Cells are the smallest structural and functional unit of life. 

Tissue is a group of cells of similar function and origin that form functional units

An organ group of tissue adapted to perform specific functions

An organ system is group of organs work together to perform more functions

Organism

Different types of tissues

Tissue preparation for light microscope

Tissue sampling

Fixation

Dehydration and clearing

Clearing

Embedding

Sectioning

Mounting and staining the sections

Covering

Light Microscope

Parts ; 

  1. Eyepiece lens
  2. Tube
  3. Arm
  4. Base
  5. Illuminator
  6. Stage
  7. Revolving nosepiece
  8. Objective lenses
  9. Condenser lens
  10. Coarse & fine focus
  11. Diaphragm

Histochemistry & Cytochemistry

Methods for localizing cellular structures in tissue sections using unique enzymatic activity present in those structures. 

Perl prussian blue reaction – iron deposits in hemochromatosis 

Immunohistochemistry 

Histological + immunological + biochemical techniques for identification of specific tissue components (antigen/antibody).

Frozen sections are commonly used. In some cases paraffin wax.

Assays – cells on slides – or tissues (frozen / paraffin)

Frozen

Paraffin Embedded

Antigen Detection

  1. Raising Antibodies
    1. Polyclonal antibodies ; multiple epitopes and several antibody types
    2. Monoclonal antibodies ; single epitope and produced by a single clone
  2. Labeling Antibodies
    1. Fluorochromes 
    2. Cronochromes enzymes
    3. Electron Scattering Compounds

Method

  1. Direct ; Tissue antigen + Labeled antibody
  2. Indirect ; Tissue antigen + Primary antibody + Secondary antibody (LBL)
  3. PAP ; Peroxidase Anti-Peroxidase method 

Applications

General Immunochemistry Protocol 

  1. Tissue Preparation
    1. Fixation
    2. Sectioning
    3. Mount Preparation
  2. Pre-treatment
    1. Antigen Retrieval 
    2. Inhibition of indigenous tissue components
    3. Blocking of nonspecific sites
  3. Staining
    1. Specimen, primary antibody, degree of sensitivity, processing time

Types of tissues

When we look into the microscopic version of the human anatomy we find many colorful stained pictures that look similar. But, they are not. There are 4 main tissue types that make up every other tissue of the body. 

  1. Muscle 
  2. Nervous
  3. Epithelial 
  4. Connective

Muscle Tissue

Skeletal Muscle ; Long. parallel fibers or striations. Multiple nuclei per fiber. Dark dots.  

Cardiac Muscle ; Exclusive to the heart. Rectangular in shape. Nucleus per cell. We can see intercalated disks. They are passages from cell to cell. As they have to send signals quickly. Fast contraction.

Smooth Muscle ; Blood vessels, Uterus, and Bladder. Contract simultaneously. Smallest muscle cells and jumbled up as sheets. 

Nervous Tissue

Brain, Spinal cord and the peripheral nerves. We have; 

Epithelial Tissue

Skin and Borders between different organs. They are named based on the

Connective Tissue

Everything else is connective tissue. We have tendons, ligaments, fat, blood, cartilage, and bone.

3 types

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