Biology: Chapter 9

Question 1

Intracellular digestion

Answer 1

involves the oxidation of glucose and fatty acids for energy

Question 2

Extracellular digestion

Answer 2

nutrients are obtained from food; occurs within the lumen of the alimentary canal

Question 3

Alimentary canal

Answer 3

runs from the mouth to the anus and is sectioned off by sphincters

Question 4

Digestion

Answer 4

involves the breakdown of food into its constituent organic molecules; starches and other carbohydrates into monosaccharides, lipids into free fatty acids and glycerol, and proteins into amino acids

Question 5

Mechanical digestion

Answer 5

-physical breakdown of large food particles into smaller food particles, but does not involve breaking chemical bonds
-mastication (chewing) breaks up large food particles into smaller particles using the teeth, tongue, and lips; tongue forms food into a bolus which is forced back to the pharynx and swallowed

Question 6

Chemical digestion

Answer 6

-enzymatic cleavage of chemical bonds
-relies on enzymes from saliva produced by salivary glands; salivary amylase hydrolyzes starch into smaller sugars, lipase catalyzes the hydrolysis of lipids

Question 7

Absorption

Answer 7

involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body’s tissues and cells

Question 8

Digestive tract

Answer 8

-oral cavity
-pharynx
-esophagus
-stomach
-small intestine
-large intestine
-rectum
-salivary glands, pancreas, liver, and gallbladder help to provide the enzymes and lubrication necessary to aid in the digestion of food

Question 9

Enteric nervous system

Answer 9

-Collection of neurons that govern the function of the gastrointestinal system
-Trigger peristalsis, or rhythmic contractions of the gut tub, in order to move materials through the system
-Heavily regulated by autonomic nervous system but can function independently of the brain and spinal cord
-All of the glands of the body (except sweat glands) are innervated by the parasympathetic nervous system

Question 10

ADH and aldosterone

Answer 10

trigger the sensation of thirst

Question 11

Glucagon and ghrelin

Answer 11

glucagon secreted by the pancreas and ghrelin by the stomach and pancreas; stimulate feelings of hunger

Question 12

Leptin and cholecystokinin

Answer 12

stimulate feelings of satiety

Question 13

Oral cavity

Answer 13

Plays a role in both mechanical and chemical digestion

Question 14

Pharynx

Answer 14

-Cavity that leads from the mouth and posterior nasal cavity to the esophagus
-Nasopharynx: behind the nasal cavity
-Oropharynx: at the back of the mouth
-Laryngopharynx: above the vocal cords
-Epiglottis: prevents food from entering the larynx during swallowing

Question 15

Esophagus

Answer 15

-Muscular tube that connects the pharynx to the stomach
-Top third is composed of skeletal muscle (voluntary motor control), bottom third is composed of smooth muscle (involuntary nervous control), middle is a mix of both
-Upper esophageal sphincter: swallowing is initiated by the muscles of the oropharynx
-Lower esophageal sphincter: muscular ring just before the stomach

Question 16

Stomach

Answer 16

-Fundus and body: contain mostly gastric glands
-Antrum and pylorus: contain mostly pyloric glands
-Lesser curvature of the stomach: inner curvature
-Greater curvature of the stomach: outer curvature
-Rugae: the lining of the stomach
-Mucosa of the stomach contains gastric glands and pyloric glands

Question 17

Gastric glands

Answer 17

respond to signals from the vagus nerve of parasympathetic nervous system, which is activated by the brain in response to the sight, taste, and smell of food

Question 18

Pyloric glands

Answer 18

contain G-cells that secrete gastrin which is a peptide hormone that induces parietal cells to secrete more HCl and signals the stomach to contract

Question 19

Mucus cells (gastric glands)

Answer 19

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

Question 20

Chief cells (gastric glands)

Answer 20

secrete pepsinogen which is the inactive form of pepsin

Question 21

Parietal cells (gastric glands)

Answer 21

secrete hydrogen ions in the form of hydrochloric acid that cleave pepsinogen into pepsin; secrete intrinsic factor which is a glycoprotein that absorbs vitamin B12

Question 22

Pepsin (gastric glands)

Answer 22

digests proteins by cleaving peptide bonds

Question 23

Duodenum

Answer 23

-First segment of the small intestine, responsible for a majority of chemical digestion and has some minor involvement in absorption
-Food leaves the stomach through the pyloric sphincter and enters duodenum
-Presence of chyme causes the release of brush-border enzymes which break down dimers and trimers of biomolecules into absorbable monomers

Question 24

Peptidases (duodenum)

Answer 24

break down proteins

Question 25

Enteropeptidase (duodenum)

Answer 25

enzyme critical for activation of trypsinogen to trypsin

Question 26

Secretin (duodenum)

Answer 26

peptide hormone that causes the pancreatic enzymes to be released into the duodenum; regulates the pH of the digestive tract by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from the pancreas

Question 27

Cholecystokinin (CCK) (duodenum)

Answer 27

secreted in response to the entry of chyme; stimulates the release of both bile and pancreatic juices

Question 28

Bile (CCK)

Answer 28

complex fluid composed of bile salts, pigments, and cholesterol

Question 29

Bile salts (CCK)

Answer 29

derived from cholesterol, serve an important role in mechanical digestion of fats and facilitate the chemical digestion of lipids; emulsify fats and cholesterol into micelles

Question 30

Pancreatic juices (CCK)

Answer 30

neutralizes acidic chyme and provides ideal working environment for digestive enzymes; contain enzymes that can digest carbohydrates, fats, and proteins

Question 31

Pancreas

Answer 31

-Endocrine functions: release of insulin, glucagon, and somatostatin which are peptide hormones necessary for the maintenance of proper blood sugar levels
-Acinar cells: produce pancreatic juices

Question 32

Liver

Answer 32

-Bile ducts connect the liver with both the gallbladder and the small intestine
-Bile is produced in the liver and travels down bile ducts where it may be stored in gallbladder or secreted into duodenum
-Receives all blood draining from the abdominal portion of the digestive tract through the hepatic portal vein
-Takes up excess sugar to create glycogen
-Stores fats as triacylglycerols
-Detoxifies endogenous compounds (made in the body) and exogenous compounds (brought from the environment)

Question 33

Gallbladder

Answer 33

-Located just beneath the liver and both stores and concentrates bile
-Upon release of CCK, the gallbladder contracts and pushes bile out into the biliary tree
-Common site of cholesterol or bilirubin stone formation which causes inflammation of the gallbladder

Question 34

Jejunum

Answer 34

second part of the small intestine

Question 35

Ileum

Answer 35

third part of the small intestine

Question 36

Role of jejunum and ileum

Answer 36

-Involved in the absorption of nutrients
-Small intestine is lined with villi which each have many microvilli that increase surface area for absorption
-At the middle of each villus there is a capillary bed for the absorption of water-soluble nutrients and a lacteal, a lymphatic channel that takes up fats for transport into the lymphatic system
-Simple carbohydrates and amino acids diffuse from the epithelial cells into the capillaries and the absorbed molecules then go to the liver via the hepatic portal circulation
-Triglycerides and esterified cholesterol molecules are packaged into chylomicron
-Vitamins are also absorbed in the small intestine
-Water passes transcellularly (across the cell membrane) and paracellularly (squeezing between cells)

Question 37

Large intestine

Answer 37

-Primarily involved in water absorption
-larger diameter but shorter length than small intestine
-3 major parts: cecum, colon, and rectum

Question 38

Cecum

Answer 38

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

Question 39

Colon

Answer 39

divided into ascending, transverse, descending, and sigmoid colons. Main function to absorb water and slats from undigested material left over from the small intestine. Concentrates remaining material to form feces

Question 40

Rectum

Answer 40

serves as a storage site for feces, which consists of indigestible material, water, bacteria, and certain digestive secretions that are not reabsorbed; anus is the opening through which wastes are eliminated and consists of two sphincters

Question 41

Internal sphincter

Answer 41

under involuntary (autonomic) control

Question 42

External sphincter

Answer 42

under voluntary (somatic) control