4.2 Epithelial Tissue

What are the 5 functions of epithelial tissue?

Protection, immune defense, secretion, transportation, and sensation

Apical

The apex, or facing the surface of the cell.

What are the 5 functions of epithelial tissue?

Protection, immune defense, secretion, transportation, and sensation

Apical

The apex, or facing the surface of the cell.

Basal lamina

Made of glycoproteins and collagen, lies below the epithelium layer and provides an attachment site.

Reticular lamina

Made by underlying connective tissue, is below the basal lamina and attaches to it. Made of reticular fibers and ground substance.

Basement membrane

Basal and reticular lamina. Anchors underlying blood vessels in place and provides a barrier between epithelia and further underlying tissues.

Tight junction

Hold cells closely together, space in between is impermeable to movement of macromolecules.

Anchoring junction

Help stabilize epithelial tissues, includes desmosomes, hemidesmosomes, and adherens.

Gap junction

Small pores, formed by protein channels, allows substances to flow freely between each cell's cytoplasm.

Squamous

Flattened

Cuboidal

Boxy

Columnar

Tall, rectangular

Microvilli

Finger-like, increases surface area for absorption.

Cilia

Propel substances through hollow organs.

Simple

One single cell layer

Stratified

More than one cell layer

Pseudostratified columnar

Single layer or irregularly shaped and sized columnar cells.

Simple squamous epithelium function

Fried egg appearance, allows for diffusion, filtration, and secretes a lubricating substance.

Simple cuboidal epithelium function

Large central nucleus, absorption, secretion, and potentially diffusion.

Simple columnar epithelium function

Cilliated or smooth, absorption, secretes mucus and enzymes.

Pseudostratified columnar epithelium function

Nuclei have varied heights, secretes mucus; ciliated tissue moves mucus.

Stratified squamous epithelium function

Protects from abrasion.

Stratified cuboidal epithelium function

Rare, protective tissue.

Stratified columnar epithelium function

Apical is columnar, basal layer is cuboidal, secretes and protects.

Transitional epithelium function

Dome-shaped, allows for the urinary organs to expand and stretch.

Simple squamous location

Lung air sacs, lining of the heart and blood vessels, kidney tubules and lymphatic vessels.

Simple cuboidal location

Gland ducts, segments of renal tubules, respiratory passages, and the thyroid.

Simple columnar location

Ciliated tissues in larger bronchioles, uterine tubes, and uterus; smooth in the digestive tract and bladder.

Pseudostratified columnar location

Ciliated tissues line the bronchi, trachea, and much of the upper respiratory tract (nasal cavity).

Stratified squamous location

Lines esophagus and mouth.

Stratified cuboidal location

Sweat, salivary, and mammary glands, and ducts.

Stratified columnar location

Male and female urethrae, cornea of the eye and some gland ducts.

Transitional location

Lines bladder, urethra, and the ureters

Keratinized stratified squamous epithelium

Apical cellular layers consist of dead cells, lack nuclei, and covered with keratin.

Nonkeratinized stratified squamous epithelium

Apical layers are alive and retain nuclei.

Gland

Made of epithelia, produces and releases chemical substances.

Endocrine

A method of release into the bloodstream via hormones.

Exocrine

A method of release onto the outside of the body.

Merocrine (Eccrine)

Secretions are enclosed in vesicles and move to the apical surface and released by exocytosis. Found in salivary and sweat glands.

Apocrine

Secretion accumulates near the apical portion and that portion is thin pinched off and released. Found in axillary areas.

Holocrine

The entire gland cell ruptures and explodes. An example is sebaceous glands which secrete sebum.

Unicellular glands

Single cells scattered about, such as goblet cells.

Multicellular (Serous glands)

Form secretory surface that secretes directly into an inner cavity such as the abdomen and chest.

Goblet cells

Common unicellular exocrine gland, found in digestive and respiratory tracts (among columnar epithelial cells). Responsible for secreting mucus.