Tissues: Histology Flashcards
4 types of tissue
- epithelial
- connective
- muscle
- nervous
cellularity
The condition of many cells and little material between
epithelium cells are
avascular (a = without + vascular = pertaining to small vessels) and innervated (receives nerve supply) tissue
Epithelial tissue function
protection from physical injury, sun radiation, and infection; control of permeability to avoid fluid loss from underlying tissues; and secretion of needed substances by specialized clusters of epithelium known as glands.
- protection
- secretion
- absorption
epithelium covers
- body
- organ surfaces
- lines all hollow structures
glandular epithelium
- clump-like epithelial tissue
- forms glands and secretes various products
exocrine glands
secrete products into body cavities and onto surfaces by way of tubular ducts
endocrine glands
- secretions diffuse into the bloodstream for their transport throughout the body.
- The products of endocrine glands are hormones.
free, or apical, surface
side of the cells exposed to a body space
basal surface
side exposed to the connective tissue layer
basement membrane
A thin layer of protein fibers beneath the basal surface connects the epithelial sheet to the underlying connective tissue
simple epithelium
single layer of cells
stratified epithelium
multiple layered arrangement
four alternative shapes of epithelial cells
- squamous
- cuboidal
- columnar
- transitional
squamous
flat with a thin nucleus
cuboidal
cube-shaped with a round nucleus near the center of the cell
columnar
tall with an oval nucleus near the basal surface of the cell
transitional
shape-changing from round when the tissue is relaxed to flat when the tissue is stretched
mesothelium
forming part of the peritoneum
endothelium
lining the inside wall of a large artery
Simple Squamous Epithelium
- a single layer of flattened cells
- forms the inner lining of hollow spaces
- thin structure supports the rapid movement of substances across it during diffusion
- its cells may also secrete products
Simple Cuboidal Epithelium
This tissue forms the walls of small tubes that carry fluids
can be found in
- the kidney tubules
- ducts of certain glands
- covers the surface of the ovary
makes up the secreting portion of some endocrine glands. The tissue functions in secretion and absorption, and often contains cilia or microvilli to assist in these functions.
Simple Columnar Epithelium
- single layer of tall, usually cylindrical cells
- The oval nucleus is near the basal surface of each cell
- has single celled exocrine glands: goblet cells, which produce and secrete mucus.
2 types of simple columnar epithelia
non-ciliated and ciliated
Nonciliated simple columnar epithelium
- forms an inner lining of the digestive, reproductive, and urinary tracts, and the ducts of many glands
- contains microvilli at the apical surface of cells, which aid in secretion and absorption.
Ciliated simple columnar epithelium
- lines portions of the respiratory tract, the uterine tubes, the uterus, the paranasal sinuses, and the central canal of the spinal cord
- cilia propel mucus and other substances.
Stratified Squamous Epithelium
- superficial cells are squamous (flat)
- the cells in the deepest layers are columnar or cuboidal. The layers between the two transition from columnar or cuboidal to squamous.
- forms the epidermis of the skin and lines the entry portals of the body
Stratified Squamous keratinized
- the squamous layer of cells is filled with the tough protein keratin, which provides an added protective benefit (epidermis)
Stratified Squamous nonkeratinized
esophagus
Transitional Epithelium
- the cells are usually in the process of changing between a relaxed, plump state and a contracted, flattened state
- lining the urinary bladder and portions of the ureter and urethra
- stretches to accommodate a temporary increase in urine volume
- then returns back to normal
Pseudostratified columnar epithelium
- a tissue that appears to have many layers, but in fact has only one
- misleading appearance of many layers is due to the varying shape of the cells
- may be ciliated or non-ciliated