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Physiology Block 8 > GI System > Flashcards

GI System Flashcards

1
Q

What is the GI system

A

Alimentary tract and associated glands

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2
Q

What happens int he GI system

A
  • digestion and absoprtion of nutrients

- excretion of waste and metabolic by products

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3
Q

Where does digestion being

A

In the mouth

-secretion of saliva and mechanical breakdown

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4
Q

What happens in the stomach

A

Storage and digestions

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5
Q

What happens in the small intestine

A

Digestion and absorption

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6
Q

What happens in the large intestine

A

Storage, reabsorption and elimination

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7
Q

Where must the venous blood from the GI tract go to

A

Portal circulation before returning to heart

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8
Q

Why does the venous blood flow go to the portal circulation before returning to the heart

A
  • protection of ingested toxins

- reason for first pass metabolism of drugs

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9
Q

When is GI blood flow reduced

A

During SNS stimulation

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10
Q

When is GI blood flow increased

A

During PNS stimulation or after a meal

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11
Q

Lymphatic drainage of the GI

A

Heavy lymphatic drainage

-required for absorption of large lipids

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12
Q

Where does most action of the gut occur

A

In the tubular secretions

-small intestine

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13
Q

How does the structure of the tubular sections change along the tract

A

Changes as function changes along the tract

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14
Q

4 layers of the tubular sections (small intestine)

A
  • mucosa
  • submucosa
  • 2 mucosal layers
  • serosa
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15
Q

What is the mucosal layer and what does it consist of

A

Innermost layer that Consists of epithelium, lamina propria and muscularis mucosae

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16
Q

What part of the small intestine is closest to the food

A

The epithelium of the mucosal layer

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17
Q

What all is involved with the epithelial layer of the intestinal mucosa

A
  • absorptive cells

- secretory cells

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18
Q

What type of cells are the epithelial cells of the mucosa

A

Primarily columnar cells linked via tight junctions

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19
Q

How are the epithelial cells of the mucosa arranged

A

Into villi (increased surface tension) and crypts (site of stem cells)

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20
Q

What do the absorptive cells of the epithelial layer of the mucosa do

A

Digest and absorb ingested molecules

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21
Q

What do the secretory cells of the epithelium of the mucosa do

A

Enteroendocrine-secrete regulatory substances

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22
Q

What are all of the marts of the intestinal mucosa

A
  • epithelial layer
  • lamina propria
  • muscularis mucosae
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23
Q

Lamina propria of the mucosal layer of the GI

A
  • directly beneath epithelium
  • conneactive tissue
  • glands, nerve endings, caps and lymph vessels
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24
Q

Muscularis mucosae of the mucosal layer

A
  • thin layer of smooth muscle

- increases epithelial surface area by folding mucosal layer

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25
Q

What are the submucosal, muscular, and serosal layers of the GI

A

CT

  • more glands, blood supply, and lymphatics
  • larger nerves forming the submucosal plexus
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26
Q

What is the muscular layer of the GI

A
  • muscularis externus is outer portion of circular layer of smooth muscle
  • longitudinal layer of smooth muscle on the inner side
  • contains the myenteric plexus
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27
Q

What is inbetween the two layers in the muscular layer of the GI

A

Myenteric plexus

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28
Q

What is the myenteric plexus

A

Integration and coordination center for nervous system

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29
Q

Serosa of GI

A

Holds GI tract in place with connections to abdominal wall

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30
Q

Which of the following layers would you expect to find a high rate of cellular transport

A

Epithelium

-increased metabolic demand here, also the first place to die from lack of blood supply

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31
Q

Which of the following layers would you expect to find the most ANS control

A

Muscularis externus

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32
Q

What are the 3 layers of control in the GI system

A
  • endocrine
  • paracrine
  • neural
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33
Q

CCK in the GI

A

An endocrine modulator signaled in a paracrine fashion

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34
Q

Where does gastric come from

A

Gastric antrum (G cells)

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35
Q

What stimulates the release of gastric

A

Oligopeptides

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36
Q

What is the pathway of action of gastric

A

Endocrine

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37
Q

What is the target of gastric

A

ECL cells and parietal cells of the gastric corpus

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38
Q

What is the effect of gastric

A

Stimulation of parietal cells to secrete H+ and ECL to secrete histamine

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39
Q

What is the source for CCK

A

Duodenum (I cells)

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40
Q

Stimulus for release of CCK

A

FA, hydroluzed protein

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41
Q

Pathway of action of CCK

A

Paracrine, endocrine

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42
Q

Targets of CCK

A

Vagaries afferent terminals, pancreatic acinar cells

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43
Q

Effect of CCK

A

Inhibition of gastric emptying and H+ secretion; stimulation of pancreatic enzyme secretion, gallbladder contraction, inhibition of food intake

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44
Q

Source of secretin

A

Duodenum (S cells)

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45
Q

Stimulus for release of secretin

A

Protons

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46
Q

Pathway of action of secretin

A

Paracrine, endocrine

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47
Q

Targets of secretin

A

A gal afferent terminals, pancreatic duct cells

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48
Q

Effect of secretin

A

Stimulation of pancreatic duct secretion (H20 and HCO3)

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49
Q

Source of GIP

A

Intestine (K cells)

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50
Q

Stimulus for release of GIP

A

FA and glucose

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51
Q

Pathway of action of GIP

A

Endocrine

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52
Q

Targets of GIP

A

Beta cells of the pancreas

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53
Q

Effect of GIP

A

Stimulation of insulin secretion

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54
Q

What are the two neural control centers for the GI system

A
  • extrinsic-normal ANS

- intrinsic-entereic nervous system (ENS)

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55
Q

Extrinsic-PNS division of GI

A

Increases GI function (enteric systems)

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56
Q

Extrinsic-SNS division of GI

A

Reduces GI functions (enteric system)

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57
Q

Besides input to the GI system, what do both branches of the ANS do to the GI system

A

Carry afferent back to CNS

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58
Q

What kind of afferent information does the ANS carry back to the brain from the gut

A
  • meal contents and wall stretch

- reflex arcs on vagus called vagovagal reflexes

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59
Q

Intrinsic neural control

A
  • enteric neurons
  • in the two plexuses described before
  • receive input from sensory cells in gut
  • integrate and send info to muscle and enteroendecrine cells
  • ANS can modulate their activity
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60
Q

What can the intrinsic nervous system do for GI

A

Can direct all GI functions

  • don’t need ANS
  • release NE/Ach and the GI hormones listed previously
  • gut has its own little brain
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61
Q

GI reflex arcs

A
  • stay within the gut (control secretions, motility, etc)
  • arcs from gut to prevertebral ganglia then back to gut (one are of gut to another, gastronomic reflex)
  • arcs from gut to brain and back (pain, control of motor functions, defecation reflex)
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62
Q

Severing the favus would lead to

A

Reduced gut sensations

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63
Q

What sites GI lined with

A

Smooth muscles

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64
Q

What is the muscle that is lining the GI

A

Muscularis externus

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65
Q

How are the smooth muscles of the GI connected

A

Via gap junctions into a syncytium

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66
Q

Resting membrane potential of GI smooth muscle

A

Unstable and generates slow waves

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67
Q

How is the RPM of the gut smooth muscle altered

A

ANS innervation

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68
Q

Generated by pacemaker cells in the gut walls and carried via gap junctions to rest of smooth muscle

A

Slow waves

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69
Q

What is it called when a slow wave initiates AP

A

Spike potentials

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70
Q

When is there more spikes in a slow wave?

A

The higher the slow wave, the more spikes

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71
Q

What is the threshold of spike potentials

A

40mv

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72
Q

What channels are sued to generate spike potentials

A

Slow Ca channels, not fast sodium

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73
Q

How are the contents of the GI tact moved

A
  • peristalsis

- segmentation

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74
Q

Propulsive movement due to gut dissension

A

Peristalsis

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75
Q

Where does the contaction occur in peristalsis

A

Behind the dissension

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76
Q

Where is there relaxation in peristalsis

A

Ahead of dissension

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77
Q

What is required for peristalsis

A

Myenteric plexus

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78
Q

Mixing only, no forward movement

A

Segmentation

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79
Q

Increasing SNS activity to the gut would

A

Increase the negativity of the RMP

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80
Q

What does the SNS do to RMP

A

Hyperpolarization

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81
Q

What does the PNS do to gut RMP

A

Hypopolarizes

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82
Q

What is the GI blood supply

A

Splanchnic circulation

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83
Q

What does the GI tract receive its blood from

A

Intestinal artery

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84
Q

Where does venous blood from the GI system pass

A

Through the liver via portal vein then on to vena cava

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85
Q

Lymph flow from splanchnic

A

Does not go through liver

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86
Q

What does the intestinal artery split into

A

Caps and found in the villus of the gut

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87
Q

Make up of villi

A

Large cap beds in each villi

Larger lymphatic lacteals to aid in fat absorption

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88
Q

Local control of blood flow

A

-dependent upon metabolic demand (O2 levels) of tissue whihc would increase following a meal

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89
Q

Neural and hormonal control of blood flow to gut

A

Many paracrine substances (CCK, VIP) released by the gut increase blood flow
-SNS reduces flow, PNS increases flow

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90
Q

You are running a marathon and decide to carb load an hour before the race. Predict the effect of exercise on gut function

A

Reduced absorption of molecules

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91
Q

Prepares tract for food, initiatives by smell, sight, or thought of food

A

Cephalopod

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92
Q

Basically the same as cephalic, food in mouth increases response

A

Oral

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93
Q

Propelling food from mouth to stomach

A

Esophageal

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94
Q

Storage, mixing, and protein digestions

A

Gastric

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95
Q

Small intestine, digestion and absorption

A

Duodenal

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96
Q

Large intestine or colonic
Involved in the digestion and absorption of food, absorption of water, production of vitamins by gut flora, and storage and excretion

A

Intestinal

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97
Q

Responses of GI before/after meal

A
  • inhibit areas behind the meal

- activate the areas ahead of the meal

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98
Q

What does the cephalic and oral phase do

A

-prepares the GI tract for a meal with sight, smell, or sound of food
. Thinking about the food starts the process as well

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99
Q

What is the difference between the cephalic and oral phases

A

Only differ in stimuli

-taste of food is prominent in oral phase

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100
Q

What does the cephalic and oral phase ultimately stimulate

A

PNS stimulation to the GI system

  • increases salivary secretions
  • gastric acids secretions
  • exocrine pancreas secretions
  • release of bile from gallbladder
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101
Q

Lubrication and moistening of food for swallowing and aids in mastication and allows taste molecules to dissolve and activate taste receptors

A

Saliva

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102
Q

What begins digestions

A

Saliva

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103
Q

What is saliva

A

Mixture of serous (watery) and mucous secretions from the 3 paired glands

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104
Q

What do the parotid glands make

A

Mostly serous

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105
Q

What do the sublingual glands make

A

Secrete mostly mucous

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106
Q

What do the submandibular glands make

A

Both serous and mucous

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107
Q

How is saliva generated

A

Filtering plasma, modified as it proceeds into excretory ducts

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108
Q

How does saliva being as

A

Isotonic fluid

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109
Q

Saliva begins as an isotonic fluid, what happens to after this

A
  • modified to hypotonic and alkaline

- higher levels of K+ and HCO3- than that of plasma

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110
Q

What happens to saliva as flow rate increases

A

Hypotonicity and alkalinity reduce, although they still remain hypotonic and alkaline

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111
Q

What are the proteins and enzymes added by acinar cells to saliva

A
  • amylase
  • lipase
  • mucin
  • lysozyme
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112
Q

What does amylase added to saliva do

A

Breaks down carbs

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113
Q

What does lipase in saliva do

A

Helps digest lipids

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114
Q

What does mucin in saliva do

A

Lubication, along with water makes it mucous

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115
Q

What does lysozyme in saliva do

A

Antibacterial, keeps teeth clean

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116
Q

Does SNS or PNS increase secretion of saliva

A

Both!

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117
Q

SNS and secretion of saliva

A
  • acinar secretion

- SNS (B1 and B2) increases a little-protein rich, sticky

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118
Q

PNS and salivary secretion

A
  • acinar secretion
  • M3
  • increases a lot- watery
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119
Q

Blood flow secretion with SNS and saliva

A
  • a1

- reduces flow a lot-less saliva made

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120
Q

PNS and blood flow for saliva

A
  • M3
  • increases flow a little
  • more saliva made
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121
Q

What does SNS stimulation make for saliva

A

Makes small amounts of proteinaceous saliva

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122
Q

What does PNS stimulation do for saliva

A

Makes a lot of watery, basic saliva

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123
Q

Which of the following is true regarding the salivary gland secretion

A

It is alkalosis at high flow rates -LESS alkalotic than at low levels, but still alkalotic none the less

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124
Q

Is swallowing voluntary or involuntary

A

Initiated voluntarily, proceeds involuntarily

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125
Q

What does swallowing do

A

Moves food from mouth to esophagus and inhibits respiration during reflex

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126
Q

When does swallowing being

A

When tongue pushes a bonus of food to back of mouth, into pharynx

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127
Q

What starts the reflex of swallowing

A

Touch receptors when the food is pushed into the pharynx

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128
Q

What covers the naspharynx

A

Soft palate

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129
Q

Epiglottis during swallowing

A

Larynx is lifted and epiglottis covers opening

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130
Q

Which sphincter opens during swallowing

A

Upper esophageal

131
Q

What does pharynx do during swallowing

A

Contracts, bonus is moved into esophagus

132
Q

What does swallowing end

A

Oral phase

133
Q

What does swalllowing being

A

Esophageal phase

134
Q

What is the esophageal phase primarily

A

A transport phase that moves food bonus from mouth to stomach

135
Q

Long, muscular tube with sphincters at both ends

A

Esophagus

136
Q

What are the two sphincters of the esophagus

A
  • upper sphincter (UES)

- lower sphincter (LES)

137
Q

Striated muscle, protects trachea from swallowed food and gastric reflux

A

Upper esophageal sphincter

138
Q

Smooth muscle, protects esophagus from gastric reflux

A

Lower sphincter (LES)

139
Q

What kind of muscle is the first 3rd of the esophagus

A

Striated

140
Q

What kind of muscle is the last 2/3 of the esophagus

A

Smooth muscle

141
Q

Which part of the swallowing reflex prevents aspiration of food

A

Closure of the epiglottis

142
Q

When does the upper esophageal sphincter (UES) open

A

Opens due to swallowing reflex

  • pharynx contracts, initiates a peristaltic wave
  • food enters esophagus
143
Q

How is food propelled

A

Peristaltic wave

  • moves bonus to stomach in <6s
  • if not sufficient, distention begins another wave
144
Q

In the esophageal phase, what is released that allows the lower esophageal sphincter (LES) to open

A

VIP (vasoactive inhibitory peptide)

145
Q

What does the stomach do during the esophageal phase to get ready to receive bonus of food

A

Reflex relaxation of stomach

-receptive relaxation

146
Q

Changes initiated due to food in stomach

A

Gastric phase

147
Q

What type of functions does the stomach have

A

Both mechanical and chemical. Mainly mechanical

148
Q

What is the mechanical function of the stomach

A

Mixing, storage, and propulsion of food

149
Q

What is the chemical action of the stomach

A
  • secretes acid
  • secretes and activates pepsinogen and intrinsic factor
  • secretion of mucus, water, and HCO3-
150
Q

What is the stomach lined with

A

Columnar epithelium in gastric pits

  • gastric pits contain secretory cells
  • three areas based on type of secretion
151
Q

What are the 3 areas of the stomach based on type of secretion

A
  • cardia: behind LES, makes mucus
  • parietal: proximal stomach, oxyntic glands contain parietal and chief cells
  • pyloric:distal stomach, pyloric glands contain G cells and mucous cells
152
Q

What part of the stomach makes mucous and sits behind the LES

A

Cardia

153
Q

What part of the stomach contains oxyntic glands that contain parietal and chief cells

A

Parietal

154
Q

What part of the stomach contains pyloric glands that contain G cells and mucous cells

A

Pyloric

155
Q

Where does gastric juice come from

A

Glands

156
Q

What are the two cell types of the oxyntic glands and what do they secrete?

A
  • chief cells: pepsinogen

- parietal cells: acid

157
Q

What are the cells of the pyloric glands and what do they secrete

A
  • G cells secrete gastric

- mucous cells secrete mucous

158
Q

Stomach acid pH

A

0.8

159
Q

What kind of transport in the stomach acid

A

Lots of active transport

160
Q

What makes acid and bicarbonate in the stomach

A

Carbonic anhydrase

  • H+ pumped into stomach
  • bicarbonate exchanged for Cl- with the blood
161
Q

How do Cl- and K+ enter the stomach

A

Through channels

162
Q

What has more K+, gastric juice or plasma?

A

Gastric juice

163
Q

What the stomach lined with

A

Highly alkaline mucous coat

  • secreted by mucous glands of the epithelium
  • high bicarbonate in the mucous protects stomach cells from secreted acid
164
Q

When does pepsinogen get activated

A

Gets activated to pepsin by low pH

165
Q

What begins protein digestion

A

Pepsinogen getting activated to pepsin at low pH

166
Q

What increases the release of pepsinogen

A

Ach from ANS and ENS

167
Q

What is intrinsic factor secreted by parietal cells important for

A

B12 absorption

168
Q

What does histamine do to acid production

A

Increases it

-can take an anti-histamine for a stomach ache

169
Q

How does histamine increase acid production

A
  • ECL cells release histamine directly onto parietal cells
  • increases acid production
  • ECL cells are activated by gastric
170
Q

What are ECL cells activated by

A

Gastric

171
Q

Where is gastric secreted from

A

G cells in the antrum in response to proteins in the food

172
Q

What things are controlled by neural control for gastric secretions

A

Parietal, ECL, G cells

173
Q

Neural control of parietal cells

A
  • mediated by PNS
  • M3 receptors on parietal cells
  • increases secretion
174
Q

Neural control of ECL

A

PNS

Produces more histamine

175
Q

Neural control of G cells

A

PNS

Produce more gastric

176
Q

What is also an important stimulus for control of gastric secretions besides neural control

A

Distention of stomach

177
Q

Reducing acid production in the stomach

A

Increasing acid levels in antrum reduces acid production

  • signals the meal is over
  • D cells make somatostatin, inhibit gastric release
178
Q

Ingestion of an H2 receptor blocker would cause

A

Reduced H+ secretion

Higher gastric pH

179
Q

Vagotomy would have what effect on the stomach

A

Increase stomach pH

180
Q

How much digestion doesthe stomach actually do

A

Very little

  • bulk job is to mix and break down food into chyme
  • increase surface area for other digestive enzymes to work
  • storage to allow small intestine time to digest and absorb
181
Q

Vagovagal reflex where the stretch of the stomach wall causes relaxation and more stretch

A

Receptive relaxation

182
Q

Where does receptive relaxation take place

A

Primarily in the cardia, fundus, and upper body

183
Q

Where does mixing and propulsion take place in the stomach

A

Lower body and antrum

184
Q

Mixing and propulsion in the stomach

A

Mixing waves being in body become thronged as they approach antrum
-force chyme against pyloric sphincter to mix, churn and crush

185
Q

Gastric emptying

A

Small amounts of chyme are pushed into duodenum through pyloric

  • occurs via peristalsis of the antrum
  • pyloric pump
186
Q

Peristaltic wave for gastric emptying

A

20% of mixing waves generate a peristaltic wave

-move chyme through pyloric sphincter into duodenum of small intestine

187
Q

What ANS will give you more peristalsis

A

PNS

188
Q

What ANS will give you less peristalsis

A

SNS

189
Q

What increases gastric emptying

A
  • Stretch of stomach, due to increased motor function

- gastrin, increases activity

190
Q

What is the rate of gastric emptying tied to

A

Duodenal digestive time

  • stomach must slowly empty to allow small intestine time to work
  • enterogastric reflex
191
Q

What are the two things that are directly from the stomach that affect gastric emptying

A

Stretch of stomach

Gastrin

192
Q

This reduces action of pyloric pump and increases pyloric sphincter tone

A

Enterogastric reflex

193
Q

What is the enterogastric reflex mediated by

A

Both the ENS and ANS

  • distention of duodenum
  • irritation of duodenal mucosa
  • low pH
  • proteins and fats in duodenal chyme
  • non-isotonic chyme
194
Q

What do duodenal hormones do to emptying

A

Inhibit it

  • CCK released in response to fat in chyme
  • secretin released due to acidic chyme
  • gastric inhibitory peptide (GIP) released in response to fat and carbs in chyme
195
Q

What is CCK released in response to

A

Fats in chyme

196
Q

What is secretin released in response to

A

Acidic chyme

197
Q

What is GIP released in response to

A

Fat and carbs in chyme

198
Q

Which of the following would increase gastric emptying

A

Increased duodenal pH

199
Q

Damage to the lining of the GI tract, either in stomach ot duodenum

A

Peptic ulcer disease

200
Q

Pernicious anemia

A
  • loss of intrinsic factor
  • no B12 absoprtion
  • no new RBCs
201
Q

Which of the following would be a treatment for peptic ulcer

A

Omeprazole (proton pump inhibitor)

202
Q

What is the most critical portion of the GI system

A

Small intestinal phase

203
Q

Where does most digestion occur

A

Duodenum

204
Q

Where does most absoprtion occur

A

Jejunum

205
Q

What does the ileum do

A

Absorbs leftovers, bile, B12

206
Q

What is the intestinal phase highlighted by

A
  • increases pancreatic secretions
  • increases gallbladder contraction
  • relaxation of the sphincter of Oddi
  • interrupting the migrating motor complex
207
Q

What does the duodenum do

A

Receives chyme from the stomach and secretions from accessory glands

  • liver
  • gallbladder
  • exocrine pancreas
208
Q

What do the secretions from the accessory glands that go to the duodenum contain

A

Digestive enzymes and bicarbonate

-digestive enzymes also held in brush border along epithelium

209
Q

What is most of the pancreas

A

Exocrine

  • makes pancreatic juice
  • digestive enzymes and bicarbonate
  • separated from small intestine by the sphincter of oddi
210
Q

What is the pancreas separated from the small intestine by

A

Sphincter of oddi

211
Q

Secrete digestive enzymes in response to PNS and CCK

A

Acinar cells

212
Q

What do the acinar cells secrete

A
  • amylase (carbs) and most lipases (fats) secreted as active enzymes
  • protease and phospholipases are inactive when secreted
  • juice is added by the ductal cells
213
Q

What cells make the pancreatic juice

A

Ductal cells

214
Q

What is pancreatic juice

A

Isotonic fluid with plasma

  • Na+, Cl-, K+ and bicarbonate secreted into duct then modified
  • increases flow increases bicarbonate and reduced Cl-
  • driven by carbonic anhydrase
  • slightly acidification of pancreatic venous blood
  • flow increases in response to secretin (released due to acid in duodenum)
215
Q

What does increased flow do to pancreatic juice

A

Increases bicarbonate and reduces Cl-

216
Q

What is pancreatic secretions driven by

A

Carbonic anhydrase

217
Q

What does the pancreatic juice do to the pancreatic venous blood

A

Slightly acidified it

218
Q

What does pancreatic secretion flow increase in response to

A

Secretin (released due to acid in duodenum)

219
Q

What does secretin do for bicarbonate

A

Increases it

220
Q

What does CCK increase

A

Digestive stuff

221
Q

What is pH sensed by in pancreatic secretion

A

S cells

222
Q

What do S cells do in pancreatic secretions

A

Release secretin

223
Q

What does secretin do for pancreatic secretion

A

Increases bicarbonate secretion which is coupled to Cl-, water also follows bicarbonate

224
Q

What pathology is associated with a disruption in pancreatic secretion regulation

A

CFTR is mutated in cystic fibrosis and cause of associated pathology

225
Q

What does enzyme secretion in pacreatic secretion increase to match

A

Chyme composition

226
Q

What do fatty acids and amino acids in chyme stimulate

A

Release of two paracrine factors

  • CCK-releasing factor
  • monitor peptide
  • also release to neural input
227
Q

What does paracrine factors in pancreatic secretion do

A

Stimulate I cells

  • increase CCK release
  • CCK increases enzymatic secretion
228
Q

What does CCK do

A

Increases enzyme secretion

229
Q

What does secretin increase

A

Bicarbonate

230
Q

Which of the following is true regarding rate of pancreatic secretion

A

Increases as chyme pH decreases

231
Q

This is produced in the liver and stored and concentrated in the gallbladder

A

Bile

232
Q

What does bile aid in

A

Digestions and absoprtion of lipids

-form micelles to allow lipids to escape water environment of intestine

233
Q

What does bile consist of

A

Bile salts, cholesterol, phospholipids, water and ions

234
Q

What is the most important constituent of bile

A

Bile salts

235
Q

What happens to bile salts after meal

A

Recycled

236
Q

What is bile derived from

A

Cholesterol

237
Q

What role does liver have in bile production

A

Produces primary bile

238
Q

What role does guys bacteria have in bile production

A

Makes secondary bile acids

239
Q

What happens to the primary and secondary bile acids once they are formed

A

Liver conjugated them into bile salts

  • makes them more water soluble
  • due to cholesterol backbone, they’re also amphipathic
240
Q

What are some other things that bile is composed of

A

-phospholipids, cholesterol, bilirubin, water and ions

241
Q

What is the water and ion comp in bile similar to

A

Pancreatic juice

242
Q

What is the phospholipids, cholesterol, bilirubin, water and ions under the control of

A

Secretin

243
Q

Is bile constantly produced in the liver or just sometimes

A

Constantly

244
Q

Where is bile stored and concentrated

A

In the gall bladder

245
Q

Ejection of bile from gall bladder is under control of ______

A

CCK

246
Q

What does the terminal ileum do to bile

A

Transports bile salts back to liver

-salts are put into gallbladder

247
Q

How much bile salts are lost in stool

A

25%

248
Q

Of the bile salts that do not get excreted, what happens to them

A

Recirculation of salts back to liver increases bile release (choleretic effect)

249
Q

Predict the effect of removal (resection) of the ileum

A

Steatorrhea (fatty stool)

250
Q

Small intestine mucous

A
  • brunners glands
  • protects wall from acid
  • increased by stimulation of duodenum, secretin, and vagus tone
  • reduced by SNS tone (stress ulcer)
251
Q

Intestinal juice of the small intestine

A
  • crypts of lieberkuhn-enterocytes
  • watery mucous
  • 2L a day
  • carries peptidases, sucrose, Maltese, isomaltase, lactase, and lipases
252
Q

What are the different peptidases, sucrose, Maltese, isomaltase, lactas and lipases in intestinal juices important for

A

Smaller sugar breakdown

253
Q

Motility of small intestine when chyme is present

A

Segmentation predominates

  • mixes chyme with enzymes
  • allows for absorption along intestine
254
Q

Motilityof small intestine once digestion and absoprtion are complete

A

Peristalsis occurs to clear intestine of remnants

  • moves food bonus to large intestine for further processing
  • Ach and NO work in conjunction to constrict and dilate smooth muscle
255
Q

When does MMC occur

A

Between meals, cycles every 90 mins until inhibited by a meal

256
Q

What does the MMC do

A

Sweeps intestines clean to prepare for next meal

257
Q

What control is the MMC under

A

Hormone motilin

258
Q

What are the 3 phases of MMC

A
  • I (quiet)
  • II (small, disorganized contractions)
  • III (large peristaltic waves move along length of intestine, moves everything into large intestine)
259
Q

What are carbs broken down into

A

Monosaccharides

260
Q

What proteins broken down into

A

Amino acids

261
Q

What are lipids broken down into

A

Fatty acid and glycerol

262
Q

What happens to macromolecules before being absorbed

A

Have to be broken down

263
Q

What are all enzymatic digestions

A

Hydrolysis reactions

-adds water to break bonds between subunits

264
Q

What do dietary carbs consist of

A

Starch (grains
Sucrose (most sugar )
Lactose (milk sugar)

265
Q

Where does carbohydrate digestion being

A

Mouth

266
Q

Where does most of carbohydrate digestion happen

A

In the small intestine

267
Q

What breaks starch down into maltose

A

Amylase

268
Q

Oral amylase

A

Not necessary for digestions

269
Q

What in the small intestine helps with carbohydrate digestions

A
  • pancreatic amylase

- generates maltose and other short polysaccharides

270
Q

Enterocytes in the small intestine and carbohydrate digestion

A
  • contain enzymes in their brush border to further digest carbohydrates
  • digestion down to a single saccharaide
  • some combination of glucose, fructose, and galactose
271
Q

How are glucose and galactose transported into the cell

A

SGLT1 transporter

-co transported with Na

272
Q

How is glucose and galactose transported in the blood

A

GLUT2 facilitated transport

273
Q

How is fructose brought into the cell

A

GLUT5

274
Q

Where does protein digestion being

A

Stomach

  • pepsinogen is activated by low pH into pepsin
  • not necessary for full digestion
275
Q

Where does most digestion of protein occur

A

Small intestine

276
Q

What in the small intestine digests protein

A
  • trypsin, chymotrypsin, elastase produce oligopeptides

- oligopeptidases in the brush border produce individual amino acids

277
Q

What are single aminoacids tranpsported into the cell with

A

Na

-each amino acid has its own specific transporter

278
Q

What are di- and tripeptides cotrasnported with

A

H+

  • pepT1-peptide transporter 1
  • can be broken down into single amino acids by cytosolic enzymes
  • pepT1 is a transporter for various peptidomimetic drugs
279
Q

What do dietary lipids consist of

A

Triglycerides, cholesterol, and phospholipids

280
Q

Why are lipids difficult to digest

A

Insolutbility in water

-broken down to fatty acids and other functional groups

281
Q

Where does lipid digestion occur

A

Stomach

282
Q

What do lingual and gastric lipase generate

A

Glycerol and free fatty acids

283
Q

Stomach mixing and lipid digestion

A

Mixes lipids into small droplets

284
Q

What do lipids in the stomach increase

A

CCH production which slows gastric emptying

285
Q

What does intestinal digestion of lipids being with

A

Emulsification

  • addition of bile salts and lecithin surrounds lipid drops
  • when mixed, forms progressively smaller drops
  • increases surface area for digestion
286
Q

As intestinal digestion of lipids progresses what happens

A

Products are taken up into micelles

-increase solubility of fatty acids, not necessary for full digestion

287
Q

What does the micelle in the small intestine for lipid digestion do

A

Moves to the brush border and allows fats to enter cells

288
Q

How does free fatty acid get absorbed

A

Can cross the cell membranes without aid

289
Q

How is diffusion of fatty acids aided for absoprtion

A

By fatty acids binding proteins in epithelium

290
Q

Once inside, what happens to the free fatty acids

A

Are reesterified back into original forms and form chylomicrons (resemble single layer cell membrane sacs full of lipids)

291
Q

What happens once the fatty acids form chylomicrons

A

Exocytosed from cell, enter lymphatics, then venous blood

-too large to enter caps

292
Q

All digestive processes occur in what kind of environment

A

Water

293
Q

All secretions are dissolved in

A

Water

294
Q

GI system secreted about _______ of fluid a day

A

7L

295
Q

GI system ingests about ______ of fluid a day

A

2L

296
Q

How much fluid does the GI system reabsorb

A

All but 100mls

297
Q

Water and solutes

A

Water follows solutes, water is reabsorbed due to osmotic differences caused by solute transport

298
Q

How are fat soluble vitamins absorbed

A

With micelles, packed into chylomicrons and transported out

-ADEK

299
Q

How are water soluble vitamins absorbed

A

Co transported with Na

300
Q

What is the exception of water soluble vitamins

A

B12

  • binds intrinsic factor which protects it from digestion
  • has a specific transporter in the ileum
301
Q

What happens if you get rid of stomach or ileum?

A

You can absorb B12

302
Q

How does free iron get absorbed

A

Binds apoferrin which transports it into the blood

303
Q

Colonic phase

A

Large intestine

  • reabsorption of water
  • absorption of bacterial produced products
  • storage
  • defecation
304
Q

How does chyme enter the large intestine

A

Though the ileocecal valve

-pushed in by the MMC of the small intestine

305
Q

What is the large intestine lined with

A

Columnar epithelium cells

-no villi, but crypts present

306
Q

What does the proximal half of the large intestine do

A

Mostly handles reabsorption

307
Q

What does the distal Half of the large intestine do

A

Storage

308
Q

Haustra

A
  • muscular arrangements
  • little pockets thats turn feces back and forth to allow for reabsorption
  • movements less efficient than in small intestine
309
Q

Where does the colon end

A

In the rectum

310
Q

Muscles of the rectum

A
  • only longitudinal
  • internal smooth muscle sphincter (involuntary)
  • external, skeletal muscle sphincter (voluntary)
311
Q

What has to occur for defamation to occur

A

Coordinated reflex of the internal and external sphincter

312
Q

What are the two types of large intestine motility

A

Haustration

Mass movement

313
Q

What is haustration in the large intestine similar to

A

Segmentation in small intestine, but produces forward movment

  • allows forming feces to be fully exposed to absorptive walls numerous times
  • can take 15 hours
314
Q

What is mass movment in large intestine

A
  • modified peristalsis, usually in transverse colon to sigmoid colon
  • forces feces towards the rectum about twice a day
315
Q

Removal of waste from body

A

Defecation

316
Q

What initiates the rectosphincteric reflex for defecation

A

Feces filling the rectum

317
Q

What sphincter must you consciously release for defecation

A

External

318
Q

How are contractions of defecation begun

A

By local distention and myenteric plexus enhanced by PNS

319
Q

Increasing abdominal pressure for defecation

A

Valsalva maneuver

320
Q

What doesthe large intestine require

A

Several reflex arc that require the ANS to some degree

321
Q

Duodenalcolic and gastrocolic reflexes of large intestine

A

Presence of food in the duodenum or stomach, respectively enhance mass movement in the colon

322
Q

Gastroileal relfex in the large intestine

A

Food in stomach opens ileocecal valve and allow remnants to enter colon

323
Q

Large intestine secretions and transport

A
  • epithelium secretes mucus to lubricate feces as it moves
  • absorbs water from feces (lost 100-200mls per day in feces, can reabsorb up to 3x more than normal if diarrhea occurs, primarily passive)

Physiology Block 8 (7 decks)

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