2 salivation physiology

Question 1

what is the first step of the digestive process? what are the three parts of this

Answer 1

mastication: 1. grind and break up food 2. mix food with saliva 3. stimulate taste buds

Question 2

what is saliva?

Answer 2

solution derived from plasma containing electrolytes produced by three main pairs of branched glands parotid, submandibular, sublingual and simple glands (buccal glands of the cheek)

Question 3

total flow and types of secretion of saliva from the glands

Answer 3

Parotid: 20% serous

Submandibular: 70% mainly serous

sublingual: 5% mainly mucus
simple: 5% mucus

Question 4

what type of secretions do acinar cells secrete

Answer 4

primary secretion

isotonic with plasma

some salivary proteins secreted

Question 5

what do duct cells do in salivary glands

Answer 5

• actively reabsorb Na+ (and Cl-)
• secretion of K+ and HCO3-
• impermeable to water, excess absorption of Na+ and Cl- means saliva hypotonic relative to plasma

Question 6

what happens when saliva flow rate increases?

Answer 6

• increased concentration of Na+, Cl-
• decreased concentration of K+
• increased concentration HCO3- (active secretion)

Question 7

what else is in saliva aside from ions?

Answer 7

mucous, proteins (IgA), enzymes (amylase and lysozyme)

Question 8

what controls saliva secretion?

Answer 8

neural control

both SNS and PNS activate- PNS is more important

simple and conditioned reflex

Question 9

What happens to acinar cells when there is parasympathetic stimulation?

Answer 9

Large volume of serous saliva rich in enzymes produced

Question 10

What happens when there is sympathetic nerve activation to saliva?

Answer 10

Small volume of thick saliva rich in mucous

Question 11

Functions of saliva (7)

Answer 11

1. Contains salivary amylase- starts breakdown polysaccharides
2. produces mucous- faciliates swallowing
3. protective function- secrete lysozyme and IgA
4. acts as solvent- stimualte taste
5. moirsturise- aids speech
6. oral hygiene
7. contains bicarbonate to neutralise acids in food to reduce dental cavities

Question 12

Two phases of swallowing (deglutition)

Answer 12

Initiated when food bolus forced by tongue to rear of mouth to pharynx

1. oropharyngeal: food bolus direced into eosophagus
   * requires sealing off by nasal passages (uvula) and trachea (glottis)
2. Esophageal

• peristalsis- gravity assisted
• protected from damage by passing bolus in mucous

Question 13

Functions of the stomach (4)

Answer 13

Storage of food

Initiation of digestion of proteins

Kill ingested bacteria (via acid)

Formation of chime, before transfer to small intestines

Question 14

Which regions of the stomach is improtant from a physiology perspective?

Answer 14

1. Antral region: glands
2. Body of stomach: important in storage of food (ingestion takes minutes, digestation takes hours)

Question 15

Why doesnt the intragastric pressure increase during digestion of food?

Answer 15

Distention of stomach wall and reflex (vagal) inhibition of smooth muscle tone