Tissues Epithelial Tissue

Tissues A group of similar cells that work together to perform a specific function. Four main types of tissues: Epithelial Connective Muscular Nervous All cells present in a tissue are surrounded by/bathed in an extracellular matrix (ECM) ECM-nonliving material (no cells), usually fluid (but can be solid), produced by the cells it surrounds.

Epithelial Tissue Widespread through out the body, present in every body system. Very diverse cell types compose it (9 types) Avascular-no blood vessels present Very little ECM present Are usually able to repair themselves and/or regenerate through the life span Located on the outside of the body, on the outside of the organs, lining hollow spaces inside organs and lining body cavities. Function to provide sensation, protect, absorb substances, secrete substances (produce) and excrete substances (eliminate). Common for intercellular connections to be present.

Intercellular Connections Many epithelial tissues have specialized connections between the individual cells. Connections are protein structures (3 Types) Desmosomes: Anchor adjacent cells to one another. Help keep epithelial tissue in tact.

2. Tight junctions: fuse cell membranes at intermittent spots Allow for more rapid diffusion of substances between cells.

3. Gap junctions: tubular channels between cells Also allow for more rapid diffusion of substances.

Distinct features of ALL epithelial tissues… Basement Membrane: nonliving material that anchors the epithelial tissue to the underlying tissue. Free surface/lumen Epithelial cells Basement Membrane Underlying tissue

2. Free surface: Open space on the side/edge of the ET. Also called the lumen when it is inside organs/cavities

Types of Epithelial Nine types Classified according to the shape of cell and the number of cell layers present in the tissue. Name consists of two parts, the Part1-Indicates the number of cell layers Part 2-Indicates the shape of the cells.

1 Cell Layer: Simple Simple Squamous Simple Cuboidal Simple Columnar Squamous: flat/squashed Simple Cuboidal Cuboidal: cubes Simple Columnar Columnar: columns Could have microvilli or cilia on free surface. Goblet cells-are secreting cells

2 or More Cell Layers: Stratified Stratified Squamous Squamous: squashed cells at free surface Stratified Cuboidal Cuboidal: many times only 2-3 layers thick Stratified Columnar No cilia or microvilli

Pseudostratified Columnar Epithelium Abbrev. Pseudostartfied Looks like more than one cell layer but it’s not Stratified Transitional Epithelium A type of stratified epithelium Tissue stretches & cells at free surface change shape. Distended= stretched tissue

Glandular Epithelium Classified because of function Could be simple cuboidal, simple columnar, stratified cuboidal, stratified columnar or pseudostratified. Specialized to secrete Are endocrine glands or exocrine glands

What type of ET do you see? Simple cuboidal

What type of ET do you see? Stratified squamous

What type of ET do you see? Simple columnar (ciliated)

What type of ET do you see? Psuedostratified

What type of ET do you see? Simple cuboidal

What type of ET do you see? Simple Squamous

What type of ET do you see? Transitional