Body Tissues Histology Tissues Histology n n Groups

Body Tissues - Histology Tissues (Histology) n n Groups of cells with similar structure and function Four primary types 1. Epithelium 2. Connective tissue 3. Muscle 4. Nervous tissue

1. Epithelial Tissues Found in different areas n n n Body coverings Body linings Glandular tissue Functions n n Protection Absorption Filtration Secretion

Epithelium Characteristics Cells fit closely together Tissue layer always has one free surface (apical) The lower surface is bound by a basement membrane (secreted by the cells) Avascular (have no or very little blood supply) Regenerate easily if well nourished (ex. skin)

Classification of Epithelium Number of cell layers n n Simple – one layer Stratified – more than one layer Figure 3. 17 a

Classification of Epithelium Shape of cells n n n Squamous – flattened Cuboidal – cubeshaped Columnar – columnlike Figure 3. 17 b

Simple Epithelium Simple squamous n n Single layer of flat cells Usually forms membranes Lines ventral body cavity Lines lungs, blood vessels, kidney glomeruli Figure 3. 18 a

Simple Epithelium Simple cuboidal n n Single layer of cube-like cells Common in glands and their ducts Forms walls of kidney tubules Covers the ovaries Figure 3. 18 b

Simple Epithelium Simple columnar n n n Single layer of tall cells Often includes goblet cells, which produce mucus Lines digestive tract (stomach to anal canal and gall bladder) Figure 3. 18 c

Simple Epithelium Pseudostratified n n Single layer, but some cells are shorter Ducts of large glands, male urethra Sometimes ciliated, such as in the respiratory tract May function in absorption or secretion (cilia) Figure 3. 18 d

Stratified Epithelium Stratified squamous n n n Cells at the free edge are flattened Found as a protective covering where friction is common Locations Skin (keratinized) Mouth Esophagus Figure 3. 18 e

Stratified Epithelium Stratified cuboidal and columnar n n Rare in human body Found mainly in ducts of large glands

Transitional epithelium n n Shape of cells depends upon the amount of stretching Lines organs of the urinary system Figure 3. 18 f

Glandular epithelium Gland – one or more cells that secretes a particular product n 1. Endocrine gland (thyroid, adrenal, pituitary) Ductless (blood stream) Secretions are hormones n 2. Exocrine gland (sweat and oil, liver, pancreas) Empty through ducts to the epithelial surface