lecture 14 - digestion Flashcards
what 2 things make up the digestive system
accessory digestie organs
digestive canal
gastrointestinal tract
continous from mouth to anus
esophagus, stomach, small intest, large intest, anal canal
accessory digestive organs
teeth, tongye, salivary glands, liver, gallbladder, pancreas
assist in digestive process
other name for GI tract
alimentary canal
very brief functions of all GI tract parts
mouth - chew/swallow
pharynx/esophagus - transport
stomach - mechanical/chemical digestion
small I - mechanical/chemical digestion and absorption
large I - absorption of water, electorlytes, and vitamins
rectum - defecation
how long does it take for food ot digest
24-72 hours
one word steps for digestion process (6 basic processes)
ingestion
secretion
motility
digestion
absorption
defecation
ingestion
taking food into the mouth
secretion
cells within GI tract wall and accessory organs release water/acid/buffers/enzymes into the lumen of the GI tract
motility
contraction/relaxation of smooth muscel within teh GI tract walls to mix and propel contents
digestion (2 types)
mechanical
- movements of GI tract that break food into smaller particles
chemical
- catabolic reactions that split larges carbs fats and proteins into smaller, usable ones
absorption
end products of digestion pass form GI tract into blood o rlymph for cells
defecation
emptying the rectum to eleminate indigestible substances from GI tract
mechanical digestion
voluntary and invountary muscle contraction like grinding, swallowing, mixing, and propulsions
regulated by feedback loops
chemical digestion
hydrpolysis of large food molecules to small molecules
aided by digestive enzymes and secretions
hormonal control of digestive feedbacks
hormonal feedbakc loops, neural FB loops, some hormones are activated by enzymes
layers of teh GI tract (mainly, 4) deep to superficial
mucosa
submucosa
muscular layer
serosa/adventitia
keep in mind some of the GI tract parts are not like this, but most are
mucosa components (3)
epithelium
lamina propria
muscularis mucosae
muscular layer components (2)
circular and longitudinal muscle
serosa/adventitia components (2)
areolar CT
epithelium (sueprficial)
epithelium of the mucosa functions (2) and what its made of
protective
- non K strat sq epi in mouth, thraot, eso, and anal canal
secretion/absorption
- simple columnar epi in stoamch and intestines
what kind of cells does the mucosa epitehlium contain (2) (hormonal)
exocrine and enteroendocrine
lamina propria of the mucosa function and waht its made of
contain routes for nutrient absorption like blood/lymph vessels, nerves, glands
made of thin areolar CT
muscularis mucosae of the mucosa function and what its made of
thin layer of smooth muscle
causes folds to fold in mucosal layer to increase SA. moves to expose absorptive cells to contents of GI tract
submucosa functions and waht its made of
areolar CT
- has blood/lymph vessels, and glands
contains extensive neuron network called teh submucosal neural plexus
muscular layer of the GI tract function and what its made of
both skeletal and smooth muscle
skeletal
- control over swallowing and defecation
smooth
- consists of inner circular fibres and outer longitudinal fibres
- breaks down and propels food by peristalsis
has a second plexus of neurons
(myenteric neural plexus)
serosa of GI tract function and what its made of
areolar CT covered with simple sq epi
forms part of the peritoneum (visceral peritonium)
neural innervation of the GI tract (2 sets of nerves)
enteric nervous system
- local, intrinsic
autonomic NS
- long, extrinsic
enteric NS parts
myenteric plexus
- located between longitudinal and circular layers of muscle in muscular layer
- controls GI tract motility
submucosal plexus
- located in submucosa
- supplies secretory cells of mucosal epi
- controls secretiosn of organs in GI tract
interneurons of ENS
- connect myenteric and submucosal plexuses
sensory neurons of END
- supply mucosal epi
- detect stretching and chemo stuff
note: the ENS can function on its own, but can also be controlled by CNS and ANS
woooo
postganglionic ANS fibres are regulated by (3)
enteric NS
ANS
CNS
ANS innervation of the GI tract
regulate neurons of the ENS
parasympathetic
- CN X - vagus, supplies most of GI tract except last half of colon (Sacral nerves)
- synapse with para postganglionic neurons in plexuses, directly innervate muscle and glands
- INCREASES ENS ACTIVITY
sympathetic
- thoracic and upper lumbar nerves, sym postganglionic neruronssynaspe with plexuses, directly supply muscle and glands
- DECREASES ENS ACTIVITY
ENS role in digestion
controls involuntary movement of muscularis
local reflexes in GI tract
stimulatedd by distension (stretching)
ANS role in digestion
controls involuntary smooth muscle movmeent
stimulates by distension
PSNS - increases
SNS - decreases contraction of muscularis
CNS role in digestion
voluntary movement like chewing swallowing and parts of defecation
stimulates by presence or sight of food
GI reflex pathway (important)(full pathway + description)
GI reflex pathway regulates GI secretion and motility in response to GI tract stimuli
sensory ENS receptors -> ENS, CNS, ANS neurons -> activate of inhibit glands and smooth muscle -> alter secretions and motility
peritoneum
largest serous membrane in the body
consists of simple sq epi with areolar CT beneath
forms large folds that supply, suspend, and support organs in abdominal cavity
parietal peritoneum
lines walls of abdominopelvic cavity
visceral peritoneum
covers some organs (as there serosa)
organs inside the visceral peritoneum are
intraperitoneal
peritoneal cavity
between visceral and parietal layers
contains serous fluid
retroperitoneal organs
organs outsid ehte visceral peri
kidneys, pancreas, duodenum
5 major folds of the peritoneum
falciform ligament
lesser omentum
mesocolon
mesentry
greater omentum
greater omentum
largest peritoneal fold
- covers transverse colona nd small intestine
- contains lymph nodes and adipose tissue
- contributes to beer belly
falciform ligament
peritoneal fold
attaches stomach to anterior abdominal wall and diaphragm
lesser omentum
peritoneal fold
connects stomach and duodenum to liver
mesentry
peritoneal fold
attaches jejunum and ileum of SI to posterior abdominal wall
mesocolon
peritoneal fold
binds transverse and sigmoid colon to posterior abdominal wall
functions of the peritoneal folds (3)
route for blood, lymph, and nerves
prevents tangling of organs during movement
anchors organs in place
fauces
opening between oral caivty and oropharynx
oral cavity
extends from lips and teeth to fauces
hard palate
body roof that separates oral from nasal cavity
soft palate
muscular rood between oropharynx and naso
together with uvulua blocks entrance to nasal cavity during swallowing
lingual frenulum
limits movement of the tonuge posteriorly
3 major salivary glands
parotid
- inferior/anterior to ears, between skin and masseter
submandibular
- mediala nd inferior to mandible in floor of mouth
sublingual
- beneath tognue
mucous vs serous acini
mucous
- muscus secreting
- lighter in colour
serous
- serous fluid secreting
darker
parotid salivary gland cell type
serous acini only
submandibular salivary gland cell typ
mostly serous, few acini
sublingual salivary gland cell types
few serous, mostly mucous
mumps
painful inflammation of the parotid salivary gland
saliva compisition
99.5% water
rest solutes (na, k, cl)
lysozyme, salivary amylase
functions of saliva
wets food for swallowing
- dissolves food for tasting
- buffer acidic foods
- chemical digestion of starch by salivary amylase
- removal of metabolic waste like urea
-
immune functions of saliva
lysozyme helps destory bacteria
IgA prevents attachment of mmicrobes to epithelium
salivation
controlled by ANS
tongue functions
movement, speech, digestion
lingual glands of the tongue function
secrete lingual lipase that breaks down triglycerides
teeth #
20 primary
32 permanent
tooth anatomy
crown - top
neck - gum part
root - in gums
pulp - inner area
- contains vessels, nerves
- nourishes tooth
where does starch begin digestion
in teh mouth by salivary amylase
ph in mouth
6.5-7
what starts triglyceride digestion
lingual lipase form lingual glands in the tongue
tehn in stomach
what inactivates salivary amylase
gastric juices
starch digests into
disaccharides / tri
pharynx anatomy
tube of skeleteal muscle lined with mucous membrane
divided into 3 parts (naso/oro/laryngo)
propels food into esophagus
esophagus anatomy
muscular tube that secretes mucus to trasnprot food to stoamach
esophagus histology (4 layers and what theya re made of)
mucosa
- strat sq epi
submucosa
- areolar, contains vessels and glands
muscular layer
- upper - skeletal
- mid - both
- lower - smooth
adventitia
- areolar CT
- NO epithelium
- attaches esophagus to structures
deglutition
swallowing
stages of deglutition (3)
voluntary stage
involuntary stage
esophageal stage
voluntary stage of deglutition
tongue pushes food bolus into oropharynx
involuntary pharyngeal stage of deglutition
bolus stimulaes receptors in oropharynx
- receptors send impulse to deglutition centre in brain
- bolus moves to esophagus
- soft palate/uvula block nasal cavity
- epiglottis covers trachea
- bolus moves to laryngopharynx
esophageal stage of deglutition
peristalsis moved bolus from esophagus to stomach
GERD
gastroesophageal reflux disease
gastroesophageal reflux disease
GERD
failure of lower esophageal sphincter to close
causes heartburn
functions of stomach
mixing
- saliva, gastric juices, forms chyme
reservoir
- holds and releases to SI
digestion
- carb/fats continue, protein begins here
secretion
- gastric juice into stomach, gastrin into blood
gastric juice components
HCI, pepsin, intrinsic factor, gastric lipase
gastrin
hormone made by G cells
4 main parts of the stomach
cardia
fundus
body
pyloric part
lesser and greater curvatures
circumerfunce of teh stomach
rugae
stomach fold for volume when stretches
fundus
top of stomach above lower eso sphiincter
cardia
right after lower eso sphinchter
body of stomach
main part
pyloris
end part of stomach
pyloric sphinchter
connects stomach and SI
pyloric canal
before pyloric sphinchter
pyloric antrum
befoer pyloric canal
surface of mucosa in stomach is lined with
simple columnar epi
epithelial cells in teh stomach descend down to
lamina propria to form gastric pits for glands (in the pits) to release stuff into
gastric gland cells (5)
surface mucous
- secrete mucous
mucous neck cells
- secrete mucous
parietal cell
- secreted HCI and intrinsic factor
chief cell
- secretes pepsinogen and gastric lipase
G cell
- secretes gastrin
exocrine cells of gastric glands
mucous neck cells
parietal cells
chief cells
pepsinogen function
protein digestion
gastric lipase funcgion
fat digestion
enteroendocrine cells in gaastric glands
G cells
gastric juice composition from glands
mucous / parietal / chief
submucosa of stomach is made of
areolar CT
muscular layer of stomach (3 layers)
inner oblique
circular
outer longitudinal
(super to deep)
permits greater churning of food
overview of stomach digestion (little things)
digestive movements are stimulated by PNS
- stretch receptors detect distension
- enteric reflexes promote peristalsis
retropulsion
churning of chyme backward when it is not ready to go into the SI
protein digestion in stomach(2 steps)
protien digestion begins here
- HCI denatures proteins
- HCI converts pepsinogen to pepsin which breaks peptide bonds in amino acids
fat digestion in teh stomach
continues (already previously started)
gastric and lingual lipases split triglycerides
activity of lingual lipase is increased by
gastric juice
what protects stomach walls
mucous cells that secrete an alkaline mucous layer 1-3 mm thick
how is HCI secreted
parietal cells secrete H and CL separately into teh stomach lumen
water and CO2 undergo reactions to form H and HCO3. HCO3 is antiported into blood with Cl. now Cl and H are released by Cl channels and proton pumps respectively
weight loss treatments in obese people
laparoscopic gastric bypass
laparoscopic sleeve gastectomy
adjustable gastric band
enterogastric relfex
stretching of duodenum wall prevents further emptying of the stomach
accessory organs that allow chemical digestion in teh SI
pancreas
liver
G bladder
pancreas ducts
pancreatic duct
- runs thru whole thing
accessory duct
- branch off near end
pathway of ducts for bile/pancreatic juice
right hepatic and left hepatic join to form common hepatic duct from liver
cystic duct from gall bladder joins common hepatic to form common bile duct.
common bile duct joins pancreatic duct to form hepatopancreatic ampulla
then into lumen of duodenum
pancreatic acini
exocrine cells that produce pancreatic juice
pancreatic islets
produce hormones
pancreatic juice contains enzymes: what are they and waht do tehy digest
pancreatic amylase - starch
pancreatic lipase - fats
ribonuclease/deoxy - nuclei acids
proteins
- trypsinogen (trypsin)
- chymotrypsinogen (chymotripsin
- procarboexypeptidase (carboxypeptidase)
- proelastase (elastase)
chymo and procarbo are inactive n pancreas and are activated by trypsin in duodenum
trypsin and trypsinogen
trypsinogen is inactive in the pancreas and is activated into trypsin by enterokinase in duodenum
what converts acidic chyme from stomach to alkaline in the small intestine
what does it inhibit/promote
sodium bicarbinate
inhibits pepsin/ promotes pancreatic enzymes
liver function
produce bile
gallbladder function
concentrates/stores bile until needed
major component of the liver (3)
heptocytes
bile canaliculi
hepatic sinusoids
hepatocytes functin
metabilic/secretory/endocrine cells of teh liver
bile canaliculi function
small canals for bile
hepatic sinusoids function
permeable capillaires between hepatocytesta
portal triad
bile duct, hepatic artery branch, hepatic vein branhc
liver blood supply
liver receives double blood supply
- O2 blod from hepatic artery
- deoxy blood from hepatic portal vein containing lots of nutrients, toxins, drugs
all blood circulates thru sinusoids where everything is taken up
central vein of the liver function
accept secretions from hepatocytes, carry blood to hepatic vein
what does bile contain
water, bile salts, pigements (bilirubin), ions
function of bile salts
emulsify fats to assits lipid digestion and absorption
liver functions in depth
fat emulsification (bile salts)
lipid metabolism
glucose homeostasis
carb metabolism
protein metabolism
detox/excretion
storage of vitamins and minerals
phagocytosis of worn out blood cells and bacteria
