Chap 5 Flashcards
Tissues
Groups of similar cells and extracellular material with common function
Histology
Study of tissues
Four types of tissues with varied structure and function
Epithelial
Connective
Muscle
Nervous
Epithelium/epithelial tissue
One or more layers of closely packed cells
Contains little to no extracellular matrix
Avascular (no room for blood vessels)
**Lines body surfaces and body cavities **
Forms most glands
Polarity
Apical surface
Exposed to external environment or material in tube
Closest to the “white space”
May have microvilli or cilia
Lateral surface with intercellular junctions
Basal surface
Epithelium attached to underlying connective tissue
via the basement membrane
Physical protection
from dehydration, abrasion, destruction
Selective permeability
Non-permeable to some substances; Promotes passage of others
Secretions
Specialized secreting cells may be scattered or in small clusters
Sensations
Contain nerve endings; Touch, pressure, temperature, pain
Undergoes frequent cell division
Necessary due to environmental exposure; replacement of lost cells
Epithelia classification indicated by two-part name
Number of epithelial cell layers
Simple Stratified Pseudostratified
Epithelia classification indicated by two-part name
Shape of cells at apical surface
Squamous Cuboidal Columnar
Simple epithelium
ONE LAYER OF CELLS
All cells in direct contact with basement membrane
In areas where stress is minimal
Filtration, absorption, or secretion is primary function
E.g., lining of air sacs of lungs, intestines, blood vessels
Stratified epithelium
2+ layers of epithelial cells
Only basal layer in contact with basement membrane
In areas subjected to mechanical stress
Better able to resist wear and tear
Basal layer cells continuously regenerate (apical cells lost)
Pseudostratified epithelium
Appears layered
Due to cells’ nuclei distribution at different levels
All cells attached to basement membrane
Some do not reach the apical surface
Simple epithelium
Squamous cells
Flat, wide, irregular in shape
Nucleus flat
Cuboidal cells
About as tall as they are wide
Nucleus spherical and in center of cell
Columnar cells
Slender and taller than they are wide
Nucleus oval; oriented lengthwise
Transitional cells
Change shape, depending on stretch of epithelium
Located where epithelium stretches and relaxes
Simple squamous epithelium
Single layer of flat cells;
Spherical to oval nucleus
Thinnest barrier
Allows rapid movement of molecules across surface
alveoli
Lines air sacs of lungs
endothelium
Lines vessel walls
mesothelium
Serous membrane of cavities
Simple Cuboidal Epithelium
Single layer of uniformly shaped cells
About as tall as they are wide; Round central nucleus
Designed for absorption and secretion
Ideal for structural components of glands
Thyroid gland
Surface of ovary
Walls of kidney tubules
Secretory regions/ducts of most glands
