Histologia

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Cell Types
Roberto J. Alfabeto,  MD, FACS, FPCS,  FPSGS

 

 

Different cell types
• • • •

Epithelial tissues Connective tissues Muscle tissues Nervous tissues

 

 

Epithelial Tissue
Surface epithelium  Glandular epithelium


 

 

Surface Epithelium
 

covers or lines all body surfaces, cavities and tubes. form continuous sheet with cells bounded togetherwith cell junctions and are supported by a basement membrane. Basement membrane is never penetrated by blood vessels. cells are polarized into basal surface and apical surface.



 

 

Surface epithelium Functions
    

Selective diffusion Absorption Secretion Physical protection Containment

 

 

Classification of Surface  epithelium


Number of cell layer
Simple Stratified




Shape of the component cell
Squamous  Cuboidal  Columnar




Presence of surface specialization
 

Cilia  Keratin


 

Surface epithelia


Simple- surface epithelia consisting of a single layer of cells


Almost always found at interfaces involved in selective diffusion, absorption, and or secretion. Not for protection against mechanical abrasionRange of shape depending on their function
 
1 Simple squamous epithelium (a) Diagram (b) H [amp ] E ×800





 

Surface epithelia

Cuboidal eithelium

 

Columnar epithelium

 

Surface epithelia


Pseudostratified columnar ciliated epithelium- shows an erroneous impression that there is more than one layer of cells. Differs from a stratified epithelium by (1)exhibit polarity with nuclei mainly confined to the basal 2/3 of the epithelium (2) cilia are never present on true stratified epithelium. Almost exclusively confined to the respiratory tracts

 

 

Stratified squamous epithelium

 

 

Squamous cell carcinoma

 

 

Surface specialization


Cilia- are motile structures that project from the apical surfaces of certainepithelial cells, notably in the respiratory and female reproductive tracts

 

 

 

 

Glandular epithelium


Classification of glands:


Exocrine glands- releases their contents onto an epithelial surface either directly or via a duct. Endocrine glands- have no duct system but releases their secretion via blood stream thus is able to act on distal tissues.



 

 

Majorclassification of exocrine glands according to its major characteristics


Morphology of the gland


Secretory component
• Tubular • Acinar • Coiled • Branched



Duct
• Compound gland- branched • Simple gland- unbranched

 

 

Simple tubular glands

 

 

Compound branched tubular

 

 

Major classification of exocrine glands according to its majorcharacteristics


Means of secretion


Merocrine (eccrine) secretion- involves exocytosis and most common Apocrine secretion- dischrage free, unbroken, membranebound vesicles containing secretory product. Applies to lipid secretion like the breast and some sweat glands Holocrine secretion- discharges whole secretory cell with later disintegration of the cells with release of products. E.g.Sebaceous glands
 





 

Endocrine glands


releases secretions directly to the bloodstream rather than via a duct source of chemical messengers (hormones) that act at a distant site from the source E.g. insulin from pancreas to muscles and adipose tissues many are solid organs but some consists of widely distributed single cells
   







Endocrine glands
   

mostendocrine glands consists of more than one hormone product several endocrine glands consists of more than one type of secretory cells pancreas is both an endocrine and an exocrine glands in general secretion of hormones by endocrine glands is controlled by metabolic factors (e.g. blood glucose levels), the secretion of other hormones (e.g. TSH controls secretion of thyroxine) and the nervous...
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