Download Chapter 27 Reproductive Endocrinology

Chapter 23 Digestive physiology
Digestive system
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nutrition = food from environment to cells
nutrition requires :
• getting nutrients
• digesting nutrients
• transporting nutrients
musculo-skeletal
digestive system
circulatory system
functions
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move food
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=
stuffing your mouth
propulsion
moving food thru tract
• swallowing
• peristalsis
egestion
defectation of wastes
digest food
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ingestion
mechanical digestion
• chewing
• churning
physically breaking food
teeth, tongue
stomach, intestines
chemical digestion
chemically breaking food
• digestive enzymes
absorption
get nutrients into the body
Digestive organs
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alimentary canal
accessory organs
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gastrointestinal tract (GI)
aid digestion
alimentary organs
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mouth
pharynx
esophagus
stomach
small intestine
large intestine
accessory organs
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teeth
tongue
salivary glands
liver
gallbladder
pancreas
goals of digestion
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protein
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polypeptide
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CHO

disaccharides  glucose ; fructose ; galactose
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lipids

fatty acids + glycerol
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nucleic acids 

peptide
bases + pentose sugar + PO4

amino acids
enzymes for protein digestion
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protein
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pepsin
protein to polypeptide
stomach
HCl
denatures proteins
stomach
trypsin
activates other enzymes
pancreas
chymotrypsin
polypeptide to peptide
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peptidases peptide to AA
activates pepsinogen
sm. intest.
• aminopeptidase
• carboxypeptidase
• dipeptidase
enzymes for carbohydrate digestion
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carbohydrate
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amylase CHO to disaccharides
pancreas
saliva
disaccharidases disaccharides to monosaccharides
sm. intest
• maltase
• lactase
• sucrase
maltose  glucose
lactose  glucose + galactose
sucrose  glucose + fructose
dextrinase
enzymes for lipid and nucleic acid digestion
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lipids
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bile
emulsifies lipids
liver
lipase
lipid to glycerol + fatty acids
pancreas
to nucleotides
pancreas
nucleic acid
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nucleases
phosphotases
removes phosphate
GI hormones
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gastrin
 gastric activity
stomach
serotonin
 churning
stomach
histamine
 HCl
stomach
somatostatin
 most digestive functions stomach
secretin
 pancreas, bile
 gastric activity
duodenum
cholecystokinin
 pancreas , gall bladder
duodenum
vasoactive intestinal peptide
 blood supply duodenum
 HCl
Salivary glands
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saliva
salivary amylase
IgA
lysozyme ; defensins
mucin
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salivary glands
parotid gland
sublingual gland
submandibular gland
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control
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sensory:
chemoreceptors ; pressoreceptors
sight ; smell ; thought
P-ANS
increase
S-ANS
decrease ; more mucin
swallowing = deglutition
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buccal phase
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voluntary
tongue forces bolus to pharynx
pharyngeal-esophageal phase
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peristalsis
involuntary
pharyngeal muscles
esophagus
stomach processes
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secretions
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digestive
pepsinogen
HCl
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hormones
gastrin
histamine
serotonin
somatostatin
absorption
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all actions
HCl
smooth muscle
all actions
aspirin , alcohol
compacting food
chyme
storage
stomach anatomy
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cardiac sphincter
fundus
body
rugae
pylorus
pyloric sphincter
cells of stomach mucosa
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chief cells
pepsinogen
parietal cells
HCl
instrinsic factor
G cells
gastrin
ECL (enterochromaffin) cells
histamine
serotonin
control of stomach actions
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cephalic phase
reflex from brain
gastric phase
local (stomach) effects
intestinal phase
control from small intestine
cephalic phase
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hunger center -
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stim:
hypothalamus
low glucose / AA
see, smell, taste, think of food
hypothalamus to medulla
vagus n.
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stim gastric glands
NT ???
inhibit :
S-ANS (fear, anxiety, excitement)
emotions ; learned behaviors
 gastric activity
gastric phase
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stim:
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controls:
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distension
protein
high pH
gastrin
 pepsinogen
 HCl
histamine
 HCl
Ach
protein +  pH -
 HCl (enteric ns ; vagal reflex)
 gastrin -  HCl  pH +  protein
high protein foods
increase gastrin and HCl
lipids
decrease gastrin and HCl
glucose
no effect
HCl production
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stim by :
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H+
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H+
gastrin G cells
Ach
(vagus and enteric)
histamine local mast cells
CO2 + H2O  H2CO3  HCO3- + H+
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Cl
from blood
H+/K+ ATPase to lumen
Cl-
diffuse to lumen
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HCO3
to blood
alkaline tide
blood from stomach is alkaline
intestinal phase
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small intestine limits gastric activity (intermittent)
enterogastric reflex
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inhibits gastric activity
inhibit P-ANS
enterogastrones
inhibit gastric secretions , motility
• secretin
• vasoactive intestinal peptide (VIP)
 gastric action
 HCl
gastric motility
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initial response to filling
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plasticity
stretch-relaxation of smooth muscle
contraction
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basic electrical rhythm (BER)
3 / min
• pacemaker cells
• gap junctions
emptying
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gastrin
enterogastrones
speeds emptying
inhibit emptying
• varies CHO empty faster than lipids or proteins
pancreas
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bicarbonate
pH 8
digestive enzymes
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trypsinogen
chymotrypsinogen
procarboxypeptidase
pancreatic amylase
lipases
nucleases
regulation of functions:
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secretin
stim bicarbonate
CCK
stim enzymes
vagal
stim enzymes
liver and gallbladder
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“emulsify fats”
bile
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bile salts cholic acid (cholesterol derivative)
bilirubin waste product of heme
• excreted as urobilinogen
( feces , urine)
toxin, drug byproducts
enterohepatic circulation
stim by secretin
gallbladder
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stores bile
CCK
gallbladder contraction
relaxes hepatopancreatic sphincter
small intestine anatomy
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duodenum
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hepatopancreatic ampulla
jejunum
ileum
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ileocecal valve
brush border
small intestine digestion
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most digestion and absorption occurs here
brush border enzymes
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disaccharidases
maltase, sucrase, lactase
dextrinase
glucoamylase
peptidases
aminopeptidase, carboxypeptidase
nucleases , phosphotases
enteropeptidase
pancreatic juice
bile
small intestine – other processes
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hormones
secretin
CCK
somatostatin
VIP
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peristalsis
segmentation
pacemaker cells
ANS
gastroileal reflex
gastrin relaxes ileocecal valve
large intestine anatomy
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= colon
ascending colon
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cecum
appendix
transverse colon
descending colon
sigmoid colon
rectum
large intestine
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absorption
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water
vitamins
electrolytes
bacterial flora
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e. coli
Vitamin K
folic acid
peristalsis
gastrocolic reflex
defecation
digestion review:
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know:
digestion by area
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what enzyme is made where
location of action
digestion by food type
absorption
absorption
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lumen to blood
transepithelial transport
stomach
aspirin, alcohol, small peptides?
small intestine
all biochemicals
most water
electrolytes
vitamins
bile salts , urobilinogen
large intestine
remaining water
electrolytes
Vitamin K, folic acid
absorption of CHO
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monosaccharides
into epithelium
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facilitated diffusion
secondary active transport
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to blood
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facilitated diffusion
absorption of proteins
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amino acids
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into epithelium
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to blood
• secondary active transport
• active transport
dipeptides
• secondary active transport
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whole peptides
endocytosis
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products of digestion
glycerol
fatty acids
cholesterol
fat soluble vitamins
into epithelium
diffusion
chylomicrons
reassembled TRIGs
into lacteals
diffusion
lipoproteins
for transport in blood
carrier facilitated
infants only
absorption of lipids
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LDL
to organs, blood vessels
HDL
to liver
absorption of nucleic acids
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products of digestion
nitrogenous bases
into epithelium
active transport
to blood
diffusion
absorption of Vitamins
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water soluble
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B, C,
diffusion
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vitamin B12
endocytosis
requires intrinsic factor
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to blood
diffusion
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Na+
absorption of electrolytes
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K
diffusion ; active transport
Na / K pumps
also stim by Aldosterone
+
diffusion
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Cl
Ca
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Fe
diffusion
++
increase absorption
PTH
increase absorption
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diffusion
Vitamin D
active transport
ferritin dependent
anions
diffusion
absorption of water
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9 L enter small intestine daily
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3 L gastric juices
1-2 L pancreas
1-2 L small intestine
3-5 L food and drinks
95% absorbed in small intestine
osmosis
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after Na active transport