Digestion II Study Guide

Question 1

term for a bolus of food after it is undergoing digestion in the stomach

Answer 1

chyme

Question 2

how tunics are modified in stomach

Answer 2

• Muscularis - added internal, oblique layer to allow increased mixing and churning – more intense mechanical breakdown
• Mucosa - contains simple columnar epithelium made entirely of mucous cells – produces a cloudy, protective double layer of alkaline mucus
• Dotted with millions of deep gastric pits
• Gastric pits lead into the gastric glands responsible for producing gastric juice

Question 3

secretory cells in gastric glands

Answer 3

Mucus neck cells, parietal cells, chief cells, Eneteroendocrine cells

Question 4

mucus neck cells

Answer 4

produce thin, soluble mucus

Question 5

Parietal cells

Answer 5

produce HCL (pH 1.5-3.5, required to activate pepsin (breakdown proteins in stomach?)) and secrete intrinsic factor (required to absorb B12)

Question 6

Chief cells

Answer 6

secrete pepsinogen (inactive pepsin) and lipases

Question 7

Eneteroendocrine cells

Answer 7

secrete chemical messengers into lamina propria as well as gastrin

Question 8

Mucosal barrier

Answer 8

produced to protect the stomach
- A thick coating of bicarbonate-rich mucus
- Tight junctions between epithelial cells
- Quick replacement of damaged mucosal cells by stem cells

Question 9

Gastritis

Answer 9

Inflammation of the stomach in response to breaches of the mucosal barrier

Question 10

peptic/gastric ulcers

Answer 10

• Erosions of the stomach-wall – cause gnawing, epigastric pain
• Pain typically appears 1-3 hours after eating and resolves with eating again, ulcers are linked to peritonitis and h. Pylori; a type of acid resistant bacteria

Question 11

different functions completed in the stomach

Answer 11

Propulsion
Mechanical breakdown
Digestion
Absorption
Secretion of intrinsic factor

Question 12

propulsion

Answer 12

peristalsis

Question 13

Mechanical breakdown

Answer 13

churning

Question 14

Absorption

Answer 14

only lipid soluble substances – alcohol and aspirin

Question 15

Digestion

Answer 15

breakdown of proteins by HCl and pepsin (rennin in infants)

Question 16

Secretion of intrinsic factor

Answer 16

essential for B12 absorption and maturation of RBCs

Question 17

Gastrin

Answer 17

hormonal mechanism of regulation of gastric secretion
- Stimulates secretion of hcl by the stomach
- Stimulates secretion of gastrin antagonists by the SI

Question 17

branch of the ANS that increases gastric secretions

Answer 17

parasympathetic

Question 18

3 phases of gastric secretions

Answer 18

cephalic/reflex phase, gastric phase, intestinal phase

Question 19

cephalic/reflex phase

Answer 19

triggered by smell, taste, and sight; act via the vagus nerve

Question 20

Gastric phase

Answer 20

triggered by stretch receptors and/or chemical stimuli – partially digested protein, caffeine, rising pH
- Activates G cells (enteroendocrine cells) to secrete gastrin
- Gastrin initiates release of HCl
- Low pH (between meals) or firing of the SNS will inhibit gastrin

Question 21

Intestinal phase

Answer 21

Partially digested food enters the SI and triggers the release of intestinal gastrin
- Distension of the SI and or the presence of acidic, fatty, or hypertonic chyme will inhibit gastric secretions – protects the SI from excess acidity and being overwhelmed * enterogastric reflex and enterogastrones

Question 22

Enterogastric reflex

Answer 22

short reflexes by the enteric nervous system and long reflexes by the sympathetic and vagus nerves inhibit acid secretion

Question 23

Enterogastrones

Answer 23

duodenal enteroendocrine cells release secretin or cholecystokinin (CCK) to inhibit gastric secretions

Question 24

digestive function of liver

Answer 24

Production of bile About 900ml per day (additional functions: processed bloodborne nutrients, stores fat-soluble vitamins, and performs detoxification)

Question 25

bile

Answer 25

fat emulsifier

Question 26

Livers functional unit

Answer 26

liver lobules (hexagonal) composed of plates of hepatocytes - Central vein: located in the longitudinal axis

Question 27

Hepatocyte

Answer 27

specialized liver cells that filter and process nutrient-rich blood - Have increased numbers of rER, sER, golgi complexes, peroxisomes, and mitochondria

Question 28

Portal triad

Answer 28

located in each corner of the lobule Hepatic artery Hepatic portal vein Bile duct

Question 29

Hepatic artery

Answer 29

supplies oxygen to the liver

Question 30

hepatic portal vein

Answer 30

brings nutrient rich blood from the intestines

Question 31

Bile duct

Answer 31

receives bile from the bile canaliculi

Question 32

function of hepatic macrophages

Answer 32

Exist in the liver sinusoids to remove debris and old RBCs

Question 33

portion of the SI that reabsorbs bile salts for recycling

Answer 33

ileum during enterohepatic circulation

Question 34

Bile salts

Answer 34

cholesterol derivatives that function in fat emulsification/absorption

Question 35

Bilirubin

Answer 35

yellow pigment formed from heme during breakdown of RBCs - Metabolized by bacteria in the SI to stercobilin which gives feces a brown color

Question 36

pathway for bile moving out of the liver

Answer 36

- Leaves liver via r and l hepatic ducts - R and l hepatic ducts fuse into common hepatic duct - Common hepatic ducts joins with cystic duct from gallbladder and forms the common bile duct

Question 37

Hepatitis

Answer 37

inflammation of the liver - Typically, viral infection, but can be caused by alcohol, drug toxicity, or wild mushrooms - Six viruses: a-f; 2 transmitted through food, remainder via blood

Question 38

Cirrhosis

Answer 38

progressive, chronic inflammation from hepatitis or alcoholism - Liver activity is depressed - Liver becomes fatty and fibrous - Portal hypertension: flow of blood through the liver is obstructed

Question 39

gall bladder

Answer 39

Store and concentrate bile - Muscular contractions release bile via the cystic duct – flows into the common bile duct

Question 40

gallstone

Answer 40

- Caused by excess cholesterol or too few biles salts (cholesterol crystallized into stones) - Can obstruct the flow of bile from the gallbladder (painful when the gallbladder contracts against sharp crystals)

Question 41

Obstructive jaundice

Answer 41

blockage causes bile salts and pigments to build up in blood – results in yellowed skin

Question 42

Exocrine function of pancreas

Answer 42

production of pancreatic juice

Question 43

endocrine function of pancreas

Answer 43

secretion of insulin and glucagon via the pancreatic islet cells

Question 44

pancreatic juice

Answer 44

contains enzymes needed to break down all categories of foodstuffs (multiple ducts secrete into the duodenum via the main pancreatic duct) - Contains electrolytes (primarily HCO3-) - Watery, alkaline solution (pH 8) used to neutralize acidic chyme from stomach

Question 45

4 macromolecules digested by the digestive tract and the enzyme responsible for its digestion

Answer 45

Proteases – for proteins; secreted in inactive form to prevent self digestion Amylase – for carbohydrates Lipase – for lipids Nucleases – for nucleic acids