Salivary Glnds
3 large bilateral glands that produce majority of saliva
- Parotid gland - Submandibular gland - Sublingual gland
Gland types
- Unicellular glands - Simple tubular glands (unbranched) - Secretory sheets - Simple tubuloalveolar glands
Mucous Secretion
- Viscous - Clear (H & E) - Rod-like - Mucous coat - MW > 10^6 D
Serous Secretion
- Watery - Pink (H & E) - Globular protein - Enz. etc. - MW < 10^5 D
Schematic diagram of ducts
- Acinus at one end, serous or mucous making saliva - Open to intercalated duct of low cuboidal epithelium - Intralobular or striated duct, columnar cells; striated because they have infoldings with mitochondria to allow them to resorb sodium from lumen making saliva slightly hypotonic - Opens to interlobular ducts between lobules
Compound tubuloalveolar gland
- Branching ducts - Example is major salivary glands - Contain individual secretory units at the end (acinar or alveolar)
Major salivary glands microscopic structure
- Connective tissue capsule, septa-lobulated - Tubuloalveolar (or compound tubuloacinar) gland - serous or mucous - Myoepithelial cell - secretory alveoli
Myoepithelium, acini to intercalated duct
- Contractile cells - Filled with actin and myosin - Have caveola - Myeopithelial cells located between secretory cells - Embrace both mucous and serous acini
Control of secretion
- Controlled by reflex mechanisms due to mechanical and chemical stimuli - 1 to 1.5 liters secreted per day
Functions of Saliva
- Controls oral flora to prevent caries - Connective tissue contains many lymphocytes and plasma cells - Plasma cells release IgA, which forms a complex with secretory component synthesized by epithelial cells of serous acini and intralobular ducts - IgA: secretory complex released into saliva resists enzymatic digestion - IgA: secretory constitutes immunologic defense mechanism against pathogens in oral cavity
Submandibular gland
- Duct enters mouth lateral to frenulum of tongue at floor of the mouth - Mix of serous and mucous secretory cells - Mucous cells surrounded by serous cells (arrangement called demilunes) - Numerous intralobular ducts
Minor Salivary glands
- In mucosa and submucosa throughout oral cavity - Secrete 10% of total volume of saliva - Ducts from serous Von Ebner's glands empty around circumvallate papillae - Circumvallate papillae house taste buds on the tongue
Parotid gland
- Largest of all 3 glands - Facial nerve passes through this gland - Duct enters mouth behind second upper molar - Composed of serous cells entirely - Numerous intralobular ducts between jaw and ear - Fat deposits present
Sublingual gland
- Located under tongue, anterior to submandibular gland - Ducts empty into submandibular duct - Mixed acini serous and mucous cell types but mostly mucous - Few intralobular ducts - Mixed acini with light mucous cells and dark serous demilunes - Located under tongue
General features of glands
- Paired structures - Surrounded by loose connective tissue that encapsulates them and cuts through to make lobules - Secretory collection of cells called acini - Acini are surrounded by contractile myoepithelial cells that can expel contents
Functions of glands
Form saliva composed of salts, mucous, water, organic compounds, enzymes (amylase, maltase) - Saliva wets and lubricates food for swallowing and starts digestion
What are the minor salivary glands?
Mucous glands
Sublingual gland structure
Starting with acinous, then intercalated duct, opening to larger striated intralobular duct
Basic secretory unit of the salivary glands
acinous which means grape.
