Transcript Digestive System Overview Oral Cavity

Digestive System Overview
Oral Cavity
• Composed of teeth, tongue, and salivary glands.
• Oral cavity receives food.
• Teeth: chewing breaks down toughconnective
tissues in meat and plant fibers.
• Tongue: mechanically manipulates food to assist
in chewing and swallowing; also has touch, taste,
and temperature receptors.
• Salivary glands: produces saliva that that
lubricates mouth and food; also controls the
amount of oral bacteria in mouth.
Oral Cavity
Pharynx
• “Back of throat”
• Passageway for food, liquid and air.
• Leads to the esophagus and trachea.
Esophagus
• Muscular tube that transports food to the
stomach.
• Posterior (behind) to the trachea.
Stomach
• Temporary storage of food
• mechanical breakdown of food
• produces acids and enzymes that break
chemical bonds in food
Small Intestine
• 90% of nutrient absorption.
• About 20ft long.
• Consist of villi and microvilli that help with
absorption by increasing surface area.
• Has three segments: Duodenum, jejunum, and
ileum.
Small Intestine
Small Intestine
Large Intestine
• Reabsorbs water and compacts waste into
feces.
• Stores fecal matter prior to defecation
• Consists of three segments: the cecum, the
colon, and the rectum.
Liver
• All blood leaving the absorptive areas of the
digestive tract flow through the liver before
circulating to the rest of the body.
• Extracts toxins from blood.
• Regulates blood sugar levels.
• Remove damaged and old blood cells from
circulation as well as pathogens
• Produces bile, which helps neutralize chyme from
the stomach before it enters the small intestine.
Liver
Gallbladder
• Stores and concentrates bile that was made in
the liver.
• Releases bile into the duodenum (small
intestine)
Pancreas
• Produces the hormone insulin, which
regulates blood sugar levels.
• Secretes pancreatic juice into duodenum
(small intestine), which contains digestive
enzymes to help chemically break down food.
Pancreas
How does food move through
digestive tract?
• Peristalsis: a series of wave-like muscle
contractions that moves food to different
processing stations in the digestive tract
Peristalsis
Sphincters
• Ring-like muscles that contract to close bodily
passageways and openings.
• There are six found in the digestive tract.
– Upper esophageal sphincter: separtes pharynx and
esophagus.
– Lower esophageal sphincter: (cardiac sphincter) separates
esophagus and stomach
– Pyloric sphincter: separates stomach and small intestine
– Ileocecal valve: separates small and large intestine
– Internal anal sphincter: smooth muscle that controls
outflow of stool
– External anal sphincter: skeletal muscle that controls
outflow of stool.
Sphincters