Chapter 18- Digestive System

Digestion

breaking down polymers into monomers

absorption

moving monomers into blood to use

ingestion

taking food in

mastication

chewing

deglutition

swallowing

segmentation

churning/mixing

What do exocrine glands secrete

digestive juices; enzymes, acid, mucus, bicarbonate

immune barrier

tight cell junctions, immune cells in tissue

GI tract

mouth —> pharynx —> esophagus —> stomach —> small intestine —> large intestine —> anus

acessory organs of digestive system

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

Saliva components

mucus, antimicrobial agents, salivary amylase

salivary amylase

starts starch digestion

oral phase

voluntary

pharyngeal phase is

involunary swallowing reflex initiated.

pharyngeal phase

pushes food into esophagus

esophageal phase happens by

peristalsis

esophageal phase

moves food to stomach

how long is the sophagus

10 inches

what are the parts of the esophagus?

top - skeletal muscle

bottom- smooth muscle

lower esophageal sphincter

prevents reflux

What does the stomach do?

• store food

• churns food with acid

• starts protein digestion

• kills bacteria

  • moves chyme into small intestine

Regions of stomach

caridac: entry

fundus: top

body: middle

pyloric: bottom

rugae

stomach folds for expansion

mucus neck cells

mucus protection

parietal cells

HCl and intrinsic factor for vitamin B12 absorption

Chief cells

pepsinogen, inacitve enzyme for proteins

length of small intestine

12ft long

parts of small intestine

duodenum, jejunum, ileum

folds in small intestine

plicae circulares, villi, microvilli

Small intestine functions

finish digesting carbs, proteins fats and absorb nutrients

what part of the small intestine absorbs sugars, lipids and amino acids?

duodenum/jejunum

what part of the msall intestine absorbs bile salts, vitamin B12?

ileum

Brush border enzymes stay attached to

membrane

Brush border enzymes

break down small molecules

enterokinase

activates trypsin for protein digestion

path of large intestine

ileocecal valve —> cecum —> ascending colon —> trasverse —> descending —> sigmoid —> rectum —> anus

Functions of large intestine

absorbtion, bacterial action, feces storage

what does the large intestine absorb

water, electrolyes, vitamin K, and some B vitamins make v

What does bacterial action in large intestine do?

makes vitamins

larges abdominal organ

liver

whats special about the liver

it regenerates

what is the process of liver regeneration called?

hepatoycte mitosis

where does blood enter the liver through?

hepatic protal vein

function of liver

bile production, blood detoxification, glucose regulation, plasma protein manufacturing

bile production

bile salts, pigments, lecithin, cholesterol

How does the liver regulate glucse

stores as glycogen and makes it through gluconeogenesis

What palsma proteins does th eliver make?

albumin and clotting factors

Enterohepatic circulation

some bile products recycles from small intestine to liver

gallbladder

stores and concentrates bile from the liver and releases it into the small intestine

Endocrine pancrease

insulin and glucagon

the endocrine pancreas controls

blood sugar

exocrine pancrease

pancreatic juicse release digestive enzymes

pancreatic digestive enzyes

amylase, trypsin, lipase

what does bicarbonate do in the pancreas?

neutralizes stomach acid

Most enzymes in the pancreas are inactive until reaching

small intestine

Enterokinase activates _____ which activates ____ which triggers ___

trpsinogen; trypsin; other enzymes

What is the immune barrier?

Simple columnar epithelium with tight junctions prevents swallowed pathogens from entering body

Bolus

dough mixed with saliva

How long is the GI tract?

30ft

wehere does carbohydrate digestion start?

mouth

where does protein digestion start?

stomach

enzyme to digest protein

pepsin

What controls the esophageal

swallowing center of brain stem

what moves bolus down esophagus to stomach?

peristalsis

What is the esophagus lined with ?

nonkeratinized stratified squamous epithelium

What is the motuh, phraynx and upper esophagud lined with?

skeletal muscles innervated by somatic motor neurons

What is the lower esophagous lined with

smooth muscle controlled by the autonomic nervous system

What opens in the esophagous to lallow food to pass into the stomach?

gastroesophageal sphincter

why does the lower esophagaeal sphincter stay closed?

to prevent regurgitation

Chyme

pasty material form of food moved into small intestine

Upper region of stomach

fundus

Lower region of stomach

body

Distal region of stomach

pyloric region

______ at base of folds lead to ++_____+ that contain several types of secretory cells

gastric pits; gastric glands

What secret mucus in the stomach?

mucus neck cells

why do mucus neck cells secrete mucus?

to protect stomach lining from acid

what do parietal cells secrete?

HCl acid and intrinsic factor

What do zygomatic cells secrete

pepsinogen

what is pepsinogen

the inactive form of the protein digesting enzyme

Where does the small intestine start and end?

pyloric sphrincter, ileocecal valve

First 10 inches of small intestien is

duodenum

middle 2/5 of small intestine

jejunum

last 3/5 of small intestine

ileum

What is folded into pilcae circulares?

mucosa and submucosa

mucosa and submucosa folded into

pilae circulares

mucosa is further folded into

villi

what is folded into microvilli in small intestien?

epithelial plasma membranes

why are there so many fold s in the small intestine?

they greately increase surface area for absorption of nutrients

intrinsic factor of stomach

helps small intestine absorb vitamin B12

Function of small intestine

complete digestion of carbohydrates, proteins and fats

Intestinal enzymes are called

brush border enzymes

What do intestinal enzymes do?

hydrolyze disaccharides, polypeptides and other substrates to simple nutrient molecules

Mucosa

simple columnar epithelial cells with goblet cells, crypts, lymphatic nodules, but no villi

Outer surface of large intestine forms pouches called

haustra

Why does liver have amazing regenerative ability?

due to mitosis of hepatocytes

what capillaries separate hepatic plates?

sinusoidal capillaries

what is the liver composed of

hepatocytes that form hepatic plates separated by sinusoids

how are products of digestion absorbed in intestiens delivered to liver?

via hepatic portal vein

What joins with the hepatic portal vein

veins from pancreas, gallbladder, stomach, omentum and spleen a

after circulating through liver capillaries, the blood leaves via the hepatic vein to join

regulat venous circulation