DIGESTIVE SYSTEM CHAPTER 24
I.
Introduction
A. Alimentary canal
(GI tract)
1. mouth
2.
pharynx
3.
esophagus
4.
stomach
5.
small intestine
6.
large intestine
7.
anus
B.
Accessory organs
1.
tongue
2.
salivary glands
3.
teeth
4.
liver
5.
gallbladder
6.
pancreas
C.
Processes
1.
ingestion
a. take in food
2.
mechanical breakdown
a. decrease size of
particles
b. churning in stomach
3.
chemical digestion
a.
enzyme action to degrade to smaller units
4.
absorption
a.
simple units from digestion taken into blood or lymph from lumen of GI
tract
5.
propulsion
a. to move contents of lumen
b.
occurs entire length of GI tract
c. tongue pushes food
into esophague
d. perstalsis
(1)waves of
contraction/relaxation
6.defecation
a.
excretion of indigestables
II. ANATOMY
A.peritoneum
1.membrane of abdominal
cavity
a. visceral over
surface of organs
b. parietal near wall
of cavity
2.
peritoneal cavity
a.
serous fluid
3.
mesentery
a.
double membrane of peritoneum
b.
contains:
(1)blood vessels
(2)lymphatics
(3)nerves
c.
positions organs in abdominal cavity
B.
circulation
1.
arterial:
a.abdominal
aorta
b.splanchnic
circulation
(1)celiac
trunk
(2)hepatic
(3)splenic
(4)gastric
(5)mesenteric
c.hepatic portal circulation
(1)venous blood from GI to
liver -first pass
C.
Histology
1.
mucosa
a.columar
epithelial membrane lining the lumen
b.
functions:
(1)absorption
(2)secretion
(a)mucus
(b)hormones
(c)digestive enzymes
and HCl
(3)protection
c.
specialized for specific sites in GI
d.
contains underlying lamina propria of loose
connective tissue and blood vessels
e.
muscularis mucosae
2.
submucosa
a.
dense CT
b.
vascular network
c.
submucosal plexus
(1)
intrinsic nerve supply (autonomics)
(a)glands
(b)smooth muscle of
mucosa
3.
Muscularis Externa
a.
circular layer of smooth muscle
b.
longitudinal layer of smooth muscle
c. myenteric plexus (autonomic) to
control motility of GI tract
How
do sympathetic and parasympathetic fibers differ
in
regulation of GI motility?
4.
Serosa
a.
areolar connective tissue
b.
mesothelium
(1)simple
squamous epithelium
c.
certain areas may contain adventitia in place of serosa
(1)esophagus
(2)rectum
D.
Organs of the alimentary canal
1.Mouth
a.oral
or buccal cavity
b.oropharynx
c.
lips(labia)
d.labial frenulum
e.palate(roof)
(1)hard
(a)palatine and
palatine process of maxillae
(2)soft
(a)skeletal muscle
(b)uvula
(c)fauces
i)contain platine tonsils
ii)opening to pharynx
(3)tongue
(a)taste buds
(b)moves food
(c)forms bolus
(d)muscles
i)intrinsic
a)unattached to bone
ii)extrinsic
a)from bones of skull
or soft palate
(e)lingual frenulum
f.salivary glands
(1)serous fluid
(2)salivary amylase
(3)3 pairs
(a)parotid
i)anterior to ear
ii)superficial to masseter
iii)mumps - viral infection
(b)submandibular gland
(c)sublingual
i)under tongue
(4)parasympathetic control
g.teeth (dentitions)
(1)deciduous teeth
(a)primary or baby
teeth
(b)20
(2)permanent teeth
(a)32 including wisdom
teeth (3rd molars)
(b)impacted if remains
in jaw
(3)types
(a)incisors
i)cutting
ii)central and lateral
(b)canines
i)tearing
(c)premolars
i)1st and 2nd set-
grind/crush
(d)molars
i)1st,2nd, and 3rd
-grind/crush
(4)structure
(a)crown
i)enamel - calcium salts
(b)gingiva
i)gums
(c)root
i)within jaw
ii)outer portion covered in
cementum
a)calcified CT
(d)periodontal ligament
(e)dentin
i)under enamel
ii)bonelike
iii)surrounds pulp cavity
iv)pulp cavity in root is
root canal
v)odontoblasts
a)cells secreting
dentin
(5)dental diseases
(a)dental caries
i)dental plaque
a)sugar, bacteria
b)calculus
(i)calcified
plaque
(b)gingivitis
i)inflammation of gums
(c)peridontal disease
i)tooth loss
(6)functions in digestion
(a)mastication
i)chewing
ii)mechanical breakdown of
food
(b)lubrication of food
(c)deglutition
i)swallowing
(d)CHO breakdown by salivary amylase
2.Pharynx
a.oropharynx and
laryngopharynx
b.stratified squanous
epithelium
(1)friction
c.skeletal muscle in outer layer
3.Esophagus
a.carries food to
stomach
b.located in
mediastinum
c.esophageal hiatus
(1)where esophagus passes
through diaphragm
(2)enters stomach at
cardiac orifice
d.skeletal muscle in superior portions of muscularis
externa
e.hiatal hernia
(1)portion of stomach or SI
enters thoracic cavity at esophageal hiatus
f.esophagus and pharynx function in deglutition
4.Stomach
a.empty 50ml volume
b.stretch to 4L
c. rugae
(1)folds of mucosa and
submucosa when empty
d.regions
(1)cardiac
(2)fundus
(3)body
(4)pylorus
(a)joins duodenum at
pyloric sphincter
e.layers
(1)muscularis externa
(a)has additional
oblique layer
(b)churning function as
well as movement
i)creates CHYME
a)semi-liquid
f.simple columar epithelium
(1)goblet cells
(a)secrete mucus
g.gastric pits
(1)lead to gastric glands
(a)secrete gastric
juice
h.cells
(1)parietal cells
(a)HCl
(b)intrinsic factor
i)vitamin B12 absorption in
SI
(2)chief cells
(a)pepsinogen
(3)enteroendocrine cells
(a)hormones of
digestion
i)gastrin
a)stimulated by
proteins
b)stimulates gastric
gland secretions
c)stimulates movement
of food through GI
ii)serotonin
a)stimulated by food
b)stimulates
contraction of Smooth muscle
iii)histamine
a)stimulated by food
b)stimulates secretion
of HCl
iv)somatostatin
a)stimulated by food
b)inhibits secretion
of stomach and pancreas
i.digestive functions of the stomach
(1)protein digestion
(2)pepsinogen converted to
pepsin
(3)Phases of gastric
secretion
(a)Cephalic phase
i)triggered by senses
ii) increase secretions
(b)Gastric phase
i)presence of food in
stomach
ii)stimuli for secretions
a)stretch
b)peptides or other
foodstuffs
c)pH- proteins act as
buffers
and tie up H ions to increase pH
d)histamine stimulates
HCl
e)Cloride ions in HCl come
from plasma and H ions from carbonic acid in parietal cell.. bicarobonate ions
are returned to capillaries and makes blood from stomach more alkaline - ALKALINE TIDE
(c)intestinal phase
i)excitatory
ii)inhibitory
iii)movement of food
through tract
(4)Motility
(a)peristalsis
(b)relaxing,
contraction of valves
(5)Vomiting reflex
(a)reverse emptying of
stomach
(b)irritants, toxins
(c)extreme stretch
5.Small Intestines
a.most digestion and
absorption occurs here
b.pyloric sphincter to
ileocecal valve
c.1 inch diameter and
20 feet long (cadaver)
d. divisions
(1)duodenum
(a)around pancreas, 10
inches
(b)hepatopancreatic ampulla
i)bile and pancreatic juice
enters
ii)regulated by sphincter
of Oddi
(2)jejunum
(a)8 feet
(3)ileum
(a)12 feet
(b)suspended by
mesentery
e.modified for absorption
(1)plicae circulares
(a)circular folds of
mucosa and submucosa
(b)mixing of chyme
-spiral
(2)villi
(a)fingerlike
projections of mucosa
(b)absorptive columnar
cells
(3)microvilli
(a)projections from
each epithelial cell
(b)increases surface
area
(c)brush border
(d)brush border enzymes
i)to complete SI digestion
of
carbohydrates
and proteins
(4)pits to intestinal glands
(a)intestinal crypts
(glands)
i)secrete intestinal juice
a)watery, mucous
ii)Paneth cells
a)lysozyme
(5)submucosa
(a)Peyer's Patches
i)lymphoid tissue
ii)more in LI
(b)Duodenal glands