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Bio 66 > Chapter 18 The Digestive System > Flashcards

Chapter 18 The Digestive System Flashcards

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1
Q

MOTILITY is

A

Movement of food through the gastrointestinal (GI) tract via:
Ingestion
mastication
deglutition
contraction of smooth muscles: peristalsis, segmental contractions

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2
Q

SECRETION is

A

Release of exocrine and endocrine secretions into lumen of GI tract for digestion

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3
Q

DIGESTION is

A

Chemical/mechanical breakdown of food from macromolecules to smaller molecules, for absorption

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4
Q

ABSORPTION is

A

Transport of digested end products into blood/lymph

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5
Q

STORAGE AND ELIMINATION is

A

Temporary storage followed by elimination of indigestible food molecules

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6
Q

IMMUNE BARRIER is

A

Immune system cells in connective tissue outside of intestinal epithelium AND physical barrier to pathological organisms and toxins due to tight junctions in epithelial lining of intestine.

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7
Q

How does digestion occur by

A

hydrolysis reactions

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8
Q

Gastrointestinal (GI) Tract/Alimentary Canal is made up of

A 
Mouth
pharynx
esophagus
stomach
small intestine
large intestine
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9
Q

Accessory Organs and Tissues are made up of

What do they do

A 
Teeth
tongue
salivary glands
liver
gallbladder
pancreas

Secrete substances into the tract via connecting ducts

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10
Q

What does the mouth produce

A

Salivary amylase
Lipase
Water

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11
Q

What does the stomach produce

A

HCL
Pepsinogen
Mucus
Intrinsic Factor

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12
Q

What does the Small intestine produce

What do they do

A

Bile
Bicarbonate
Enzymes

Absorb nutrients

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13
Q

What does the large intestine do

A

Absorb water/vitamins

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14
Q

What are the 4 layers of the gut wall

A

Mucosa
Submucosa
Muscularis
Serosa

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15
Q

What is the first layer (innermost)

What does it do

What is unique about it and what does this do

A

MUCOSA:

Absorption and secretion
Mucus secretion

Muscularis mucosae (FOLDS):
Folds increase surface area for absorption
Produces movement of villi

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16
Q

What is the second layer

What does it have

A

SUBMUCOSA:

Connective tissue that serves mucosa
Blood/lymph vessels

Submucosal plexus: neuronal innervation for muscularis mucosae

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17
Q

What is the third layer

What is its main function

What is different between its outside and inside

A

MUSCULARIS EXTERNA:

Involved in segmental and peristaltic contractions, to move food through tract, and pulverize and mix it with digestive enzymes

Inner circular layer of smooth muscle

Myenteric plexus: neurons for entire GI tract

Outer longitudinal layer of smooth muscle

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18
Q

What is the fourth layer (Outermost)

A

SEROSA:

Connective tissue covered with epithelium

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19
Q

What lines the lumen in the gut

A

Absorptive cells

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20
Q

Where are the neural and muscular components in the gut

A

below the lumen

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21
Q

Blood and lymph vasculature are abundant to transport absorbed nutrients

A

True

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22
Q

What do the villi do

A

Increase the surface area for absorption of nutrients

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23
Q

What is Mastication

A

chewing of food in mouth

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24
Q

What does salivary amylase digest

A

Starch (carbohydrate)

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25
Q

What is Deglutition

A

Swallowing

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26
Q

What does food and drink stimulate

What does this result in

A

pressure receptors in the pharynx

afferent input to the medulla and efferent output to muscles in pharynx and esophagus

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27
Q

What is a bolus

A

mix of food with saliva

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28
Q

What prevents food from entering the nasal passages

A

Soft palate

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29
Q

What closes off the opening to the larynx

A

Glottis

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30
Q

What prevents food from entering the trachea

A

Epiglottis

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31
Q

What relaxes to allow food to descend into the esophagus

A

esophageal sphincter

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32
Q

What is Peristalsis

A

wavelike muscular contraction that pushes bolus to the stomach

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33
Q

What allows for the bolus to be pushed down the esophagus to the stomach

What happens just before reaching the stomach

A

Circular smooth muscle contracting behind bolus and relaxing in front

The lower esophageal sphincter muscle relaxes

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34
Q

What is Chyme

A

Partially digested food with gastric juices

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35
Q

What does the stomach do (5)

A
  1. Stores food
  2. Kills bacteria with acidity of gastric juice
  3. Starts digestion of proteins (not carbs or fats)
  4. Peristaltic waves mix and propel the chyme
  5. Moves chyme to the small intestine, where most digestion and absorption occur
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36
Q

What does the inner surface of the stomach contain

A

Folds called gastric rugae

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37
Q

What 4 things do specialised cells in the stomach produce

A

Mucus fluid
Enzyme precursors
Hydrochloric acid
Hormones

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38
Q

What secretes mucus in the stomach

A

Mucous neck cells

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39
Q

What secretes Pepsinogen in the stomach

A

Chief (zymogenic) cells

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40
Q

What secretes Hydrochloric acid in the stomach

A

Parietal cells

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41
Q

What secretes Histamine and serotonin in the stomach

A

Enterochromaffin like cells

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42
Q

What secretes gastrin

A

G cells

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43
Q

What secretes somatostatin

A

D cells

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44
Q

What secretes intrinsic factor

A

Gastric mucosa

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45
Q

What does intrinsic factor do

A

Allows for intestinal absorption of vitamin B12

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46
Q

What does ghrelin do

A

regulates hunger

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47
Q

What is gastric juice

A

Secretions of gastric cells + water

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48
Q

What does acid production by parietal cells depend on

A

Carbonic acid

Secretion of hydrogen into the stomach (active transport by H/K atpase pumps)

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49
Q

What happens when carbonic acid dissociates in the stomach

A

Bicarbonate secreted into the bloodstream

Exchanged for Cl via facilitated diffusion

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50
Q

What stimulates the secretion of HCl

What inhibtis secretion of HCl

A

Gastrin
ACh
Histamine

Somatostatin

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51
Q

What stimulates gastrin

A

Presence of partially digested proteins in stomach

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52
Q

How does Gastrin effect secretion of HCl (3)

A

Binds to receptors on parietal cells

Stimulates ECL cells to secrete histamine

Paracrine stimulation of parietal cells secretes HCl

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53
Q

What happens when gastric juice is acidic (3)

A

Activates pepsin
Optimizes activity of pepsin
Accelerates digestion of proteins

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54
Q

What protects the lining of the stomach

A

mucus layer containing bicarbonate

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55
Q

What converts pepsinogen to pepsin

A

HCl aciditiy

56
Q

What does pepsin actually do

A

accelerates the digestion of proteins

57
Q

What does the mucosa in the small intestine contain

A

Goblet cells for secreting mucus and lymphocytes

Folds called Villi

Microvilli on villi which increase the surface area for food absorption

58
Q

What do microvilli also have

A

digestive enzymes

59
Q

The small intestines is where there is digestion of… (3)

A

Carbohydrates
Lipids
Proteins

60
Q

The villi in the small intestine project where

A

into the lumen - increases surface area for absorption

61
Q

What are brush border enzymes

A

Enzymes on the plasma membrane of microvilli

62
Q

What is the main contraction in the SI and why

A

Segmentation

Mixes and moves chyme
Controlled by enteric nervous system

63
Q

The large intestine has no… (2)

A

Villi or digestion

64
Q

The large intestine absorbs…

A

Electrolytes
Water
Vitamins

65
Q

What is haustra

A

Pouches on outer surface of LI

66
Q

What is the main activity in the LI

A

Active transport of sodium

And

Absorption of water

To concentrate the feces

67
Q

Microbes in the LI produce… (2)

A

Vitamin K for blood clotting

B vitamins

68
Q

How does defecation occur

A

Longitudinal rectal muscles contract

Increases rectal pressure

Internal and external sphincters relax

Contraction of abdominal and pelvic muscles

69
Q

Gallbladder function

A

storage of bile from liver

70
Q

Pancreas function

A

pancreatic juice (exocrine) for digestion

71
Q

What are the 5 major functions of the liver

A 
Detoxication of blood
Carbohydrate metabolism
Lipid Metabolism
Protein synthesis
Secretion of bile
72
Q

What separates hepatocytes in the liver

A

Sinusoids

73
Q

What is the passage of blood in the liver (4)

A

Blood enters a liver lobule through the portal triad

Passes through hepatic sinusoids

Leaves the lobule through a central vein

The central veins converge to form hepatic veins that take venous blood from the liver

74
Q

What are the main components of bile

A 
bile pigment
bile salts
lecithin
bicarbonate ions
cholesterol
trace metals
75
Q

What is the bile pigment

A

Bilirubin - breakdown of heme

76
Q

Characteristics of Bilirubin

A

Not water soluble = carried in blood attached to albumin

Liver converts to water soluble from that can be secreted into bile

77
Q

Bilirubin that is excreted in feces and urine is excreted as

A

Urobilinogen

78
Q

Bile salts are…

They form…

A

Cholesterol based

Micelles

79
Q

Emulsification is the

A

breakdown of large fat globules by bile salts into smaller globules, for digestion by lipase enzymes

80
Q

The major pathway of cholesterol breakdown is activated when

A

cholesterol is used to produce bile salts

81
Q

Where in the liver is bile produced

Where is it then secreted to

A

Hepatocytes

Bile caniculi

82
Q

The caniculi are drained by…

A

Bile ducts at end of each lobule

83
Q

Where do the bile ducts transport the bile

What then stimulates bile to move into the SI

A

into the gall bladder

Cholecystokinin (CCK)

84
Q

How does bile enter the SI

A

Via the common bile duct

85
Q

What happens to the cholesterol based bile salts along the intestine

A

Reabsorbed into the liver

86
Q

What is unique about bile salt structure

A

Has one polar and one no polar end

87
Q

What do the nonpolar ends of bile acid do

A

Emusify fats in water

88
Q

What forms in bile acids

A

Micelles which are readily broken down

89
Q

`What are the endocrine functions in the pancreas

A

Insulin
Glucagon

Secreted into the blood

90
Q

What are the exocrine functions of the pancreas

A

Pancreatic juice

Secreted through pancreatic duct into duodenum of SI

91
Q

What is pancreatic juice made up of

A

Bicarbonate and 20 enzymes

92
Q

What does Amylase digest

A

Starch

93
Q

What does Trypsin digest

A

Protein

94
Q

What does Lipase digest

A

Triglycerides

95
Q

The Exocrine cells in the pancreas produce what type of enzymes

they travel via the

A

Digestive enzymes

Pancreatic duct

96
Q

When do digestive enzymes become active

A

In the SI

97
Q

What are zymogens

A

Inactive enzyme precursors

98
Q

Gastric motility and secretion is a ______ process

This process results in the presence of

A

automatic

Chyme

99
Q

The GI tract is both an

A

Endocrine gland

And

Target for hormones

100
Q

The regulation of GI processes can be controlled by

A

Hormonal (endocrine cells)

Neural (enteric nervous system)

101
Q

What are the 3 phases of GI control

A

Cephalic phase
Gastric phase
Intestinal phase

102
Q

What happens in the Cephalic phase (3)

A

Gastric secretion stimulated by sight, smell, taste, chewing, talking about food; continues into first 30 minutes of meal

Vagus nerves stimulate chief cells to secrete pepsinogen, parietal cells to secrete HCl, and G cells to secrete gastrin

Gastrin stimulates ECL cells to secrete histamine, which stimulates parietal cells to secret HCl

103
Q

What happens in the gastric phase (9)

Focus on what cells secrete what and what acidity inhibits

A

Starts when food enters stomach

Casues: distension, acidity, AAs, peptides

Presence of AAs and peptides

Stimulates chief cells to secrete pepsinogen and G cells to secrete gastrin

Stimulates secretion of histamine from ECL cells to stimulate HCL from parietal cells

Acidity inhibits gastrin secretion

via somatostatin secreted by D cells when pH decreases.

Somatostatin also inhibits acid secretion by parietal cells

Distension

104
Q

What happens in the Intestinal phase

What are the inhibitory hormones secreted by SI

A

Inhibition of gastric activity and motility by vagus nerves when chyme enters SI = time to digest and absorb food

gastric inhibitory peptide (GIP)
somatostatin
cholecystokinin (CCK)
glucagon-like peptide-1 (GLP-1).

105
Q

The myenteric plexus is

A

the outer network

entire length of GI tract

106
Q

The Submucosal plexus is

A

The inner network

Only in SI and LI

107
Q

What is the sensory stimulus that activates interneurons

What does this then stimulate

A

Chyme

Motor neurons = smooth muscle contraction

108
Q

Intestinal Reflexes affect what

A

Motility

109
Q

What does Paracrine Regulation affect

A

Contraction
Absorption
Secretion

110
Q

What is Cholecystokinin (CCK)

A

Protein and fat in chyme stimulate secretion of CCK by duodenum

111
Q

What does the Cholecystokinin stimulate

A

secretion of pancreatic juice enzymesto digest protein and fat

112
Q

What does Chyme stimulate in the SI

What does it inhibit

A

Gastric phase and reflex secretion of pancreatic juice and bile

Inhibits entry of additional chyme into SI, to allow digestion

113
Q

What stimulates secretion of Secretin

What does it then stimulate

A

Reduced pH in SI (due to acidic chyme)

Secretion bicarbonate and water secretion from pancreas

114
Q

The secretion of bile is

but…

A

Continuous

Does increase with meal

115
Q

What causes bile volume to increase

A

Secretin and CCK stimulate liver to secrete bicarbonate into bile

116
Q

What causes more bile to be delivered to the duodenum from the contracting gallbladder

A

Chyme in duodenum

CCK secretion in response to fat in chyme

117
Q

During a meal, the arrival of bile in the duodenum causes what to happen

A

Liver to secrete more bile

118
Q

Salivary amylase digests from…

A

mouth to upper stomach

119
Q

Pancreatic amylase digests in…

Results in..

A

SI

Results in Disacc, trisacc, oligosacc

120
Q

Brush border amylases hydrolyze in

Results in..

A

SI

hydrolyse into their components monosaccharides

121
Q

How are carbohydrates absorbed

A

Via secondary active transport coupled to Na into SI

Then via facilitated diffusion in membrane

122
Q

When Na is absorbed what follows

A

CL follows passively

Water then follows NaCl for absorption into blood

123
Q

How do AAs enter the cells of the SI

A

via secondary active transport coupled to Na

124
Q

Where are Dipeptides and tripeptides transported into

How…

What happens to them when they get there

A

epithelial cells of SI

via a different carrier

hydrolyzed into AAs in the cytoplasm

125
Q

Lipids in chyme stimulate what into the SI

This results in

A

Bile

Emulsification

126
Q

Digestion of lipid droplets in SI is by

A

Pancreatic lipase

Aided by colipase - bind lipases with lipid droplet

127
Q

What does Phospholipase A digest

A

Phospholipids into fatty acids + lysolecithin

128
Q

What is more polar undigested lipids or digested lipids

A

Digested lipids

129
Q

Where do digested lipids then enter

A

Micelles of bile salts

130
Q

Digestion of triglycerides releases what

What happens to the products

A

fatty acids and monoglycerides

Assoicate with micelles of bile salts, then secreted by liver

131
Q

What are chylomicrons

A

Resynthesize triglycerides and phospholipids, cholesterol combine with protein

132
Q

Where do free fatty acids and monoglycerides go after they leave micelles

A

SI cells

133
Q

By what process are chylomicrons secreted by

A

exocytosis into lymphatic vessels, then into blood

134
Q

What happens to Chylomicrons in the blood

A

Are modified to release triglycerides for energy, fat storage and cholesterol

135
Q

Chylomicrons =

A

Triglycerides + protein

136
Q

What is an ulcer

A

Erosion due to a failure of protective mechanisms in the stomach, esophagus, or duodenum

Bio 66 (22 decks)

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