chapter 23/24

Question 1

what are the 6 major steps involved in processing food

Answer 1

1- ingestion
2- propulsion
3- mechanical digestion
4- chemical digestion
5- absorption
6- defecation

Question 2

describe intrinsic digestive activity

Answer 2

happens within they are the gut responses to stimuli and are short, and involve nerve pluses and hormone producing cells.

Question 3

describe extrinsic digestive activity

Answer 3

initiated by stimuli arising inside or outside the GI tract but involving CNS and extrinsic nerves. These are long.

Question 4

list the organs involved in mechanical digestion

Answer 4

mouth, teeth, tongue, palate, pharynx, esophagus, stomach, small intestine

Question 5

Describe how the mouth plays a role in chemical digestion

Answer 5

salivary aimless begins the digestion of (fats) and carbohydrates, converting it from a polysaccharide to the disaccharide maltose.

Question 6

Describe how the stomach plays a role in chemical digestion

Answer 6

the stomach wall is lined with million of gastric glands that secrete gastric juice. Three main cells are found in gastric glands, parietal cells (HCl), chief cells (pepsinogen), and mucous-secreting cells. An important part of gastric juices is the substance pepsinogen, which produces the active enzyme pepin which begins the digestion of proteins into peptides

Question 7

At what pH does salivary amylase work best

Answer 7

6-7, once it reaches the stomach it has no effect

Question 8

Describe how the small intestine plays a role in chemical digestion

Answer 8

The small intestine is the site of the final digestion for proteins and carbohydrates

Question 9

Describe how the small intestine plays a role in chemical digestion

Answer 9

The small intestine is the site of the final digestion for proteins and carbohydrates, and fats have not yet been digested. Bill have cells that produce intestinal enzymes that complete the digestion of peptides and sugars.

Question 10

Describe how the Duodenum plays a role in chemical digestion

Answer 10

most active site in the small intestine of digestion. secretions form the liver and pancreas are used for digestion in the duodenum. epithelial cells of the duodenum secrete mucous to prevent damage form pepsin and HCl.

Question 11

Describe how the pancreas plays a role in chemical digestion

Answer 11

The pancreas secretes digestive enzymes and stomach acid-neutralizing sodium bicarbonate. The sodium bicarbonate neutralize the acidic chyme, allowing the enzymes in the small intestine to function and protecting the intestinal wall.

Question 12

Describe the four tunics of the gut wall

Answer 12

1) mucosa: secrete, absorb, and protect
2) sub mucosa: services blood vessels, lymphatic tissue, follicles, and nerve fibres
3) musclaris: segmentation and peristalsis
4) Serosa: visceral perioneum

Question 13

What types of teeth do we have

Answer 13

-molars -premolars -incisors -canines

Question 14

what are the various salivary glands (3)

Answer 14

1) parotid gland:
2) submandibular gland:
3) sublingual glands: drains through numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of ravines, the largest is the major duct of the sublingual salivary gland called bartholin duct.

Question 15

what are the properties of salvia

Answer 15

97% water, IgA antibodies, lysozyme, defences, and friendly bacteria. functions to dissolve food chemicals, moisten food, and aids in compacting, initiates breakdown of starchy foods.

Question 16

list the various sphincters from start to finish

Answer 16

1st = upper esophageal (enter of food into esophagus)
2nd = lower esophageal sphincter (entrance of stomach)
3rd = plyoric sphincter (leaving stomach entering duodenum) 
4th = Ileocecal valve (not a sphincter, mediates movement of small intestine contents into the large intestine (caecum)
5th = internal anal sphincter 
6th = external anal sphincter

Question 17

what are endocrine cells

Answer 17

they are g-cells that release chemical messengers, including gastrin, which regulates stomach secretions.

Question 18

what are the main regions of the SI and lengths

Answer 18

1) duodenum: 25cm
2) Jejunum: 2.5 m
3) Ilium: 3.6 m

Question 19

describe the cephalic phase of gastric secretion

Answer 19

the cephalic phase occurs in response to stimuli received by the senses, sights, sound, smell and taste. This is mediated by the vagus nerve (10th cranial) –> gastric juices are secreted in response to vagal stimulation, either directly by electrical impulses or indirectly by stimuli from senses.

Question 20

describe the gastric phase

Answer 20

the gastric phase is mediated by the vagus nerve, gastric juices release acid to break down food, proteins buffer the gastric juices so that the pH remains around 3. the gastric phase continues until the food has left the stomach.

Question 21

describe the intestinal phase

Answer 21

chyme enters duodenum, stimulates intestinal glands to produce enteric gastrin, which further stimulates gastric glands.

Question 22

discuss regulation of gastric motility and emptying

Answer 22

the NS and endocrine system work together to increase gastric juices during food digestion and to suppress them as the stomach empties

Question 23

what is the main function of the liver

Answer 23

to process and filter blood

Question 24

what is the digestive function of the liver

Answer 24

produces bile: emulsification of fat. The gall bladder temporarily stores bile

Question 25

what are the four lobes of the liver

Answer 25

left, right, caudate, quadrate,

Question 26

Hepatocytes contain large amounts of…?

Answer 26

RER, and SER (rough endoplasmic reticulum, smooth endoplasmic reticulum).

Question 27

list the pathway of liver blood flow

Answer 27

hepatic portal vein and hepatic artery –> sinusoids –> central vein –> hepatic veins –> exit liver

Question 28

what are the main enzymes in the paceas

Answer 28

1) trypsinogen: inactive enzyme, once activated in the duodenum into trypsin, breaks down proteins at the basic amino acids.
2) chymotrypsinogen: inactive protease that, once activated by duodenal enterokinase, breaks down proteins at their aromatic amino acids.
3) carboxypeptidase: a protease that takes off the terminal amino acid group from a protein
4) pancreatic lipase: degrades triglycerides into fatty acids and glycerol
5) pancreatic amylase: breaks down starch and glycogen which are alpha linked glucose polymers. humans lack the cellulases to digest the carbohydrate cellulose which is a beta linked glucose polymer.