The Gastrointestinal System

Question 1

What are the primary functions of the gastrointestinal system?

Answer 1

• regulated intake of food and water
• conversion of food into nutrients
• absorption of nutrients and water
• energy storage
• excretion of waste products
• protection against bacteria and toxins

Question 2

What are the processes involved in the gastrointestinal system?

Answer 2

• sensory inputs: appetite, taste, smell, and sight
• mechanical and chemical breakdown of food
• secretion, absorption, and excretion
• the system is regulated by nerves, hormones, and local factors

Question 3

What are the major subdivisions of the digestive tract?

Answer 3

(from mouth to anus)
- oral cavity, teeth, tongue
- pharynx
- esophagus
- stomach
- small intestine
- large intestine

Question 4

How do the oral cavity, teeth and tongue contribute to the digestive tract?

Answer 4

Mechanical processing, moistening, mixing with salivary secretions

Question 5

How does the pharynx contribute to the digestive tract?

Answer 5

Muscular propulsion of materials into the esophagus

Question 6

How does the esophagus contribute to the digestive tract?

Answer 6

Transport of materials to the stomach

Question 7

How does the stomach contribute to the digestive tract?

Answer 7

Chemical breakdown of materials via acid & enzymes; mechanical through muscular contractions

Question 8

How does the small intestine contribute to the digestive tract?

Answer 8

Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions

Question 9

How does the large intestine contribute to the digestive tract?

Answer 9

Dehydration and compaction of indigestible materials in preparation for elimination

Question 10

What are the accessory organs of the digestive system?

Answer 10

• salivary glands
• liver
• gallbladder
• pancreas

Question 11

What are the 4 components of the gastrointestinal system’s structure?

Answer 11

(innermost to outermost)
- mucosa
- submucosa
- muscularis propria/externa
- serosa
(slide 5)

Question 12

What are the components of the mucosa layer of the gastrointestinal system?

Answer 12

composed of three parts:
- mucosa epithelium
- lamina propria
- muscularis mucosa

Question 13

What are the components of the submucosa layer of the gastrointestinal system?

Answer 13

• loose connective tissue
• exocrine glands
• nerves, blood and lymphatic vessels

Question 14

What are the components of the muscularis propria/externa layer of the gastrointestinal system?

Answer 14

• inner circular smooth muscle
• outer longitudinal smooth muscle

Question 15

What is the serosa composed of?

Answer 15

outer connective tissue

Question 16

What is the enteric nervous system?

Answer 16

A network of autonomic nerves within the gastrointestinal tract that contains ganglia at the myenteric and submucosal plexus.
(slide 6)

Question 17

What is the function of the enteric nervous system?

Answer 17

Controls smooth muscle contraction and exocrine/endocrine gland secretions within the gastrointestinal tract.

Question 18

How is the enteric nervous system regulated?

Answer 18

Regulated by sympathetic and parasympathetic nerves, as well as sensory reflexes

Question 19

What are interstitial cells of Cajal?

Answer 19

Specialized smooth muscle cells found in the gastrointestinal tract that act as pacemaker cells for gut motility.

Question 20

What is the function of interstitial cells of Cajal?

Answer 20

Generate pacemaker activity that determines the frequency of slow waves in the gastrointestinal tract - crucial for the regulation of gut motility.

Question 21

How do interstitial cells of Cajal control gut motility?

Answer 21

They generate and propagate electrical signals called slow waves, which in turn regulate the frequency and strength of muscle contractions in the gastrointestinal tract.

Question 22

What is the circulation of the gastrointestinal system?

Answer 22

Collectively known as the splanchnic circulation, refers to the blood supply to the digestive organs.

Question 23

How much blood volume does the splanchnic circulation contain?

Answer 23

approximately 15% of the total blood volume in the body

Question 24

What is the function of the splanchnic circulation?

Answer 24

Transports absorbed nutrients and waste products for excretion from the digestive organs.

Question 25

What is the portal circulation in the splanchnic circulation?

Answer 25

The blood flow between the gastrointestinal tract (GI) and the liver

Question 26

How does the splanchnic circulation regulate blood flow?

Answer 26

Has adjustable resistance and acts as a reservoir of blood. It can undergo:
- vasodilation by parasympathetic control
- vasoconstriction by sympathetic control

Question 27

What are the phases of digestion?

Answer 27

The different stages of the digestive process that are controlled by gut motility and secretions

Question 28

What are the 3 phases of digestion?

Answer 28

• cephalic
• gastric
• intestinal

Question 29

What is the cephalic phase of digestion?

Answer 29

• anticipation of feeding
• sensory input from food - thoughts, sights, smells, tastes
• mediated by vagal parasympathetic nerves

Question 30

What is the gastric phase of digestion?

Answer 30

• presence of food in the stomach
• sensory input from food - stretch and chemicals
• mediated by parasympathetic and enteric nerve reflexes, hormones (e.g. gastrin)

Question 31

What is the intestinal phase of digestion?

Answer 31

• presence of food in the intestines
• sensory input from food - stretch and chemicals
• mediated by parasympathetic and enteric nerve reflexes, hormones (e.g. secretin, CCK)