Mastication

Question 1

What is mastication?

Answer 1

chewing - solid food is chewed, cut, torn and ground into smaller pieces

Question 2

What structures are involved in chewing?

Answer 2

1. upper and lower jaws with teeth 2. the striated mandibular muscles 3. the tongue and cheeks

Question 3

Course of the food during mastication?

Answer 3

food is forced from oral cavity to the vestibule and back, crossing and recrossing the occlusional surfaces

Question 4

Importance of chewing?

Answer 4

1. exposing starches in food to salivary amylase
2. increase surface area of ingested material for enzymatic attack
3. Taste sensations are enhanced by mastication by dissolving or suspensions of solid components in the saliva
4. prevent injury to the lining of the pharynx and eosophagus by reducing size of ingesta

Question 5

What stimulates salivation?

Answer 5

1. taste sensations - also stimulate gastric secretions 2. chewing

Question 6

Centres integrating chewing lie where?

Answer 6

1. lower brainstem in the basal ganglia

2. cerebral cortex

Question 7

Function of the tongue after mastication and salivation?

Answer 7

the tongue compacts food into a bolus

Question 8

What structures produce saliva?

Answer 8

1. buccal glands
2. 3 pairs of extrinsic salivary glands
   - produce 1 litre

Question 9

Structure of extrinsic glands?

Answer 9

connected to oral cavity via ducts

Question 10

Describe the kinds of saliva?

Answer 10

1. serous - producing saliva rich in protein, water and electrolytes (parotid gland)
2. mucous gland (sublingual gland) - produce mucus
3. mucus + protein - submandibular gland

Question 11

What is the composition of saliva?

Answer 11

1. Constitutes 99% Water, hypoosmotic to plasma
2. Electrolytes: Na+, K+ , Ca2+, Cl- and bicarbonate (HCO3-)
3. Digestive enzymes: α-amylase, lysozymes
4. Proteins: mucus (mucins), IgA and IgM

Question 12

What are the functions of saliva?

Answer 12

1. keeps mouth moist
2. facilitates speaking
3. health of the mouth
4. facilitates swallowing
5. digestion of starches
6. facilitates food taste
7. immunity

Question 13

How does saliva maintain the health of the mouth?

Answer 13

1. contains substances that limit and regulate bacterial growth 2. contains alkali that neutralises acid

Question 14

How does saliva aid in the digestion of starch?

Answer 14

1. Saliva contains salivary amylase (ptyalin or alpha-amylase) 2. Mediates starch digestion in the mouth

Question 15

How does saliva ease swallowing?

Answer 15

Saliva moistens and lubricates food so that it can be broken down by chewing before being swallowed : 1. the water in the saliva moistens the food particles 2. salivary mucins bind masticated food into coherent and slippery bolus that can easily slide through the esophagus without damaging the mucosa

Question 16

What regulates secretion of saliva?

Answer 16

autonomic nervous sytem - sympathetic + parasympathetic

Question 17

Sympathetic stimulation causes?

Answer 17

secretion of small amounts of viscous saliva

Question 18

Parasympathetic stimulation causes?

Answer 18

profuse secretion of watery saliva with a relatively low content of organic material

Question 19

Where does the parasympathetic outflow originate?

Answer 19

salivary nuclei of the medulla oblongota

Question 20

The salivary nuclei receives afferent signals from?

Answer 20

1. mouth + palate - taste and touch 2. nose - smell 3. higher centres - brain stem nuclei

Question 21

What causes reflex secretion of saliva?

Answer 21

1. food in the mouth 2. stimulation of the vagal afferent fibres at the gastric end of the oesophagus

Question 22

What accelerates salivary production?

Answer 22

1. chewing with an empty mouth
2. smell
3. irritating stimuli

Question 23

What is swallowing/deglutition?

Answer 23

the movement of food from the mouth through oesophagus into the stomach - facilitated by saliva and mucus

Question 24

What structures are involved in swallowing?

Answer 24

mouth, pharynx + esophagus

Question 25

What are the 3 reflex stages involved in swallowing?

Answer 25

1. oral 2. pharyngeal 3. oesophageal

Question 26

What is the oral (buccal) phase?

Answer 26

the voluntary phase where food is moved from mouth to pharynx

Question 27

Describe the oral stage?

Answer 27

food is compressed into a bolus against the hard palate by the tongue and the bolus is then moved backwards into the pharynx - once the bolus enters the oropharynx it stimulates touch receptors that initiate the swallowing reflex

Question 28

Describe the pharyngeal stage?

Answer 28

the upper oesophageal sphincter relaxes and it lasts less than a second - Elevation of the larynx and folding of the epiglottis direct the bolus over the closed glottis while the uvula and soft palate block passage back to the nasopharynx

Question 29

How do the swallowing reflexes begin?

Answer 29

as tactile receptors on the palatal arches and uvula are stimulated by the passage of the bolus

Question 30

Describe the swallowing reflex?

Answer 30

1. The information is relayed to the swallowing centre of the medulla oblongata via the trigerminal and glossopharyngeal nerves 2. Motor commands originating at this point cause the soft palate and uvula to close nasopharynx, and epiglottis to close opening to larynx 3. During this period, the respiratory centres are inhibited, and breathing stops

Question 31

Describe the oesophageal stage?

Answer 31

1. Food enters the oesophagus and initiates peristaltic wave that sweeps the bolus to the stomach in 5 to 6 seconds 2. Once within the oesophagus, the bolus is pushed toward the stomach by a peristaltic wave 3. The approach of the bolus triggers the opening of the lower oesophageal sphincter, and the bolus proceeds to the stomach

Question 32

Name the types of peristalsis in the oesophagus?

Answer 32

1. primary 2. secondary

Question 33

Describe primary peristalsis?

Answer 33

1. Initiated by swallowing and reflexely controlled by medullary swallowing centres 2. Coordinated by afferent and efferent fibres within the grossopharyngeal and vagus nerves

Question 34

Describe secondary peristalsis?

Answer 34

1. Occurs in the absence of pharyngeal phase 2. Sweeps the oesophagus clean of material left after previous swallow or refluxed from stomach 3. Driven by local reflexes triggered by the stimulation of sensory receptors in the oesophageal walls 4. May be caused by dry or poorly lubricated bolus 5. These receptors relay information by way of the submucosal and myenteric plexus

Question 35

When can food enter the stomach?

Answer 35

when the lower oesophageal sphincter relaxes