Histology - Epithelia Tissue (Lab)

Histology

The study of tissues found in the body

Tissues

Groups of similar cells that perform a similar function

4 types of tissues in the body

• Connective

• Muscle

• Epithelial

• Nervous

Epithelial Tissue

• Lines body cavities

• Covers body surfaces

• Forms glands in the body

Characteristics of Epithelial Tissue

Multiple cells packed closely together with little extracellular material

Avascular

High rate of cellular division

Basal (bottom) cells rest on a basement membrane

Why is high rate of diffusion so important?

To regenerate abrased injury (lost cells restoring)

Avascular

(no blood vessels)

Receive their nutrients through diffusion from surrounding tissue

Basement membrane

What anchors the epithelia to the underlying (connective) tissue

Cell layers

• Simple

• Stratified

• Pseudostratified

Simple

Single layer of cells

Stratified

2 or more layers

Pseudostratified

A single layer of cells that appears to be more than one layer – all cells do not reach the free surface

Cell Shape

• Squamous

• Cuboidal

• Columnar

• Transitional

Squamous

Flattened irregular shaped cell

Cuboidal

Cube-shaped cells

Columnar

Elongated rectangular shaped cells

Transitional

Cells change shape between squamous and cuboidal depending on needs of tissue (urinary bladder)

Simple Squamous

Single layer of flattened cells

Location: Lines heart, blood, and lymphatic vessels, alveoli of the lungs

We want a thin layer to be able to pass through (helps with diffusion)

Not rough and want to expand

Simple Cuboidal

Single layer of cube-shaped cells

Line kidney tubules, ducts of many glands, surface of the ovary, capsule of the lens of eye

Ciliated Simple Columnar

Functions to move the cell using hair-like structures (cilia)

Location: Lines bronchioles of the respiratory tract, uterine tubes, and uterus

What function does cilia have?

Moving the cells through their surrounding fluid, for food uptake, and for sensing the environment

Non-ciliated Simple Columnar

Lines digestive tract, ducts, glands and gallbladder

Pseudostratified Columnar

• A single layer of cells, but appears to be multiple layers

  • • All cells contact the basement membrane, but not all reach the free surface

• Can be ciliated or non-ciliated

• Lines airways of the respiratory tract, lines glands, and ducts

Stratified Squamous

• Multiple layers of flattened cells → to protect lots of its cells

  • Deeper layers may be cuboidal or columnar

• Location: Makes up the epidermis of the skin, lines oral cavity, esophagus, and vagina

What purpose would having multiple layers serve?

Tissue is very thick (many layers) -> Safe penetration + protection

Stratified Cuboidal

• Multiple layers of cube-shaped cells (apical layers or cuboidal)

• A rare type of epithelium found in the ducts of adult sweat glands and the male urethra

• Location: exocrine glands (sweat glands)

Stratified Columnar

• Several layers of irregularly shaped cells; only the apical (top) layer is columnar

• Location: Lines part of the urethra and the excretory ducts of some glands

Transitional Epithelial Tissue

Cells vary from flat (squamous) to cuboidal

Allows for change and shape of the tissue and to tighten or stretch

Lines the urinary bladder, parts of the ureters and urethra

Why is it necessary for the cells in these locations to alter their shape?

The lining would expend to prepare for penetrations, therefore not ripping the skin when intercourse occurs