(2) groups of organs compose digestive system
Gastrointestinal (GI) tract
Accessory digestive organs
Gastrointestinal (GI) tract
mouth, most of pharynx, esophagus, stomach, small intestine & large intestine
Accessory digestive organs
teeth, tongue, salivary glands, liver, gallbladder & pancreas
(6) functions of digestive system
ingestion
secretion of water, acid, buffers & enzymes into lumen
mixing & propulsion
digestion (mechanical & chemical)
absorption
defecation
(4) LAYERS of GI Tract
Mucosa
Submucosa
Muscularis
Serosa
Mucosa - inner lining
epithelium - protection, secretion & absorption
lamina propria - CT with blood & lymphatic vessels & MALT
muscularis mucosae - thin layer of folded smooth muscle
Submucosa
CT binding mucosa to muscularis
contains many blood & lymphatic vessels
submucosal plexus - network of neurons
Muscularis
voluntary skeletal muscle in pharynx, mouth, upper 2/3 of esophagus & anal sphincter
involuntary smooth muscle elsewhere
arranged in inner circular fibers & outer longitudinal fibers
myenteric plexus between muscle layers
Serosa
outermost covering of organs suspended in abdominopelvic cavity
also called visceral peritoneum
esophagus lacks serosa - has adventitia
Neural Innervation (2)
Enteric Nervous system
Autonomic nervous system
enteric nervous sytem
intrinsic set of nerves - "brain of gut"
neurons extending from esophagus to anus
(2) plexuses
- myenteric (GI tract motility)
- submucosal (controlling secretions)
Autonomic Nervous system
extrinsic set of nerves
Parasympathetic stimulation - increases secretion & activity by stimulating ENS
Sympathetic stimulation - decreases secretion & activity by inhibiting ENS
Peritoneum
divided into? (2)
largest serous membrane of body
parietal - lines wall of cavity
visceral (aka serosa) - covers organs
(5) major peritoneal folds
greater omentum
falciform ligament
lesser omentum
mesentery
mesocolon
Oral Cavity
formed by?
cheeks, hard & soft palates & tongue
Oral cavity proper
space from gums & teeth to fauces (opening between oral cavity & oropharynx)
(3) pairs of major salivary glands secrete most of saliva
parotid
submandibular
sublingual
Salivation controlled by?
parasympathetic stimulation
sympathetic stimulation
ANS
parasympathetic stimulation - promotes secretion
sympathetic stimulation - decreases salivation
Teeth - (3) major regions
crown
root
neck
Dentin of crown covered by ___
enamel
2 sets of teeth
deciduous (baby teeth)
permanent teeth
Mechanical Digestion in mouth
chewing
tongue, teeth, saliva
forms bolus
Chemical Digestion
salivary amylase - secreted by salivary glands acts on starches
inactived by stomach acid
lingual lipase - secreted by lingual glands of tongue acts on triglycerides
activated in acidic environment of stomach
Pharynx
(3) parts
food passes from mouth into pharynx
nasopharynx - respiration
oropharynx - digestive & respiratory
laryngopharynx - digestive & respiratory
Esophagus
secretes mucous, transports food - no enzymes produced, no absorption
Esophagus
1) mucosa
2) submucosa
3) muscularis
4) adventitia
1) protection against wear & tear
2) ---
3) divided into third
superior - skeletal
middle - skeletal & smooth
inferior - smooth
2 sphincters
(2) sphincters in esophagus muscularis
Upper esophageal sphincter (UES) - regulates movement into esophagus
Lower esophageal sphincter (LES) - regulates movement into stomach
Swallowing involves (3)
(3) stages
mouth, pharynx, esophagus
voluntary - bolus → oropharynx
pharyngeal - pharynx → esophagus
esophageal - esophagus → stomach
Stomach
(4) main regions
cardia
fundus
body
pyloric part - pyloric antrum, pyloric canal, pylorus
Stomach mucosa
gastric glands open into gastric pits
(3) types of exocrine gland cells
- mucous neck cells, parietal cells, chief cells (pepsinogen & gastric lipase)
G cell - endocrine cell - secretes gastrin
