PHYSIOLOGY OF salivary gland

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Introduction Not limited in the Rx of primary tumours ,duct obstruction & infection Disturbance of salivary gland function or abnormal salivary flow Dry mouth & Drooling of saliva Biotechnology of diagnostic test Collection of saliva Antibodies , Drug & hormones

Salivary secretion:

Salivary secretion Autonomic nervous system Glandular functions Drugs Dehydration Disease Destruction of Salivary gland parenchyma

Autonomic control:

Autonomic control Sympathetic & parasympathetic activity Parasympathetic : Exocytosis Vasodilation with in the gland Contraction of myoepithelial cells Sympathetic: Modulate the composition Exocytosis

Mechanism of salivary secretion:

Mechanism of salivary secretion Baum Neurotransmitter stimulation 1 ) Afferent stimulatory pathways 2 ) Afferent neural pathways 3 ) Efferent pathway 4) Central control of salivation

Afferent stimulatory pathway:

Afferent stimulatory pathway Steady or resting state : Minimal volume Psychic stimuli Psychosalivary reflex Smell Taste

Afferent stimulatory pathway:

Afferent stimulatory pathway Tactile stimulation Sensory endings in the oral & oropharyngeal mucosa Pressure sensor in the peridontal membrane Interorgan stimuli : Oesophagosalivary reflex Stomach,liver,Gallbladdera&appendix Vagus N of afferent pathways

Afferent neural pathways:

Afferent neural pathways 1 st ,5 th ,7 th & 9 th Connect through a series of synaptic links with the salivary nuclei Responsible for the effector side of the cycle

Central control of salivation:

Central control of salivation Parasymapthetic salivary nuclei Pons close to the nucleus of FN Medulla near the nucleus of the IX CN Superior & inferior salivary nuclei Superior : Submandibular & sublingual Inferior : Parotid Stimulation of hypothalamus : Hypersialia

Central control of salivation:

Central control of salivation Cell bodies of the sympathetic system Lateral columns of the spinal cord 2 nd thoracic N Fibres passing Hypothalamus & medulla

Efferent pathway:

Efferent pathway Acetylcholine Released in the ganglia & nerve endings in the glands Sympathetic nerves Nerve fibres in the cervical sympathetic pathway synapse in the superior cervical ganglion Post ganglionic fibres travel in company with the nearest blood vessels to reach the salivary glands Superior cervical ganglion : Acetylcholine Glandular nerve endings : Noradrenaline

Efferent pathway:

Efferent pathway Nerve stimulation 1) Secretory activity 2) Rate of blood flow 3) Contraction of myoepithelial cells Parasympathetic fibres : Vasodilatory Bradykinin : Once secretion started


FORMATION OF SALIVA Saliva : End product of a process of secretion in the acinus , which is then modifeid by the activity of the intercalated and striated ducts Hydrostatic pressure : Capillaries surrounding the acini water,ions,glucose,urea,amino acids & glucose Proteins of LMW in to the interstices

Formation of saliva:

Formation of saliva Acinar epithelium is freely permeable to water & lipid soluble substance. Amino acid & glucose : active diffusion Sodium & chloride with in the acini is similar to that of interstitial fluid Stimulation of secretomotor : Acetylcholine & nor adrenaline Receptors located in the surface membrane of acini Influence the degree of contractility of the local blood vessels

Formation of saliva:

Formation of saliva Neutralization of neurochemical mediators is brought about by specific enzymes such as acetylcholinesterase & monomine oxidases Migration of potassium ions with interstitial fluid through the acini to their respective lumina,increase in the level of intracellular potassium

Formation of saliva:

Formation of saliva Proteins are synthesized by ribosomes Before being assimilated in to the endoplasmic reticulum From which granules or vacuoles are formed. High level of intracellular Ca for mobilization & extrusion in to the acinar lumen. This is brought about by a rise in the cell Ca In response to the increased basement membrane permeability induced by acetylcholine.

Formation of saliva:

Formation of saliva Ca ions attach themselves to the secretory granules and help them to fuse with apical or luminal membrane before their extrusion into the acinar lumen. Intercalated ducts modify the acinar fluid by adding further potassium ions Striated ducts converts acinar fluid from a slightly hypertonic to a low NaCl hypotonic solution

Formation of saliva:

Formation of saliva Na ions are actively transported back from the lumen in to the cells,accompanied in the process by a passive diffusion of Cl ions Potassium ions & bicarbonate permeate in the reverse direction. Water is not reabsorbed & helps to preserve the hypotonicity of the intraluminal fluid.

Formation of saliva:

Formation of saliva Stimulation – influences the activity of the striated ducts Sympathetic stimulation produces a small volume of saliva rich in potassium & poor in sodium. Finally,as a result of the passage of water & potassium back in to the extracellular compartment Concentration of ions in the saliva in the excretory ducts once again begins to approach that of plasma..

Composition of saliva:

Composition of saliva Na K Cl Ca Phosphate Bicarbonate Thiocynate Iodine Bromide Fluoride Copper Magnesium Mucoproteins Serum proteins Enzymes Amylase Lysozyme Glycoproteins Fructose Neuraminic acid Mannose Galactose Glucose Urea INORGANIC Organic

Hormonal influences:

Hormonal influences Aldosterone Reabsorption of sodium in the striated duct in conjunction with the movement of potassium in the reverse direction Anti diuretic hormone Water reabsorption Salivation pregnancy,testosterone,thyroxine Salivation : Menopause

Other influences:

Other influences Starvation – massive enlargement Hypoproteinaemia High protein & low carbohydrate Increase buffering power but deficient in amylase Irradiation

Functions of saliva:

Functions of saliva Lubricant : Glycoprotein & mucoprotein Moisturazing Bacteriostatic function: Lysozyme ,& globulin Globulin which reacts with thiocynate Buffering effect Digestive function –Amylase Water balance –Infants Solvent- Spreading agent Excretory organ - Incidently

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