • High water + electrolyte production
    • Can be increased by stimulus
377
Q

Pancreatic juice

A

6-9.5

378
Q

Pancreatic juice

A

6-8

379
Q

Pancreatic juice

A

0.2-0.5

380
Q

Pancreatic juice

A

0.3-0.9

381
Q

Pancreatic juice

A

0.06-1

382
Q

Pancreatic juice

A

0.0015-0.02

383
Q

Pancreatic juice

A

1.2-1.5

384
Q

Bicarbonate is produced in…

A

Tubular cells

385
Q

Describe HCO3- production

A
  1. Na+/H+ pumps H+ toward interstitium
  2. H+ released from water decomposition
  3. OH- + CO2 → HCO3- with carbonic anhydrase
  4. HCO3- → Lumen via bicarbonate channel
  5. Na+ + K+ + H2O enter lumen
386
Q

Pancreatic proenzymes

A
  • Activated in the lumen of the ileum
  • Activated by enzymatic cleavage in the duodenum
  • Initiated by enteropeptidase (brush border enzyme)
    • Produces trypsin from trypsinogen
387
Q

Secretory activity of the ducts and acinar cells are regulated by…

A
  • Hormones
  • Neurotransmitters
388
Q

The effect of vagal stimulus on pancreatic juice secretion

A
  • Increased enzyme secretion
  • An increase of electrolytes + water
389
Q

The effect of the sympathetic stimulus on pancreatic juice secretion

A
  • Pancreatic juice decreased
  • Secretin + CCK release
  • Water-electrolyte + enzyme content altered
390
Q

Pancreatic juice regulation during the cephalic phase

A
  • Small volume of pancreatic juice released
  • High protein content
391
Q

Pancreatic juice regulation during the gastric phase

A
  • Parasympathetic predominance
  • Gastrin appears in blood, secreted in the stomach
  • Increased enzyme secretion
392
Q

Pancreatic juice regulation during the intestinal phase

A
  • Stimulated by secretin
  • Presence of peptides/amino acids leads to enzyme rich secretion
  • Presence of fatty acids/monoglycerides leads to CCK secretion
  • Secretin + CCK amplify each others effect
393
Q

Secretory and excretory functions of the liver

A
  • Bilirubin secretion
  • Carb, lipid and protein metabolism
  • Glycogen storage
  • Bile production (emulsifies lipids)
  • Parenchyma cells
    • Bile salts
    • Cholesterol
    • Phospholipids
  • Epithelial cells
    • Electrolytes
394
Q

The openings of the biliary duct into the duodenum form a circular ring called…

A

Oddi-sphincter

expressed well in carnivores

395
Q

Fate of pancreatic juice in goats and sheep

A

Juice flows into the bile duct

396
Q
A

Perisinusoid gap

397
Q
A

Pericellular space

398
Q
A

Junctional complex

399
Q
A

Bile canaliculi

400
Q

The wall of the sinusoids between liver cells is formed by…

A

Fenestrated endothelial cells

401
Q

Perisinusoid space is found…

A

Between endothelial cells and liver cells

402
Q

What can be found between liver cells?

A

Bile canaliculi

403
Q

Which species have periodical bile evacuation?

A

Cats + Dogs

404
Q

Bile in the gall bladder can be condensed 20-30x by…

A

Reabsorbing:

  • NaCl
  • Water
  • NaHCO3
405
Q

Fate of bile in the horse

A

No gall bladder:

  • Continuous evacuation to the duodenum in high amounts
406
Q

List the components of the bile

A
  • Bile salts
  • Cholesterol
  • Lecithin
  • Bile pigment
  • Electrolytes
407
Q

Lecithin and cholesterol play an important role in…

A

Formation of micelles containing bile salts

408
Q

Because of the amphipathic character of the lecithin molecule it can be…

A

Detected in the border of micelles

409
Q

What can be traced inside the micelle?

A

Cholesterol

410
Q

What increases the amount of dissolved cholesterol in micelles?

A

Lecithin

411
Q

If the amount of cholesterol is high in the bile…

A
  • Lecithin solubilises the solution
  • Extra solution may form crystals (Pathological significance)
412
Q

What forms 50% of the dry mass of bile?

A

Bile acids

these are synthesised from cholesterol

413
Q

Give examples of bile acids

A
  • Cholic acid
  • Chenodeoxycholic acid
414
Q

Primary bile acids can be conjugated with…

A
  • Taurine
  • Glycine

in liver cells

415
Q

The function of conjugation of bile acids

A
  • Increases water solubility
  • Increasing emulsification efficiency
416
Q

Primary bile acids are dehydroxylated by…

A

Bacteria in the intestines

  • Forming secondary bile acids
417
Q

Deoxycholic acid is the product of…

A

Cholic acid

418
Q

Lithocholic acid is the product of…

A

Chenodeoxycholic acid

419
Q

Conjugated bile acids form…

A

Bile salts

Made mainly Na+ cations

420
Q

Micelles

A
  • Aggregated bile salts
  • Hydrophobic parts turn inward
  • Hydrophilic parts turn outward
421
Q

Bile acid function

A

Emulsify nutritional lipid in mixed micelles

422
Q

Where are bile acids reabsorbed?

A

Terminal ileum

423
Q

What deconjugates and dehydroxylates bile acids?

A

Bacteria in the terminal ileum

  • increasing lipid solubility
  • and increasing absorption with passive diffusion
424
Q

Bile acids enter the blood via

A

Portal vein

then taken up by hepatocytes

425
Q

The life cycle of bile acids is known as…

A

Enterohepatic circle of bile acids

426
Q
A

Cholesterol

427
Q
A

Liver

  • Primary bile acids
428
Q
A

Cholic acid

429
Q
A

Chenodeoxycholic acid

430
Q
A

7a-dehydroxylation

431
Q
A

Deoxycholic acid

432
Q
A

Intestines

  • Secondary bile acids
433
Q
A

Lithocholic acid

434
Q

What is shown?

A

Conjugation of bile acids

435
Q

Why doe cholic acid and chenodeoxycholic acid dissolve weakly in the bile or duodenum?

A

Because they dissociate at a slightly alkaline pH

436
Q
A

Primary bile acid

437
Q
A

Conjugation

438
Q
A

Primary bile acid

439
Q
A

Secondary bile acid

440
Q
A

Bacterial dehydroxylation

441
Q
A

Passive

  • From jejunum
442
Q
A

Active

  • From the ileum
443
Q

95-98% of bile salts are absorbed from the…

A

Ileum

444
Q

What inhibits bile acid synthesis?

A

Repression mechanism

Bile salts transported to liver by the enterohepatic circle cause inhibition

445
Q

Why do absorbed and secreted bile acids increase the amount of the secreted bile?

A
  • Bile salt anions and accompanying Na+ attract water into the lumen
  • Osmotic activity therefore depends on bile acid conc.
446
Q

What is required for gall bladder evacuation?

A

Vagus nerve activity (Paras.)

447
Q

Substances causing gall bladder emptying are called…

A

Cholagogues

448
Q

What inhibits gall bladder contraction?

A
  • Sympathetic nervous stimuli
  • VIP
449
Q

Effect of lipid metabolites on gall bladder contraction

A
  1. Lipid metabolites → CCK release
  2. CCK → Gall bladder contraction
450
Q

When does bile synthesis in the liver reach maximal level?

A

When absorption of bile acids is temporarily ceased

451
Q

When can the gall bladder reduce its volume by 20-30x?

A

During significant Na+, Cl- and bicarbonate ion absorption

452
Q
A

Secretin

453
Q

Bile produced by secretin regulation is…

A

Diluted with a high level of bicarbonate

454
Q

Secretin plays a role in…

A

Buffering the intestinal fluid

similarly to pancreatic juice

455
Q

High intestinal lipid content increases…

A

Cholecystokinin release from the mucosa

  • Results in gall bladder contraction + Oddi sphincter relaxation
456
Q

How do bile salts regulate bile synthesis?

A
  • Inhibit synthesis of bile salts
  • Increase bile production (choleretic effect)
457
Q

List the regulators of bile synthesis

A
  • Bile salts
  • Cholecystokinin
  • Secretin
  • Vagus nerve
458
Q

Secretion of the glands in the duodenum is increased due to…

A
  1. Local mechanic effects
  2. Parasympathetic stimulus (Vagus)
  3. Hormones of the ileum (Secretin primarily)
459
Q

Inorganic components of the ileum are produced in the…

A

Lieberkuhn crypts

460
Q

The conc. of intestinal juice is similar to that of…

A

Plasma filtrate

  • However bicarbonate conc. increases in contradiction to chloride with increasing distance from pylorus
461
Q

Function type of undifferentiated enterocytes

A

Secretory

Later becoming absorptive

462
Q

What is secreted from the Lieberkühn crypt?

What are their functions?

A
  • Cl-
  • H2O
  • Primary function - Dilute intestinal content
  • Secondary function - Buffer intestinal content
463
Q

Describe secretion in the small intestine

A
  • Na+/K+/2Cl- co-transporter in basolateral membrane
  • Na+ → cell→ lumen
  • K+ → Interstitium (via K+ channel)
  • Cl- → Lumen (via channel protein)
    • This is regulated by VIP receptor by increasing cAMP level
464
Q

Effect of cholera in the small intestine

A
  1. Cholera toxin maintains high cAMP conc. by stimulating adenylate-cyclase
  2. Cl- channel remains open
  3. Cl- and water get into the intestinal lumen
465
Q

The function of mucin in the colon

A
  • Mechanical protection
  • Faeces formation
466
Q

The function of bicarbonate in the colon

A

Buffering the volatile fatty acids

467
Q

The colon doesn’t possess…

A

Villi

468
Q

Lieberkühn glands in the colon produce…

A
  • Mucin
  • Bicarbonate ions
469
Q

The majority of chemical reaction in the colon are processed by which reaction…

A

Hydrolysis

470
Q

Contraction of the villi is caused by…

A

Villikinin

471
Q

Give the absorption surfaces of the small intestine in order of size (starting smallest)

A
  1. Length of the intestine
  2. Folds
  3. Villi
  4. Brush border
472
Q

Movement of the villi play a role in…

A
  • Passing on nutritive material to be transported to the capillaries + lymphatic vessels
  • Influenced by villikinin
473
Q

Give the classifications of enterocyte

A
  1. Absorptive cylindrical epithelium
  2. Mucinous cells
  3. Enteroendocrine cells
  4. Paneth’s cells
  5. Non-differentiated cylindrical epithelium
474
Q

Location of non-differentiated cylindrical epithelium

A

At the base of the crypt

475
Q

Which is the most abundant enterocyte cell type?

A

Absorptive epithelial cell

476
Q

Location of enterocyte cell division

A

Base of the crypts

477
Q

Mature enterocytes are released from…

A

The apex of the villus

478
Q

Enterocyte division rate is affected by…

A

Gastrin

479
Q

Cellulose can be broken down only by…

A

Microbial fermentation

480
Q

Describe hydrolysis of starch in the oral cavity

A

Ptyalin in the saliva cleaves the molecules

481
Q

Describe starch breakdown in the small intestine

A

Two phases:

  1. Alpha-amylase from the pancreatic juice reduces molecule size
  2. Molecules are cleaved to its basic units in the brush border
482
Q

Monosaccharides are primarily digested in the…

A
  • Duodenum
  • Upper jejunum
483
Q

Glucose and galactose enter the enterocytes via…

A

Co-transporter

Exchange of Na+ + glucose + galactose

484
Q

Ptyalin cleaves…

A
  • Only the straight chain of starch (1, 4 glycosidic bond)
  • This forms:
    • Maltose
    • Maltotriose
    • Dextran
485
Q

Describe carbohydrate breakdown in the stomach

A
  • Swallowed boluses form layers
  • They are mixed with the gastric juice
  • Gastric juices denature salivary amylase
486
Q

Carbohydrate digestion in the small intestine is…

A

A biphasic process

487
Q

Phase 1 of carbohydrate digestion in the small intestine

A

Alpha-amylase hydrolyses starch to di- and oligosaccharides

488
Q

Phase 2 of carbohydrate digestion in the small intestine

A
  • ‘Brush-border digestion’
  • Small molecules bind to specific receptors → Enzymatic effects
  • Localised on the enterocyte surface
  • Generation of monosaccharides
  • Transport to blood
489
Q

Fructose absorption

A
  • GLUT-5 transporter needed
  • Found in both the:
    • Luminal membrane
    • Basolateral membrane
490
Q

Glucose/galactose absorption

A
  1. Luminal receptor takes up glucose/galactose (Only after binding Na+)
  2. Conformational change
  3. The two molecules are released intracellularly
  4. Glucose/galactose binds to GLUT-2
  5. Glucose/galactose enters intestinal space
491
Q

Carbohydrate breakdown in the colon (Herbivore)

A
  • Fibrous carbohydrates can only be digested by microbial enzymes
  • Microbial fermentation produces volatile fatty acids (VFA)
  • 75% of energy is provided by VFAs
492
Q

Carbohydrate breakdown in the colon (Carnivore)

A
  • An amount of soluble carbohydrate isn’t digested and absorbed from the small intestines
  • This would be lost without microbial digestion (Caecum/colon)
  • Unabsorbed carbohydrates affect the osmotic pressure
  • Cause a loss of water if they weren’t digested to VFAs
493
Q

Requirements of microbial digestion in the large intestine

A
  • Neutralisation of acidic products
  • Ensuring ‘retention time’
  • Dilution of fermentation products
  • Acidic end-product absorption
494
Q

Fundamental conditions for microbial digestion

A
  • Neutralisation of acidic end products (of digestion)
  • Long retention time (to allow fermentation)
  • Proper volume of fluid in the large intestine
    • So that microbial processes aren’t inhibited
  • Continuous absorption of the end products
495
Q

Which buffer systems are responsible for the proper pH of the large intestines?

A
  • Bicarbonate buffer
  • Phosphate buffer
496
Q

Horses and pigs largely possess which kind of buffer?

A

Bicarbonate buffer

  • From pancreatic juice and intestinal juice
497
Q

Dogs and cats largely possess which kind of buffer?

A

Phosphate buffer

498
Q

Why can bicarbonate buffer systems precisely regulate pH in the large intestine?

A

Mucosa of the large intestine is able to secrete HCO3​-

499
Q

In ruminants, phosphate originates from…

A

Saliva

500
Q

In non-ruminants, phosphate originates from…

A

Food

501
Q

Why is phosphate conc. increased in the large intestine?

A

Absorption of phosphate is weak

502
Q

Catabolism of proteins beings through…

A

Luminal digestion

  • With proteolytic enzymes produced by stomach and pancreas
503
Q

Peptides containing 2, 6 amino-acid residues appear in…

A

Small intestines

504
Q

Catabolism of oligopeptides is proceeded by…

A

Brush border digestion

505
Q

Peptidases being present in the membrane of the enterocytes catabolise…

A
  • Bound peptides to tri- and dipeptides
  • Free amino acids
506
Q

The majority of the released small peptides and amino-acids get through the luminal membrane by…

A

Secondary active transport

507
Q

How many Na+ amino acid co-transport systems are there in the brush border membrane?

A

8-10

508
Q

Protein digestion in the stomach

A
  1. Pepsinogen cleaved by HCl → Pepsin
  2. Pepsin activates other pepsinogens
  3. Pepsin hydrolyses peptide bonds of:
    1. Phe
    2. Tyr
    3. His
509
Q

Protein digestion in the small intestine

A
  1. Peptidase is produced in the duodenum and jejunum
  2. Peptidases catabolise peptides → amino acids + oligopeptides
  3. These enter the enterocyte cytoplasm via brush border membrane
  4. Amino acids + dipeptides → portal circulation
  5. Some amino acids enter the enterocytes via facilitated diffusion
  6. The other amino acids enter the enterocytes via active transport
510
Q

What activates carboxypeptidases originating from pancreatic juice?

A

Trypsin + enteropeptidase

511
Q

Fate of trypsin and chymotrypsin originating from the pancreatic juice

A

Become active enzymes in the intestines

512
Q

Trypsin hydrolyses…

A

Carbonyl bonds containing arginine or lysine

513
Q

Fate of chymotrypsin

A

Cleaves carbonyl bonds formed by tyrosine or phenylalanine

514
Q

List the brush border digestion enzymes

A
  • Amino peptidases
  • Dipeptidases
  • Dipeptidil-aminopeptidases
515
Q

Amino peptidase function

A

Cleaves amino acid from the n-terminal of the peptide

516
Q

Dipeptidase function

A

Cleaves dipeptidases to amino acids

517
Q

Dipeptidyl-aminopeptidase function

A

Cleave dipeptides from the n-terminal of the peptides

518
Q

What is released from brush border enzymes?

A

Di- and tripeptides

519
Q

Amino-acid enter enterocytes in which ways?

A
  • Facilitated diffusion (F)
  • Active transport (symport-S)
520
Q

Amino-acid transporting active transports is based on…

A

Secondary active transport (Na+ symport)

521
Q

Na-symport systems are responsible for the transport of…

A
  1. Neutral amino-acids
  2. Phenylalanine, methionine
  3. Proline, hydroxyproline
522
Q

Which amino-acid groups can get into the cell by facilitated transport?

A
  • Hydrophobic, neutral amino acids
  • Alkaline amino acids
523
Q

From among the transport mechanisms operating with Na-symport (S) which two are emphasised?

A
  1. Small hydrophilic amino-acids
  2. Structure-dependent uptake of neutral amino acids

Facilitated transport plays a role in transport of neutral, hydrophobic amino acids

524
Q

Microbial protein digestion

A
  • Protein → Amino acids in the small intestine
  • Enzymatic catabolism of protein + amino acid absorption isn’t in monogastric herbivores
525
Q

Bacterial population balances its N/metabolism using urea from…

A

Blood

526
Q

Catabolism of lipids

A
  • Most lipids are triglycerides
  • Lipids digested by pancreatic lipase
  • Bile acids emulsify lipids with lecithin
    • Fatty acids and 2-monoglycerides form micelles
  • Digested products get to the brush border
527
Q

Absorption of lipids

A
  1. Product enters enterocyte → Smooth ER
  2. Fatty acids are re-esterified (resynthesis)
  3. Triglycerides are synthesised, these absorb cholesterol and phospholipid
  4. Apolipoproteins emerge onto the chylomicron surface
  5. Further transport and metabolism
  6. Chylomicrons exit the cell through exocytosis
  7. These enter the lymphatic capillaries → to blood
528
Q

Lipid catabolism in the stomach

A
  • Lipids emptied later than other gastric content
  • Fat droplets appear
  • Inhibition of emulsion formation by high acidity
  • Duodenal lipid content inhibits gastric motility
529
Q

Lipid catabolism in the small intestine

A
  1. Bile acids + lecithin emulsify lipids
  2. The large surface area of lipids allow digestion (due to pancreatic lipase)
  3. Lipase digestion
  4. Triglycerides + phospholipids + cholesterol ester enter the intestinal canal
530
Q

Function of lipase

A
  • Cleaves ester bonds in the 1st and 3rd position of the triglycerides
  • Forms:
    • 2 x fatty acids
    • 1x 2-monoglyceride molecule
531
Q

Function of phospholipase A2

A

Cleaves phospholipids in the presence of co-lipase

532
Q

Function of cholesterol-esterase

A
  • Hydrolyses cholesterol ester
    • 2nd ester bond of triglycerides
    • Ester bonds of the other lipids (nonspecifically)
533
Q

Micelle formation

A
  • Made from
    • Lipid catabolism products
    • Bile salts
    • Cholesterol
    • Phospholipids
  • Hydrophilic inside; Hydrophobic outside
534
Q

Why do free fatty acids arriving at the enterocytes become pronated and therefore neutral ?

A

Superficial microclimate is slightly acidic

535
Q

Fatty acids becoming negative means that…

A

They can dissolve through the lipid membrane → cytoplasm

536
Q