MSI Week 2: Epithelium IS

Epithelium lines free surfaces (whether internal or external) and forms glands

False- epithelium is in fact avascular

Epithelium is:
1. Highly cellular
2. No direct blood supply
3. High regenerative power
4. Cell have polarity (apical, basal, and lateral surface)

Simple surface epithelia is 1 cell thick

Stratified surface epithelia is 2 or more cells thick

Pesudostratified surface epithelium appears to be >1 cell thick but each cell actually contacts the basement membrane

The general rule for naming epithelium that is layered and contains cells of more than one shape: it is named for the cell shape forming the most superficial layer

Squamous epithelium has flattened scale-like cells with a flattened nuclei

Cuboidal epithelium has cells that are as tall as they are wide with round nuclei

Columnar epithelium has cells taller by 2x or more than they are wide with oval nuclei parallel to long axis of cell

Dysplastic cells have increased ratio of nuclear to cytoplasmic volume

Endothelium- simple squamous epithelium that lines blood and lymphatic vessels

Mesothelium- simple squamous epithelium that lines major body cavities and covers the free outside surface or organs

Neuroepithelium- sheets of sensory receptors cells

Germinal Epithelium- epithelium that gives rise to spermatozoa

Transitional Epithelium- pseudostratified epithelia

When the bladder is full, the transitional epithelium appear to be stratified squamous epithelium

When the bladder is empty, the transitional epithelium appear to be pseudostratified columnar or cuboidal

The basement membrane is composed of basal lamina and reticular lamina

Type IV collagen and laminin produced by epithelium make up the basal lamina

Type III collagen produced by fibroblasts makes up the reticular lamina

Stereocilia is found in the epididymis

Microvilli and stereocilia are nonmotile, cilia are motile

Zonula occludens (tight junction), zonula aherens (intermediate junction), macula adherens (desmosome) compose junctional complexes

Junctional complexes appear as darkly staining spots or lines near the apical surfaces of adjoining epithelial cells

Goblet cells in the epithelium of the intestine or respiratory tract are single cell exocrine

Salivary glands and exocrine portion of pancreas are multicellular exocrine

Myoepithelial cells are specialized for contraction, the share the basal lamina of secretory acinar cells

Myoepithelial cells exhibit sparse fibrillar cytoplasmic processes that radiate out from the cell body, wrapping around the acini

Serous acinus cells:
1. Pyramidal shaped
2. Indistinct cell boundaries
3. Spherical nuclei
4. Apical secretory granules
5. Basophilic cytoplasm
6. Secretory product is proteinaceous, thin, watery, contains enzymes
7. Located in pancreas

1. Pyramidal cells
2. Distinct cell boundary
3. Flattened nucleus at the base of the cell
4. Slight basophilia
5. Secretory product is viscous
6. Located in salivary gland

Merocrine secretion- proteinaceous secretions released via secretory granules (ex. eccrine and apocrine sweat glands, a misnomer)

Apocrine secretion- large droplets of product are released from the apical surface of the cell

Holocrine secretion- whole cell is secreted or destroyed in the process of secretion (ex. sebaceous gland)