Ch. 25 Digestive System

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Ingestion

intake of food

digestion

breakdown of molecules

absorption

uptake nutrients into blood/lymph

defecation

elimination of undigested material

rennin

a milk protein digesting enzyme in children uncommon in adults

vestibule

area between lips and teeth

churning action of stomach

layer of smooth muscle

accessory organs

teeth, tongue, liver, gallbladder, pancreas, salivary glands

tongue

mixes the food in the mouth

visceral peritoneum

serosa of stomach and intestines

parietal

serosa of abdominal wall

lesser omentum

attaches stomach to the liver

greater omentum

covers small intestines like an apron

mesentery of small intestine

holds many blood vessels; suspends small intestine from posterior body wall

tongue

sensitive, muscular maipulator of food

hard and soft palate

-uvula is here
-allow breathing and chewing at the same time

hard and soft palate

anterosuperior boundary of oral cavity

amylase

begins starch digestion

salivation

gum chewing is a mechanical stimulus to help prevent dry mouth

esophagus

-food chute
-straight muscular tube 25-30 cm long

pharynx

common passageway for food and air

stomach

mechanically breaks up food particles, liquifies the food and begins chemical digestion of protein and fat

chyme

soupy mixture from the stomach

pylorus

opening to duodenum (pyloric sphincter)

mucous cells

secrete muscus and consist of folds called rugae

HCl acid and intrinsic factor

gastrin causes an increase hormonal response

functions of hydrochloric acid

activates enzymes pepsin and lingual lipase

pepsin

-chief cell, protein digestion
-secreted as pepsinogen (an inactive zymogen)
-HCl converts it to pepsin (active form)
-pepsin then activates more pepsinogen

lipase

-digests butterfat of milk in infants (Rennin)
-comes from the pancreas

cephalic phase

vagus nerve stimulates gastric secretion and motility just with sight, smell, taste or thought of food (psychological)

liver secretion

causes liver to increase bile output

cholecystokinin

causes release of bile

gallbladder

-sac on underside of liver
-stores and concentrates bile

bile

-yellow-green fluid containing minerals, bile acids, cholesterol, bile pigments and phospholipids
-between meals, it is concentrated by factor of 20

pancreas

-protein digesting enzymes amylase and nucleases
-pancreatic juice into duodenum

hormone control by

cholecystokinin and secretin

small intestine

nearly all chemical digestion and nutrient absorption occurs here

lleocecal valve

separates small intestine from large

plicae circularis

circular folds of small intestine; up to 10mm tall

villi

-fingerlike projections 1 mm tall
-contain blood vessels and lymphatics

microvilli

-1 micron tall
-brush border on cells
-brush border enzymes for final stages of digestion

peyer patches

-populations of lymphocytes to fight pathogens
-also known as collection of lymphatic tissue

intestinal motility

intestinal juice, bile and pancreatic juice

digestion

occurs as food is broken down both chemically and mechanically

mesentery

structure that suspends the small intestine from the posterior body wall

oral cavity, stomach

two anatomical regions involved in the physical breakdown of food

three extensions/modifications of the peritoneum

greater omentum, lesser omentum, mesentery

esophagus

literally a food chute, no digestion or absorption occurs

rugae

folds of the stomach mucosa

haustra

saclike outpocketings of the large intestine wall

microvilli

projections of the plasma membrane of a cell that increase the cells surface area

ileocecal valve

prevents food from moving back into the small intestine once it has entered the large intestine

small intestine

organ responsible for most food and water absorption

colon

organ primarily involved in water absorption and feces formation

appendix

blind sac hanging from the initial part of the colon

stomach

organ in which protein digestion begins

lesser omentum

membrane attached to the lesser curvature of the stomach

small intestine

organ in which the stomach empties

pyloric sphincter

sphincter, controlling the movement of food from the stomach into the duodenum

soft palate

uvula hangs from its posterior edge

small intestine

organ that receives pancreatic juices and bile

parietal peritoneum

serosa of the abdominal cavity wall

anal canal

region containing 2 sphincters, through which feces are expelled from the body

hard palate

anterosuperior boundary of the oral cavity; supported by bone

ingestion

eating

propulsion

includes swallowing, segmentation and peristalsis

mechanical digestion

chewing, churning

chemical digestion

enzymatic breakdown

absorption

transport of nutrients from lumen to blood

defecation

elimination of feces

salivary amylase

starch digestion begins in the mouth when ___ is ducted in by the salivary glands

hormonal stimulus

gastrin, which prods the stomach glands to produce more enzymes and HCl represents a ___

psychological stimulus

the fact that the mere thought of a relished food can make your mouth water is an example of ___

mechanical stimulus

many people chew gum to increase saliva formation when their mouth is dry. This is an example of ___

pepsin

protein foods are largely acted on in the stomach by ___

HCl

for the stomach protein-digesting enzymes to become active, ___ is needed

mucus

since living cells of the stomach are largely protein, it is amazing that they are not digested by the activity of stomach enzymes. The most important means of stomach protection is the ___ it produces

rennin

a milk protein-digesting enzyme found in children but uncommon in adults

churning

the third layer of smooth muscle found in the stomach wall allows mixing and mechanical breakdown by ___

brush border enzymes

important intestinal enzymes

bicarbonate-rich fluid

the small intestine is protected from the corrosive action of hydrochloric acid in chyme by ___, which is ducted in by the pancreas

lipases

the pancreas produces protein-digesting enzymes, amylase and nucleases. It is the only important source of ___

bile

a nonenzyme substance that causes fat to be dispersed into smaller globules

cholecystokinin and secretin

these two hormones stimulate the pancreas to release its secretions

gastrin

this hormone stimulates increased production of gastric juice

cholecystokinin

this hormone causes the gallbladder to release stored bile

secretin

this hormone causes the liver to increase its output of bile

fructose, galactose, glucose

the building blocks of carbohydrates are monosaccharides, or simple sugars. The three common simple sugars in our diet are __, __, __

fatty acids

fats are broken down to two types of building blocks, __ and glycerol

glucose

of the simple sugars, ___ is most important because it is the sugar referred to as "blood sugar"

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