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Physiology 2nd Midterm > Digestive 1 > Flashcards

Digestive 1 Flashcards

1
Q

Functions of the G.I. tract

A

Motility
Secretions
Digestion
Absorption
Storage and elimination
Immune barrier 

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2
Q

Function of GI tract: Motility

A

Push ingested food from the mouth toward the rectum and mixes and reduces the size of the food

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3
Q

 Function of GI tract: secretions

A

From the salivary glands, pancreas, and liver etc.
(Fluid, electrolytes, enzymes, mucus etc) 

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4
Q

Function of GI tract: digestion

A

Breakdown of food into absorbable molecules

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5
Q

 Function of GI tract: absorption

A

Nutrients, electrolytes, water etc. are absorbed from the intestinal lumen into the bloodstream

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6
Q

Function of GI tract: Storage and elimination

A

Temporary storage and subsequent elimination of indigestible food molecules

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7
Q

Function of GI tract: immune barrier

A

Prevent pathological organisms and toxins

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8
Q

Role of mouth and oropharynx

A

Top food, lubrication, initiate carbohydrate/fat digestion, and pushing the food into esophagus

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9
Q

Where does carbohydrate and fat digestion first occur

A

In mouth and oropharynx

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10
Q

Role of esophagus

A

Pushes food down to the stomach

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11
Q

Role of the stomach

A

Temporarily stores food, initiate digestion by churning and by secreting proteases and acid

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12
Q

Role of small intestine

A

Continues digestion, primary site for nutrient absorption

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13
Q

Where is the primary site for nutrient absorption

A

Small intestine

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14
Q

Role of large intestine

A

Reabsorbs fluids/electrolytes , Stores fecal matter before expulsion 

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15
Q

Role of pancreas

A

Secretes digestive enzymes into duodenum , Secretes bicarbonate to neutralize gastric acid

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16
Q

Role of liver

A

Secretes bile and stores it in the gallbladder for future delivery to Duodenum during a meal 

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17
Q

Role of bile

A

Contains bile acids, which play a key role in digestion of fats

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18
Q

What are the four layers of the wall of the G.I. tract

A
  1. Mucosa
  2. Submucosa
  3. Mascularis
  4. Serosa
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19
Q

Wall of GI tract: Mucosa

What is it and what does it consist of

A

It’s the lumen (has direct contact with food)

Consists of 3 things/layers:

  • epithelial cells : for absorption and secretion
  • lamina propria: connective tissue, blood and lymph vessels
  • muscularis mucosa : smooth muscle cells (changes surface area)
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20
Q

Wall of GI tract: submucosa

What is it and what does it consist of

A

Connective tissue

Consists of:
- blood vessels
- glands
- submucosal plexus (nerves)

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21
Q

Wall of GI tract: mascularis

What is it responsible for, and what does it consist of

A

Responsible for motility

Consists of:
- inner circular smooth muscle
- outer longitudinal smooth muscle
- myenteric plexus

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22
Q

Wall of GI tract: serosa

What is it and what is its role

A

Outer most layer for support and protection 

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23
Q

The enteric nervous system is made up of

A
  1. Submucosal plexus (Meissner’s plexus)
    
  2. Myenteric plexus
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24
Q

The submucosal plexus (Meissner’s plexus) is between

A

Submucosa and circular muscle

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25
Q

The myenteric plexus is between

A

Circular muscle and longitudinal muscle

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26
Q

Innervation of G.I. tract is done by two components

A

Extrinsic components :
1. Sympathetic
2. Parasympathetic

Intrinsic components:
3. Enteric nervous system
- myenteric plexus
- subcosal plexus

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27
Q

Which nervous system Overall innervates the G.I. tract

A

Autonomic nervous system

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28
Q

Effect of sympathetic stimulation on G.I. tract

A

Decreased G.I. activity

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29
Q

Effect of parasympathetic stimulation on G.I. tract

A

Increase G.I. activity

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30
Q

What is considered the “mini-brain of the gut”

A

Enteric nervous system

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31
Q

Effects of stimulation of myenteric plexus on GI tract

A

Increase in motor activity (motility)

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32
Q

Effect of stimulation of submucosal plexus on G.I. tract

A

Control secretion and blood flow

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33
Q

Nerves and neurons involved in parasympathetic innervation of G.I. tract

A

( long preganglionic fibers that synapse IN or near target)

  1. Vagus nerve: innervates UPPER G.I. tract
    2. Pelvic nerve: innervates LOWER G.I. tract
  • Cholinergics neurons: release acetylcholine
  • peptidergic neurons: Release substance P and VIP 
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34
Q

Fibers of Sympathetic innervation of G.I. tract

A

Short preganglionic fibers:
- synapse outside of G.I. tract

Postganglionic nerve fibers (adrenergic- release NE)
- synapse on ganglia in myenteric and submucosal plexus
Or
- directly innervate smooth muscle, endocrine, or secretory cells.

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35
Q

Actions of acetylcholine

A

Contraction of smooth muscle
Relaxation of sphincters
Increase salivary secretion
Increase gastric secretion
Increase pancreatic secretions

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36
Q

Actions of norepinephrine

A

Relaxation of smooth muscle
Contraction of sphincters
Increase salivary secretion

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37
Q

Actions of VIP

A

Relaxation of smooth muscle
Increase intestinal secretion
Increase pancreatic secretion

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38
Q

Actions of GRP

A

Increase gastric secretion

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39
Q

Actions of enkephalins

A

Contraction of smooth muscle
Decrease intestinal secretion

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40
Q

Action of neuropeptide Y

A

Relaxation of smooth muscle
Decrease intestinal secretion

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41
Q

Action of substance P

A

Contraction of smooth muscle
Increase salivary secretion

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42
Q

Ingestion of food involves two processes

A
  1. Mastication (chewing)
  2. Deglutition (swallowing)
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43
Q

What is mastication

A

Mechanical grinding/shearing of food to increase total surface area

Mixes food with saliva, lubrication to facilitate swallowing

Carbohydrates are digested by amylase 

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44
Q

What are the three phases of deglutition/swallowing

A
  1. Oral phase
  2. Pharyngeal phase
  3. Esophageal phase 
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45
Q

What initiates swallowing reflex

A

When pressure receptors in walls of pharynx are stimulated by food or drink

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46
Q

Swallowing is coordinated by

A

Swallowing center in brain stem (medulla oblongata)

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47
Q

Which nerves carry information between the G.I. tract and the medulla

A

Vagus
Glossopharyngeal

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48
Q

Oral phase of swallowing

A

VOLUNTARY

Elevation of bolus by tongue against hard palate to push it into pharynx

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49
Q

Pharyngeal phase of swallowing

A
  • respiration is inhibited
  • closure of nasopharynx
  • epiglottis closes larynx
  • peristaltic wave is initiated
  • opening of upper esophageal sphincter UES
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50
Q

Esophageal phase of swallowing

A

Bolus is pushed down the esophagus by PRIMARY peristalsis.

But if this fails clearing the bolus, SECONDARY peristalsis is initiated

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51
Q

What is peristalsis

A

A wave like contraction of muscles of esophagus that pushes food down towards the stomach via the lower esophageal sphincter LES

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52
Q

Primary peristaltic contraction creates an area of _________ pressure behind the bolus.

A

High

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53
Q

Movement of the bolus occurs because

A
  • Circular smooth muscle contracts behind, and relaxes in front of bolus
  • Longitudinal muscle contraction causes tube shortening
  • gravity
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54
Q

If lower esophageal sphincter is weak or not fully closed , what can occur?

A

Gastric reflux (heartburn)

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55
Q

Explain receptive relaxation of the stomach‘s

A
  1. Food moves down esophagus by peristalsis
  2. LES opens before arrival of food
  3. Stomach relaxes before arrival of food
  4. Filling of the stomach INCREASES relaxation of smooth muscles of stomach

Receptive relaxation REDUCES pressure and INCREASES volume of stomach

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56
Q

How much food can the stomach accommodate

A

1.5 L

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57
Q

Relaxation of both LES and stomach occur through ⁣⁣⁣⁣⁣…….

A

VAGAL fibers secreting VIP

(VIP relaxes smooth muscles)

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58
Q

Effect of vagotomy on receptive relaxation

A

Vagotomy (removing a part of the vagus nerve) will ELIMINATE receptive relaxation because the vagus nerve can no longer stimulate that relaxation

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59
Q

Structure of the stomach

A

Fundus
Body
Antrum

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60
Q

The Fundus and body of the stomach are responsible for

A

Storage

61
Q

The antrum of the stomach is responsible for

A

Mixing and emptying

62
Q

Function of the stomach

A

Storage of food
Mixing of food
Emptying of food into small intestine

63
Q

The process of mixing food in the stomach is called

A

Retropulsion

64
Q

Gastric exocrine secretions

A
  1. HCL
  2. Pepsinogen
  3. Intrinsic factor
  4. Mucus
65
Q

What cells secrete HCL

A

Parietal (oxyntic) cells

66
Q

Functions of HCL

A
  • keeps stomach free of microorganisms
  • converts pepsinogen (inactive) into pepsin (active enzyme
  • lowers pH (acidic) to below 2
67
Q

Which cells secrete pepsinogen ?

A

Chief cells

68
Q

Function of pepsinogen

A

Digestion of proteins
(when it is converted to pepsin at below pH3 by HCL)

69
Q

Which cells secrete intrinsic factor

A

Parietal cells

70
Q

Function of intrinsic factor

A
  • absorption of vitamin B12 in ileum
  • the ONLY essential component of gastric juice
71
Q

Where is vitamin B12 absorbed

A

Ileum

72
Q

What is the only essential component in gastric juice

A

Intrinsic factor

73
Q

Which cells secrete mucus

A

Mucus neck cells

74
Q

Function of mucus

A
  • protects gastric mucosa from mechanical and chemical (HCL) destruction by releasing bicarbonate
  • lubricates gastric contents
75
Q

What are the endocrine gastric secretions

A
  1. Gastrin
  2. Somatostatin
76
Q

What cells secrete gastrin

A

G cells

77
Q

Function of gastrin

A
  • stimulates acid secretion by parietal cells

(So increases HCL and pepsin)

(Reaches parietal cells via endocrine mechanism)

78
Q

Which cells secrete somatostatin

A

D cells

79
Q

Function of somatostatin

A

Inhibits G cells from producing gastrin

(Therefore no gastrin, no HCL, no pepsin)

80
Q

Paracrine gastric secretion

A

Histamine

81
Q

Which cells secrete histamine

A

Enterochromaffin-like cells (ECL)

82
Q

Function of histamine

A
  • stimulates acid secretion by parietal cells
  • stimulates enzyme secretion by chief cells

( so increase HCL and pepsinogen and pepsin)

83
Q

What part of the stomach has parietal cells

A

Body

84
Q

What do parietal cells secrete

A

HCl
Intrinsic factor

85
Q

What part of the stomach has chief cells

A

Body

86
Q

What do chief cells produce

A

Pepsinogen 

87
Q

What part of the stomach has G cells

A

Antrum

88
Q

What do G cells produce

A

Gastrin

89
Q

Which part of the stomach has mucous cells

A

Antrum

90
Q

What do mucus cells produce

A

Mucus

(In the table it also says pepsinogen) 

91
Q

Activation of pepsin

A

Parietal cells produce HCl.

Chief cells produce pepsinogen.

Pepsinogen (inactive enzyme) is then converted into pepsin (active enzyme) by HCl.

Pepsin breaks down ingested protein to short peptides

92
Q

How does the stomach protect itself from digestion

A
  1. Chief cells are extremely impermeable to HCl
  2. A layer of alkaline HCO3- mucus covers the mucosa, neutralizing the acid
  3. Mucosa cells are tightly fused to each other = no leakage of HCL
  4. Rapid rate of cell division in the mucosa
  5. Pepsin is secreted in inactive form (pepsinogen)
93
Q

What is the longest part of the G.I. tract

A

Small intestine

94
Q

What parts of the small intestine are the primary site of absorption of carbohydrates, lipids, amino acids, calcium and iron

A

Duodenum and jejunum 

95
Q

Which part of the small intestine is the main site for absorption of bile salts, vitamin B 12, water and electrolytes

A

Ileum 

96
Q

What structures of the small intestine increase surface area

A

Plicae circulares
Villi 

97
Q

What does Villi contain

A

Columnar epithelial cells
Goblet cells

98
Q

What are goblet cells

A

Mucus secreting cells

99
Q

Lamina propria forms the connective tissue core of each villus. What does it consist of ?

A

Lymphocytes
Blood capillaries
Central lacteals (lymphatic vessels)

100
Q

Absorbed monosaccharides and amino acids from the small intestine enter the _________________, while the absorbed fat enters the ________________.

A

Blood capillaries
Central lacteals

101
Q

What two cells are present in the intestinal crypt and what is their function

A
  1. Paneth cells : Secrete antibacterial molecules, and protect intestine from inflammation
  2. Stem cells : replenish cells of intestinal mucosa
102
Q

Intestinal enzymes: Disaccharidase

A

Sucrase : digest sucrose ➡️ glucose + fructose
Maltase: digests maltose ➡️ glucose + glucose
Lactase : digests lactose ➡️ glucose + galactose

103
Q

Deficiency in what enzyme causes lactose intolerance

A

Lactase

104
Q

Intestinal enzymes: peptidase

A

Aminopeptidase: Produces free amino acids, dipeptide, tripeptides

Enterokinase: activates trypsin

105
Q

Deficiency in what enzyme causes protein malnutrition

A

Enterokinase

106
Q

Intestinal enzymes: phosphatase

A

Ca2+, Mg2+ ATPase : Absorption of dietary calcium

Alkaline phosphatase: removes phosphate groups from organic molecules

BOTH are regulated by vitamin D

107
Q

Brush border enzymes:

A

Are attached to cell membrane of microvilli (not secreted into lumen)

They hydrolyze disaccharides, polypeptide, and other substrates

108
Q

Intestinal contractions and motility :

A
  1. Segmentation: mixes chyme and expose it to pancreatic enzymes and secretions
  2. Peristalsis: pushes chyme along small intestine toward large intestine 
109
Q

The dominant mixing movement in small intestine is called

A

Rhythmic segmentation 

110
Q

_____________ Are unique pacemaker cells which produce SLOW waves that depolarize adjacent muscle cells and determine the rate at which action potentials and contractions occur

A

Interstitial cells of cajal (ICC)

111
Q

The effect of ANS on rhythmic segmentation is ______________

A

Modulatory

(Meaning it can increase or decrease the slow waves produced by the ICC , but the ANS does not produce these waves)

112
Q

Effect of sympathetic stimulation on contraction intensity in small intestine

A

Decreases it (inhibits slow waves)

113
Q

Effects of parasympathetic stimulation on contraction intensity in small intestine

A

Increases it

114
Q

Propulsive movement in small intestine is called

A

Peristalsis

115
Q

Where is peristalsis faster in the small intestine

A

Proximal part > distal part

116
Q

Describe Orad and Caudad states during intestinal peristalsis

A

Orad : behind bolus
- circular contract
- longitudinal relax

Caudad: in front of bolus
- circular relax
- longitudinal contract

117
Q

Presence of bullets and small intestine causes local Distention, and this activates ______________.

A

Myenteric plexus
(b/w circular and longitudinal muscles)

118
Q

Similar to rhythmic segmentation, peristalsis is also under the control of __________, while the _________ only has a modulatory effect.

A

ENS
ANS

119
Q

Mixing movements in the small intestine is called

A

Haustrations

120
Q

Haustrations are characterized by contractions of :

A

Inner circular muscles

121
Q

Propulsive movement in large intestine are of two types:

A

Mass peristalsis

Reverse peristalsis

122
Q

Difference between mass peristalsis and reverse peristalsis

A

Mass peristalsis = strong peristalsis
- directed aborally (away from mouth)
- occurs several times a day in cecum and entire colon

Reverse peristalsis
- orally directed (towards mouth)
- gives more time to the fecal matter to expose of water absorption 

123
Q

Functions of the liver

A

Detoxification of blood
Carbohydrates metabolism
Lipid metabolism
Protein synthesis
Secretion of bile

124
Q

What does bile contain

A

Bile salts
Urobilinogen
Cholesterol
Lecithin
Bilirubin
Electrolytes
Bicarbonate

125
Q

What is the principal digestive function of the liver

A

Bile secretion

126
Q

Enterohepatic circulation

A

Bile from the liver and gallbladder are taken to the small intestine through a common bile duct. The bile emulsifies and digests fat. Then 90% of the bile secreted is reabsorbed into the hepatic portal vein back to the liver

127
Q

The bile secreted by the liver is stored and concentrated in the ______________.

A

Gall bladder

128
Q

Functions of gallbladder

A
129
Q

Pancreas secretions are both ___________ and ____________

A

Endocrine
Exocrine

130
Q

Endocrine secretions of the pancreas occur in which region

A

Islets of Langerhans

131
Q

What are the two endocrine hormones secreted by the pancreas

A

Insulin and glucagon

132
Q

Exocrine secretion of the pancreas produces

A

Pancreatic juice

133
Q

Pancreatic juice is secreted by which cell

A

Acini cells

134
Q

What does pancreatic juice contain

A

Water and electrolytes
Bicarbonate : neutralization of acid
Digestive enzymes 

135
Q

What are the digestive enzymes in pancreatic juice

A

(Hint: L DART)

Lipase
Deoxyribonuclease
Amylase
Ribonuclease
Trypsin

Etc

136
Q

Regulation of the digestive system

A

Neural mechanisms:
- ANS
Sympathetic: inhibits GI activity
Parasympathetic : stimulates GI activity

  • ENS
    Myenteric: controls contractions
    Submucosal: controls secretions and blood flow

Hormones (endocrine):
- secretin (small intestine)
- gastrin (stomach)
- CCK (small intestine)

137
Q

Reflexes in the intestine

A
  1. Enterogastric reflex
  2. Gasdtroilial reflex
  3. Ileogastric reflex
138
Q

What is enterogastric reflex

A

Signals from small intestine inhibit gastric emptying

139
Q

What is gastroilial reflex

A

Increase gastric activity causes increased motility of ileum and movement of chyme through ileocecal valve 

140
Q

What is ileogastric reflex

A

When ileum is distended, this decreases the motility and emptying of the stomach

141
Q

Regulation of pancreatic secretion is done by 

A

Hormones ( secretin and CCK)

142
Q

Regulation of pancreatic secretion by secretin

A

Released from intestinal mucosa when ACIDIC food enters intestine

Secretin goes into bloodstream > pancreas > secretion of bicarbonate = neutralization

143
Q

Dysfunction of secretin’s regulation of pancreatic secretion will lead to

A

Duodenal ulcer

144
Q

Regulation of pancreatic secretion by CCK

A

CCK is released when FATTY food enters intestine
CCK is secreted by I cells of duodenal and jejunal mucosa

CCK goes into bloodstream > pancreas > releases digestive enzymes to digest the fat , proteins and carbs

145
Q

Actions of CCK

A
  1. Contraction of gall bladder
  2. Secretion of pancreatic enzymes
  3. Secretion of pancreatic bicarbonates
  4. Growth of exocrine pancreas and gallbladder
  5. Inhibition of gastric emptying (ensures adequate digestion time)
146
Q

Both ___________ and __________ stimulate secretion of bile by the liver

A

Secretin
CCK

147
Q

___________ is a major stimulator of gallbladder contraction

A

CCK

148
Q

Which nerve is involved with gallbladder contraction and bile release into duodenum

A

Vagus (Acetylcholine)

Physiology 2nd Midterm (7 decks)

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