Topic 2: Nutrition and the Digestive System

Question 1

What are the four processes in the gastrointestinal (GI) tract?

Answer 1

1. ingestion
2. mixing
3. digestion
4. absorption

Question 2

What happens in ingestion?

Answer 2

foods and liquids are taken into the mouth

Question 3

What happens in mixing?

Answer 3

the smooth muscle in the walls of the GI tract mixes the food and pushes it along

Question 4

What happens in digestion?

Answer 4

food is broken down into its component parts by both mechanical and chemical processes

Question 5

What happens in absorption?

Answer 5

the epithelial cells lining the GI tract absorb the digested food molecules and pass them to the blood

Question 6

What are the four layers of the GI tract?

Answer 6

1. mucosa
2. submucosa
3. muscularis
4. serosa

Question 7

What are the functions of the mucosa?

Answer 7

functions are secretion and absoprtion

Question 8

What is the submucosa?

Answer 8

thick connective tissue layer; blood and lympth vessels, nerves, and glands

Question 9

What is the muscularis?

Answer 9

the main muscular layer of the tract (smooth muscle)

Question 10

What layer is responsible for the movement of food?

Answer 10

inner circular layer and outer circular layer

Question 11

What is the serosa?

Answer 11

epithelial sheet that covers all the organs and also lines the abdominal cavity

Question 12

What are the three phases of swallowing?

Answer 12

1. oral
2. pharyngeal
3. esophageal

Question 13

What is the oral phase (voluntary)?

Answer 13

tongue consciously moves bolus of food towards the oropharynx

Question 14

What is the pharyngeal phase (involuntary/structure)?

Answer 14

1. uvula covers nasal activity
2. epiglottis covers opening to respiratory system
3. respiratory centers in brainstem are inhibited so you don’t gasp for air while swallowing because trachea is closed
4. tongue closes off mouth from pharynx. No place for food that go except down the hatch

Question 15

What is the esophageal phase (involuntary)?

Answer 15

peristaltic waves of muscle contractions move food toward the stomach

Question 16

What are the two sphincter muscles in the esophagus?

Answer 16

1. top: pharyngoesophageal sphincter (upper esophageal sphincter)
2. bottom: gastroesophageal sphincter (lower esophageal sphincter)

Question 17

What is the function of the pharyngoesophageal sphincter?

Answer 17

ring of muscles that prevents air from entering esophagus–occasionally breached–eructation (burping)

Question 18

What is the function of the gastroesophageal sphincter?

Answer 18

prevents acid from stomach from entering esophagus–occasionally breached–acid reflux (heart burn)

Question 19

What is the structure of the stomach?

Answer 19

1. J-shaped
2. bounded by the lower esophageal sphincter and the pyloric sphincter

Question 20

What are the three parts of the stomach?

Answer 20

1. fundus: above the esophagus
2. body: main part
3. antrum: lower part: heavier musculature

Question 21

What is the volume of the stomach?

Answer 21

empty: 50 mL; full: 1 liter

Question 22

How can the stomach volume range 50 mL-1 liter

Answer 22

1. rugae: folds in mucosa that can be flattened
2. smooth muscle can be stretched

Question 23

What is the mechanical function of the stomach?

Answer 23

stomach contractions: blend the food and gastric secretions into chyme; chyme is propelled through the pyloric sphincter into the small intestine

Question 24

What is the chemical function of the stomach?

Answer 24

the chyme is mixed with enzymes and acid to begin the process of breaking it into its component parts

Question 25

Where is gastric juice made?

Answer 25

(2-3 quarts per day) made in gastric pits and glads that line the stomach mucosa

Question 26

What cells make up the gastric pits and glands?

Answer 26

1. mucous neck cells 2. chief cells 3. parietal cells 4. G-cells

Question 27

What is the function of mucous neck cells?

Answer 27

mucus to protect stomach wall from stomach acid

Question 28

What is the function of chief cells?

Answer 28

pepsinogen (breaks down protein) released as inactive precursor

Question 29

What is the function of parietal cells (2)?

Answer 29

1. hydrochloric acid (HCl): kills bacteria and activates pepsinogen 2. intrinsic factor: aids in the absorption of vitamin B12 (important for RBC maturation). Pernicious anemia-autoimmune attack on parietal cells

Question 30

What is the function of G-cells?

Answer 30

gastrin: stimulates chief and parietal cells

Question 31

What are the three phases of the control of gastric digestion?

Answer 31

1. cephalic phase 2. gastric phase 3. intestinal phase

Question 32

What happens in the cephalic phase?

Answer 32

1. initiated by the senses 2. stimulates gastric secretion

Question 33

What happens in the gastric phase?

Answer 33

1. food enters the stomach stimulates the brain to increase gastric secretion 2. gastrin, produced by G cells stimulates chief and parietal cells

Question 34

What happens in the intestinal phase?

Answer 34

1. if digestion complete: gastric secretion decreased 2. if digestion incomplete, gastric secretion increased

Question 35

How long is the small intestine?

Answer 35

20 feet, the longest digestive organ

Question 36

What are the three regions of the small intestine?

Answer 36

1. duodenum 2. jejunum 3. ileum

Question 37

What is the function of the duodenum?

Answer 37

(10 inches) digestion

Question 38

What is the function of the jejunum?

Answer 38

(8 feet) absorption of sugars, fatty acids and amino acids

Question 39

What is the function of the ileum?

Answer 39

(11.5 feet) absorption of vitamin B12 and bile ducts

Question 40

What are the three levels of folding in the mucosa?

Answer 40

1. circular folds 2. villi 3. microvilli (brush border)

Question 41

What does mucosa layer folding cause (3)?

Answer 41

1. increased surface area 2. churning 3. increased time to digest and absorb nutrients

Question 42

The villus is connected to what two systems?

Answer 42

blood stream and lymphatic system

Question 43

What is the mechanical digestion of chyme?

Answer 43

segmentations allow chyme to interact with the mucosa layer: food moves back and forth as it is pushed along

Question 44

What is the chemical digestion of chyme?

Answer 44

digestive juices contain enzymes added to chyme to further break down macromolecules

Question 45

What are the macromolecules for chemical digestion of chyme (3)

Answer 45

1. carbohydrates 2. proteins 3. fats

Question 46

What are the types of carbohydrates?

Answer 46

1. lactase (lactose) 2. sucrase (sucrose) 3. maltase (maltose) 4. amylase (starches)

Question 47

What are the types of proteins?

Answer 47

proteases: trypsin and chymotrypsin

Question 48

What are the types of fats?

Answer 48

lipase

Question 49

Where are carbohydrates produced?

Answer 49

all but amylase produced by the cells of the small intestine; amylase produced by the pancreas

Question 50

Where are proteins produced?

Answer 50

produced by the pancreas

Question 51

Where are fats produced?

Answer 51

produced by the pancreas

Question 52

Where do nutrients from chyme move?

Answer 52

into the villi and enter the bloodstream

Question 53

What is the function of accessory organs?

Answer 53

aid in digestion and absorption of nutrients?

Question 54

What are the four accessory organs?

Answer 54

1. salivary glands 2. pancreas 3. gall bladder 4. liver

Question 55

What is the function of the salivary glands?

Answer 55

produce amylase to digest starches

Question 56

What is the function of the pancreas (4)?

Answer 56

1. digestive enzyme factor buffers the acidity of chyme 2. secretes enzymes (proteases, amylase, lipase) 3. produces bicarbonate 4. delivers products to duodenum via ducts

Question 57

What is the function of the gall bladder (3)?

Answer 57

1. stores bile: aids in fat digestion 2. stores and concentrates bile 3. delivers bile to the duodenum via the common bile duct

Question 58

What is the function of the liver (2)?

Answer 58

1. removes toxins and impurities from the bloodstream 2. produces bile

Question 59

What is bile?

Answer 59

water, cholesterol, bile salts, lecithin, and pigments

Question 60

What is the direction of nutrients to the liver?

Answer 60

blood carrying nutrients away from the intestine and stomach travels directly to the liver in the hepatic portal vein; other veins collect and drain into the vena cavae

Question 61

What vein carries blood to the liver?

Answer 61

hepatic portal vein

Question 62

What does the special vascular arrangement in the liver allow?

Answer 62

digested molecules can be "screened" for toxins by the liver

Question 63

What happens to the hepatic portal vein in the liver?

Answer 63

breaks up into a second bed of capillaries called liver sinusoids that gets blood from the hepatic artery

Question 64

What happens to blood after it leaves the capillaries?

Answer 64

returns to the heart

Question 65

What is the function of the large intestine?

Answer 65

1. removes almost all the water from the chyme 2. absorption of electrolytes (ions) 3. form and store feces; evolved for good reason to keep away predators

Question 66

Ileocecal sphincter has a _ valve

Answer 66

one-way

Question 67

What opens the sphincter?

Answer 67

1. pressure in small intestines causes relaxation and opening 2. gastrin released in response to food in the stomach and intestine

Question 68

What closes the sphincter?

Answer 68

pressure in the large intestine pushes the valve closed and prevents bacteria from entering small intestine