Lecture 6 - anatomy of salivation and swallowing

Question 1

Saliva contents

Answer 1

Mostly water
Hypotonic
Rich in K+ and HCO3- - alkaline pH
Mucin - lubrication
Lingual amylase and lipase - chemical digestion
Immune proteins - IgA, lysozymes and lactoferrin

Question 2

Functions of saliva

Answer 2

Lubricate and hydrate bolus
Chemical digestion of food 
Keeps mouth moist 
Immune defence
Transmits diseases e.g. rabies
Speech production as can easily move tongue and cheeks

Question 3

Xerostomia

Answer 3

Dry mouth

Question 4

Secretion of saliva from acinus

Answer 4

1. Myoepithelial cells on the acinus contracts and secretes saliva which is watery, isotonic and contains Kallikrein
2. The saliva travels through the duct and becomes modified to a hypotonic solution
3. The duct cells reabsorb Na+ and Cl- and secretes K+ and HCO3- into the saliva

(More electrolytes are reabsorbed than secreted)

Question 5

Salivary glands

Answer 5

Submandibular gland
Parotid gland
Sublingual gland

Question 6

Low flow saliva

Answer 6

Greatest modification when there is slow flow except HCO3- secretion which is selective

Question 7

Blocked salivary duct via stone

Answer 7

Intermeitrent pain when eating and salivating.

Increased pressure in gland can dislodge the stone

Question 8

Babies eating and breathing

Answer 8

Short neck where epiglottis is higher up and overlapping soft palate.

Food diverted into oesophagus and can breath at same time

Question 9

Neural control of swallowing and gag reflex

Answer 9

1. Mechanoreceptors in the pharyngeal wall activated
2. Glossopharyngeal wall afferents stimulated
3. Impulses sent to medulla
4. Vagus nerve motor efferents sends impulses to pharyngeal constrictors

[Not hormonal as too slow]

Question 10

4 narrowings of oesophague

Answer 10

1. Junction of pharynx with oesophagus
2. Where aortic arch crosses oesophagus
3. Where left main bronchus compresses oesophagus
4. At the oesophageal hiatus passing through the diaphragm

Question 11

Prevention of oesophageal reflux

Answer 11

1. Lower oesophageal sphincter (functional) - smooth muscles of distal oesophagus
2. Diaphragm
3. Oesophagus enters at oblique angle into stomach creating a flap valve that can close with increased intra-gastric pressure
4. Intra -abdominal oesophagus compressed when intra-abdominal pressure rises
5. Mucosal rosette at cardia

Question 12

Barret’s oesophagus

Answer 12

1. Chronic reflux
2. Squamous cell metaplasia to columnar cells
3. Adenocarcinoma

Question 13

Salivary gland imagery

Answer 13

Sialography

Question 14

Swallowing phases

Answer 14

Oral preparatory phase
Pharyngeal phase
Oesophageal phase

Question 15

Oral preparatory phase

Answer 15

Voluntary
Pushes bolus towards the pharynx - tongue lifted against hard palate
Ends when bolus touches the pharyngeal wall

Question 16

Pharyngeal phase (8)

Answer 16

Involuntary
Soft palate is elevated, closing off the nasopharynx
Pharyngeal constrictors push bolus downwards (CNX)
Hyoid bone is elevated by suprahyoids and longitudinal muscles
Larynx is elevated and moves anteriorly
Epiglottis moves down and over the laryngeal inlet
Vocal cords adduct
Opening of the oesophageal sphincter

Question 17

Oesophageal phase

Answer 17

Involuntary
Closure of the upper oesophageal sphincter
Peristaltic waves carries bolus downwards into the oesophagus