8.2 Overview of Digestive System Functions

Question 1

What is the function of the digestive system?

Answer 1

Transfer nutrients, water, and electrolytes from food into the internal environment

Question 2

What is the process by which food is broken down so that it can be absorbed?

Answer 2

Digestion

Question 3

What percentage of the food we ingest is digested?

Answer 3

95%

Question 4

Is the gastrointestinal tract part of the internal environment?

Answer 4

No; it is continuous with the external environment (like the inside of a straw)

Question 5

What comprises the digestive system?

Answer 5

Digestive tract+ accessory digestive organs

Question 6

What is the digestive function of the mouth?

Answer 6

• Mastication
• Some carb. digestion

Question 7

What is the digestive function of the pharynx & oesophagus?

Answer 7

Swallowing and transporting food to the stomach

Question 8

What is the digestive function of the stomach?

Answer 8

Mixing, churning, digestion

Question 9

What is the digestive function of the small intestine?

Answer 9

Digestion and most absorption (with help from liver and pancreas secretion)

Question 10

What is the digestive function of the large intestine?

Answer 10

Completes absorption of water and electrolytes

Question 11

What are the four accessory glands of the digestive system?

Answer 11

• Salivary glands
• Pancreas
• Liver
• Gall bladder

Question 12

What is the digestive function of the salivary glands?

Answer 12

• Secretes amylase
• Mucous for lubrication
• Lysosyme
• Dilutes, cools, and buffers

Question 13

What is the digestive function of the pancreas?

Answer 13

• Pancreatic juice (enzymes and aqueous, bicarbonate-rich solution)
• Enzymes can almost digest everything

Question 14

What is the digestive function of the liver?

Answer 14

• Secretes bile

Question 15

What is the digestive function of the gallbladder?

Answer 15

• Stores bile

Question 16

What are the three layers of the digestive mucosa?

Answer 16

• Simple columnar epithelium (endo/excorine glands, secretion of mucous)
• Lamina propria (gut associated lymphoid tissue)
• Muscular mucosa (thin layer of smooth muscle separating mucosa from submucosa)

Question 17

What is the function of the gut-associated lymphoid tissue? Where is it?

Answer 17

• Defending against pathogens
• Found in lamina propria of GI mucosa

Question 18

What is contained within the submucosa?

Answer 18

• Larger blood vessels
• Larger lymph vessels
• Nerve network (submucosal plexus)

Question 19

What are the two layers of the muscularis externa?

Answer 19

• Inner circular
• Outer longitudinal

Question 20

What do the contractions of the two layers of the muscularis externa do?

Answer 20

Circular: changes diameter
Longitudinal: changes length

Question 21

Where is the myenteric plexus located?

Answer 21

Between the circular and longitudinal layers of muscularis externa

Question 22

What is the serosa continuous with? What does it secrete?

Answer 22

• Continuous with mesentery
• Secretes serous fluid for lubrication of organs

Question 23

What are the four basic digestive processes?

Answer 23

1. Motility
2. Secretion
3. Digestion
4. Absorption

Question 24

What are the two main kinds of digestion?

Answer 24

• Mechanical
• Chemical

Question 25

Where are substances absorbed into from the digestive system?

Answer 25

Blood and lymph

Question 26

What type of muscle is important in digestive motility? How does this make sense in terms of involuntary control?

Answer 26

• Smooth
• Makes sense: smooth muscle cannot voluntarily be controlled

Question 27

Describe the tone of digestive smooth muscle

Answer 27

Constantly low; prevents permanent distension

Question 28

What are the two types of phasic digestive mobility?

Answer 28

• Propulsive (peristalsis)
• Mixing (segmentation)

Question 29

What is the main chemical process underlying digestion?

Answer 29

Hydrolysis

Question 30

Which substances can be actively/passively absorbed?

Answer 30

Active: protein & carbs
Passive Fat (into lymph)

Question 31

What are the four factors that regulate digestion?

Answer 31

• Autonomous smooth muscle function
• Intrinsic nerve plexuses
• Extrinsic nerves
• Gut hormones

Question 32

What are the autonomic pacemakers of the GI tract? How are they connected to smooth muscle?

Answer 32

Cells of Cajal; connected by gap junctions to smooth muscle cells

Question 33

Name one neurotransmitter that causes contraction/relaxation of enteric smooth muscle

Answer 33

Relax: NO
Contract: Ach

Question 34

Do the inrinsic nerve plexuses coordinate long-range, local activity, or both?

Answer 34

Local (e.g. food stuck)

Question 35

Describe the types of nerves in the enteric system

Answer 35

• Sensory (Intrinsic Primary Afferent)
• Interneurons
• Motor (excitatory and inhibitory)

Question 36

What section of the nervous system makes up the extrinsic nerves of the enteric nervous system?

Answer 36

Autonomic

Question 37

In what ways do extrinsic nerves influence the enteric nervous system?

Answer 37

• Acting on intrinsic nerves
• Changing hormone secretion
• Acting on effector cells

Question 38

True or false: extrinsic nerves cannot coordinate activity between different regions of the digestive tract

Answer 38

False. They can, and do.