Anatomy: Digestive System
1.
1.
1.
2.
3.
Structure and Function
1.
Organization- 2 parts
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1.
Alimentary canal (GI tract) - 9m tube w/ lumen
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mouth, pharynx, esophagus, stomach, sm. and lg. intestine
2.
2.
Accessory organs - teeth, tongue, salivary glands, liver,
gallbladder, pancreas
2.
Digestive Processes - 7
1.
1.
ingestion
2.
2.
propulsion - swallowing and peristalsis
3.
3.
secretion - enzymes, adjust pH, liquifies food
4.
4.
mechanical digestion - chewing (mastication), mixing w/ tongue,
stomach, SI
5.
5.
chemical digestion
6.
6.
absorption- from lumen into blood or lymph
7.
7.
defecation
3.
Structure of Wall of GI Tract - 4 layers
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1.
Mucosa- mucous mem. lining lumen, protects, secretes, and
absorbs, 3 layers
1.
1.
epithelium - str. squamous or columnar w/ goblet cells
2.
2.
lamina propria - areolar CT w/ blood and lymphatic
vessels
(1)
(1)
MALT - lymph tissue that protects GI tract
3.
3.
muscularis mucosae- smooth muscle, folds that increase
surface area
2.
2.
Submucosa - areolar CT w/ blood and lymph vessels and nerves
and glands,
3.
4.
2.
2.
1.
3.
Muscularis - 2-3 layers of smooth or skeletal muscle, mechanical
digestion and propulsion
1.
1.
sphincters - circular layers of smooth muscle that form
valves
4.
Serosa - serous mem. lining outside of organs
1.
1.
parietal peritoneum - lines walls of abdominalpelvic
cavity, folds attach and anchor internal organs
2.
2.
visceral peritoneum - lines digestive organs
(1)
(1)
mesentery - attaches SI to rear wall
(2)
(2)
greater omentum - fold from stomach that covers
SI like an apron
Digestive Organs
1.
Mouth (oral ar buccal cavity)- mechanical and chemical digestion
1.
1.
lips and cheeks form ext. walls, vestibule - space btwn teeth and
lips
2.
2.
palate - forms roof of mouth, divided into hard and soft regions
1.
1.
uvula - fingerlike projection that closes opening to nasal
3.
4.
5.
2.
3.
4.
6.
2.
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3.
3.
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2.
3.
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cavity during swallowing
3.
tongue - forms floor of mouth, composed of skeletal muscles,
moves food during mastication and swallowing, covered w/ papillae for
friction and taste
4.
teeth
1.
1.
2 sets - 20 deciduous (baby), 32 permanent (adolescence
onward)
2.
2.
3 types
(1)
(1)
incisors - chisel edge for cutting
(2)
(2)
canines - pointed for tearing
(3)
(3)
premolars and molars - flat for grinding and
crushing
3.
3.
tooth structure
(1)
(1)
crown - visible part above gingivae (gums)
(2)
(2)
root - region embedded in bone
(3)
(3)
dentin - bulk of tooth, bone-like substance
(4)
(4)
enamel - hard, nonliving material covering crown
(5)
(5)
pulp cavity - inside tooth, contains blood vessels,
nerves and CT
(6)
(6)
cementum - bonelike substance covers root and
binds to periodontal ligament
5.
saliva
1.
1.
composed of 99% water, lysozyme (enzyme destroys
bacteria), salivary amylase (enzyme breaks down starch), proteins,
antibodies, and ions
2.
2.
lubricates mouth, moistens food, begins chemical dig.
3.
3.
produced by 3 pairs of glands
(1)
(1)
parotid glands - in front of ears
(2)
(2)
submandibular glands - inner surface of jaw in
floor of mouth
(3)
(3)
sublingual glands - in front of submandibular
glands
6.
digestion in mouth
Pharynx
1.
3 regions
2.
transports food from oral cavity to esophagus
3.
process of swallowing
Esophagus
1.
25cm muscular tube behind trachea, transports food to stomach
2.
esophageal hiatus - opening in diaphragm
3.
sphincters at both ends control direction of food
1.
1.
upper esophageal
2.
2.
lower esophageal (cardiac sphincter)
(1)
(1)
heartburn
Stomach
1.
structure 25cm long, holds 2 l
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3.
2.
3.
5.
5.
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2.
3.
4.
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2.
3.
(1)
(2)
(3)
(4)
rugae - deep folds in inner lining, disappear when full
greater and lesser curvatures
4 regions
(1)
cardia - receives food from esophagus
(2)
fundus - temporary storage
(3)
body - main part
(4)
pylorus - narrow inferior region
(1)
(1)
pyloric sphincter - controls food into SI
2.
stomach wall - 4 basic layers, mucosa is specialized
1.
1.
gastric pits - connect to gastric glands which secrete
gastric juice
(1)
(1)
zygmogenic (chief) cells - digestive enzymes
(2)
(2)
parietal cells - HCL
(3)
(3)
mucous cells - mucus
2.
2.
3 muscle layers - aid mechanical dig. and mixing
3.
functions of stomach
1.
1.
mechanical dig. - more than any other organ
2.
2.
chemical dig. - enzyme pepsin, splits protein, needs acidic
environ.
3.
3.
absorption - limited
4.
4.
propulsion - food converted to paste called chyme, passes
thru pyloric sphincter
5.
5.
intrinsic factor - secreted by parietal cells, aids B12
absorption in SI
Small Intestine
1.
6m x 2.5cm
2.
3 regions
1.
1.
duodenum - receives chyme, immovable
2.
2.
jejunum - mobile
3.
3.
ilium - longest region, ends in ileocecal valve
3.
SI wall-adaptations to mucosa and submucosa
1.
1.
intestinal villi - tiny projections of mucosa
2.
2.
microvilli - cell mem. modification, increases absorption
surface
3.
3.
intestinal glands - at base of villi, secrete water and mucus
w/ neutral pH
4.
4.
Peyers patches - in submucosa, protect from infections
5.
5.
Brunners glands - submuc. secrete alkaline mucus into
duodenum
4.
functions of SI
1.
1.
chemical dig. - mix chyme w/ enzymes from pancreas and
bile from gall bladder, also produces intestinal enzymes
2.
2.
absorption - main site of nutrient absorption, facilitated or
active transport into epithelium, diffusion into blood and lymph
3.
3.
propulsion - mixing back and forth for increased
absorption
6.
6.
1.
2.
3.
4.
3.
3.
1.
2.
(1)
(1)
diarrhea Large Intestine
1.
1.5m x 7cm
2.
4 regions
1.
1.
cecum - receives food from ileum, short pouchlike,
(1)
(1)
vermiform appendix
2.
2.
colon - longest region, ascending, transverse, descending,
and sigmoid colons
3.
3.
rectum - located in pelvic cavity
4.
4.
anal canal - opens into anus, 2 sphincters
3.
wall of Lg I.
1.
1.
4 basic layers, lack villi
2.
2.
plicae circulares - permanent folds in mucosa and
submucosa of sm. and lg. intestines, moves chyme in spiral flow
3.
3.
anal columns - parallel folds in anal canal, reduce friction
4.
functions
1.
1.
feces formation - absorption of water and electrolytes,
hardening of chyme into feces
2.
2.
defecation - feces stored in rectum until its full, nerve
receptors initiate def. reflex >>increased peristalsis and relaxation
of internal sphincter and urge
Accessory Organs
1.
Pancreas
1.
1.
structure
1.
1.
acini 2.
2.
pancreatic juice 3.
3.
pancreatic duct 2.
2.
functions
1.
1.
p. amylase
2.
2.
trypsin, chymotrypsin, carboxypeptidase 3.
3.
p. lipase
4.
4.
nuclease
3.
3.
regulation
1.
1.
control center 2.
2.
secretin 3.
3.
cholecystokinin
2.
Liver
1.
1.
structure
1.
1.
lobes and lobules
2.
2.
hepatocytes 3.
3.
sinusoids
4.
4.
Kupffer cells
5.
5.
bile
6.
6.
hepatic duct, cystic duct, common bile duct
2.
2.
functions
1.
1.
bile
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3.
4.
(1)
(2)
2.
3.
(1)
4.
(1)
emulsification
(2)
Vitamins A, D, E, K
blood glucose
fat metabolism
(1)
lipoproteins
(1)
(1)
HDLs, LDLs, VLDLs
(2)
(2)
atherosclerosis
protein metabolism
3.
3.
1.
2.
3.
5.
5.
toxic materials
6.
6.
red blood cells
Gallbladder
1.
location
2.
function
1.
1.
store and concentrate bile
3.
sphincter of Oddi