Epithelial Tissues BIO 1110

Tissues Tissues: A group of similar cells, having a similar origin, and functioning together to carry out specialized activities. Tissues can be solid, semi-solid or liquid. From conception until approximately day 14, all cells look and function the same (undifferentiated=stem cells). Around day 15 post conception, cells start to differentiate or take on new characteristics. This is the start of tissue formation.

Tissues Histology is the study of tissues. There are 4 main types of tissues in the human body: Epithelial Connective Muscular Nervous

Epithelial Tissue (Epithelium) Tightly packed cells arranged in continuous single or multi-layered sheets. Characteristics: Avascular- without blood vessels. Epithelium gets nutrients from the adjacent connective tissue. Bottom surface of epithelium is attached to the basement membrane (fibers that act like glue) Has a nerve supply.

Covering/Lining Epithelium This type of tissue is found on the outer covering of the skin and some internal organs as well as lining body cavities and some internal hollow organs. There are 9 different types of lining/covering epithelium. Epithelial tissue is classified based on the number of cell layers present and the shape of the cells of the tissue.

Number of Layers Simple- Stratified- Single layer of tightly packed cells Stratified- 2 or more layers of tightly packed cells

Number of Layers Continued.. Pseudostratified Looks like many layers because not all cells reach the surface and the nuclei lie at different levels

Cell Shape Squamous Thin, flat and irregularly shaped Cuboidal Square/cube shaped Columnar taller than wide Transitional change shape due to stretching or movement of body parts

Simple Squamous A single layer of tightly packed thin, flat, irregularly shaped cells Location: Lines the blood vessels Forms the peritoneum, pericardium and pleural linings Found in the air sacs of lungs (alveoli) Function: Allows for easy diffusion of gases and blood components

Simple Squamous – Top View – found in the walls of capillaries and alveoli of lungs

Simple Cuboidal A single layer of tightly packed cube shaped cells. Location: Lines kidney tubules, ducts of glands, and secreting parts of glands Function: Secretion (force materials out of the cells) and absorption (pull materials into the cells)

Simple Cuboidal Epithelial Tissue – this is of ducts of the kidney

Simple Columnar A single layer of tightly packed rectangular cells Can be non-ciliated or ciliated (tiny hairs) Non-ciliated have microvilli (finger-like projections) on the free surface of the cells Non-ciliated Location: Lines the gastrointestinal tract (from stomach to anus) Non-ciliated Function: Secretion and absorption Microvilli (folds in the cell membrane) increase surface area 200-300 times for absorption

6/22/2018

Simple Columnar Continued… Ciliated Location: Lines tubes of the respiratory tract, fallopian tubes, and ventricles of the brain Ciliated Function: The cilia beat in unison to move substances outside the cell like mucus and egg cells.

Simple Columnar Non-Ciliated Epithelial Tissue - This is a cross section through the small intestine – for absorption – microvilli on surface of cells

Pseudostratified Columnar A single layer of tightly packed columnar cells that appear to be multi-layered Location: Ciliated- Lines respiratory tract Non-ciliated- Male urethra Function: Ciliated- moves materials across the apical surface of a tissue. Non-ciliated- Absorb and protect

Stratified Squamous Multiple layers of tightly packed squamous epithelial cells. Location: Areas that are subject to much “wear and tear”. Skin and vagina Function: Protection

Stratified Cuboidal Two layers of cube shaped epithelial cells Rare Location: Lining the ducts of glands found in the esophagus Function: Moderate protection from the stomach acid that refluxes

Stratified Columnar Multiple layers of columnar epithelial cells Rare Only the layer closest to the lumen (opening in a duct) is columnar in shape. The outer layers are somewhat squashed. Location: Lining the ducts of glands lining the esophagus Function: Moderate protection from stomach acid that refluxes

Transitional Epithelial tissue that has a variable shape Can stretch and relax multiple times without being damaged Location: Lines the urinary bladder Function: Protection

Let’s Practice! 6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73

6/22/2018 Bio 111-73