Histologia

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

 

 

Different cell types
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Epithelial tissues Connective tissues Muscle tissues Nervous tissues

 

 

Epithelial Tissue
Surface epithelium  Glandular epithelium
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Surface Epithelium
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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.

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Surface epithelium Functions
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Selective diffusion Absorption Secretion Physical protection Containment

 

 

Classification of Surface  epithelium
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Number of cell layer
Simple Stratified
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Shape of the component cell
Squamous  Cuboidal  Columnar
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Presence of surface specialization
 

Cilia  Keratin
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Surface epithelia
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Simple- surface epithelia consisting of a single layer of cells
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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

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Surface epithelia

Cuboidal eithelium

 

Columnar epithelium

 

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

 

 

 

 

Glandular epithelium
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Classification of glands:
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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.

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Majorclassification of exocrine glands according to its major characteristics
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Morphology of the gland
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Secretory component
• Tubular • Acinar • Coiled • Branched

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Duct
• Compound gland- branched • Simple gland- unbranched

 

 

Simple tubular glands

 

 

Compound branched tubular

 

 

Major classification of exocrine glands according to its majorcharacteristics
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Means of secretion
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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
 

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Endocrine glands
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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
   

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Endocrine glands
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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...