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z:Physl 210A/B > GIT Lec 1: Intro > Flashcards

GIT Lec 1: Intro Flashcards

1
Q

Function of GIT

A
  • transfer of nutrients, minerals, water from external to internal
    (digestion - absorption - excretion)
    -immune defense (host defense) - GIT is continuous with exterior
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2
Q

Digestion is

A

chemical changes of food to absorbable materials

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3
Q

Absorption is

A

transfer of digested food from intestine into blood and lymphatic vessels

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4
Q

Excretion is

A

removal of components not absorbed

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5
Q

Things that are excreted

A

bacteria, intestinal cells, drugs, cholesterol, steroids

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6
Q

Two parts of the GI system

A

tract and accessory organs

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7
Q

Tract in GIT is composed of

A

mouth, pharynx, esophagus, stomach, small intestine, large intestine

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8
Q

Accessory organs of GIT

A

pancreas, liver, gall bladder

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9
Q

composition of muscle from top of esophagus..

A

skeletal muscle

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10
Q

composition of muscle from mid-esophagus to anus..

A

smooth muscle

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11
Q

Layers of GIT (LUMEN TO EXTERIOR)

A
  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa
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12
Q

Layers of Mucosa

A
  1. Epithelium
  2. Lamina propria
  3. Muscularis mucosa
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13
Q

Epithelial layer has..

A
  • polarized layer (basolateral and apical side)

- villi and microvilli (cellular level)

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14
Q

basolateral

A
  • also serosal, blood

- facing blood vessels

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15
Q

apical

A
  • luminal,mucosal

- facing lumen

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16
Q

SA of GIT increased by

A

villi (finger-like projection in epithelial layer), microvilli, crypts (invaginations in epithelial layer)

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17
Q

Epithelial layer performs…

A

selective uptake of nutrients, electrolytes, water

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18
Q

polarized layer of epithelium caused by

A

different transport proteins at apical and basolateral surface and tight junctions that prevent movement of transport proteins to membrane regions

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19
Q

Crypts in epithelial layer..

A

have stem cells that divide and migrate up the villus (rapid cells turnover)

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20
Q

paracellular pathway through epithelium (GIT)

A
  • between the cells
  • limited by tight junction seal
  • water, small ions pass through
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21
Q

transcellular pathway through epithelium (GIT)

A
  • through the cells

- 2 step (transport on apical side then basolateral)

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22
Q

Lamina propria

A
  • second layer of mucosa after epithelial layer

- connective tissue, small blood vessels, nerve fibers (end), lymphatic vessels, immune cells

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23
Q

Muscularis mucosa

A
  • third layer of mucosa after epithelial layer and lamina propria
  • thin layer of smooth muscle for villi movement not contraction of GIT
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24
Q

Submucosa

A

-second layer of GIT after mucosa

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25
Q

Submucosa has

A
  • nerve cell bodies, that relay info from mucosa

- connective tissue, blood, lymphatic vessels

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26
Q

Muscularis externa

A

-third layer of GIT, after mucosa, submucosa before serosa

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27
Q

Muscularis externa has..(layers)

A
  • thick inner layer of circular muscle
  • myenteric nerve plexus
  • thin outer layer of longitudinal muscle
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28
Q

myenteric nerve plexus

A

plexus of nerves from the sympathetic and parasympathetic systems between the two layers of muscle in the small intestine

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29
Q

Thick inner layer of circular muscle in small intestine is responsible for the..

A

narrowing of lumen

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30
Q

Thin outer layer of longitudinal muscle is responsible for the..

A

shortening of tube

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31
Q

Serosa

A
  • last layer of GIT

- connective tissue, encasing intestine, connection to abdominal wall

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32
Q

Blood moves in GIT through

A

intestine then liver through via portal vein

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33
Q

portal vein drains..

A

blood from digestive tract into the liver

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34
Q

blood in the portal vein is

A

nutrient rich but oxygen poor

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35
Q

blood circulation between gut and liver is called…

A

portal circulation

36
Q

the purpose of portal circulation is..

A

to remove harmful materials and process nutrients

37
Q

the unique aspect of blood supply to the liver is..

A

it has arterial and venous circulation via hepatic artery and portal vein

38
Q

GI secretion and motility is controlled by..

A

-volume of type of contents

39
Q

Reflexes of GIT caused by..

A
  • distension of wall by luminal contents
  • osmolarity of contents
  • pH of contents
  • concentration of monosacc., fatty acids, peptides, a.a
40
Q

Reflexes measured by..

A
  • mechanoreceptors (pressure, stretch)
  • osmoreceptors (osmolarity)
  • chemoreceptors (binding of specific chemicals)
41
Q

The enteric nervous system is…

A
  • the intrinsic nervous system in GIT
  • “brain of the gut”
  • dense and complex network of neurons (10^8)
42
Q

The enteric nervous system controls..

A

the activity of secretomotor neurons

43
Q

Secretomotor neurons control

A

motility and secretory function

44
Q

The enteric nervous system can function

A

independently of CNS which is crucial for involuntary function

45
Q

The enteric nervous system has two nerve networks:

A
  • submucosal plexus (innermost)

- myenteric plexus

46
Q

Submucosal plexus influences

47
Q

myenteric plexus influences

A

smooth muscle

48
Q

Extrinsic regulation of GIT is by

A

autonomic nervous system (parasympathetic and sympathetic)

49
Q

Autonomic nervous system influences..

A

motility and secretion of GIT

50
Q

Extrinsic factors that influence motility and secretion of GIT

A
  • hunger
  • sight/smell of food
  • emotional state
51
Q

parasympathetic (rest/digest) system (GIT)

A

-simulates saliva, peristalsis, gallbladder, secretion

52
Q

sympathetic (fight/flight) system (GIT)

A
  • stimulates saliva

- inhibits peristalsis,gallbladder, secretion

53
Q

Short reflexes in GIT:

A

stimulus => receptors => nerve plexus => smooth muscle/gland => response

54
Q

Long reflexes in GIT:

A

stimulus => CNS => efferent autonomic neurons => nerve plexus

55
Q

types of chemical messengers:

A
  • endocrine
  • neurocrine
  • paracrine
  • autocrine
56
Q

endocrine

A

hormone target cells by blood circulation in distant places in the body

57
Q

neurocrine

A

neurotransmitter effects neuron/effector close by

58
Q

paracrine

A

chemical messenger released by cell to effect nearby cells

59
Q

autocrine

A

chemical messenger released by cell to act on itself

60
Q

endocrine cells in GIT are (location)

A

on the epithelium of the stomach and small intestine

61
Q

endocrine cells in GIT (lumen vs lamina propria)

A

substances in lumen stimulates hormone release on basolateral side into blood vessels in lamina propria

62
Q

Four main GI hormones

A
  • secretin
  • cholecystokinin (CCK)
  • gastrin
  • glucose dependent insulinotropic peptide (GIP)
63
Q

Four main GI hormones generalized

A
  • all peptides
  • feedback control system
  • target more `than one type of cell
64
Q

gastrin released by

A

G cells in stomach antrum

65
Q

stimuli for gastrin release

A

peptides/a.a in stomach, parasympathetic nerves

66
Q

gastrin major actions

A
  • increases HCl in stomach

- increases motility of stomach, ileum, large intestine

67
Q

secretin released by

A

S cells in small intestine

68
Q

stimuli for secretin release

A

acid in small intestine (pH<4.5)

69
Q

secretin major actions

A
  • decreases HCl
  • decreases stomach motility
  • increase bicarbonate and water from pancreas and in bile
70
Q

CCK released by

A

I cells in small intestine

71
Q

stimuli for CCK release

A

digested fat/protein in small intestine

72
Q

CCK major actions

A
  • decreases HCl
  • decreases stomach motility
  • increases enzymes from pancreas
  • increase bile expulsion
73
Q

GIP released by

A

K cells in small intestine

74
Q

stimuli for GIP release

A

glucose or fat in small intestine

75
Q

GIP major actions

A

-increases insulin before sugar is absorbed into blood

76
Q

Intestinal motlity

A

-contraction and relaxation of two outer smooth muscle layers of GIT allows movement of contents from one site to another

77
Q

Two components of intestinal motility

A

peristalsis and segmentation

78
Q

peristalsis (propulsion)

A
  • first => oral side: circular muscle contracts and longitudinal relaxes
  • second => anus side: circular muscle releases and longitudinal contracts
79
Q

segmentation (mixing)

A
  • contraction and relaxation of intestinal segments

- little net movement towards large intestine

80
Q

segmentation occurs in

A

small intestine for the mixing of contents with enzymes, absorption of nutrients and water

81
Q

GIT pacemaker cells are in

A

smooth muscle

82
Q

GIT pacemaker cells are (action)

A

constantly undergoing spont. depolarization and repolarization cycles known as slow waves

83
Q

slow waves are

A

basic electrical rhythm of GIT (below threshold)

84
Q

Frequency of contraction in GIT is set by

A

slow waves, basic electrical rhythm,

85
Q

Slow waves are propagated

A

through circular + longitudinal muscle layer through gap junctions

86
Q

neural + hormonal input and slow waves

A

depolarize membrane and bring it to threshold for contractions to occur

87
Q

action potentials is proportional to

A

force of contraction which is mediated by neuronal/hormonal input

z:Physl 210A/B (28 decks)

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