Histology

Histology- The Study of Tissues Groups of tissues that are similar in structure and function

Epithelial tissue 1. Epithelial Tissue: cover outside surfaces and surfaces exposed to outside. Ex. Inside of mouth, nose intestines, rectum, skin.

Muscle tissue 2. Muscle tissue: Causes movement of bones, movement of heart, movement of blood vessels, intestines, esophagus.

Connective tissue 3. Connective tissue: most common in the body. Supports organs, covers muscle, connects bones and organs.

Nervous Tissue 4. Nervous tissue: controls the body. Important in homeostasis.

General Characteristics of Epithelial Tissue 1. Fits tightly to form continuous sheets. Neighboring cells are tightly bound together by cell junctions. (to keep fluid from going between cells)

General Characteristics of Epithelial Tissue 2. Epithelial membranes have a free edge unattached to other tissues or organs – called apical surface. The apical surface is exposed to the body’s exterior or the cavity of an internal organ, like the urinary bladder.

Characteristics of apical surface Some apical surfaces are slick and smooth, some have cilia (long hairs), or microvilli (short infoldings of membrane).

General Characteristics of Epithelial Tissue 3. The lower surface of the epithelial cell rests on a basement membrane – a structureless glue secreted by the cell. Attaches to the layers below it.

General Characteristics of Epithelial Tissue 4. Epithelial tissue is avascular- they have no blood supply of their own. They depend on diffusion of nutrients and oxygen from capillaries in the underlying tissue.

General Characteristics of Epithelial Tissue 5. Regenerates easily!

Classification of Epithelial Tissue Cells Simple Squamous Epithelium: Looks like fish scales Rests on basement membrane Thin membrane, good for diffusion and exchange of nutrients Found in alveoli (lungs) and capillaries (blood vessels)

Classification of Epithelial Tissue Cells Simple Cuboidal Epithelium: Shaped like dice Rest on basement membrane They are common in ducts and glands (like salivary glands) and kidney tubules

Classification of Epithelial Tissue Cells Simple Columnar Epithelium: Found in entire digestive tract, from stomach to anus Found in mucous membranes that line body cavities open to outside May have cilia to trap dust and particles

Classification of Epithelial Tissue Cells Simple Pseudo Stratified Epithelium: Really one layer- looks like multiple layers but all are attached to basement membrane Not all reach surface, cells have different heights May have cilia Function in absorption and secretion Line most of the respiratory tract

Classification of Epithelial Tissue Cells Stratified Squamous Epithelium: Apical layer squamous cells Most common stratified epithelium in body Near basement membrane, cells are more cuboidal or columnar Found on surfaces that have a lot of abuse or friction

Classification of Epithelial Tissue Cells Stratified Cuboidal Epithelium: Usually only two layers Rare in body, but can be found in large glands and ducts

Classification of Epithelial Tissue Cells Stratified Columnar Epithelium: Apical cells columnar, inner cells vary in size and shape Rare in body, but can be found in large glands and ducts

Classification of Epithelial Tissue Cells Stratified Transitional Epithelium: Apical layer is squamous when stretched Highly specialized and modified for stretching Found in places that need to stretch like the urinary bladder Bottom layer is usually cuboidal or columnar