The Digestive System

Question 1

Intracellular digestion

Answer 1

Involves of oxidation of glucose and fatty acids for energy

Question 2

Extracellular digestion

Answer 2

The lumen of the alimentary canal (gastrointestinal tract) communicates directly with the outside world as it runs from the mouth to the anus and is sectioned off by sphincters

Question 3

Mechanical digestion

Answer 3

Physical breakdown of large food particles into smaller food particles

Question 4

Chemical digestion

Answer 4

Enzymatic cleavage of chemical bonds

Question 5

Sequence of digestive tract

Answer 5

Oral cavity (mouth), pharynx, esophagus, stomach, small intestine, large intestine, rectum (accessory organs are salivary glands, pancreas, liver, and gallbladder)

Question 6

Enteric nervous system

Answer 6

Collection of neurons that govern function of the GI system, present in the walls of the digestive tract and trigger peristalsis (rhythmic contractions of gut tube) to move materials through system

Question 7

Hormones that stimulate feelings of thirst, hunger, and satiety

Answer 7

Thirst: ADH and aldosterone
Hunger: Glucagon and ghrelin
Satiety: Leptin and cholecystokinin

Question 8

Salivary glands

Answer 8

Innervated by parasympathetic nervous system, produce saliva, which acts in chemical digestion of food and aids in mechanical digestion of food through moistening and lubricating food

Question 9

Salivary amylase

Answer 9

Enzyme found in saliva that is capable of hydrolyzing starch into smaller sugars

Question 10

Lipase

Answer 10

Enzyme found in saliva that is capable of hydrolyzing lipids

Question 11

Three parts of pharynx

Answer 11

Nasopharynx (behind the nasal cavity), oropharynx (at the back of mouth), laryngopharynx (above the vocal cords)

Question 12

Esophagus

Answer 12

Muscular tube that connects pharynx to stomach, top third of esophagus is made of skeletal muscle, bottom third is composed of smooth muscle, middle third is mixture of both (because top of esophagus is under voluntary/somatic motor control and the bottom is under involuntary/autonomic nervous control

Question 13

Emesis (vomiting)

Answer 13

Reversal of peristalsis that occurs as a result of exposure to chemicals, infectious agents, physical stimulation in posterior pharynx, and cognitive stimulation

Question 14

Upper esophageal sphincter

Answer 14

Made up of the muscles of the oropharynx, where swallowing is initiated and bolus is pushed towards stomach

Question 15

Lower esophageal sphincter (cardiac sphincter)

Answer 15

Muscular ring that relaxes and opens to allow passage of food as bolus approaches the stomach

Question 16

Gastroesophageal reflux disease (GERD)

Answer 16

Caused by weakness in the lower esophageal sphincter and leading to heartburn symptoms as a result of pain receptors being stimulated by food and acid refluxing into lower esophagus

Question 17

Gastric glands

Answer 17

Found in the stomach, respond to signals from the vagus nervous of parasympathetic nervous system, contain mucous cells, chief cells, and parietal cells

Question 18

Mucous cells

Answer 18

Produce the bicarbonate-rich mucus that protects muscular wall from harshly acid and proteolytic environment of the stomach

Question 19

Gastric juice

Answer 19

Combination of the secretions from chief cells and parietal cells

Question 20

Chief cells

Answer 20

Secrete pepsinogen, which is the inactive (zymogen) form of pepsin, a proteolytic enzyme

Question 21

Parietal cells

Answer 21

Secretes hydrochloric acid to cleave pepsinogen, secreted by chief cells, into pepsin
Also secretes intrinsic factor

Question 22

Pepsin

Answer 22

Digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments

Question 23

Intrinsic factor

Answer 23

A glycoprotein involved in the proper absorption of vitamin B12, secreted by parietal cells

Question 24

Pyloric glands

Answer 24

Contain G-cells that secrete gastrin

Question 25

Gastrin

Answer 25

Peptide hormone that induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract to mix its contents

Question 26

Chyme

Answer 26

Acidic, semifluid mixture that results from digestion of solid food in the stomach

Question 27

Small intestine

Answer 27

Consists of the duodenum (responsible for majority of chemical digestion) and the jejunum and ileum (both of which are responsible for most of the absorption in the small intestine)

Question 28

Pyloric sphincter

Answer 28

Where food leaves the stomach and enters the duodenum

Question 29

Brush-border enzymes

Answer 29

Present on the luminal surface of cells lining the duodenum that break down dimers and trimers of biomolecules into absorbable monomers, released by presence of chyme in duodenum

Question 30

Disaccharidases

Answer 30

Digest disaccharides, include maltase (digests maltose), isomaltase (digests isomaltose), lactase (digests lactose), and sucrase (digests sucrose)

Question 31

Peptidases

Answer 31

Break down proteins, peptides can be broken down into di- and tripeptides and can still be absorbed across small intestine wall unlike carbohydrates that have to be broken down into monosaccharides

Question 32

Aminopeptidase

Answer 32

Peptidase secreted by glands in duodenum that removes N-terminal amino acid from a peptide

Question 33

Dipeptidase

Answer 33

Peptidase that cleaves the peptide bonds of dipeptides to release free amino acids

Question 34

Enteropeptidase (formerly called enterokinase)

Answer 34

Enzyme critical for activation of trypsinogen, a pancreatic protease, to trypsin
Also activates procarboxypeptidases A and B to their active forms

Question 35

Secretin

Answer 35

Peptide hormone that causes pancreatic enzymes to be released into the duodenum, also regulates the pH of digestive tract by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from pancreas (thus increasing pH of tract)
It is an enterogastrone, a hormone that slows motility through digestive tract and allows increased time for digestive enzymes to act on chyme

Question 36

Cholecystokinin (CCK)

Answer 36

Secreted in response to entry of amino acids and fat in chyme into the duodenum, stimulates the release of both bile and pancreatic juices, and promotes satiety

Question 37

Bile

Answer 37

Complex fluid composed of bile salts, pigments, and cholesterol

Question 38

Bile salts

Answer 38

Derived from cholesterol, have hydrophobic and hydrophilic regions (similar to soaps and detergents), they emulsify fats and cholesterol into micelles to make them them accessible to water-soluble pancreatic lipase

Question 39

Pancreatic juices

Answer 39

Complex mixture of several enzymes in a bicarbonate-rich alkaline solution that helps to neutralize acidic chyme as well as provide an ideal working environment for digestive enzymes that are most active at pH 8.5, contains enzymes that can digest carbs, fats and proteins

Question 40

Acinar cells

Answer 40

Exocrine cells in the pancreas that produce pancreatic juices, which contain pancreatic amylase, peptidases, and lipase

Question 41

Pancreatic amylase

Answer 41

Breaks down large polysaccharides into small disaccharides, res

Question 42

Pancreatic peptidases

Answer 42

Include trypsinogen, chymotrypsinogen and carboxypeptidases A and B
Released in their zymogen form and are responsible for protein digestion in their active form
Enteropeptidase is the master switch for this activation process (activates trypsinogen to trypsin, which activates the other zymogens and procarboxypeptidases A and B)

Question 43

Pancreatic lipase

Answer 43

Capable of breaking down fats into fatty acids and glycerol

Question 44

Major and minor duodenal papillae

Answer 44

Through which the ducts in the pancreas empty out products of acinar cells into the duodenum

Question 45

Bile ducts

Answer 45

Connect the liver with the gallbladder and small intestine, as bile is produced in liver and travels down these ducts where it may be stored in gallbladder or directly secreted into duodenum

Question 46

Functions of livef

Answer 46

Take up excess sugar and store it as glycogen, store fats as triacyglycerols, produce glucose through glycogenolysis and gluconeogenesis, mobilize fats into lipoproteins, detoxify endogenous and exogenous compounds, detoxify and metabolize alcohol and medications, produce urea, produce bile, and synthesize albumin and clotting factors

Question 47

Billirubin

Answer 47

Major pigment in bile, byproduct of the breakdown of hemoglobin, travels to the liver where it is conjugated (attached to a protein) and secreted into the bile for excretion

Question 48

Jaundice

Answer 48

Yellowing of the skin that occurs if the liver is unable to process or excrete billirubin due to liver damage, excessive red blood cell destruction or blockage of bile ducts

Question 49

Cirrhosis

Answer 49

Scarring of the liver (as a result of chronic alcohol consumption, autoimmne hepatitis, hepatitis C infection, fatty liver disease), with the scar tissue building up and increasing resistance within the portal vein to result in portal hypertension, causing a backup of fluid within the portal system and resulting in swollen veins in the digestive system, which may rupture and cause life-threatening bleeding (often manifests as hematemesis, or vomiting of blood), also causes bleeding disorders, affects mentation due to increased ammonia in blood, and possible cancer of the hepatocytes

Question 50

Gallbladder

Answer 50

Located beneath the liver and both stores and concentrates bile, upon CCK release the gallbladder contracts and pushes bile out into the biliary tree, in which the bile duct system merges with the pancreatic duct before emptying into duodenum

Question 51

Villi

Answer 51

Small fingerlike projections from the epithelial lining that lines the small intestine, with each villus having microvilli to increase surface area for absorption

Question 52

Chylomicrons

Answer 52

Packages of triglycerides and esterified cholesterol molecules that enter the lymphatic circulation through lacteals rather than entering the bloodstream like simple carbohydrates and amino acids, these lacteals converging and entering venous circulation at the thoracic duct

Question 53

Fat-soluble vitamins

Answer 53

A,D,E,K

Dissolve directly into chylomicrons to enter the lymphatic circulation

Question 54

Water-soluble vitamins

Answer 54

B and C vitamins
Taken up, along with water, amino acids, and carbohydrates, across endothelial cells of small intestine and passing directly into plasma

Question 55

Sections of large intestine

Answer 55

Cecum, colon, rectum

Question 56

Cecum

Answer 56

Outpocketing that accepts fluid exiting the small intestine through the ileocecal valve and is the site of attachment of the appendix

Question 57

Appendix

Answer 57

Small projection that was once thought to be vestigial but now could have role in warding off bacterial infections and repopulating large intestine with normal flora after diarrhea

Question 58

Colon

Answer 58

Divided into ascending, transverse, descending, and sigmoid colons
Main function is to absorb water and salts from the undigested material left over from the small intestine, primarily concentrating the remaining material to form feces that will be stored in the rectum

Question 59

Anus

Answer 59

Opening through which wastes are eliminated and consists of internal anal sphincter (under autonomic/involuntary control) and external anal sphincter (under somatic/voluntary control)