Chapter 64 - Guyton

Question 1

Glands of the GI tract.

Answer 1

goblet cells - mucus
pits (crypts of Lieberkühn in small intestine) - secretions
tubular glands - secretion (acid- and pepsinogen-secreting gland of the stomach)
salivary glands, pancreas, and liver - secretions for digestion or emulsification of food

Question 2

What is the primary stimulus of secretions in the GI tract?

Answer 2

food contact with the epithelium

Question 3

Parasympathetic stimulation of the gut ________ secretions.

Answer 3

increases

Question 4

Control of secretions.

Answer 4

local - tactile, distention, irritation
reflex - nervous input
hormonal - GI hormones

Question 5

Sympathetic stimulation of the gut _________ secretions.

Answer 5

increases or decreases (decreases if parasympathetic is already increasing)

Question 6

What is secreted along with a substance to move it?

Answer 6

water and electrolytes

Question 7

Mucus composition.

Answer 7

mainly water, electrolytes, glycoprotein

Question 8

Mucus properties that make it essential for digestion.

Answer 8

adherent - sticks to food
body - coats the walls well
low resistance - provides lubrication
self adherent - sticks together (form poop)
resistant to digestion by GI enzymes
buffering - neutralize acids

Question 9

Salivation glands.

Answer 9

parotid, submandibular, sublingual (also smaller buccal)

Question 10

Saliva contains two major types of protein secretion:

Answer 10

1) serous secretion that contains ptyalin (an
a-amylase), an enzyme for digesting starches
2) mucus secretion that contains mucin for lubricating and surface protective purposes

Question 11

Types of secretion by gland.

Answer 11

parotid - serous
submandibular and sublingual - serous and mucus
buccal - mucus

Question 12

90% of total secreted saliva comes from which glands?

Answer 12

parotid and submandibular

Question 13

Two stages of formation and secretion of saliva.

Answer 13

acini - primary secretion similar to plasma (Cl is primary ion that is secreted actively not Na)
salivary ducts - modified as it passes through the ducts

Question 14

Sodium and chloride in saliva is _____ than in plasma, while potassium and bicarbonate is _____ than in plasma.

Answer 14

less; greater

Question 15

Saliva is always hypotonic, but its osmolarity _________ as its flow rate increases.

Answer 15

increases

Question 16

Xerostomia

Answer 16

absence of saliva (dry mouth)

Question 17

____________ stimulation directly increases salivation but can decrease Ach stimulated effects because of blood vessel constriction.

Answer 17

Sympathetic (T1-T3, superior cervical ganglion)

Question 18

Parasympathetics to the salivary glands through which cranial nerves primarily?

Answer 18

CN IX and X (Ach)

Question 19

Tubular glands of the stomach mucosa.

Answer 19

The oxyntic (acid-forming) glands secrete hydrochloric acid, pepsinogen, intrinsic factor, and mucus. The pyloric glands secrete mainly mucus for protection of the pyloric mucosa from the stomach acid. They also secrete the hormone gastrin.

Question 20

What occurs in order for pepsinogen to be converted into its active form pepsin?

Answer 20

contact with HCl and pepsinogen is cleaved into pepsin

Question 21

In chronic gastritis, if the parietal cells are destroyed, a person can develop achlorhydria (lack of stomach acid secretion) but often also pernicious anemia due to what?

Answer 21

lack of secretion of intrinsic factor by the parietal cells leads to failure to absorb B12

Question 22

The _______ cells, located deep in the oxyntic glands of the main body of the stomach, are the only cells that secrete hydrochloric acid.

Answer 22

parietal

Question 23

The rate of formation and secretion of hydrochloric acid by the parietal cells is directly related to the amount of histamine secreted by which cell?

Answer 23

enterochromaffin-like cells (ECL cells)

Question 24

Stimulates histamine production by ECL cells:

Answer 24

1) gastrin
2) Ach (vagus nerve)
3) hormonal substances secreted by enteric nervous system in the stomach wall

Question 25

Regulation of pepsinogen secretion by the peptic cells in the oxyntic glands:

Answer 25

1) Ach from the vagus nerves or gastric enteric nervous plexus 2) acid in the stomach

Question 26

Phases of gastric secretion and their regulation.

Answer 26

``` Cephalic phase: 1. vagus nerve to stomach Gastric phase: 1. local nervous secretory reflexes 2. vagal reflexes 3. gastrin-histamine stimulation Intestinal phase: 1. nervous mechanisms 2. hormonal mechanisms ```

Question 27

Hormones that inhibit gastric secretions.

Answer 27

secretin, GIP, VIP, somatostatin

Question 28

The combined product of enzymes and sodium bicarbonate from the pancreas flows through a long pancreatic duct that joins the hepatic duct immediately before it empties into the duodenum through the papilla of _____, surrounded by the sphincter of ____.

Answer 28

Vater; Oddi

Question 29

Secrete pancreatic digestive enzymes.

Answer 29

pancreatic acini

Question 30

Pancreatic enzymes for digesting proteins.

Answer 30

trypsin, chymotrypsin, carboxypolypeptidase

Question 31

Pancreatic enzyme for digesting carbohydrates.

Answer 31

pancreatic amylase

Question 32

Pancreatic enzymes for digesting fats.

Answer 32

pancreatic lipase, cholesterol esterase, phospholipase

Question 33

Why do the pancreatic enzymes not digest the pancreas under normal conditions?

Answer 33

the pancreatic acini simultaneously secrete trypsin inhibitor to prevent trypsin from forming and activating the enzymes from their inactive state

Question 34

Stimuli for pancreatic secretion:

Answer 34

1. Ach from parasympathetic vagus nerve endings and other cholinergic nerves in the enteric nervous system 2. Cholecystokinin secreted by the duodenal and upper jejunal mucosa when food enters the small intestine 3. Secretin secreted by the duodenal and jejunal mucosa when highly acid food enters the small intestine

Question 35

Stimulates secretion of large quantities of water solution of sodium bicarbonate by the pancreatic ductal epithelium.

Answer 35

secretin

Question 36

These two stimuli are largely responsible for the pancreatic enzyme production by acinar cells of the pancreas.

Answer 36

Ach and CCK (CCK is responsible for 70-80% of secretion)

Question 37

Composition of bile.

Answer 37

bile salts, bilirubin, cholesterol, lecithin, and the usual electrolytes of plasma

Question 38

The most important stimulus for gallbladder contraction.

Answer 38

CCK

Question 39

The stimulus for cholecystokinin entry into the blood from the duodenal mucosa is mainly?

Answer 39

the presence of fatty foods in the duodenum

Question 40

What is the primary function of bile salts?

Answer 40

emulsification of fats and also help with absorption by forming micelles

Question 41

Causes of gallstones:

Answer 41

1) too much absorption of water from bile 2) too much absorption of bile acids from bile 3) too much cholesterol in bile 4) inflammation of epithelium

Question 42

These glands secrete large amounts of alkaline mucus in response to (1) tactile or irritating stimuli on the duodenal mucosa; (2) vagal stimulation, (3) gastrointestinal hormones, especially secretin.

Answer 42

Brunner's glands (in the wall of the first few centimeters of the duodenum)

Question 43

Located over the entire surface of the small intestine are small pits called?

Answer 43

crypts of Lieberkühn (goblet cells - mucous and enterocytes - water and electrolytes)

Question 44

As food particles pass through the small intestine epithelium, several enzymes further break down the food. Which enzymes?

Answer 44

peptidases, sucrase, maltase, isomaltase, lactase, intestinal lipase

Question 45

By far the most important means for regulating small intestine secretion are _______________, especially reflexes initiated by tactile or irritative stimuli from the chyme in the intestines.

Answer 45

local enteric nervous reflexes

Question 46

The mucosa of the large intestine, like that of the small intestine, has many crypts of Lieberkühn; however, unlike the small intestine, there are no ____.

Answer 46

villi