Veterinary Histology UFF
Department of Morphology - Biomedic Institute
LaBEc - Laboratory of Cellular and Extracellular Biomorphology 		 
Veterinary Histology Atlas
    Versão em Português
Introduction
Epithelial Tissue

General Characteristics

• Polyhedral Shape
• Scarce intercellular substance
• Produce the basal lamina
• High mitotic rate
• Don’t have a direct vascularisation
• Polarization: Apical and Basal

Membrane Specializations - Apical Pole

Microvilli:
• Digit-like projections whose shape is maintained by the cytoskeleton
• Observed only in Electron Microscopy
• In Optical Microscopy they are called Striated Borders
• Function: increase of the surface area, increase of exchanges and better absorption of substances

Cilia:
• Formed by 9 peripheral pairs of microtubules, surrounding a central pair
• They need mitochondria to supply energy for the ciliary beating
• Cilia beat in a coordinated pattern
• Example: Beating of the cilia of the respiratory epithelium dislocates the mucus towards the upper respiratory ducts

Estereocilia:
Long static microvilli that exist in the epididymis (male)

Basal Lamina
• Responsible for the adherence between connective and epithelial sheets
• Formed by Glycoproteins
• Act as a molecular filter
• Guide for cellular replication and migration

Lining Epithelial Tissue

Classification:

According to number of Stratums:

 

 
• Simple: All cells are in contact with the basal lamina • Stratified: At least one cell does not touch the basal lamina

 

 

 		  
• Pseudostratified: All cells are in contact with the basal lamina, but they have variably placed nuclei.  

According to the Shape of the Cell:

The shape is always given by the more SUPERFICIAL layers.

• Squamous • Cuboidal
• Columnar or Prismatic
• Globulous
According to membrane specializations and Cells or Accessories :
• Keratin • Goblet Cells • Striated border • Cilia

Glandular Epithelial Tissue

Group of Epithelial Cells that associate themselves and differentiate cellularly, being capable of producing and secreting substances.
Exocrine:
• Releases its secretion through ducts to the outside
• Composition:
- Glandular Portion (adenomere)
- Conducting Portion (duct)

Classification:

According to Excretion Mechanism :
• Holocrine
- Cell disintegrates along with its excreted content
- Stem-cells originate new secreting cells
- Example: Sebaceous Gland
• Merocrine
- There is no alteration in the cell’s morphology
- Cytoplasmic granules fuse themselves with the cell membrane and release their contents
- Example: Sweat Gland
• Apocrine
- Loss of the cell’s apical portion when excretion is released
- Example: Mammary Gland

According to the Morphology of the Secreting Portion:
• Acinar
• Tubular
• Alveolar

According to the Conducting Portion:
• Simple: One duct
• Compound or Branched: More than one duct
According to the Quality of the Secretion:
 
• Mucous: Glycoproteic, viscous, flat nucleus
• Serous: Proteic, liquid, round nucleus
• Mixed: Demilunes serous on mucous acinus
  
Endocrine:
• Releases its secretion directly into the connective tissue
• Morphology:
- Cordonal ( cordon of cells, no deposit)
- Follicular (in the shape of a hollow “ball”, possess a colloidal deposit)
    

Specialized:
• Gametogenesis: epithelial cells differentiate into sperms
Credits
Tissues
Epithelial
Connective
Cartilaginous
Osseous
Nervous
Muscle
Systems
Circulatory
Blood
Imune
Digestive
Accessory Gls.
Respiratory
Integumentary
Urinary
Endocrine
Male Reprod.
Female Reprod.
Birds Histology
Quiz
Videos
Bibliography