Section 1

Question 1

Name the four basic digestive processes.

Answer 1

• motility
• secretion
• digestion
• absorption

Question 2

What are the components of digestive juices secreted into the digestive tract?

Answer 2

Digestive juices contain water, electrolytes, enzymes, bile salts, and mucus.

Question 3

Contraction of what SKELETAL MUSCLE within the walls of digestive organs accomplishes movement of material through which of the following parts of the digestive tract (ie which ones DONT use smooth muscle:

• The top of the esophagus
• The bottom of the esophagus
• Opening of the small intestine
• Mouth
• The colon
• Opening of the large intestine
• Stomach
• External anal sphincter

Answer 3

top of esophagus
mouth
and external anal sphincter

USE VOLUNTARY COMPONENTS THEREFORE SKELETAL MUSCLE

Question 4

What does motility refer to in the digestive system, and what are the two types of movements involved?

Answer 4

Motility refers to the muscular contractions that mix and propel the contents of the digestive system. Propulsive movements push contents forward, while mixing movements help mix food with digestive enzymes and promote absorption.

Question 5

What are the components of digestive juices secreted into the digestive tract, and how are these secretions released?

Answer 5

Digestive juices contain water, electrolytes, enzymes, bile salts, and mucus. Secretions are released on appropriate neural or hormonal signals

Question 6

What is the main biochemical process involved in digestion, and how are carbohydrates, fats, and proteins digested?

Answer 6

Digestion is the enzymatic breakdown of structurally complex foods into small, absorbable units.

• Carbohydrates are broken down into monosaccharides through enzymatic hydrolysis
• Fats are broken down into free fatty acids and monoglycerides
• Proteins are broken down into single amino acids and small polypeptides for absorption.

Question 7

Where does absorption primarily occur in the digestive system, and what are the definitions of polysaccharides, monosaccharides, and triglycerides?

Answer 7

Most absorption occurs in the small intestine, where absorbable units move into the blood and lymph.

Polysaccharides are complex carbohydrates consisting of many glucose molecules, monosaccharides are simple sugars like glucose, and triglycerides are composed of three fatty acids attached to a glycerol molecule.

Question 8

What are the four major layers of the digestive tract walls?

Answer 8

The four layers are mucosa, submucosa, muscularis externa, and serosa.

Question 9

Describe the mucosa layer of the digestive tract.

Answer 9

The mucosa is the innermost layer lining the luminal surface. It’s highly folded to increase surface area, with less folding in the esophagus and the highest amount in the small intestine where absorption occurs.

Question 10

What is the composition and function of the submucosa layer?

Answer 10

The submucosa layer is thick and made of connective tissues supporting the mucosa. It provides distensibility, elasticity, and contains larger blood and lymph vessels. It also houses the submucosal plexus, a network of nerves.

Question 11

Explain the structure and function of the muscularis externa.

Answer 11

The muscularis externa is the smooth muscle layer surrounding the submucosa. It typically has two muscle layers: an inner circular layer and an outer longitudinal layer. Contraction of these layers facilitates propulsive and mixing contractions.

The myenteric plexus along with hormones and chemical mediators, located between the muscle layers, helps regulate local gut activity.

Question 12

What is the role of the serosa in the digestive tract? What is it continous with?

Answer 12

The serosa is the outer connective tissue layer covering the digestive tract. It’s continuous with the mesentery, suspending digestive organs in the abdominal cavity while allowing movement for mixing and propulsion.

Question 13

Give two facts of the submucosa of the digestive tract.

Answer 13

(1) Made of connective tissues that support the mucosa
(2) Contains the submucosal plexus, which is a network of nerves

Question 14

Give two facts of the serosa of the digestive tract.

Answer 14

(1) outermost layer
(2) continuous with the mesentery

Question 15

Give two facts of the mucosa of the digestive tract.

Answer 15

(1) innermost layer
(2) surface is highly folded to increase its surface area

Question 16

Give two facts of the muscularis externa of the digestive tract.

Answer 16

(1) it is two two layers of smooth muscle layer that surround the submucosa
(2) both layers provide the propulsive and mixing contractions

Question 17

What are the four factors that regulate digestive system function?

Answer 17

The four factors are autonomous smooth muscle function, intrinsic nervous plexuses, extrinsic autonomic nerves, and gastrointestinal hormones.

Question 18

Why are digestive motility and secretion regulated?

Answer 18

In order to maximize digestion and absorption of ingested food

Question 19

What are the two components of the intrinsic nerve plexuses, and what is their alternate name?

Answer 19

The intrinsic nerve plexuses consist of the submucosal plexus and the myenteric plexus, also known as the enteric nervous system (ENS).

Question 20

What is the primary purpose of the enteric nervous system (ENS)?

Answer 20

The primary purpose of the ENS is self-regulation, although it receives significant input from the autonomic nervous system (ANS).

Question 21

How is the enteric nervous system (ENS) involved in digestive tract function, and what types of cells does it innervate?

Answer 21

The ENS is involved in sensory perception of local stimuli, regulation of motility, and secretion of digestive juices. It innervates smooth muscle cells, exocrine glands, and endocrine glands within the digestive tract.

Question 22

How are neurons of the enteric nervous system (ENS) interconnected?

Answer 22

Neurons of the ENS are interconnected by interneurons, similar to the connections seen in the central nervous system (CNS).

Question 23

What would occur if a large piece of food got stuck in the esophagus, based on the role of the enteric nervous system (ENS)?

Answer 23

Sensory receptors within the ENS would detect the blockage. These receptors would signal interneurons, which would coordinate a response in local motor neurons to induce contraction of smooth muscle cells, increasing motility to push the food forward.

Question 24

What are extrinsic autonomic nerves, and what systems do they originate from?

Answer 24

Extrinsic autonomic nerves, originating from both the sympathetic and parasympathetic nervous systems, innervate various digestive organs.

The autonomic nervous system modifies the activity of the enteric nervous system, regulates gastrointestinal hormone secretion, and directly innervates smooth muscle and glands to influence motility and secretion.

Question 25

What effects do the sympathetic and parasympathetic nervous systems have on digestive tract function?

Answer 25

The sympathetic system slows down digestive tract contractions and secretions, while the parasympathetic system increases smooth muscle contractility and promotes secretion of digestive juices and hormones.

Question 26

What is unique about the parasympathetic nerve supply of the digestive system?

Answer 26

Postganglionic parasympathetic nerve fibers are part of the intrinsic nervous system, which is unique to the parasympathetic nerve supply of the digestive system.

Question 27

Provide an example of discrete activation of extrinsic innervation in the digestive system and its purpose.

Answer 27

An example is the act of chewing food, which reflexively activates salivary enzyme secretion and also triggers secretions from the stomach, pancreas, and liver via vagal reflexes in preparation for food arrival. This coordination ensures synchronized digestive activity across multiple regions of the digestive system.

Question 28

Where are gastrointestinal hormones released, and how do they affect digestive function?

Answer 28

Gastrointestinal hormones are released from endocrine glands in the mucosa of some parts of the digestive tract.

They can have either excitatory or inhibitory actions on motility and exocrine gland secretions.

Question 29

What is the significance of autonomous smooth muscle function in the digestive system?

Answer 29

Some smooth muscle cells exhibit pacemaker-like rhythmic, spontaneous changes in membrane potential, known as slow-wave potentials, which are essential for regulating digestive motility.

Question 30

What is the significance of gastrointestinal hormones being found in other locations throughout the body?

Answer 30

Many gastrointestinal hormones are found in other locations such as the brain, where they function as neurotransmitters and neuromodulators in addition to their role in the digestive system.

Question 30

What is the significance of autonomous smooth muscle function in the digestive system?

Answer 30

Some smooth muscle cells exhibit pacemaker-like rhythmic, spontaneous changes in membrane potential, known as slow-wave potentials, which are essential for regulating digestive motility.

Slow-wave potentials are rhythmic changes in membrane potential in smooth muscle cells. They originate from the non-contractile interstitial cells of Cajal (ICC) located at the boundary of the circular and longitudinal muscle layers.

Question 30

What role do interstitial cells of Cajal (ICC) play in autonomous smooth muscle function?

Answer 30

ICC are responsible for generating slow-wave potentials, serving as pacemakers for rhythmic contractions in the digestive system.

They are located at the boundary of the circular and longitudinal muscle layers

Question 31

What determines whether an action potential is initiated in smooth muscle cells?

Answer 31

Slow-wave potentials cause oscillations in the membrane potential of smooth muscle cells, moving closer to threshold and further away. If these waves reach threshold at the peak of depolarization, they trigger action potentials and subsequent contractions.

Mechanical, neural, and hormonal factors modulate the membrane potential around which the slow-waves oscillate. If the starting membrane potential is closer to threshold, then the peak of the oscillations can trigger an action potential. This occurs when food is in the digestive tract, leading to increased muscle activity for mixing and propulsion.

Question 31

How do slow-waves differ from action potentials in smooth muscle cells?

Answer 31

Slow-waves themselves are not action potentials because they cannot directly induce contractions. They serve as electrical signals that modulate the frequency and intensity of smooth muscle contractions.