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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
Paneth cells
release antimicrobial agents determining which bacteria can colonize the intestine
26
Stem cells
continuously divide with daughter cells differentiating into the 4 other cell types
27
Two motility patterns in small intestine
segmentation peristalsis
28
After a meal, ____ is principal form of motility
segmentation
29
segmentation
Ensures mixing and absorption Intrinsic pacemaker cells in duodenum depolarize more frequently than ileum Can be altered by ANS
30
Between meals, a type a peristalsis called ____ is observed
migrating motor complex
31
Waves of peristalsis begin in the _____ and sweep distally
proximal duodenum
32
Peristalsis
Controlled by the hormone motilin Every few hours, sweeps all material into large intestine
33
Large Intestine : Gross Anatomy Subdivisions :
cecum ascending colon > hepatic (right colic) flexure transverse colon > splenic (left colic) flexure descending colon sigmoid colon rectum anal canal
34
Special features of the Large Intestine
“Valve” at each end: Ileocecal valve – prevents backflow of chyme into SI Internal/External anal sphincters at anal canal
35
Teniae coli -
Longitudinal layer of muscularis reduced to 3 strips
36
Haustra -
pockets in wall due to smooth muscle tone
37
Appendix –
worm-like appendage contains immune cells and stores of bacteria to recolonize gut; vulnerable to blockage
38
Appendicitis =
inflammation of appendix; risk of rupture and bacterial spread throughout peritoneal cavity
39
Histology of Large Intestine: Mucosa
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
Histology of Large Intestine: Muscularis Externa
incomplete outer longitudinal layer forms teniae coli
41
The Microbiome (gut bacteria) is important for health
Thousands of different types of bacteria – weigh several pounds Help us recover energy from indigestible foods and synthesize some vitamins
42
Fermentation of _____ produce short chain fatty acids our cells use for energy – also produce mixture of gases (flatulence)
indigestible carbohydrates
43
Gut bacteria synthesize _____used by liver to produce clotting proteins
B complex vitamins and vitamin K
44
Microbiome =
Interaction between immune system & microbiome
45
Beneficial gut bacteria help control _____ like Clostrium difficile
pathogenic bacteria
46
Gut bacteria vulnerable to long term ____
antibiotic treatment
47
Main digestive functions of large intestine :
Absorb remaining water Absorb metabolites from bacteria Package, store and release feces
48
Diarrhea =
transit time too fast : too little water absorbed
49
Constipation =
transit time too slow : too much water
50
Common Disorders of the Intestinal Mucosa =
Irritable bowel syndrome (IBS) Inflammatory bowel disease (IBD)
51
Irritable bowel syndrome (IBS)
diarrhea, constipation or both abnormal motility, no damage to wall due to hypersensitivity or reactivity of enteric nervous system
52
Inflammatory bowel disease (IBD)
Crohn’s, ulcerative colitis - chronic inflammation and ulcerations of intestinal wall treat with anti-inflammatory or immunosuppression drugs, monoclonal Abs
53
____ is the last section before anal canal
Rectum
54
Anal canal =
~ 3 cm long opens to exterior at anus lined by stratified squamous epithelium that merges with surrounding skin
55
2 muscular sphincters control anus:
Internal anal sphincter involuntary smooth muscle External anal sphincter voluntary skeletal muscle; part of pelvic floor
56
Hemorrhoids =
dilated and inflamed varicose veins of anal canal/anal opening
57
Defecation reflex =
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
Valsalva maneuver –
Glottis (larynx) is closed, diaphragm and abdominal muscles are contracted to increase intra-abdominal pressure
59
Defecation reflex Steps:
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
Digestion =
catabolic process breakdown foods into chemical building blocks (monomers) most digestive enzymes require neutral pH for optimum function – exception: stomach
61
Most of absorption occurs in ____
small intestine
62
Nutrients, ions and water are absorbed by moving across the ____ and through the _____
brush border enterocytes
63
Transporter proteins are involved in absorption except for______, and water follows the movement of solutes by ____.
lipid soluble substances osmosis
64
Most nutrients diffuse into blood capillaries, travel to liver through _____
portal vein system
65
some fat digestion products enter ______ and reach bloodstream at subclavian vein
lacteals (lymphatic capillaries),
66
_______ diffuse across plasma membrane by simple diffusion
Lipid soluble molecules (fats)
67
Many breakdown products of ______ and _____ are co-transported with Na+ across apical membrane secondary active transport
carbohydrates (monosaccharides) proteins (amino acids)
68
______ are transported across basolateral membrane by facilitated diffusion
Monosaccharides, amino acids
69
Most dietary carbohydrates in form of ____
starch (plant storage form of glucose)
70
____ breaks down starch and glycogen (polysaccharides) into oligosaccharides.
Amylase Salivary amylase in mouth Pancreatic amylase in small intestine
71
Oligosaccharides and Disaccharides must be broken down into _____ by brush border enzymes Sucrose (table sugar) - Maltose (grain sugar) – Lactose (milk sugar) –
monosaccharides sucrase maltase lactase
72
Only monosaccharides can be absorbed by _____
enterocytes of small intestine
73
Lactose intolerance -
lactase deficiency lactose sugars stay in lumen creating osmotic pressure and attracts water gut bacteria metabolize lactose creating gas, cramping, diarrhea
74
Cellulose –
indigestible polysaccharide in humans (we lack the enzyme) acts as dietary fiber
75
Protease =
enzyme that breaks down protein
76
Proteins to be digested include:
dietary protein enzyme proteins proteins from dead cells
77
Protein digestion begins in ____ : pepsinogen from chief cells activated to ____ in stomach acid breaks proteins down into polypeptides and amino acids.
stomach pepsin
78
In small intestine more ____ from pancreas break polypeptides down further: _______ break proteins into smaller pieces.
proteases trypsin, chymotrypsin, carboxypeptidase
79
______ finish digestion by breaking oligopeptides and dipeptides into individual amino acids.
Brush border enzymes
80
Individual ______ are absorbed into enterocytes of small intestine.
amino acids
81
Lipase
enzyme that digests fat
82
Fats –
hydrophobic, emulsified by bile salts from liver (and gall bladder) – form small fat droplets
83
Lipase hydrolyzes triglycerides into _____
monoglycerides and free fatty acids
84
Form ____ with bile salts and lecithin – transport products to microvilli.
micelles
85
At _____, lipids leave micelles and diffuse into enterocyte
apical membrane
86
In smooth ER of cell, converted back to triglycerides, combined with proteins to form ____ which are released at basal surface by ____
chylomicrons exocytosis
87
_____ 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
Chylomicrons lacteals
88
_____ don’t have to go through this process and can just diffuse across membrane of enterocyte.
Short chain fatty acids
89
Enterohepatic Circulation recycles bile salts Steps:
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
The ____ does first processing of absorbed substances
liver
91
Any substance picked up by intestine ______ travels through portal vein to liver excludes most fats, which are picked up into _______
blood capillaries lymphatic capillaries
92
Liver processes :
nutrients bile salts absorbed drugs
93
Liver may detoxify drugs and ______ their effects
decrease or eliminate
94
“first pass metabolism” =
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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