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AP WINTER
DIGESTIVE SYSTEM
LEC 24: intestines
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Cards (20)
Deep circular folds
Force
chyme
to
spiral
Increase
mixing for
nutrient
absorption
Villi & microvilli
Finger-like
projection
Increase
surface
area
Intestinal crypts
Tubular glands
Produce
mucus
, hormones, antimicrobial compounds that can destroy
invasive bacteria
(paneth cells)
Villus epithelium
Contains
rapidly dividing
cells
Goblet cells
Secrete
mucous
Protect
intestinal
lining
Enterocytes
Absorb nutrients from
chyme
into
bloodstream
Primary
absorptive
cells
Paneth cells
Produce
antimicrobial
compounds
Maintain
gut
health
Roles of cell types in the intestinal mucosa
Enterocytes
- absorb nutrients from
chyme
into bloodstream
Goblet
cells - secrete mucous, protect
intestinal lining
Enteroendocrine
cells - produce
hormones
involved in
digestion
& gut function
Paneth
cells - produce
antimicrobial
compounds, maintain
gut
health
Stem
cells - replace other
cell types
, regenerate
intestinal
epithelium
Major functions of large intestine
Absorbs
water
from ingestible food residues
Forms and stores
feces
Houses bacteria that ferment indigestible
carbohydrates
Synthesizes
B
complex vitamines and vitamin
K
Influences the behaviour of the
immune
system
Protects against ingested
pathogens
Diarrhoea
Watery
stool - large intestine does not have enough
time
to absorb remaining
water
in
chyme
Causes of
diarrhoea
Irritation
of the
colon
by
bacteria
or jostling of digestive viscera
Constipation
Difficulty passing
stool
Hard
and
dry
stool
Infrequent
bowel
movements
Causes of constipation
Food remaining in the colon for
extended
periods of time
Excessive water
reabsorption
Components of bowel transit time
Stomach
transit time - influenced by
food
volume,
composition
, gastric
emptying
rate
Small intestine
transit time - affected by
motility
, presence of food
particles
,
absorption
rate
Colon
transit time - determined by
peristaltic
contractions,
water
absorption,
stool
consistency
Intestinal juice
Secreted in response to
acidic chyme
Between meals, migrating motor complexes move remnants toward the
large intestine
in
waves
The
large intestine
(also known as the
colon
) absorbs
water
from indigestible food residues and eliminates the latter as
faeces
what transit time is influenced by food volume, composition, and emptying rate?
stomach
what transit time is affected by motility, presence of food particles, and absorption rate?
small intestine
what transit time is determined by peristaltic contractions, water reabsorption, and stool consistency?
colon