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My MCAT Biology > Digestive System > Flashcards

Digestive System Flashcards

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1
Q

Catabolic reactions vs anabolic reactions

A

C: break down molecules to supply energy

A: synthesis of macromolecules

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2
Q

Digestion is ____ and is accomplished by _____

A

Breakdown of polymers into their building blocks accomplished by enzymatic hydrolysis

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3
Q

Primary and secondary function of the digestive system

A

P: digestion and absorption of foods
S: protection from disease

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4
Q

Digestion is accomplished in these locations: (3)

A

GI tract, gut or alimentary canal

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5
Q

GI tract is

A

Muscular tube from the mouth to the anus

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6
Q

GI lumen

A

inside of the gut, compartment where usable components of food are extracted and wastes are left to be excreted as feces

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7
Q

Innermost lining of the lumen is composed of ____ which are attached to the ____

A

Epithelial cells

Basement membrane

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8
Q

Surface of epithelial cells on basement membrane facing the lumen care called:

Sides and bottom of epithelial cells forming the opposite surface of the lumen are called:

A

Apical surface

Basolateral surface

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9
Q

In the small intestine, the apical surface epithelial cells have outward folds on their plasma membranes called ___ meant to

A

Microvilli

INC surface area

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10
Q

Apical surface is separated from the remained of the cell surface by: ___ which

A

Tight junctions

Create a barrier separating body fluids from exterior environment

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11
Q

Two layers of smooth muscle lining the gut:

A

Circular: encircles it
Longitudinal: length of the gut

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12
Q

GI motility definition

A

Rhythmic contraction of the GI smooth muscle

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13
Q

GI motility is determined by 5 factors:

A
  1. Automaticity (spontaneous depolarization)
  2. Functional syncytium (one cell has AP the impulse spreads to other cells)
  3. Enteric nervous system (GI own NS)
  4. Hormonal input
  5. PNS allows sphincters to relax (food passes through gut) and SNS does opposite
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14
Q

GI motility serves two purposes:

A

Moves food through the gut and mixes food

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15
Q

Mixing of food in GI is accomplished by:

A

Disordered contractions resulting in churning

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16
Q

Movement of food through GI is accomplished by:

A

Orderly contraction (peristalsis)

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17
Q

How does peristalsis (orderly contraction of GI) operate?

A

Contraction of circular muscle at point A prevents food at point B from moving backward

Contraction of longitudinal muscle at point B contract to shorten the gut so it is pulled up over the food and the food moves toward point C

Circular muscles contract at point B to prevent food moving backwaters and longitudinal muscles contract, and so on

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18
Q

Bolus

A

Ball of food moving through the GI tract

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19
Q

Enteric NS relation to the PNS and SNS

A

SNS and PNS can control the ENS but the ENS can also operate independently of them (without their control)

PNS/SNS still have overriding ability

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20
Q

ENS relates

A

local blood flow, gut movement and exchange of fluid from gut-lumen

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21
Q

ENS is made up of two networks of neurons

A

Myenteric plexus: gut motility

Submucosal plexus: enzyme secretion, gut blood flow and ion/water balance to lumen

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22
Q

Submucal plexus is sparse:

A

in areas where enzyme secretion, gut blood flow and ion/water balance to lumen is not needed (i.e. anus and esophagus)

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23
Q

Two types of secretion: endocrine glands and exocrine glands

A

Endocrine: Ductless glands whose secretions are picked up by capillaries and enter the bloodstream

Exocrine: secrete products into DUCTS that drain into GI lumen

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24
Q

Exocrine glands are composed of

A

Specialized epithelial cells organized into sacs called acini (acinus) that secrete products to pass into ducts

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25
Q

Gastric glands

A

In stomach; release secretions directly into the gut

Secrete acid and pepsinogen

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26
Q

Goblet cells

A

Found along entire GI tract

Specialized mucus secreting cells

Mucus: slimy liquid that lubricates and protects the gut

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27
Q

Mucus membrane

A

Any surface covered with mucus

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28
Q

Water as a secretion in the GI system

A

Any meal must be dissolved in water and most of the water is then reabsorbed into the small intestine and colon is responsible for reclaiming whatever water is left

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29
Q

Endocrine secretion from the pancreas

A

Don’t empty into glands, are picked up into the blood stream (endocrine glands)

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30
Q

Mouth three roles in digestion of food

A

Fragmentation, lubrication and enzymatic digestion

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31
Q

Mastication

A

chewing to accomplish fragmentation

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32
Q

Incisors and cuspids and molars

A

I: Front teeth for cutting
C: Canine teeth for tearing
M: grinding

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33
Q

Saliva

A

Accomplishes lubrication and some digestion

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34
Q

Salivary amylase (ptyalin)

A

Hydrolyzes starch, breaking it into fragments (smallest yield is disaccharide)

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35
Q

Lingual lipase

A

Fat digestion enzyme in saliva

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36
Q

No digestion of ___ occurs in the mouth

A

Proteins

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37
Q

Lysozyme

A

Attacks material cell walls in the mouth

–Innate immunity happens in the mouth

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38
Q

A bolus of food passes through the ___, over the ____ and into the ___ where it is conveyed into the stomach by ____

A

A bolus of food passes through the pharynx, over the epiglottis and into the esophagus where it is conveyed into the stomach by peristalsis

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39
Q

Upper esophageal sphincter and lower esophageal sphincter

A

U: near top of esophagus
L: near heart at end of esophagus at entrance to stomach to regulate reflux from stomach into esophagus

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40
Q

Stomach three purposes

A

partial digestion, regulated release of food into small intense and destruction of microorganisms

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41
Q

Stomach pH is ___ and the effects of this are (3)

A

2

  1. destruction of microorganisms
  2. acid-catalyzed hydrolysis of proteins
  3. conversion of pepsinogen (inactive) to pepsin (active)
42
Q

Pepsin is secreted by ___ in the stomach wall

Its function:

A

Chief cells

Catalyzes proteolysis (protein breakdown)

43
Q

Inactive form of pepsin secreted by the GI tract

A

Zymogen

44
Q

Chyme

A

Food mixed with gastric secretions

45
Q

Pyloric sphincter

A

Prevents passage of food from stomach into duodenum (first part of the small intestine)

46
Q

Opening of the pyloric sphincter occurs to:

And is inhibited when:

A

Empty the stomach

Small intestine already has a large load of chyme

47
Q

Opening of the pyloric sphincter is mediated by the hormone

A

Chloecystokinin (secreted by epithelial cells in the wall of the duodenum / small intestine)

48
Q

G cells secrete Gastrin which is

A

hormone that stimulates acid and pepsin secretion and gastric motility

49
Q

Histamine is stimulated by ___ and causes:

A

Stomach stretching and gastrin release

Stimulates acid release

50
Q

Small intestine takes food from the ____ and is made up of three parts:

A

Stomach

Ileum, jejunum and duodenum

51
Q

Digestion is completed in the

Absorption begins in the

A

Duodenum and jejunum

Duodenum

52
Q

Key feature allowing small intestine to accomplish absorption is its ____ which is made possible from (3)

A

Surface area

Length, villi, microvilli

53
Q

Villi and microvilli of small intestine

A

V: Macroscopic multicellular projections in the wall of the small intestine
M: Microscopic foldings of the cell membrane of individual epithelial cells

54
Q

Brush border

A

Brush like appearance of microvilli give the lumen surface of the small intestine this name

55
Q

Three important features of the villus on the intestine

A
  1. Capillaries allowing carb nutrients and AA to be transported from the gut to the liver
  2. Lacteals (small lymphatic vessels) absorb dietary fats and transport them to the thoracic duct, emptying into the bloodstream
  3. Peyer’s patches: Lymphocytes that monitor GI contents and confer immunity to gut pathogens and toxins
56
Q

Pancreatic duct on the duodenum

A

delivers exocrine secretions of pancreas (digestive enzymes and bicarbonate)

57
Q

Common bile duct on the duodenum

A

Delivers bile containing acids

58
Q

Bile is stored in the ___ until it is needed and has two main functions:

A

Gallbladder

Vehicle for disposal/excretion of waste by the liver
Essential for digestion of fats

59
Q

Sphincter of Oddi

A

Both the pacreatic duct and common bile duct empty into the duodenum via the sphincter of oddi

60
Q

Duodenal enterokinase

A

Activates pancreatic zymogen trypsinogen to trypsin

61
Q

Brush border enzymes

A

DO work on the surface of the epithelial cell rather than being secreted

Hydrolyze the smallest carbs and proteins into monosaccharides and AA

62
Q

Three main duodenal hormones:

Chloecystokinin (CCK)
Secretin
Enterogastrone

A

Chloecystokinin (CCK): response to fats in the duodenum

Secretin: response to acid in the duodenum

Enterogastrone: decreases stomach emptying

63
Q

Chloecystokinin (CCK) duodenal hormone causes

A

Pancreas to secrete digestive enzymes, stimulate gall bladder contraction/bile release and decreases gastric motility

64
Q

Secretin hormone in the duodenal causes

A

Pancreas releases large amounts of high-pH/basic aqueous buffer, usually HCO3- in water

Neutralizes HCL released by the stomach (Duodenum pH must be slightly basic or neutral)

65
Q

Ileocecal valve

A

Separates the ileum from the cecum (first part of the large intestine) and controls entrance of chyme into the colon

66
Q

Jejunum and ileum function

A

To absorb substances not absorbed in the duodenum

67
Q

Colon/Large intestine role

A

Absorb water and minerals

Form and store feces until defecation

68
Q

Cecum

A

First part of the colon

69
Q

Appendix

A

Appendage of the cecum composed of lymphatic tissue

70
Q

Rectum

A

last part of the colon where feces exits the rectum

71
Q

Anal sphincter

A

Controls defecation

72
Q

Internal vs external anal sphincter

A

I: smooth muscle under autonomic control
E: skeletal muscle under voluntary control

73
Q

Colonic bacteria are important for two reasons:

A
  1. Presence of normal bacteria help keep dangerous bacteria from proliferating due to competition for space and nutrients
  2. Supply vitamin K which is essential for blood clotting
74
Q

GI accessory organs include

A

Pancreas, liver, gallbladder and salivary glands

75
Q

Pancreatic hormones

Pancreatic amylase function

A

Hydrolyzes polysaccharides into disaccharides

76
Q

Pancreatic hormones

Pancreatic lipase function

A

Hydrolyzes triglycerides at surface of micelle

77
Q

Pancreatic hormones

Pancreatic nuclease function

A

Hydrolyze dietary DNA and RNA

78
Q

Pancreatic hormones

Pancreatic proteases function

A

hydrolyzing polypeptides to di- or tri- peptides

secreted in zymogen inactive form, must be activated by removal of a portion of the polypeptide chain

79
Q

PNS and SNS function over pancreatic secretion

A

PNS: increases it “rest and digest”

SNS: reduces it

80
Q

Endocrine pancreas consist of islets of langerhans which is made up of three cells, each:

A

secrete a particular hormone into the bloodstream

81
Q

Three types of cells in the islets of langerhans

A

alpha cells, beta cells and delta cells

82
Q

Islets of Langerhans:

alpha cell function

A

secrete glucagon in response to low blood sugar to mobilize stored fuels by stimulating the liver to hydrolyze glucose into the bloodstream and stimulating adipocytes to release fats into the bloodstream

83
Q

Islets of Langerhans:

beta cell function

A

Secrete insulin in response to elevated blood sugar to remove glucose from the blood for storage as glycogen and fat

84
Q

Islets of Langerhans:

delta cell function

A

Secretes somatostatin

Inhibits digestive processes

85
Q

Lowering blood glucose

What does this and why

A

Insulin does this

Essential because excess glucose in the bloodstream will destroy many cellular systems

86
Q

Raising blood glucose

What does this and why

A

Glucagon, epinephrine, cortisol

Makes sense that there is more means of raising blood glucose than lowering it because low blood glucose is fatal immediately whereas high levels is harmless in short term

87
Q

Function of the liver

A

Create and release bile

88
Q

Function of bile

A

Turns large fat particles into small fat particles called micelles which have more surface area and are easily digested

Helps fatty particles to diffuse across the intestinal mucus membrane

89
Q

Gallstone

A

Large crystal formed from bile made with ingredients in incorrect proportions

90
Q

Gallbladder secretion is controlled by

A

PNS & CCK stimulate the gallbladder wall’s contraction

91
Q

Hepatocytes function (2)

A

Extract nutrients from blood passing through the liver

Makes changes based on what is and is not present in the blood

92
Q

Both the liver and skeletal muscle are capable of storing and breaking down glycogen into glucose BUT

A

Only the liver can secrete it into the bloodstream because it has the enzyme needed to dephosphorylate it

93
Q

Lipids exist in the intensive and enter the lymphatic system in molecules called chylomicrons which are degraded by lipases into chylomicron remnants

These remnants are taken up by ____ and combined with proteins to make ___ that ____

A

These remnants are taken up by hepatocytes and combined with proteins to make lipoproteins that re-enter the bloodstream

94
Q

Many ___ and ____ are made in the liver and secreted into the bloodstream

A

Lipoproteins and plasma proteins

95
Q

Ghrelin hormone

A

Stimulates hunger when the stomach is empty

96
Q

Peptide YY

A

Colon is full the jejunum produces this to reduce appetite

97
Q

Leptin hormone

A

Appetite suppressant released from fat that maintains stable lipid content in fat

INC triglyceride levels and suppresses appetite until levels are normal

98
Q

Ghrelin, peptide YY and leptin are all primarily regulated by

A

Hypothalamus

99
Q

Chylomicrons (large particles of proteins and fats) enter tiny lymphatic capillaries known as ___ which merge into larger lymphatic vessels which eventually empty into the _____

A

Lacteals

Thoracic duct which empties into the blood stream

Causing milky blood “lipemia”

100
Q

Fat soluble vitamins

A

A, D, E, K

Require bile acids for absorption

Excess stored in adipose tissue (fat)

101
Q

Water soluble vitamins

A

B(all), C, Biotin and Folate

Excess secreted by kidneys in urine

My MCAT Biology (13 decks)

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