Unit 4: The Digestive System: Structures and Functions (Module 3)

ingestion, secretion, motility, digestion, absorption, defecation

functions of the digestive system (6)

enzymes, buffers, acids

what does the digestive system secrete?

motility

propulsion and mixing (function)

chemical and mechanical

two types of digestion

chemical

digestion that involves enzyme secretion

mechanical

digestion that involves chewing and churning

nutrients; blood and lymph

what is being absorbed and into where?

defecation

elimination of wastes (function)

mucosa, submucosa, muscularis, serosa

4 layers of the GI tract

mucosa

the innermost layer of the GI tract; has direct contact with the contents of the GI tract; subdivided into three layers

stratified squamous/simple columnar ET, lamina propria, muscularis mucosae

what are three layers of the mucosa layer?

absorption and secretion

what is the function of the stratified squamous/simple columnar ET of the mucosa layer?

5-7 days

the stratitied squamous/simple columnar layer of the mucosa is renewed every ____

areolar CT

the lamina propria is made of _______

lamina propria

has blood and lymph supply that absorbs nutrients; has MALT/lymph nodules for immunity

muscularis mucosae

thin layer of smooth muscle in the mucosa

areolar CT

the submucosa is made of ______

submucosa

layer of the GI tract that is highly vascularized

submucosal plexus

network of nerves in the submucosa that is part of the enteric NS

submucosal plexus

stimulates smooth muscle contractions and stimulates secretory cells of mucosa

muscularis

has both skeletal muscle and smooth muscle as well as the myentreric plexus

mouth, pharynx, upper esophagus, external anal sphincter

what structures are made of skeletal muscle in the muscularis?

all other locations of the GI tract (middle section)

what structures are made of smooth muscle in the muscularis?

inner circular and outer longitudinal

two layers of smooth muscle in the muscularis

myenteric plexus

stimulates the movements of GI tract (peristalsis)

parasympathetic

peristalsis is stimulated by _____ neurons

peristalsis

mixing and propulsions are referred to as ______

myenteric plexus and submucosal plexus

two parts of the enteric NS

serosa

serous membrane layer

areolar CT and simple squamous epithelium

what is the serosa made of?

visceral peritoneum

the serosa is the same as the ______

produces serous fluid, lubricates

functions of the serosa

mouth → pharynx → esophagus → stomach → small intestine → large intestine → anal canal → anus

digestive organs that form the GI tract (in order from eating to pooping)

pancreas, liver, gallbladder

accessory structures

peritoneum

serous membrane that lines the abdominopelvic cavity

peritoneal cavity; serous fluid

spaces between the parietal and visceral layer of the peritoneum (and what fills it)

greater omentum

apron extending from the transverse colon to the small intestine and stomach

lesser omentum

peritoneum folds that extends between the liver and the stomach

mesentery

fold of peritoneum that extends from post abdominal wall to surround intestines (suspends them); anchors the small intestines while still allowing for movement

mastication

chewing; mechanical breakdown of food

keep mouth moist, moistens food, lubricates (to protect esophagus)

functions of salivary glands

parotid, sublingual, submandibular

what are the three salivary glands?

H2O (99.5%)

what is saliva mostly made of?

ions, mucus (proteins, lipids, polysaccharides), immunoglobulin A

what is the other 0.5% of saliva made of?

immunoglobulin A

prevents the growth of microorganisms; found in saliva

salivary amylase

breaks down starch (carbs) into sugar (in mouth)

lingual lipase

breaks down TG (lipids); produced in the mouth but not activated until it reaches the acidic environment of the stomach

1000-1500mL/day

how much saliva is made per day?

parasympathetic NS, food, learned behavior, irritants of stomach, small intestine, nausea

what are things that stimulate saliva production?

food stimulates taste buds → salivary nucleus in brain stem → salivation

how does food promote salivation? arrows

sympathetic NS (to conserve H2O) and dehydration

what inhibits saliva production?

mumps

infection of the parotid glands; causes pain in throat, fever

inflamed testes

what can mumps cause in men?

bolus

amount of food you consume then swallow in one big bite

deglutition

swallowing

ok

read this info about deglutition:
tongue pushes bolus into oropharynx. Pons and medulla initiate a series of reflexes: breathing ceases as respiratory passage closes, uvula and soft palate move upward to close off airways, larynx moves forward and upward to cause epiglottis to fold over larynx. Once bolus passes into esophagus, all return to prior state

10” long

how long is the esophagus?

upper esophageal sphincter

as ____ relaxes, food enters the esophagus

lower esophageal sphincter

______ relaxes while swallowing to allow food into stomach

hiatal hernia

stomach protrudes upward above esophageal hiatus of diaphragm

gastroesophageal reflux disease (GERD)

lower esophageal sphincter does not close properly after bolus enters stomach; acids in stomach can creep into esophagus

1. avoid foods that increase acid production

2. neutralizers

3. acid reducers

3 treatments for GERD

coffee, chocolate, onions, orange juice

4 high acid foods

tums (antiacids)

example of neutralizer

H2 Blockers and Proton Pump Inhibitors

two examples of Acid Reducers

tagament, pepcid AC

examples of H2 Blockers

prilosec and protonix

two examples of proton pump inhibitors