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Digestive System (General Functions and Structure (Peristalsis (does not…
Digestive System
General Functions and Structure
Major functions
break down food into pieces small enough to be absorbed into the circulatory system (blood, lymphatic)
eliminate what we can't break down
gastrointestinal (GI) tract vs. accessory digestive organs
gastrointestinal (GI) tract
accessory
liver (makes bile)
gallbladder
pancreas
salivary glands
chemical vs. mechanical
mechanical
teeth
stomach (churn)
cut up food, makes smaller
small intestine (segmentation: mixes content and squeezes back and forth)
chemical
saliva (mouth)
stomach
add chemical enzymes
small intestine (many enzymes from pancreas)
Peristalsis
does not move back and forth just downward
occurs from esophagus through large intestine
another type of movement
wave of contraction
Trace the pathway of food
oral cavity --> pharynx --> esophagus --> stomach --> small intestine --> large intestine --> anus
Peritoneum and Mesenteries
Intraperitoneal vs. retroperitoneal
intraperitoneal
within peritoneum
transverse colon
jejunum
stomach
liver
illeum
sigmoid colon
retroperitoneal
no within peritoneum
pancreas
ascending colon
duodenum
descending colon
rectum
Mesentery locations
mesocolon
connected to the transverse colon and sigmoid colon to the posterior wall
lesser omentum
starts at the lesser curvature and extends up to the liver
greater omentum
starts at the greater curvature
drapes over all organs and attaches up over transverse colon to the posterior wall
mesentery proper
within the jejunum an dilleum
Define mesentery and explain function
hold organs in place
stores fat
from the body wall to the digestive organs
provides place for blood vessels to travel through
double layer of peritoneum
ability to migrate and wrap around/enclose an infected or inflamed organ
Gross and microscopic anatomy of stomach
gastric glands
parietal cells
produce hydrochloric acid (HCL)
produce instrinsic factor needed for vitamin B12
chief cells
secrete pepsinogen (pepsinogen + acid = pepsin)
sphincters
cardiac
prevent the reflux of acid into the esophagus
pyloric
regulating the amount of chyme moving on to the small intestine
General functions
mechanical digestion - churning
chemical digestion begins in the stomach
store food
rugae
mucosa of the somach
further breaks down food with raised ridges
Gross and microscopic anatomy of small intestine
Features
Villi
helps to increase the surface area for nutrient absorption
microvilli
anchor sheets of mucus or increase surface area for absorption
circular folds
slow down movement of chyme through the small intestine
Small intestine structures
intestinal glands
secrete watery interstitial fluid to keep everything in liquid state
peyer patches
collections of lymphocytes
duodenal glands
secrete alkaline mucus (protection)
alkaline neutralizes acidity of chyme from the stomach
General functions
mechanical digestion - segmentation
chemical digestion - enzymes
illeocecal valve
located internally surrounding the cecum's medial wall
formed by two raised edges of mucosa
sphincter in distal ileum keeps valve closed until food is in the stomach
Gross and microscopic anatomy of large intestine, rectum and anal canal
General functions
rectum
storage of feces
well developed muscle to expel feces
anal canal
has mucus glands for lubrication
internal sphincters
smooth muscle
external sphincters
skeletal muscle
large intestine
water and electrolyte absorption
haustra
"to draw up"
sacs caused by the puckering of large intestine
teniae coli
"ribbons of the colon"
three longitudinal strips around cecum and colon
thickenings of longitudinal layer of the muscularis externa
epiploic appendages
fat filled pouches of visceral peritoneum that hang from the intestine
Gross and microscopic anatomy of accessory digestive organs
general functions of gallbladder
stores and concentrates bile
internal mucosal foldings enable the mucosa to expand and the gallbladder fills
general functions of pancreatic acini
cells that make up bulk of pancreas
exocrine gland that produces and secretes 22+ enzymes
duct cells - produce bicarbonate to neutralize stomach acid
general functions of liver
produces bile
picks up glucose from nutrient rich blood
processes fats and amino acids and stores certain vitmamins
detoxifies many poisons and drugs in the blood/makes blood proteins