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Digestive System (Small intestine (Functions (Absorption …
Digestive System
Small intestine
Functions
Absorption
Mechanical digestion
segmentation
Chemical digestion
enzymes
Circular folds
Slow down chyme
Villi
Increase surface area
Microvilli
Absorption
Duodenal glands
Secrete alkaline mucus
Protection
Neutralize acid from stomach
Intestinal crypts
Secretes watery intestinal juice
Lymphatic nodules
Collection of lymphocytes
Mesentery
Function
Stores fats
Holds organs in place
Provides space for blood vessels and nerves
Double layer of peritoneum from body wall to GI organs
Mesentery proper
Within jejunum and ileum
Mesocolon
Connected to transverse colon and sigmoid colon (posterior wall)
Lesser omentum
Connected to lesser curvature and liver
Greater omentum
Drapes over intestines
Function
Wraps around and encloses inflamed organs / infections
Stomach
Function
Store food
Mechanical digestion
churning ---> chyme
Chemical digestion
Gastric glands
Parietal glands
Hydrochloric acid
Intrinsic factor
needed to absorb vitamin B12
produce erythrocytes
Chief glands
Pepsinogen and acid ---> pepsin
enzyme breaks down proteins
Cardiac sphincter
Prevents reflux of acid into esophagus
Pyloric sphincter
Regulates chyme amount moving into small intestine
Rugae
Allows for more storage space
Large intestine
Function
Water and electrolyte absorption
e.g. K+, Na+, Ca2+, Cl
Teniae coli
3 longitudinal strips of muscle
Contract and pull colon into pouches / sacs called haustra
Haustra
Pouches / sacs in colon
Epiploic appendages
Fat filled visceral peritoneum
Liver
Functions
Produce bile
stored in gallbladder ---> emulsify fat
Filters toxins out of blood
Stores glucose as glycogen
Stores some vitamins
Processes fats and amino acids
Makes blood proteins
albumin
globulin
fibrinogen
Gallbladder
Stores bile
Portal circulation
Heart ---> arteries ---> capillaries ---> veins (hepatic portal vein)---> capillaries (liver) ---> vein (inferior vena cava) ---> heart
Mechanical digestion
Teeth
cut food up
Stomach
Small Intestine
Segmentation
Organs in GI tract move food back and forth
Functions
Break down food into small enough pieces to be absorbed in blood
Eliminates what cannot be broken down
GI tract
Esophagus
Small intestine
Large intestine
Sigmoid colon
Rectum
Anal canal
Anus
Chemical digestion
Mouth
saliva
Stomach -- adds chemicals
Pepsin
Hydrochloric acid
Small intestine
adds enzymes from pancreas
Pathway for food
Mouth ---> pharynx ---> esophagus ---> stomach ---> duodenum ---> jejunum ----> ileum ---> ascending colon ---> transverse colon ---> descending colon ---> rectum ---> anal cavity ---> anus
Ileocecal valve
Prevents liquids / waste from moving backwards
Accessory digestive organs
Liver
Gallbladder
secretes bile
Pancreas
secretes enzymes
Salivary glands
parotid salivary gland
sublingual salivary gland
submandibular salivary gland
Peristalsis
Organs in GI tract move food in one direction
esophagus ---> large intestine
Intraperitoneal
Within peritoneum:
Liver
Stomach
Jejunum
Ileum
Transverse colon
Sigmoid colon
Retroperitoneal
Not within peritoneum:
Duodenum
Pancreas
Ascending colon
Descending colon
Rectum
Rectum
Storage place for feces
Well developed muscles to expel feces
Anal canal
Mucus glands for lubrication
Internal sphincter
smooth muscle
involuntary
External sphincter
skeletal muscle
voluntary
Pancreas
Pancreatic acini
Produce and secrete 22+ enzymes ---> enter duodenum
Duct cells
Produce bicarbonate