Human Tissues Dr S Nishan Silva MBBS Basic

Human Tissues Dr. S. Nishan Silva (MBBS)

Basic Terminology • Histology : • histos - tissue • logos - study of • So, study of tissue. • Might be better defined as the study of the structure of tissues. 2

Cell Adhesions/Junctions • Nearly all cells are connected to neighboring cells by cell junctions • Occluding junctions join cells together to form impermeable barrier • Adhering junctions provide mechanical attachment between cells. • Communicating junctions permit movement of ions or molecules between cells

Cell Junctions • Occluding – the most apical junction – Zonula occludens, tight junctions • Adhering – 2 types: – Zonula adherentes – Macula adherens = desmosomes • Communicating – Gap junctions

Histology = 2 dimensional image • A section is a slice of tissue • Orientation when sectioned affects what you see.

Section of Round Solid Object A B

Sections cut through a curved tube

Light Microscope = tool of the histologist • • • Oculars (eyepieces) Stage Objective Lens Condenser Light source Focus knobs

Specimen Preparation • Fixation, dehydration, embedding • Sectioning • Staining: most common is H&E – Hematoxylin: cationic dye (+ charge) that binds to negatively charged (acidic) structures in the cell. Example: nucleus = blue – Eosin: anionic dye (- charge) adheres to basic structures in the cell. Example: amine groups (NH 3+) on proteins make cytoplasm pink.

Tissue Types • • Muscle Epithelial Connective Nervous

Muscle Tissue 3 types of muscle tissue • Cardiac –heart • Skeletal – attached to bones • Smooth – internal organs and blood vessels

Cardiac Muscle

Skeletal Muscle

Smooth Muscle

Epithelial Tissue 3 types of epithelial tissue • Squamous • Cuboidal • Columnar Descriptive layers Simple – one layer Stratified – more than one layer