L63a: salivary gland functions and control

MCQ: what two digestive enzymes are present in the saliva of omnivores?

amylase and lingual lipase

what are the three physiological phases of digestion?

1. pregastric

2. gastric

3. intestinal

digestion

breaking down macro-molecules to micro-molecules for nutrient absorption

pregastric

before the stomach

how much saliva (%) do the major glands make?

90%

what are the major glands of the salivary glands?

1. parotid gland

2. sublingual gland

3. mandibular gland

what are the components of the compound acinar glands?

1. acini

2. duct system

what cells make up the acini?

1. mucous cells

2. serous cells

3. myoepithelial cells

what nerves provide parasympathetic innervation to the salivary glands?

1. facial nerve (CN 7)

2. glossopharyngeal nerve (CN 9)

what provides sympathetic innervation to the salivary glands?

vago-sympathetic trunk (thorocolumbar region part of spinal cord), follows closely with blood vessels

function of acinar serous cells

actively pumps chloride ions into the acinar space = water follow electrical chemical gradient = water follows osmolality gradient

what is primary saliva rich in?

NaCl

what do the duct cells do in regards to saliva?

actively reabsorbs sodium and chloride (pumped out) in exchange for bicarbonate and potassium (pumped in)

what are duct cells impermeable to and what does this mean?

impermeable to water meaning that water will stay in saliva

describe the saliva that is reaching the mouth.

slightly hypotonic, K+ rich and slightly alkaline (HCO3-)

function of acinar mucus cells

produce and exocytose a mucin mixture (glycoproteins) into the acinar space

what is the digestive function of having water in saliva?

1. moisten and soften food for swallowing

2. solvent for all other components of mouth including taste molecules

what is the digestive function of having mucous in saliva?

1. lubricates food for swallowing

2. binding into a bolus

3. provides protection to mucosa lining of mouth and esophagus

what is the digestive function of having bicarbonate and phosphates in saliva?

1. buffer acidic foods

2. maintain oral pH

why is bicarbonate essential in ruminants?

rumen acidic due to fermentation products being volatile fatty acids, HCO3- helps buffer this

what happens when hypotonic saliva mixes with hypertonic food?

becomes normotonic 

what electrolyte is needed in the stomach?

potassium needed to make HCl

what digestive enzyme begins carbohydrate digestion in omnivores?

alpha amylase

what digestive enzyme begins milk fat digestion in neonates?

lingual lipase

what components in the saliva are antibacterial and antifungal enzymes?

1. lysozymes

2. histatins

3. peroxidases

4. defensins

what is the function of lactoferrin in saliva?

binds iron to prevent bacteria from multiplying

what is the function of growth factors in saliva?

tissue healing

what immunoglobulins are important for mucosal immunity in salvia?

1. IgA

2. IgM

3. IgG

how does saliva protect teeth?

through a protein called statherin, it keeps calcium and phosphorous in solution to prevent precipitation and tartar build up

what animals is thermoregulation important through panting?

dogs and birds 

what animals is thermoregulation important through licking?

rodents and ruminants

what are the benefits of an animal licking its wounds?

1. growth factors (tissue healing)

2. antibacterial components and antibodies

3. physical cleaning of wound from dirt and debris

how does saliva become a hypotonic solution?

removal of sodium and chloride ions while retaining potassium, resulting in a lower concentration of solutes

what are the risks of an animal licking its wounds?

1. introduce infection

2. further tissue damage (animal does not stop licking once it starts)

should we let an animal lick its wounds?

no

constant basal secretion

no stimulation, this is to keep oral mucosa moist

what is the stimulus for the unconditioned parasympathetic reflex in control of salivation?

stimulation of oral taste and touch receptors transmit signals to the medulla

what cranial nerves are stimulated in the unconditioned parasympathetic reflex in control of salivation?

CN 7 and CN 9

explain how the parasympathetic reflex works to stimulate saliva flow

1. stimulation of oral taste and oral receptors transmit signal to medulla

2. salivary centers stimulate CN 7 and 9 to increase saliva rate, blood flow, and cell contraction

3. saliva flow increases

what are stimuli for conditioned reflex of salivation?

visuals, anticipation, smells, and certain sounds

what reflex will increase saliva flow during food intake?

unconditioned parasympathetic reflex

what reflex will increase salivation without food intake?

conditioned reflex

xerostomia

dry mouth

what are the causes of dry mouth in animals?

1. sympathetic dominance (fear, anxiety)

2. anti-cholinergic drugs

3. dehydration

4. hypothyroidism

what does norepinephrine directly act on and what is the result?

• acinar mucous cells

• increases mucin secretion and saliva becomes viscous

what does norepinephrine lead to in salivation and what is the effect?

• vasoconstriction

• less fluid is available = decreased volume of saliva

how does hypothyroidism lead to an inhibition of saliva?

“sad face” can occur in oral mucosa leading to compression of salivary glands and decreased saliva flow

what structures are involved in mastication?

1. jaw

2. teeth

3. tongue

4. muscles

what cranial nerve transmits sensory stimuli to mastication centers in the brain stem?

trigeminal nerve (CN 5)

what structures are involved in the contraction of mastication from stimulation of CN 5?

1. masseter

2. temporalis

3. pterygoid

what happens as a result of trigeminal nerve damage?

paralysis of muscles of mastication (drop jaw)

what cranial nerve is stimulated during “warming up” of the stomach?

vagal nerve (CN 10)

“warming up” of stomach during cephalic phase

1. to start secretion of gastric fluids

2. to increase stomach motility

what is CNX not involved in?

salivation or mastication

what is the main nerve of the GI?

vagus nerve

what nerve stimulates the stomach?

vagus nerve

how does saliva become a hypotonic solution?

more electrolytes are reabsorbed from primary saliva than secreted, but water cannot fallow this osmotic gradient since ducts are impermeable to water