Learning Objectives
By the end of lecture student should be able to
- • Enlist salivary gland
- Mention type of secretion of each salivary gland
- Explain the secretion of saliva
- Summarize the functions of saliva
- Summarize the regulation of salivation
SALIVA
- Saliva is a clear, tasteless, odorless, slightly acidic (pH 6-7) viscid fluid containing normal oral bacteria, desquamated epithelial cells and transient residues of food or drink.
- Saliva is secreted by salivary glands.
- Average daily flow- 800ml to 1500ml
- Unstimulated 0.3-0.4ml/min
- Stimulated 0.2-7ml/min
- Hypotonic to plasma
Structure of Salivary Gland
- alivary glands are made up of acini– a small group of cells surrounded by a central globular cavity.
- Each acini drains into intercalated duct.
- Intercalated ducts join to form striated
- Striated ducts join to form excretory
- Which unite to form the main duct of the gland.
Salivary Glands
SALIVARYSECRETIONISTWOSTAGEOPERATION:
- The first stage involves the acini, while second stage
involves the salivary ducts.
- Acini secrete a primary secretion that contains ptyalin and/or mucin.
- As primary secretion flows through the ducts, two major active
transport processes take place.
- First, sodium ions are actively reabsorbed from all the salivary ducts and potassium ions are actively secreted in exchange for the sodium.
- Sodium ion concentration reduced and potassium ions increases, Creating electrical negativity of about −70mv.
- This negativity causes chloride ions to be reabsorbed passively.
Second, bicarbonate ions are secreted by the ductal epithelium into lumen of the duct in exchange for chloride ions.
Concentration
- Under resting conditions saliva is rich in Potassium ions & Bicarbonate ions and has low concentration of Sodium and chloride ions.
- During maximal salivation salivary ionic concentrations change because the rate of formation Of primary secretion by the acini can increases up to 20-fold,causes rapid flow in ducts—–less time for ionic changes to take place.
Regulation
- Just nervous regulation
- No hormonal or chemical mechanism is involved
- Blood supply –a secondary factor-increase supply means increase secretion.
Click here for Download slideshow