Kaplan Ch. 9 - The Digestive System

Question 1

State the pathway that food takes in the digestive tract.

Answer 1

Oral cavity —> pharynx —> esophagus —> stomach —> small intestine —> large intestine (colon) —> rectum —> anus

Question 2

What role does the oral cavity play in digestion?

Answer 2

1) mechanical digestion (masticulation) —> increase surface area to volume ratio to give more access for chemical digestion later
2) starts chemical digestion with enzymes in saliva

Question 3

3 subdivisions of pharynx?

What causes choking?

Answer 3

Nasopharynx
Oropharynx
Laryngopharynx

Failure of epiglottis to block larynx from food, food enters larynx.

Question 4

Describe the composition of the esophagus.

What parts of the nervous system control the esophagus?

Answer 4

The top is made of skeletal muscle, the bottom is made of smooth muscle, the middle is a mix of both

Too enervated by somatic NS (voluntary) bottom enervated by autonomic NS (involuntary)

Question 5

Peristalsis and emesis

Answer 5

Peristalsis is rhythmic contraction of smooth muscle that propels food down digestive tract.

Emesis = vomiting, reversal of peristalsis, causes by chemicals, infection, cognitive processes

Question 6

What two sphincters are there in the esophagus?

Answer 6

Upper esophageal sphincter (oropharynx), bolus enters esophagus from mouth

Lower esophageal sphincter (cardiac sphincter), bolus leaves esophagus to stomach

Question 7

What are the 2 kinda of glands in the stomach and where are they located?

Answer 7

Gastric glands (located in the fungus and the body)

Pyloric glands (located in the pylorus and the antrum)

Question 8

What is the name for the folded lining of the stomach?

Answer 8

Rugae

Question 9

Describe the environment of the stomach in general.

Answer 9

Stomach uses HCl and enzymes to digest food, highly acidic, has thick mucosa to protect itself from being digested by its own environment

Question 10

Gastric glands:

1) respond to signals from _____?
2) what are the 3 different cell types of gastric glands and what are their functions?

Answer 10

1) vagus nerve of parasympathetic NS
2) a) mucous cells (produce bicarbonate rich mucous to protect stomach walls)
b) chief cells (secrete pepsinogen = zymogen or inactive protein that is later cleaved to become enzyme pepsinogen)
c) parietal cells (secrete hydrogen ions in form of HCl to cleave pepsinogen to pepsin, which cleaves amino acids near aromatic residues)

Question 11

What is the significance of the acidic environment of the stomach?

Answer 11

• needed for stomach enzymes to function
• kills most harmful bacteria
• chemical digestion (denature proteins, break bonds)

Question 12

What cells do pyloric glands secrete? What is the function of these cells?

Answer 12

G - cells : secrete gastric (peptide hormone) that induces parietal cells to secrete more HCl, also signals stomach to contract to mix contents

Question 13

Chyme

Answer 13

Acidic, semi fluid mixture that is the result of digestion in the stomach

Question 14

Is the stomach responsible for absorption?

Answer 14

No - very few compounds are dissolved directly from the stomach. Absorption primarily responsibility of small intestine.

Question 15

What are the 3 segments of the small intestine?

Answer 15

Duodenum
Jejunum
Ileum

Question 16

Duodenum:

1) what is it’s main responsibility?
2) what does the passage of chyme into the duodenum cause?

Answer 16

1) majority of chemical digestion
2) release of brush border enzymes (disaccharidases and peptidases) that break down carbohydrates and proteins into smaller components that are absorbable

Question 17

Flatulence

Answer 17

If you lack disaccharidase, then you don’t break down the carbohydrate but bacteria in the intestines may be able to instead which produces methane gas as a byproduct

Undefeated sugars also pull water into stool resulting in diarrhea

Question 18

Enteropeptidases

Answer 18

Activated trypsinogen to trypsin (pancreatic protease)

Question 19

What is secretin?

What are it’s functions? (3)

Answer 19

Secretin is a peptide hormone that is secreted by the duodenum

It causes pancreatic enzymes to be released into the duodenum

It regulates pH by reducing HCl (antagonist to gastrin) secretion from parietal cells

Slows motility through tract to allow for increased digestive time (enterogastrone)

Question 20

Cholecystokinin (CCK):

1) when is it secreted?
2) what is it?
3) what are it’s functions

Answer 20

1) when chyme passes into duodenum
2) peptide hormone
3) release of pancreatic juices and bile and also promotes satiety in the brain

Question 21

Bile

Answer 21

Fluid composed of bile salts, pigment, and cholesterol

Question 22

Bile salts

Answer 22

Amphiphilic molecules derived from cholesterol, emulsify fats in small intestine into micelles allowing an environment for lipases to act

Question 23

Pancreatic juices

Answer 23

Mixture of several enzymes in a bicarbonate alkaline solution. Bicarbonate is present to neutralize the acidic chyme and enzymes present to digest all 3 major types of macromolecules

Question 24

Acinar cells

Answer 24

Make up bulk of pancreas, produce pancreatic juices

Question 25

Where is bile produced?

Answer 25

The liver

Question 26

Bile ducts

Answer 26

Connect the liver to gallbladder and small intestines

Question 27

Hepatic portal vein

Answer 27

Allows liver to receive all blood draining from abdominal portion of digestive tract before passing into inferior vena cava. This is so the liver can uptake any glucose or lipids what are present

Question 28

What are the 4 major functions of the liver?

Answer 28

1) produce bile
2) process nutrients (store glucose and fat or break down glycogen and triacylglycerols)
3) detoxification
4) synthesize albumin (responsible plasma oncotic pressure)

Question 29

What is bilirubin?

Answer 29

The pigment of bile, byproduct of breakdown of hemoglobin

Question 30

How is bilirubin processed in liver?

What happens if the liver is not able to do this?

Answer 30

Conjugated to a protein and released in bile for excretion

Jaundice

Question 31

What is the function of the gallbladder?

Answer 31

Store and concentrate bile. Upon release of CCK, gallbladder contracts and pushes bile into bile duct system.

Question 32

Describe the lining of the jejunum and ileum and how this lining is essential for nutrient absorption.

Answer 32

The jejunum and ileum are lined with villi (small fingerlike projectiles) which is in turn covered with microvilli that increase surface area available for nutrient absorption. In middle of villi is lacteal, which takes up fats for transport to lymphatic system. The lacteal is also surrounded by capillaries for uptake if water soluble nutrients.

Question 33

What is the major function of the large intestine (note: the small intestine does this as well)?

Answer 33

Water absorption

Question 34

What is the function of the colon?

Answer 34

Concentrate remaining undigested material into feces.

Question 35

What marcomolecules begins being digested in SaLiva?

Answer 35

Sugar (carbohydrates)

And

Lipids