Bsci 440 Exam 4

Front 1

digestion

Back 1

mechanical breakdown of food into particles followed by chemical cleavage into small molecules that can be taken by the transport epithelium.

Front 2

two major digestion questions

Back 2

How do we digest different substances that we eat?\

How the entire process is regulated and coordinated?

Front 3

evolutionarily, developmentally and anatomically talk about the lumen of GI tract....

Back 3

Evolutionarily, developmentally and anatomically, the lumen of GI is an external compartment (no strict homeostatic control)

Front 4

relate a chemical plant to the GI system in 5 ways

Back 4

lecture 38

1c

Front 5

go over anatomy highlights of GI system

Back 5

Pharynx, larynx, glottis (vocal folds) and epiglottis

Esophagus, upper* and lower esophageal sphincters

Stomach: fundus, body, antrum, pyloric sphincter

Small intestine: duodenum, jejunum, ileum, minor papilla, major papilla (openings that discharge bile and pancreatic juices into the duodenum)

Ileocecal sphincter (valve)

Large intestine (colon): ascending, transverse, descending, sigmoidal and rectum

Internal and external* anal sphincters

* the sphincters under voluntary control

Front 6

what kind of control are the internal and external anal sphincters under?

Back 6

voluntary control

Front 7

major papilla

Back 7

openings that discharge bile and pancreatic juices into the duodenum)

Front 8

oral cavity and esophagus major points

Back 8

chewing, swallowing, salivary secretions contain amylase and lipase, no real absorption takes place

Front 9

stomach major points

Back 9

mixing and propulsion, acidic secretion containing pepsinogen and gastric lipase. Proteins and fats are partially digested. No active absorption except alcohol, and lipophilic drugs.

Front 10

small intestine major points

Back 10

Small intestine: mixing and propulsion, basic secretions from the pancreas containing proteases, amylases and lipases, bile and nucleases. Carbohydrates, fats, polypeptides and nucleic acids are digested.

Peptides, amino acids, sugars, vitamins and ions are absorbed by primary and secondary active transport.

Fats are taken up by simple diffusion.

Front 11

how are fats taken up in the small intestine?

Back 11

simple diffusion

Front 12

diagram of fluid input and fluid output in the digestive tract

Back 12

Front 13

picture of stomach

Back 13

yellow stuff is mesentery

Front 14

draw the stomach wall

Back 14

also see lecture 38 3d

Front 15

what is intestinal surface area enhanced by?

Back 15

finger like villi

Front 16

draw GI muscle membrane potential and how it relates to force of muscle contraction

Back 16

contraction depends on amplitude and frequency of action potentials

Front 17

myenteric plexus

Back 17

Peristalsis and ENS
Myenteric plexus = linear fibers that extend all the way through the GI tract. When stimulated:

increase the tonic contraction on the wall

increase the the intensity of rhythmic contractions

increase the velocity of peristaltic waves

releases VIP (inhibitory NT) which relaxes sphincters

stimulation arrives from parasympathetic fibers

sympathetic signals inhibit peristalsis

Front 18

Submucosal plexus

Back 18

controls processes at the inner surface facing the lumen:

local secretion and absorption

conduction of sensory signals from GI epithelium, where the afferent nerves terminate

Front 19

long reflexes

Back 19

originate in the CNS, outside of the GI system. Also called cephalic reflexes. Anticipation of food, traveler’s constipation, psychologically induced diarrhea.

Front 20

short reflexes

Back 20

originate in the GI system via sensory endings in the submucosal plexus. Direct connection of submucosal neurons to myenteric motor neurons.

Front 21

GI peptides

Back 21

released by some cells in the GI tract act as hormones or paracrines.

Front 22

draw the digestive CNS and ENS connection

Back 22

ENS: enteric nervous system: the little brain

see scheme on lecture 38 on page 6a

Front 23

salivary glands

Back 23

parotid

sublingual

submaxillary: provide the majority of secretion

Front 24

Acinar Vs. Duct cells

p

what does ps stim cause?

saliva rich in what?

Back 24

duct cells are blue

salivary gland

Acinar cells: secrete fluid that is close to the plasma in its composition (Na+, K+, Cl-, HCO3-)

Duct cells :modify the ionic contents by extracting Na+ and Cl-


.....
As a result, saliva is rich with K+, HCO3- and hypotonic

Contains: Salivary Amylase, Lingual Lipase, Lysozyme, Mucin

Prasympathetic stimulation increases the release of watery saliva

Front 25

Cell types in the gastric mucosa

source
substance secreted
stimulus for release
function

Back 25

Front 26

2 safety measures and picture

Back 26

Safety measure #1

Most of the digestive enzymes are secreted in the form of inactive precursors and get activated only in the lumen by other secreted factors


Safety measure #2

The intestinal wall is separated from the active digestive enzymes with the mucous layer

Front 27

picture of acid secretion by parietal cells

p

Back 27

cl- channel is a CLC channel

Front 28

Gastric acid

Back 28

gastric secretion

(HCl) secreted by parietal cells
the same cells secrete the Intrinsic Factor, a protein that binds Vitamin B12 and transports it across the epithelium

Front 29

Pepsin

Back 29

gastric secretion

protease, most effective on collagen,
released by chief sells as a precursor, Pepsinogen.
Pepsinogen is converted into Pepsin in the presence of HCl

Front 30

Gastric Lipase

Back 30

gastric secretion

Secreted by chief cells

Front 31

trypsinogen

Back 31

pancreatic secretion (exocrine)

Trypsinogen, converted to Trypsin by Enteropeptidase secreted by intestinal wall

8.5-8.8 ph optimum

Front 32

chymotrypsinogen

Back 32

pancreatic secretion (exocrine).....into small intestine

(converted to Chymotrypsin by Trypsin)

7.5-8.5ph optimum

Front 33

procolipase and prophospolipase

Back 33

pancreatic secretion (exocrine) into small intestin

converted into colipase and phospolipase by trypsin....colipase displaces bile from surface of fat so that pancreatic lipase can break it down.

Front 34

HCO3-

Back 34

pancreatic exocrine secretion

neutralizes gastric acid

Front 35

water

Back 35

pancreatic secretion (exocrine)

Front 36

endocrine pancrease secretions

Back 36

Endocrine pancreas (Islets of Langerhans) secretes:
Glucagon (a cells), Insulin (b cells), Somatostatin (D cells)

Front 37

summary of pancreatic secretion (exocrine)

Back 37

Trypsinogen, converted to Trypsin by Enteropeptidase secreted by intestinal wall

Chymotrypsinogen (converted to Chymotrypsin by Trypsin)

Procolipase and Prophospholipase are converted into Colipase and Phospholipase by Trypsin

HCO3- - neutralizes gastric acid

Water

Front 38

summary of gastric secretion

Back 38

Gastric acid (HCl) secreted by parietal cells
the same cells secrete the Intrinsic Factor, a protein that binds Vitamin B12 and transports it across the epithelium

Pepsin – protease, most effective on collagen,
released by chief sells as a precursor, Pepsinogen.
Pepsinogen is converted into Pepsin in the presence of HCl

Gastric Lipase is also secreted by chief cells

Front 39

draw bicarbonate secretion in the pacrease

Back 39

Front 40

enterokinase

Back 40

intestinal secretions:

also called entropeptidase,

activates trypsin

Front 41

peptidases

Back 41

intestinal secretions

Endopeptidase: break inner peptide bonds

Exopeptidase: break outer end peptide bonds

Front 42

disacharidases

Back 42

intestinal secretions:

Sucrase, Maltase, Lactase

Sucrose = Glucose-Fructose,

Maltose = Glucose-Glucose

Lactose = Glucose-Galactose

MN: SML is sweet

Front 43

intestinal secretions overview

Back 43

disacharidases.....
intestinal secretions:

Sucrase, Maltase, Lactase

Sucrose = Glucose-Fructose,

Maltose = Glucose-Glucose

Lactose = Glucose-Galactose




Enterokinase or enteropeptidase: activates Trypsin from trypsinogen

Peptidases
Endopeptidase

Exopeptidases (Amino- and Carboxypeptidases)

Front 44

picture of large intestine

Back 44

Front 45

draw and talk about large intestine secretions

Back 45

lecture 39 4a

Front 46

pH ranges of following

pepsin
trypsin
chymotrypsin

Back 46

pepsin: 2-4

trypsin: 8.5-8.8

chymotrypsin: 7.5-8.5

Front 47

types of fat

Back 47

Phospholipids
Triglycerides
Fatty acids
Cholesterol
Lipid-soluble vitamins

Front 48

talk about basics of bile salts

Back 48

*picture shows a micelle that is a collection of bile

.....picture a bile yellow goo in the washing machine

*bile is a natural detergent....has a polar head and a apolar tail

*bile salts coat lipids to make emulsions (2 substances that can't be mixed, but are dispersed equally amongst one another)

Front 49

draw the bile pathway

Back 49

Front 50

talk about summary of fat digestion

Back 50

Bile stabilizes small fat droplets

Colipase displaces bile from the surface allowing the Pancreatic lipase to break down triglycerides into fatty acids and monoglycerides. These form small micelles and are partially water-soluble. They diffuse across the brushborder into the cytoplasm of epithelial cells. Cholesterol is actively transported.

In the ER of enterocytes triglycerides are re-synthesized.

Combined with cholesterol and proteins triglycerides form larger droplets called chylomicrons.

Chylomicrons leave cells via exocytosis and enter the lymph. Bile is absorbed in ileum and recycled back into the liver.

Front 51

draw the hepatic portal system

Back 51

Front 52

what do hepatocytes form?

Back 52

hexagonal lobules

Front 53

scheme with functions of liver

....liver functions

Back 53

bilirubin is catabolic product of heme: a component of RBC

Front 54

diagram with taste perception

Back 54

Front 55

5 types of taste

Back 55

sweet

sour

salty

bitter

umami

Front 56

draw the response that occurs in a taste bud cell and what receptors are responsible for what

Back 56

Bitter
(caffeine,
strychnine)
T2R GPCR

Sweet
GPCR
T1R2+T1R3

Amino acids
GPCR
T1R1+T1R3

Umami (MSG)
mGluR4
GPCR

Salt
ENaC

Sour
H+-gated
K+ channels
HCN

Amino acid taste perception is greatly potentiated by purine nucleotides

Front 57

what is found in hot food

Back 57

capsaicin

TRPV1 channel

Front 58

Phases of digestion

Back 58

Cephalic phase: anticipation of a meal. Signals from medulla oblongata reach salivary glands and stomach ECL and G cells (through vagus). Secretions begin.

Mastication = chewing, mechanical preparation of the food in the mouth. Saliva dilutes the food. Amylase and Lipase begin their work. Lysozyme and antibodies guard from infections. The food mass turns into chyme.

Deglutition = swallowing. Epiglottis directs the food into esophagus.

Gastric phase: HCl kills microorganisms, denatures proteins; salivary amylase is inactivated by low pH; proteolysis by pepsin; about 10% of total fat is digested by gastric lipase.

.....Regulation: parasympathetic stim. releases gastrin from G cells into the blood; gastrin promotes histamine and acid release; acid stimulates release of pepsinogen from chief cells; then acid triggers somatostatin release from D cells, which inhibits all gastric secretions

Intestinal phase: chyme enters the small intestine; bile is added; HCO3- from pancreas neutralizes gastric acid; motility mixes chyme; proteins, sugars and lipids are digested; the products are absorbed by enterocytes and put into the portal vein; endocrine secretions from the intestine coordinate gastric emptying, HCO3- secretion and bile release from the galbladder.

.....Regulation: hyperosmotic chyme blocks gastric motility; large amounts of carbohydrates block acid secretion via GIP; large amounts of fats release CCK, which also blocks acid secretion and motility, too much acid triggers release of secretin, which blocks gastric motility and secretion and stimulates release of HCO3-

Front 59

digestive hormones...name 5

Back 59

Digestive hormones (16-39 amino acid peptides, all endocrine) Table 20-2

Gastrin (from G cells), stimulates secretion of gastric acid

Cholecystokinin (CCK, from intestinal endocrine cells, neurons ) stimulates pancreatic secretion, bile release, inhibits gastric emptying

Secretin (intestinal endocrine cells) stimulates pancreatic secretion, inhibits secretion of gastric aci
d
GIP (glucose-dependent insulinotropic peptide, from endocrine cells) releases insulin in a feed-forward fashion.

Motilin (from endocrine cells) stimulates motility

Front 60

Talk about the following digestive disorders

1)swallowing
2)aerphagia
3)gastroesophagial reflux disease
4)peptic ulcers
5)gallstones
6)pancreatitis
7)malabsorption by small intestinal mucosa
8)intestinal colic
9)constipation
10)diarrhea
11)vomiting

Back 60

Swallowing disorders (muscular dystrophy, myasthenia gravis, botulism)

Aerphagia (causes belching and flatus)

Gastroesophagial reflux disease (irritation of lower esophagus by gastric acid, causes ‘heart burns’)

Peptic ulcers caused by imbalance of secretion of gastric juices and protective mucous coating

a)Helicobacter pylori (disrupts the mucosa barrier)

b)Aspirin (reduces protective prostaglandin production and mucosa secretion)

c)excessive secretion of gastrin prolongs HCl secretion



Gallstones (mostly cholesterol) may occlude the bile duct

Pancreatitis = inflammation of pancreas predominantly due to gallstone occlusion of the ducts. Trypsinogen and chymotrypsinogen accumulate and may spontaneously convert into their active form causing self-digestion of the pancreas

Malabsorption by the small intestinal mucosa = sprue, may result from poisoning by gluten or from some tropical infections)


Intestinal colic (cramping pain in the event of mechanical obstruction)

Constipation (atonic colon, usually due to inactivity of myenteric plexus)

Diarrhea can result from infectious enteritis as well as may be phsychogenic from emotional stress

Vomiting = reverse emptying of the upper GI tract. Chemoreceptots and nosiceptors in the stomach signal to vomiting center in the medulla oblongata. Antiperistalsis and distension of duodenum precedes vomiting. Strong downward contraction of the diaphragm and abdominal muscles. Esophageal sphincter relaxes at the same time.

Vomiting is also triggered by neural stimuli integrated in the chemoreceptor trigger zone near the fourth ventricle of the brain.

Front 61

area of frequent ulceration

Back 61

pyloric valve and area pointing to esophagus