Digestive System

Question 1

Main structures of the digestive system

Answer 1

oral cavity
esophagus
stomach
small and large intestines

Question 2

accessory organs in digestive system + basic role

Answer 2

pancreas- releases pancreatic juice that neutralizes chyme and contains enzymes needed for carbs, pro, lipid digestion
liver- produce bile for lipid digestion
gallbladder- stores and releases bile for lipid digestion

Question 3

state layers of the lumen

Answer 3

1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa

Question 4

Mucosa function

Answer 4

epithelial on contact with food, innermost layer
- acts as a membrane, lined with epithelial cells
- 3 parts: mucosal membrane, lamina propria (connective and lymphoid tissues), muscularis mucosa (smooth muscle)

Question 5

submucosa function

Answer 5

controls GI secretions, local blood flow control
o Connective tissues
o Blood
o Lymphatic vessels
o Lymphoid tissues
o Submucosal plexus

Question 6

Muscularis externa function

Answer 6

o Outer smooth muscle around submucosal
o Controls movement (strength, frequency)

Question 7

Serosa Function

Answer 7

Outermost layer, lubricant fluids
o Flat mesothelial cells

Question 8

Oral cavity structures

Answer 8

mouth and pharynx
salivary glands:
- parotid
- submandibular
-sublingual
enzymes in saliva (amylase)

Question 9

esophagus functions

Answer 9

Moves bolus (chewed food) from oral cavity to stomach
Swallowing stages: Voluntary, pharyngeal, esophageal
Peristalsis (rhythmic contraction and relaxation of esophagus muscles, happens throughout entire GI tract)
Gastroesophageal sphincter (relaxed = open esophagus)
Esophagus disorder: GERD (Acid)

Question 10

stomach 4 regions

Answer 10

1. cardia region
2. fundus
3. body
4. Antrum or distal pyloric

Question 11

3 gastric glands

Answer 11

cardiac, oxyntic, pyloric

Question 12

3 phases of digestion

Answer 12

1. Before food reaches the stomach
   o Acetylcholine, gastrin
   o Prepares GI system for food (salivation)
2. Once food is in stomach
   o Stomach distension enhances gastric secretions
   o Digestion
   o Prepare for absorption
3. After food has left stomach
   o Reduction in chyme volume and pH (below 2) trigger release of somatostatin
    Somatostatin: helps reset stomach to normal and prepare for more food

Question 13

pancreas functions

Answer 13

• Ductless endocrine cells that secrete hormones into the blood (insulin, glucagon)
• Digestive enzymes produces by acinar exocrine cells

Question 14

pancreatic juice contains:

Answer 14

o Water
o Electrolytes
o Bicarbonate
o Pancreatic digestive enzymes

Question 15

liver structure

Answer 15

• Consists of lobes made of lobules (right and left)
• Portal circulation
• Bile canaliculi (between liver cells)
• makes bile

Question 16

bile functions

Answer 16

o Bile composed of bile acids and salts, cholesterol, phospholipids and bile pigments in alkaline solution
o Bile acts like a detergent to emulsify fats and oils
o Large fat globules to droplets

Question 17

gallbladder function

Answer 17

• Concentrates and stores bile
• Disorders: gallstones
  o Common in older adults
  o Cholesterol bile is not released
  o Lipids and Calcium deposit around cholesterol
• Recirculation and excretion of bile:
  o Most bile salts are reabsorbed
• Bile circulation and hypercholesterolemia

Question 18

Absorptive process/path

Answer 18

• Absorption beings in the duodenum and continues through jejunum and ileum
• Absorption is rapid (few hours for macros)
• Absorption methods:
  o Diffusion, facilitated diffusion, active transport or pinocytosis/endocytosis

Question 19

large intestine function

Answer 19

• Contracts to mix materials
• proximal colonic mucosal cells absorb sodium and water (influenced by hormones, materials dehydrated)
• colonic secretions:
  o goblet cells secrete mucus- help move remaining material through large GI
  o bicarbonate- gastric juice, acidic

Question 20

Neural regulation

Answer 20

• local regulation
• myenteric plexus: peristalsis, motility
• submucosal plexus: secretions, local blood flow
• regulatory peptides: hormones, paracrines

Question 21

Regulation of Gastric Motility and Gastric emptying

Answer 21

• peristaltic waves propel digestive contents:
  o basic electrical rhythm is initiated by pacemaker cells
• gastric emptying is affected by factors in stomach and duodenum
• dietary fat intake has an inhibitory effect on gastric emptying (increase fat = decrease digestion)

Question 22

regulatory peptides

Answer 22

• paracrine-acting substances
• Neurocrine peptides
• Other hormones: ghrelin, leptin, CRH
  o Appetite and satiety

Question 23

EAR

Answer 23

average amount of a nutrient required for good health. If everyone in the population consumed this amount, only 50% would obtain enough of the nutrient to meet their requirements

Question 24

RDA

Answer 24

set by adding a safety factor to the EAR. About 98% of the population meets its needs by consuming this amount
- RDA= EAR + 2SD (standard deviations)

Question 25

UL

Answer 25

set well above the needs of everyone in the population. Represents the highest amount of the nutrient that will not cause toxicity symptoms in the majority of healthy people - RDA= EAR + 2SD (standard deviations)