Lecture 12

Question 1

What is meant by the term prehension?

Answer 1

Process of using lips, teeth and tongue to get food into the oral cavity

Question 2

What is meant by the term mastication?

Answer 2

Chewing

Question 3

What are the three main salivary glands and what are their secretions?

Answer 3

Parotids- serous secretion

Secretion mandibular + sublingual = mixed

Question 4

Briefly describe the formation of saliva

Answer 4

1. Acini glands release lysozyme, mucin, electrolytes @ similar concentrations to plasma
2. Along the ducts Na+ and Cl- is secreted, K+ and HCO3- is reabsorbed

Question 5

What is the function of mucin?

Answer 5

Forms mucus when mixed H20

Question 6

Function of amylase?

Answer 6

Starch breakdown

Question 7

Function of lysozyme?

Answer 7

Stop bacteria

Question 8

Function of bicarbonate?

Answer 8

Neutralise acid produced by bacteria

Question 9

What is a specialisation of ruminant saliva and what is its significance?

Answer 9

Urea diffuse from blood to saliva. Make proteins from N when they are low

Question 10

How is saliva secretion regulated?

Answer 10

Autonomic only- mainly parasympathetic

Question 11

How is the involuntary control of swallowing regulated?

Answer 11

Central pattern generator in medulla

Question 12

Describe the main phases in the voluntary and involuntary phases of deglutition:

Answer 12

Voluntary: 
- Oral 
Involuntary: 
- Pharyngeal 
- Cricopharyngeal 
- Oesophageal 
- Gastro-Oesophageal

Question 13

What are the main steps involved in the pharyngeal phase?

Answer 13

Pharynx changes from a food to an air channel:

1. Pathway back into oral cavity closed by muscles of mouth + tongue
2. Epiglottis tips caudally and the glottis constricts
3. Soft palate lifts up protecting the nasopharynx

Question 14

What is the main event that occurs in the cricopharyngeal phase of swallowing?

Answer 14

In the absence of swallowing the upper oesophageal sphincter, is kept tonically closed by vagus nerve. UES kept open for the length of the bolus.

Question 15

Describe the oesophageal phase of swallowing

Answer 15

Behind: LM- relaxed, CM- contracted
Forward: LM- contracted, CM-relaxed

Question 16

Describe the gastro-oesophageal phase:

Answer 16

Has a lower oesophageal sphincter that is normally kept closed. But it opens to allow the passage of the bolus

Question 17

Describe the main mechanisms for preventing reflux:

Answer 17

• valve like nature of oesophagus
• oesophagus enters the stomach at acute angles
• diaphragmatic contractions