Anatomy books

Thursday, August 10, 2017

Histological features of hard palate

Histology of hard palate :
 The hard palate is a thin horizontal bony plate of the skull, located in the roof of the mouth.
Formations:  It is formed by the palatine process of the maxilla and horizontal plate of palatine bone.


It has two surfaces:

1. nasal surface and 
2. oral surface 

functions : it is important for feeding and speech
 

Histology of nasal surface of hard palate:


  1. It is lined by pseudo-stratified ciliated columnar epithelium.
  2. This epithelium contains intraepithelial gland.
  3. Sub-epithelial connective tissue contains glands, blood vessels and lymph vessels.
  4.  The epithelium and the sub-epithelial connective tissue are collectively known as the mucoperiosteum, which is firmly attached to the bony shelf of the palate.

Histology of oral surface of hard palate 

Parts of oral surface of hard palate: 

1. Anteriorly fatty part 

2. Posteriorly glandular part   

 

The oral surface of hard palate  is covered by masticatory mucosa,  it is a specialized mucosa of oral cavity 

 

Masticatory mucosa :
It is found in the gingival (gums) and the hard palate. 
From superficial to deep it has three layers
1.      Lining epithelium: Keratinized stratified squamous epithelium and in some place parakeratinized
Keratinized epithelium of hard palate likes skin but stratum lucidum layer is absent.
Criteria of parakeratinized stratified squamous epithelium :
·         Superficial cells have nuclei like keratinized stratified squamous epithelium but nuclei are pyknotic (highly condensed) remain until the cell is exfoliated and
·         cytoplasm is not intensely stain by eosin
  Rete ridges are present in epithelium they are deep invagination of epithelium with
   subepithelial connective tissue  

2.      Lamina propria is formed by connective tissue contain dense collagen fibres, blood vessels and nerves. Hard palate's lamina propria  is also containing large deposits of adipose tissue at its anterior part and mucous gland at its posterior part.
3.  Reticular layer of dense connective tissue : Deep to lamina propria contain reticular fibre rich dense connective tissue which firmly bind the palatine mucosa to the periosteum. 

Glands in general : easy and brief description

Glands:
Definition: glands are specialized epithelium which are formed by proliferation of epithelium into the underlying tissues
Parts of a gland:
Parenchyma: glandular portion which responsible for secretion
Stroma: it is the supporting portion of a gland which is formed by connective tissue
Classification of glandular epithelium
 According to presence or absence of duct: glands are two types: exocrine gland (gland with duct) and endocrine gland (gland without duct)
According to the mode of secretion :gland are three types
         Merocrine: secretory granules leave the cell by exocytosis.  exm: pancreatic acinar cells secretion
         Apocrine: secretion discharge with parts of apical cytoplasm. exm: lactating mammary glands   
         Holocrine: secretory product is shed with the whole cell. exm: sebaceous gland                       
According the nature of secretion : glands are three types
         Mucous : viscous secretin. exm: goblet cells
         Serous: thin secretion. exm: parotid gland contain only serous acini
         Seromucous: exm: submandibular glands
Distribution of different types of exocrine glands:
 According to the number of cells. Exocrine glands are two types
1) Uni-cellular: goblet cells
2) Multi-cellular: they are two types’ simple (single duct) and compound (more than one duct)
Simple (single duct)
Compound (more than one duct)
Simple tubular: G.Of L.intestine
Simple acinar: G.Of penile part of urethra
Simple coiled tubular : Sweat gland
Simple bran. Acinar: Sebaceous gland
Simple bran. Tubular: G of pylorus
Com. Bra. Tubular: Brunner’s gland
Com. Acinaer g: pancreas
Com. Tubuloacinar: Submandibular gland

Distribution of different types of endocrine glands:
Cord or clump type: ex: Adrenal glands
Follicular type: ex: Thyroid