Anatomy and Physiology / Unit 2: Cells and Tissues
2.4 Epithelial and Connective Tissue
Notes
The four primary tissue types are epithelial, connective, muscle and nervous tissue.
- Epithelial tissue covers surfaces and lines cavities and forms glands. Features: cells packed closely, one free (apical) surface, rests on a basement membrane, avascular (no blood vessels), regenerates quickly.
- Classified by layers (simple = one layer, stratified = many) and shape (squamous flat, cuboidal, columnar). Simple squamous suits diffusion (air sacs, capillaries). Stratified squamous protects against abrasion (skin, mouth). Simple columnar absorbs and secretes (small intestine).
- Connective tissue supports and connects. It has few cells in an abundant extracellular matrix. Types: connective tissue proper (loose areolar, adipose, dense), cartilage, bone, and blood.
- Cartilage is avascular and slow to heal; bone is well supplied with blood.
Practice
Which tissue is best suited for the lining of the air sacs (alveoli), where gas diffusion must be quick?
A single layer of thin flat cells reduces the diffusion distance.
Which feature is typical of connective tissue but NOT of epithelial tissue?
Connective tissue is mostly matrix with scattered cells. Epithelium is tightly packed cells.
A person scrapes the surface of their forearm. Which epithelial type protects the skin from this wear?
Multiple layers of flat cells protect against abrasion.
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