TONGUE. TONSIL. MAJOR SALIVARY GLANDS.

TONGUE.

1. On cross section (starting from dorsal surface to ventral surface) tongue has 4 layers: a) tunica mucosa – b) lingual muscular body – c) tunica submucosa – d) tunica mucosa.
2. Tunica mucosa is composed of 2 sublayers:a)stratified squamous epithelium, b)lamina propria (loose irregular connect. tis). Tunica mucosa of dorsal surface has projections, named lingual papilla. Epithelium, covering filiform papilla – is stratified squamous keratinized and has not taste buds. Epithelium, covering rest 3 papilla types – is stratified squamous nonkeratinized and contains taste buds. Tunica mucosa of ventral surface has not papillae.
3. Taste bud –is intraepithelial sensory organ, that percept the taste. It is composed of 60 epithelial cells, that are classified on 3 types: a) sensory light cells (tall columnar), b)sensory dark cells(tall columnar). Both types have apical microvilli and are innervated by afferent nerve fibres, c) basal cells.
4. Lingual muscular body is composed of striated skeletal muscle tissue. It presented by 3-D mashwork of skeletal muscle fibres.

It is peripheral hemopoietic organ. It function –is antigenDEPENDENT proliferation and differentiation of B- andT-lymphocytes. Histologically tonsil is- aggregation of lymphoid tissue in lamina propria of tunica mucosa.
On the cross section palatine tonsil has 3 layers (from externally to deeper): a) stratified squamous nonkeratinized epithelium, that infiltrated by immune cells,
b) lamina propria (loose irregular connect. tisue), that infiltrated by lymphoid tissue. Lymphoid tissue presented by lymphoid nodules. Nodule-is B-zone. Function of it-is antigenDEPENDENT proliferation and differentiation of B-lymphocytes, resulting in development of PLASMA cells.
c) capsule from dense connective tissue. All glands have same plan of strucrure: capsule from dense connective tissue, septae extend from capsule and divide organ on LOBULES. Lobule is composed of epithelial cells (parenchyma). Epithelium form 3 portions of lobule a) secretory portion, b) intercalated duct, c) striated duct.
PAROTID gland contains ONLY 1 type of secretory portions - it is serous secretory portions. Serous secretory portion is composed of 2 types of epithelial cells a) inner layer presented by serous sells, b) myoepithelial cells (it form outer layer). Serous sells are pyramid-shaped and contain secretory granules in apical surface. Function: serous sells secrete enzyme amylase. Myoepithelial cells are star-shaped. Funct.: it contract and compress secretory portion. Saliva from parotid gland is pure protein and WATERY, but not viscous. (“Serous” means “protein”).
SUBMANDIBULAR gland contains 2 types of secretory portions: a) 80% serous secretory portions, b) 20% mixed portions. Mixed secretory portion contains 3 types of cells: a) inner layer –it presented by mucous cells, b) intermediate layer- serous sells, in the form of “serous demilunes”, c) outer layer- myoepithelial cells. Mucous cells are pyramid-shaped and contain secretory granules in apical surface. Function: mucous sells secrete mucinogen. It gives viscosity for saliva. Saliva from submandibular gland is moderately viscous. Submandibular gland is mixed gland, because secreets amylase+mucinogen-containing saliva.
SUBLINGUAL gland contains 3 types of secretory portions: a) 80% mixed secretory portions, rest are: b) mucous portions, c) serous portions. Mucous secretory portion contains 2 types of cells: a) inner layer – it are mucous cells, b) outer layer is composed of myoepithelial cells. Sublingual gland is also mixed gland. Saliva from it is with MOST viscous properties.
Wall of intercalated duct is composed of simple squamous,or cuboidal, epithelium.
Wall of striated duct is composed of simple columnar epithelium. One cell has deep invaginations of basal plasma membrane –basal folds. Numerous mitochondria locate between folds and give view of “striation”. Funct.: Striated duct cells a) secrete K+ and bicarbonate ions into saliva and reabsorb Na+ ions from saliva, b) secrete growth factors into blood and saliva.