18A/B: Digestive System

Question 1

Explain the process of peristalsis

Answer 1

• peristalsis: moving bolus along digestive tract by coordination of smooth muscle contractions
  1. bolus of food arrives
  2. circular muscle contracts behind the bolus
  3. longitudinal muscle contracts ahead of the bolus
  4. contractions of circular muscle push bolus forward

Question 2

Explain segmentation

Answer 2

• rhythmic cycles of contraction in most areas of small and some areas of large intestine for mechanical digestion
• don’t follow a set pattern; doesn’t push materials in any one direction
• churns and fragments bolus

Question 3

Explain the process of degluttion

Answer 3

• swallowing
  1. buccal phase: bolus compresses against hard palate; tongue retracts; bolus moves into oropharynx; soft palate elevates to seal off nasopharynx (voluntary phase)
  2. pharyngeal phase: tactile receptors in uvula stimulated; larynx elevated; epiglottis folds over it; palatal muscles elevate uvula and soft palate to block nasopharynx; bolus forces through pharynx
  3. esophageal phase: bolus pushed through esophagus by peristalsis; triggers opening of lower esophageal sphincter

Question 4

rugae

Answer 4

temporary mucosal folds in the stomach lining that can flatten to expand the stomach

Question 5

Describe the structures and functions of the following teeth structures: dentin, enamel, gingival sulcus, root canal

Answer 5

• dentin: mineralized matrix that makes up the bulk of each tooth, similar to bone but does not contain cells
• enamel: covers dentin in the grown; contains calcium phosphate
• gingival sulcus: surrounds neck of the tooth
• root canal: narrow tunnel within root of the tooth, supplies blood vessels and nerves

Question 6

mumps

Answer 6

viral disease causing swelling of parotid salivary glands in the face

Question 7

hepatitis

Answer 7

inflammation of liver

Question 8

cirrhosis

Answer 8

hepatocytes die faster than they are replaced; hardening of liver

Question 9

major functions of the liver

Answer 9

• produces bile

- filters blood coming from the digestive tract

Question 10

Describe the functional anatomy of the liver.

Answer 10

1. blood enters sinusoids through interlobular artery and interlobular vein
2. as blood flows through sinusoids, adjacent hepatocytes regulate nutrient levels, absorbing/secreting solutes
3. stellate macrophages line sinusoids and engulf pathogens
4. central vein collects blood from sinusoids, merge into hepatic veins, which empties into inferior vena cava
5. hepatocytes secrete bile (containing bile salts) for fat digestion

Question 11

pancreatitis

Answer 11

inflammation of the pancreas due to blockage of excretory ducts

Question 12

Name the cells of the gastric gland and their secretions.

Answer 12

• parietal cells: HCl
• G cells: gastrin
• chief cells: pepsinogen

Question 13

gastrin

Answer 13

• stimulates acid production of parietal cells and gastric motility
• food in stomach

Question 14

GIP (gastric inhibitory peptide)

Answer 14

• stimulates release of insulin from pancreas
• inhibits gastrin
• chyme in duodenum

Question 15

secretin

Answer 15

secretion of bile and pancreatic buffers

Question 16

VIP (vasoactive intestinal peptide)

Answer 16

• dilation of intestinal capillaries

- facilitates nutrient absorption

Question 17

enterocrinin

Answer 17

• stimulates production of alkaline mucus to neutralize acidic chyme

Question 18

Discuss the cephalic phase of gastric activity regulation.

Answer 18

• the first phase
• prepares the stomach to receive food
• directed by CNS to stimulate submucosal plexus and stimulate secretions of parietal cells, chief cells, G cells and mucous cells

Question 19

Discuss the gastric phase of gastric activity regulation

Answer 19

• the second phase
• when food arrives in the stomach
• stimulation of submucosal and myenteric plexuses
• secretory cells activated and powerful contractions produced

Question 20

Discuss the intestinal phase of gastric activity regulation

Answer 20

• the third (last) phase
• controls rate of gastric emptying
• when chyme enters duodenum
• secretion of CCK, GIP and secretin inhibit chief cells and parietal cells
• inhibition of myenteric plexus stops muscle contractions
• duodenal stretch and chemoreceptors stop peristalsis

Question 21

__ tells the liver to make more bile, while __ stimulates the release of stored bile.

Answer 21

secretin; CCK

Question 22

CCK

Answer 22

secretion of pancreatic enzymes and contraction of gallbladder (release of bile)