physiology of swallowing

Question 1

What is the daily amount of saliva secretion?

Answer 1

800-1500ml/day

Question 2

What is the normal pH of the saliva?

Answer 2

6-7

• It is made up of 99.5% water and 0.5% solute

Question 3

What are the major glands that secretes saliva?

Answer 3

1) Parotid gland (serous secretions containing ptyalin “a-amylase” for starch digestion)

2) Submandibular gland (it secretes a mix of serous and mucus secretions)

3) Sublingual gland (it secretes a mix of serous and mucus secretions)

Question 4

What does the tiny buccal glands secrete?

Answer 4

• It secretes mucus that contains mucin-lubrication and surface protection

Question 5

What is the process of saliva secretion?

Answer 5

1) First stage (involves acini)

• The primary secretion is produced by acini and contains ptyalin and or mucin and it is isotonic

2) Second stage (involved the salivary ducts)

• The primary secretion flows through the ducts and are modified

2a) Sodium and chloride are absorbed

2b) Potassium and bicarbonate are secreted

2c) The ducts are relatively impermeable to water

• The final saliva secretion is a hypotonic aqueous solution

Question 6

What is are the different composition of the saliva during rest compared to maximal salivation?

Answer 6

1) During rest:

• The saliva contains sodium and chloride ions only about 15mEq/L
• Potassium is 30 mEq/L
• Bicarbonate is 50-70 mEq/L

2) During excessive salivation:

• Sodium and chloride ion conc increases
• Potassium conc increases by 4 times

Question 7

How is the salivary secretion regulated?

Answer 7

By the autonomic nervous system, (Parasympathetic “Ach/Muscarinic”, Sympathetic “Norepinephrine/neurotransmitters)

Question 8

What is the effect of the parasympathetic regulation on the production of the saliva?

Answer 8

1) It increases the production of saliva

2) The saliva produced will have a watery texture

• This will occur as there will be more vasodilation and because blood will flow more to the glands

Question 9

What is the effect of the sympathetic nervous system on salivation?

Answer 9

1) It increases the modification of the saliva

2) The saliva produced will be thicker

3) The saliva will have a more proteinaceous content

Question 10

What is the route of parasympathetic regulation of the saliva?

Answer 10

• Parasympathetic nervous signals from the superior and inferior salivatory nuclei located at the junction of the medulla and pons
• The Facial nerve takes information to the submandibular and sublingual glands
• The glossopharyngeal nerve takes information to the parotid gland

Question 11

What inhibits or stimulates the salivatory nuclei of the parasympathetic control

Answer 11

1) Taste

2) Tactile stimuli

3) Mouth

4) Pharynx

• Sour food → increased saliva production
• Smooth food → increased saliva production
• Spiky food → decreased saliva production
• Favorite food → increased saliva production

Question 12

What is the relationship between the dilation of blood vessels and saliva production?

Answer 12

• Increased blood supply will increase the production of saliva
• Parasympathetic stimulation moderately dilates blood vessels, in addition to the secretion of kallikrein via activated salivary cells which splits the blood protein (a2-globulin) forming bradykinin which is a strong vasodilator

Question 12

When does salivation occur as a reflex?

Answer 12

Salivation occurs as a reflex originates in the stomach and upper small intestine, when irritating foods are swallowed or when a person is nauseated due to some GI abnormality

Question 13

What is the route of sympathetic control of salivation?

Answer 13

The originate from the superior cervical ganglia and travel to the salivary glands

Question 14

What are the functions of saliva?

Answer 14

1) It contains bactericidal agents like (thiocyanate ions, lysozymes and antibodies)

2) It lubricates the ingested food with mucus

3) It dilutes and buffers the ingested food

4) It Aids in speech by facilitating the movement of the lips and tongue

5) It facilitates swallowing

6) It keeps the mouth and teeth clean

7) It starts the initial process of starch and lipid digestion via the salivary enzymes

8) It serves as a solvent for molecules that stimulates the taste buds

Question 15

What are the special things our body has or does in regards to mastication?

Answer 15

1) The teeth are designed for chewing (incisors for cutting and molars for grinding)

2) Lubrication and reduced size of food particles facilitates swallowing

3) Mastication mixes the ingested carbohydrates with the salivary amylase

4) Involuntary reflexes are: initiated by the food in the mouth, sensory input from the mechanoreceptors, reflex oscillatory pattern

5) Voluntary chewing can override involuntary/reflex chewing

• The final product is called a bolus

Question 16

Describe the process of mastication

Answer 16

1) Food into the mouth

2) Reflex inhibition of he muscles of mastication

3) The lower jaw drops

4) Stretch reflex of the jaw muscle is initiated

5) Rebound contraction

6) The jaw raises and closes the mouth

7) The bolus is then compressed against the lining of the mouth

8) Reflex inhibition of the muscles of mastication

9) The process is then repeated again and again

Question 17

Which nerve innervated most of the chewing muscles?

Answer 17

The motor branch of the fifth cranial nerve

Question 18

What are the nuclei that regulates chewing?

Answer 18

It is regulated by the nuclei in the brainstem, areas in the hypothalamus, amygdala, cerebral cortex near the sensory areas for taste and smell

Question 19

When is deglutition/swallowing initiated?

Answer 19

• It is initiated voluntarily in the mouth, after that it is involuntary/reflex control once it touches the oropharynx (tonsillar pillar)
• Inhibition of respiration and glottis closure are part of the reflex response