BIOL 0800 Reading- Chapter 15 Flashcards
(228 cards)
What acid is in the stomach?
HCl
What is pepsin?
Protein-digesting enzymes in the stomach
What two molecule types are typically not digested well by acid in the stomach?
Polysaccharides and fats
How much absorption of organic nutrients occurs in the stomach?
Virtually none
Where does most absorption of nutrients occur?
In the small intestine
What is the duodenum?
The initial segment of the small intestine
What is the jejunum?
The second segment of the small intestine
What is the ileum?
The third, longest segment of the small intestine
What are the three segments of the small intestine?
Duodenum, jejunum, ileum
What two organs secrete substances into the duodenum?
Pancreas and liver
How does the pancreas contribute to digestion?
Secretes digestive enzymes and a fluid rich in HCO3- to neutralize the acidic chyme
What does the liver do?
Secretion of bile to break down fast
What does the gallbladder do?
Stores secreted bile
What are the four layers of the GI wall?
Mucosa, submucosa, muscularis externa, serosa
What are the three layers of the mucosa?
Epithelium, lamina propria, muscularis mucosa
What is the submucosa?
Major blood and lymphatic vessels, submucosal plexus
What is the submucosal plexus?
Network of neyrons
What is the muscularis externa?
Circular muscle and myenteric plexus
How do circular muscles work?
Fibers oriented in circulate pattern around the tube so that contraction produces a narrowing of the lumen
What is the myenteric plexus?
Second network of neurons: innervated by nerves from the autonomic NS and has neurons that project to the submucosal plexus
What kinds of nerves innverate the myenteric plexus?
Autonomic nervous system
What is the serosa?
Thin layer of connective tissue to connect outer surface of tube to abdominal wall
What is a lacteal?
Single, bind-ended lymphatic vessel that is at the center of each villi
Most of the fat absorbed in the small intestine goes where?
Through the lacteals, to be emptied through the lymphatic systme into the thoracic duct