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Anatomy Exam 3 > Lecture 9 : Gastrointestinal System III : Intestines and Physiology of Digestion > Flashcards

Lecture 9 : Gastrointestinal System III : Intestines and Physiology of Digestion Flashcards

1
Q

main location of digestion and absorption =

A

Small intestine

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2
Q

Small intestine : Single convoluted tube running from ____ to ______ – divided into 3 sections:

A

stomach
large intestine

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3
Q

3 sections of small intestine

A

Duodenum

Jejunum

Ileum

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4
Q

Duodenum

A

(12 in)

Most digestion

Alkaline and mucous secretions neutralize acidic chyme

Retroperitoneal position

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5
Q

Jejunum

A

(8 ft)

A lot of absorption

Intraperitoneal and suspended by mesentery

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6
Q

Ileum

A

(12 ft)

Absorption of vitamin B12 and bile salts

Peyer’s patches – immune tissue in wall

Intraperitoneal and suspended by mesentery

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7
Q

Histology of the Small Intestine : 4 layered wall

A

mucosa

submucosa

muscularis externa

serosa

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8
Q

has both extensions into lumen _____ and extensions into lamina propria ______

A

(villi)

(intestinal crypts)

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9
Q

Specializations of Small Intestine :

A
  1. Circular Folds
  2. Villi
  3. Microvilli
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10
Q

Circular Folds

A

Extensions of mucosa & submucosa into lumen to increase surface area for absorption

Visible at the gross anatomical level (to the naked eye)

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11
Q

Villi

A

Finger-like projections of the mucosa into the lumen: increase surface area for absorption

Contain blood capillaries and lacteals (lymph capillaries) that collect absorbed nutrients

Villi=plural; individual=villus

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12
Q

Microvilli

A

Apical surface extensions off of individual absorptive cells (=enterocytes)

Make apical surface appear fuzzy = “brush border”

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13
Q

Two types of proteins in apical surface membrane:

A

Transport proteins : more surface area for each enterocyte to absorb nutrients

Brush border enzymes hang from microvilli to complete carbohydrate & protein digestion in lumen

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14
Q

4 Features of Small Intestine to Maximize Absorption

A

Circular Folds
Villi off circular folds
Microvilli off individual cells of villi
Small intestine is 32 feet long

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15
Q

More surface area =

A

more absorption

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16
Q

The ____ absorbs most all nutrients passing through

A

intestine

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17
Q

Absorption is not regulated –

A

absorbs nutrients whether we need them or not

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18
Q

Only way to reduce absorption is to remove surface area –

A

bypass surgeries remove or detour part of intestine

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19
Q

Cell Types of the Small Intestine Mucosa

On the Villi:

A

Epithelial cells

Enterocytes

Goblet cells

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20
Q

Epithelial cells at the tip of the villus

A

constantly shed – new epithelium every 3-5 days

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21
Q

Enterocytes

A

form the bulk of the epithelium; simple columnar absorptive cells with microvilli bound to each other by tight junctions

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22
Q

Goblet cells

A

mucous secreting cells

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23
Q

Cell Types of the Small Intestine Mucosa

In the Intestinal Crypts:

A

Enteroendocrine cells

Paneth cells

Stem cells

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24
Q

Enteroendocrine cells

A

secrete hormones (enterogastrones) like CCK and secretin, sense food in the lumen

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25
Q

Paneth cells

A

release antimicrobial agents determining which bacteria can colonize the intestine

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26
Q

Stem cells

A

continuously divide with daughter cells differentiating into the 4 other cell types

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27
Q

Two motility patterns in small intestine

A

segmentation

peristalsis

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28
Q

After a meal, ____ is principal form of motility

A

segmentation

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29
Q

segmentation

A

Ensures mixing and absorption

Intrinsic pacemaker cells in duodenum depolarize more frequently than ileum

Can be altered by ANS

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30
Q

Between meals, a type a peristalsis called ____ is observed

A

migrating motor complex

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31
Q

Waves of peristalsis begin in the _____ and sweep distally

A

proximal duodenum

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32
Q

Peristalsis

A

Controlled by the hormone motilin

Every few hours, sweeps all material into large intestine

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33
Q

Large Intestine : Gross Anatomy
Subdivisions :

A

cecum
ascending colon
> hepatic (right colic) flexure
transverse colon
> splenic (left colic) flexure
descending colon
sigmoid colon
rectum
anal canal

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34
Q

Special features of the Large Intestine

A

“Valve” at each end:

Ileocecal valve – prevents backflow of chyme into SI

Internal/External anal sphincters at anal canal

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35
Q

Teniae coli -

A

Longitudinal layer of muscularis reduced to 3 strips

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36
Q

Haustra -

A

pockets in wall due to smooth muscle tone

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37
Q

Appendix –

A

worm-like appendage

contains immune cells and stores of bacteria to recolonize gut; vulnerable to blockage

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38
Q

Appendicitis =

A

inflammation of appendix; risk of rupture and bacterial spread throughout peritoneal cavity

39
Q

Histology of Large Intestine:
Mucosa

A

simple columnar through most of colon, smooth surface – no circular folds or villi

enterocytes - absorptive cells to absorb water, electrolytes

Intestinal glands (crypts) – contain many more goblet cells to help lubricate and protect epithelium as feces move through

40
Q

Histology of Large Intestine:
Muscularis Externa

A

incomplete outer longitudinal layer forms teniae coli

41
Q

The Microbiome (gut bacteria) is important for health

A

Thousands of different types of bacteria
– weigh several pounds

Help us recover energy from indigestible foods and synthesize some vitamins

42
Q

Fermentation of _____ produce short chain fatty acids our cells use for energy – also produce mixture of gases (flatulence)

A

indigestible carbohydrates

43
Q

Gut bacteria synthesize _____used by liver to produce clotting proteins

A

B complex vitamins and vitamin K

44
Q

Microbiome =

A

Interaction between immune system & microbiome

45
Q

Beneficial gut bacteria help control _____ like Clostrium difficile

A

pathogenic bacteria

46
Q

Gut bacteria vulnerable to long term ____

A

antibiotic treatment

47
Q

Main digestive functions of large intestine :

A

Absorb remaining water

Absorb metabolites from bacteria

Package, store and release feces

48
Q

Diarrhea =

A

transit time too fast : too little water absorbed

49
Q

Constipation =

A

transit time too slow : too much water

50
Q

Common Disorders of the Intestinal Mucosa =

A

Irritable bowel syndrome (IBS)

Inflammatory bowel disease (IBD)

51
Q

Irritable bowel syndrome (IBS)

A

diarrhea, constipation or both

abnormal motility, no damage to wall

due to hypersensitivity or reactivity of enteric nervous system

52
Q

Inflammatory bowel disease (IBD)

A

Crohn’s, ulcerative colitis - chronic inflammation and ulcerations of intestinal wall

treat with anti-inflammatory or immunosuppression drugs, monoclonal Abs

53
Q

____ is the last section before anal canal

A

Rectum

54
Q

Anal canal =

A

~ 3 cm long

opens to exterior at anus

lined by stratified squamous epithelium that merges with surrounding skin

55
Q

2 muscular sphincters control anus:

A

Internal anal sphincter
involuntary smooth muscle

External anal sphincter
voluntary skeletal muscle; part of pelvic floor

56
Q

Hemorrhoids =

A

dilated and inflamed varicose veins of anal canal/anal opening

57
Q

Defecation reflex =

A

Stretching of rectum wall initiates reflex

Parasympathetic spinal reflex causes:

contraction of sigmoid colon & rectum wall

relaxation of internal anal sphincter

Sensory signals to brain – conscious decision to voluntarily relax external anal sphincter

58
Q

Valsalva maneuver –

A

Glottis (larynx) is closed, diaphragm and abdominal muscles are contracted to increase intra-abdominal pressure

59
Q

Defecation reflex
Steps:

A

1) feces move into and distend the rectum = stimulating stretch receptors there = receptors transmit signals along afferent fibers to spinal cord neurons

2) spinal reflex is initiated = parasympathetic motor (efferent) fibers stimulate contraction of rectum and sigmoid colon = relaxation of internal anal sphincter

3) if it is convenient to defecate, voluntary motor neurons are inhibited = external anal sphincter relaxes so feces may pass

60
Q

Digestion =

A

catabolic process

breakdown foods into chemical building blocks (monomers)

most digestive enzymes require neutral pH for optimum function – exception: stomach

61
Q

Most of absorption occurs in ____

A

small intestine

62
Q

Nutrients, ions and water are absorbed by moving across the ____ and through the _____

A

brush border

enterocytes

63
Q

Transporter proteins are involved in absorption except for______, and water follows the movement of solutes by ____.

A

lipid soluble substances

osmosis

64
Q

Most nutrients diffuse into blood capillaries, travel to liver through _____

A

portal vein system

65
Q

some fat digestion products enter ______ and reach bloodstream at subclavian vein

A

lacteals (lymphatic capillaries),

66
Q

_______ diffuse across plasma membrane by simple diffusion

A

Lipid soluble molecules (fats)

67
Q

Many breakdown products of ______ and _____ are co-transported with Na+ across apical membrane secondary active transport

A

carbohydrates (monosaccharides)

proteins (amino acids)

68
Q

______ are transported across basolateral membrane by facilitated diffusion

A

Monosaccharides, amino acids

69
Q

Most dietary carbohydrates in form of ____

A

starch (plant storage form of glucose)

70
Q

____ breaks down starch and glycogen (polysaccharides) into oligosaccharides.

A

Amylase

Salivary amylase in mouth

Pancreatic amylase in small intestine

71
Q

Oligosaccharides and Disaccharides must be broken down into _____ by brush border enzymes

Sucrose (table sugar) -
Maltose (grain sugar) –
Lactose (milk sugar) –

A

monosaccharides

sucrase

maltase

lactase

72
Q

Only monosaccharides can be absorbed by _____

A

enterocytes of small intestine

73
Q

Lactose intolerance -

A

lactase deficiency

lactose sugars stay in lumen creating osmotic pressure and attracts water

gut bacteria metabolize lactose creating gas, cramping, diarrhea

74
Q

Cellulose –

A

indigestible polysaccharide in humans (we lack the enzyme)

acts as dietary fiber

75
Q

Protease =

A

enzyme that breaks down protein

76
Q

Proteins to be digested include:

A

dietary protein
enzyme proteins
proteins from dead cells

77
Q

Protein digestion begins in ____ : pepsinogen from chief cells activated to ____ in stomach acid breaks proteins down into polypeptides and amino acids.

A

stomach

pepsin

78
Q

In small intestine more ____ from pancreas break polypeptides down further: _______ break proteins into smaller pieces.

A

proteases

trypsin, chymotrypsin, carboxypeptidase

79
Q

______ finish digestion by breaking oligopeptides and dipeptides into individual amino acids.

A

Brush border enzymes

80
Q

Individual ______ are absorbed into enterocytes of small intestine.

A

amino acids

81
Q

Lipase

A

enzyme that digests fat

82
Q

Fats –

A

hydrophobic, emulsified by bile salts from liver (and gall bladder) – form small fat droplets

83
Q

Lipase hydrolyzes triglycerides into _____

A

monoglycerides and free fatty acids

84
Q

Form ____ with bile salts and lecithin – transport products to microvilli.

A

micelles

85
Q

At _____, lipids leave micelles and diffuse into enterocyte

A

apical membrane

86
Q

In smooth ER of cell, converted back to triglycerides, combined with proteins to form ____ which are released at basal surface by ____

A

chylomicrons

exocytosis

87
Q

_____ are too big for blood capillaries, so are picked up by ____ (lymph capillaries) and eventually enter bloodstream near heart – not picked up into portal vein

A

Chylomicrons

lacteals

88
Q

_____ don’t have to go through this process and can just diffuse across membrane of enterocyte.

A

Short chain fatty acids

89
Q

Enterohepatic Circulation recycles bile salts
Steps:

A

1) bile salts are secreted into the duodenum

2) as bile salts travel through the small intestine = they allow lipid digestion and absorption to occur

3) 95% of bile salts are reabsorbed by the ileum

4) reabsorbed bile salts travel via the hepatic portal vein back to the liver where they are recycled
(only 5% of bile salts are newly synthesized each time)

90
Q

The ____ does first processing of absorbed substances

A

liver

91
Q

Any substance picked up by intestine ______ travels through portal vein to liver

excludes most fats, which are picked up into _______

A

blood capillaries

lymphatic capillaries

92
Q

Liver processes :

A

nutrients
bile salts
absorbed drugs

93
Q

Liver may detoxify drugs and ______ their effects

A

decrease or eliminate

94
Q

“first pass metabolism” =

A

how much of an orally-administered drug’s action is lost on its first pass through the liver, before it even reaches the target of the drug

Anatomy Exam 3 (11 decks)

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