The digestive system “ The digestive system takes in food, breaks it down into nutrient molecules and absorbs them into the bloodstream, and then rids the body of the indigestible remains.” -E. Marieb
Jan 23, 2016
The digestive system
“ The digestive system takes in food, breaks it down into nutrient molecules
and absorbs them into the bloodstream, and then rids the body of
the indigestible remains.”-E. Marieb
PARTS
1. Gastrointestinal (GI) tract
2. Accessory organs
Digestive processes(disassembly)
1. Ingestion2. Propulsion
a. swallowingb. peristalsis
3. Mechanical digestion4. Chemical digestion5. Absorption6. Defecation
1. MOUTH (oral cavity) Mechanical digestion -
teeth/tongue Chemical digestion -
salivary glands: Contains enzymes
2. pharynx Skeletal muscle
3. esophagus Propels food using muscles (peristalsis)
4. stomach Mechanically and chemically
digested into chyme Limited absorption Neural control
Stretch receptors activated. Impulse to neurons in stomach wall. Continued gastric gland production and causes peristalsis
Hormonal control: Food triggers release of gastrin
(hormone). Goes in blood. Triggers: gastric gland juices constricts sphincter to prevent acid-
reflux, relaxes lower stomach sphincter.
What food type is chemically digested in the mouth?
What is the function of the esophagus?
5. Small Intestine
Mechanical digestion Chemical digestion
(all) Done with enzymes
from pancreas and bile (formed in liver).
Pancreatic duct and bile duct empty into superior small intestine
Absorption (nutrients)
6. Large Intestine Mechanical digestion:
Peristalsis Mass peristalsis
Chemical digestion: Bacteria
Absorption: Water Some vitamins
ACCESSORY ORGANS
Don’t write:What is bile?
Bile is a yellow, brown, or green, watery solution containing bile salts, bile pigments, cholesterol, phospholipids and a variety of electrolytes. pH of 7.6 – 8.6
Liver Produces bile Bile: part waste
product, part digestive secretion (mechanical digestion of lipids)
Metabolism of carbs, lipids, and proteins
Processing of drugs and hormones
Excretion of bilirubin (from heme of old RBCs)
liver summary…
Blood from stomach and intestines passes through liver. When the liver has broken down harmful substances, they are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the feces. Blood by-products are filtered out by the kidneys and leave the body in the form of urine.
gallbladder Stores bile releases in response
to fatty food
PANCREAS
Releases enzymes into
duodenum (s. intestine)
has an endocrine function
Summary questions
1. What mainly happens in the small intestine?
2. Where is bile made?
3. What organ stores bile?
4. In which organ is water mainly absorbed?
5. What is the circular muscle contraction called that involuntarily moves food through the GI tract?
6. Where is chyme produced?