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BIOLOGICAL SCIENCES
By:
MARIA KRISIA FAE DELOS REYES DE ASIS, BSN-RN
TISSUE LEVEL OF ORGANIZATION
COVERING AND LINING EPITHELIUM- classified according to two characteristics:
1. Arrangement of cells in layers- Depends on the function
a. SIMPLE EPITHELIUM- a single layer of cells
that functions in DIFFUSION, OSMOSIS, FILTRATION, SECRETION, and ABSORPTION
TISSUE LEVEL OF ORGANIZATION
b. PSEUDOSTRATIFIED EPITHELIUM- appears to have multiple
layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface
- cells that do not extend to the apical surface may contain cilia (TRACHEA & LUNGS); others (GOBLET CELLS) secrete mucus
TISSUE LEVEL OF ORGANIZATION
- they are actually simple epithelium because all cells are attached to the basement membrane. However, they appear like stratified epithelium, thus the term pseudostratified; pseudo meaning “false”
TISSUE LEVEL OF ORGANIZATION
c. STRATIFIED EPITHELIUM- consists of two or more
layers of cells that protect underlying tissues and locations where there is considerable wear and tear
HARD PALATE
TISSUE LEVEL OF ORGANIZATION
2. Cell shapesa. SQUAMOUS CELLS
- arranged like floor tiles and are thin, which allows the rapid passage of substancesb. CUBOIDAL CELLS
- as tall as they are wide and are shaped like cubes or hexagons. May have microvilli at apical surface (secretion/absorption)
TISSUE LEVEL OF ORGANIZATION
c. COLUMNAR CELLS- consists of two or more
layers of cells that protect underlying tissues and locations where there is considerable wear and teard. TRANSITIONAL CELLS
- change shape from flat to cuboidal. Ex. Uterus, urinary bladder
URINARY BLADDER
TISSUE LEVEL OF ORGANIZATION
- Combining the two characteristics, the types of covering and lining epithelia are as follows:
I. SIMPLE EPITHELIUMA. SIMPLE SQUAMOUS EPITHELIUMB. SIMPLE CUBOIDAL EPITHELIUMC. SIMPLE COLUMNAR EPITHELIUM
(CILIATED AND NON-CILIATED)D. PSEUDOSTRATIFIED COLUMNAR
EPITHELIUM (CILIATED AND NON-CILIATED)
TISSUE LEVEL OF ORGANIZATION
II. STRATIFIED EPITHELIUMA. STRATIFIED SQUAMOUS EPITHELIUM
(KERATINIZED AND NON-KERATINIZED)
B. STRATIFIED CUBOIDAL EPITHELIUM*C. STRATIFIED COLUMNAR EPITHELIUM* D. TRANSITIONAL EPITHELIUM
* - based on the shape of the cells at the APICAL surface
GASTROINTESTINAL TRACT
Transitional epithelium