Chapter 4: Overview of Tissue Types and Histology

Tissue

Group of cells found together within a body that share an embryonic origin

Histology

Microscopic study of tissue appearance, organization, and function

Light microscopy

Can view many different tissues and dyes

Transmission electron microscopy (TEM)

Views high magnification in grayscale

Scanning electron microscopy (SEM)

Allows 3D views of tissue

Epithelial Tissue

Sheets of cells exposed to the environments

Polarity

Characteristic of epithelial tissue indicating distinct structural differences between the apical and basal surfaces

Tight junctions

Specialized connections between epithelial cells that prevent leakage

Desmosomes

Anchoring junctions that provide mechanical stability to epithelial tissues

Highly regenerative

Ability of epithelial tissue to quickly replace lost or damaged cells

Avascular and innervated

Epithelial tissue lacks blood vessels but has nerve endings

Simple squamous epithelium

Found in endothelium of vessels and mesothelium of serous membranes

Simple cuboidal epithelium

Specialized for secretion and absorption

Simple columnar epithelium

Specialized for absorption and secretion

Stratified squamous epithelium

Most common type of stratified epithelium

Pseudostratified epithelium

Single layer of cells with varying heights, nuclei at different levels

Transitional epithelium

Stratified tissue that can change shape from cuboidal to squamous to enable stretch

Gland

One or more cells that produce and secrete a specific product

Endocrine glands

Ductless glands that secrete hormones directly into tissues

Exocrine glands

Glands with ducts that lead to the epithelial surface

Merocrine secretion

Vesicles emptied into extracellular space

Apocrine secretion

Release of a portion of the cell

Holocrine secretion

Cell ruptures and is destroyed

Connective Tissues

Loosely dispersed cells in a matrix with extensive extracellular material

Ground substance

Material filling space between cells in connective tissue

Fluid Connective Tissue

Includes blood and lymph

Neuron

Cell that propagates information via electrochemical signals (action potential)

Synapse

Gap between neurons

Neuroglia

Support cells for neurons

Cutaneous membrane

Skin, keratinized epidermis attached to connective tissue (dermis)

Mucous membranes

Line all body cavities that open to outside, bathed in secretions

Serous membranes

Line closed ventral body cavities, consist of visceral and parietal layers

Regeneration

Replacement of destroyed tissue with correct tissue type

Fibrosis

Replacement of destroyed tissue with scar tissue

How do we study tissues?

1. Samples are fixed, preserved in formalin or frozen