Epithelial Cells Structure One surface of the cell is exposed to the outside (exposed) surface, the other is anchored to connective tissue, holding the cell in place. Function The function varies with the cell, but includes one or more of the following: Secretion Absorption Excretion Forms a protective barrier

Location 1.Found in lining of body cavities (mouth, respiratory tract, stomach, intestine etc.). 2. Found in the lining of hollow regions of organs (ducts, tubules etc.). Epithelial Cells The shape of epithelial cells varies Cuboidal Squamous (squashed) Columnar

Simple Cuboidal Epithelium Structure Single layer of cube-shaped cells with centrally located nuclei. Function Absorb or secrete molecules Location 1.Cover ovaries 2.Line kidney tubules 3.Line ducts of glands Kidney Tubules

Simple Squamous Epithelium Structure Single layer of flattened cells with thin, broad nuclei. Function Thin cells allow materials to rapidly pass through. Used for diffusion (lungs) or filtration (capillaries). Location 1. Lung alveoli (air sac) where O 2 and CO 2 diffuse. 2. Wall of capillaries, blood vessels, where filtration occurs. Lung alveolar sacs

Simple Columnar Epithelium Structure Tall narrow cells with the nucleus near the bottom of the cell. Function Secrete digestive fluid and absorb nutrients. One surface exposed to lumen and has tiny extensions called microvilli which increase surface area available for absorption. Location 1.Line uterus 2.Line organs of the digestive tract (stomach, small & large intestine

The small intestine is lined with simple columnar epithelial cells which absorb nutrients on the brush border surface, using active transporters. The opposite side of the cell is attached to connective tissue. This surface has transporters which move nutrients from the cell into the surrounding fluid by facilitated diffusion. The nutrients than diffuse to the blood and are carried to the rest of the body. Simple Columnar Epithelium

Pseudostratified Columnar Epithelium Structure 1.While there is only a single layer of cells, the cells appear to be stratified because nuclei are found in 2 or more distinct layers. 2.The cells often have cilia on the free surface. 3.Goblet cells are frequently scattered amongst pseudostratified columnar cells. Location These cells line the passages of the respiratory system.

Pseudostratified Columnar Epithelium Function The goblet cells secrete mucus, which traps dust, pollen, and microorganisms. The cilia on the pseudostratified columnar epithelial cells then sweep mucus and trapped particles out of the lungs. Cystic fibrosis is a hereditary disease which results in very thick mucus in the lungs. The cilia cannot move the mucus out of the lungs. The trapped bacteria thrive, causing frequent lung infections. Cells lining the bronchioles.

Stratified Squamous Epithelium Structure Thick tissue consisting of many layers of cells. Cells in the deep layers divide. The new cells push the cells above toward the surface, causing them to flatten. Function and Location 1. These cells line the mouth, throat, vagina, and anal canal, where they form a protective barrier. As the surface cells are worn away, they are replaced by new cells being formed by the polygonal basal cells. 2. These cells form the outermost layer of skin and form a protective barrier.

Skin Stratified Squamous Epithelium The stratified squamous cells of the skin synthesize and accumulate the protein keratin. As the cells are pushed to the surface, the keratin hardens and the cells die. The resulting layer of dead cells provides a dry, tough protective surface which prevents water loss from the body and blocks chemicals and microorganisms from entering. Pigments in the skin also provide a barrier to UV light. Melanoma (skin cancer)

Stratified Cuboidal Epithelium Sweat Duct Structure Two to three layers of cells lining a lumen. Function The layering of cells provides greater protection than that of a single layer. Location 1. Line larger ducts of mammary glands, sweat glands, salivary glands, and pancreas. 2. Line developing ovarian follicles and seminiferous tubules.

Stratified Cuboidal Epithelium Developing ovarian follicle

Stratified Columnar Epithelium Structure Consists of 2 or more layers of cells. The superficial cells are elongated. The basal layers contain cube- shaped cells. Function The cells function in secretion and protection. Location 1.Male urethra and vas deferens 2.Line the eye socket 3.Major ducts in salivary glands Goblet Cell Stratified columnar Salivary Gland