Lecture 28

Question 1

What is the main function of the fundus?

Answer 1

receiving chamber of food

Question 2

What is the main function of the corpus?

Answer 2

mixing and secreting chamber where the vast majority of the secretions will be released from

Question 3

What is the function of the pyloric region?

Answer 3

region that is involved with the mixing, emptying and pushing back up of the stomach contents so that further mixing is able to occur

Question 4

Describe the anatomy of the various different layers of the stomach:

Answer 4

1. Outer serosa layer 2. Muscle layer (the outer is longitudianl, then circular, then oblique layer 3. Submucosa 4. Inner mucosa layer

Question 5

What type of contractions occur in the proximal stomach?

Answer 5

tonic contractions

Question 6

What are the two different types of relaxations that occur within the proximal stomach? Differentiate between them

Answer 6

A.) Receptive relaxation- mediated by the central pattern generators. The process mainly involves the stimulation of pharyngeal mechanoreceptors that then travel in afferents to the CNS and then affect efferent vagal fibres to inhibitory nerves of the CNS B.) Adaptive relaxation- much more of a local reflex. Distension in the gastric wall activates stretch receptors that lead to efferent vagal fibres to inhibitory nerves within the gastric wall

Question 7

Does the distal stomach have phasic or tonic contractions?

Answer 7

Phasic

Question 8

Describe the stages that are involved in the process of gastric emptying:

Answer 8

1. The contraction starts in the corpus and then moves downward 2. The contraction then reaches the antrum and the pyloric sphincter opens pushing chyme into the duodenum 3. The wave reaches the pyloric sphincter and then it closes 4. Propels chyme back up into the duodenum facilitating the whole mixing action

Question 9

Name the blank spaces that are shown on the flow diagram below:

Answer 9

1. Dilation of the stomach
2. Increase in the activity of stretch sensitive sensory cells
3. peptides in the stomach
4. increase in gatrin

Question 10

Fill out the following blanks in the table below:

Answer 10

1. Increase in the activity of the cells in the duodenum
2. Central nervosu system
3. Increase in the release of hormones from the duodenal epithelium
4. Emptying of the stomach decreases

Question 11

What types of cells are in the cardiac region of the stomach, and what secretions do they produce?

Answer 11

mucous glands- mucous

Question 12

What cells are present within the cardiac/fundic region of the stomach and what are their secretions?

Answer 12

Parietal cells- HCL

Chief cells- pepsingen

Mucous neck cells

Endocrine cells- mainly histamine

Question 13

What are the cells in the antrum of the stomach?

Answer 13

1. mucous neck cells
2. D cells (produce somatostatin)
3. G cells (gastrin releasing)
4. No chief cell
5. Few parietal cells

Question 14

Name each of the following in the diagram below:

1. Name of the acid that is produced
2. Name of ion
3. Nam of ion
4. Type of pump
5. Type of ion
6. Name of enzyme
7. Product that is produced

Answer 14

1. hydrochloric acid
2. chloride ion
3. hydrogen ion
4. hydrogen and potassium ATP-ase
5. potassium ion
6. carbonic anyhydrase
7. bicarbonate ion

Question 15

Describe the path of bicarbonate from where it is produceed in the secretion:

Answer 15

1. bicarbonate is produced by the parietal cells
2. Enters the mucosal capillaries at very high concentrations
3. Travels to the mucous layer
4. Contributes to the production of mucous

Question 16

What are the three main regulators of gastric acid secretion:

Answer 16

A.) gastrin

B.) histamine

C.) Acetylcholine

Question 17

Explain how inhibition of gastric secretion occurs:

Answer 17

Somatostatin is released from the antral D-cells in response to acid. This paracrine then leads to inhibition of gastrin release from G-cells that then inhibits acid secretion. Somatostatin also acts on the parietal and histamine producing cells leading to inhibited acid secretion. CCK and secretin released from duodenum causes supression of gastric acid secretion.