Classification of Tissues Flashcards
Simple Squamous epithelium
Description: Single layer of flattened cells with disc-shaped nuclei and aparse cytoplasm; the simplest of the epithelia
Function: Allows passage of materials by simple diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae
Locations: Air sacs of lungs; kidney glomeruli; lining of heart, blood vessels, and lymphatic vessels; serosae in ventral body cavity
Simple Cuboidal epithelium
Description: Single layer of cube-like cells with large, spherical central nuclei
Function: Secretion and absorption
Locations: Kidnry tubules; ducts and secretory portions of small glands; ovary surface
Simple Columnar epithelium
Description: Single layer of tall cells with round to oval nuclei; some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)
Function: Absorption; secretion of mucus, enzymes and other substances;ciliated type propels mucus by ciliary action.
Location (nonciliated): Digestive tract; gallbladder; excretory ducts of some glands
Location (ciliated): Small bronchi; uterine tubes; some regions of the uterus
Pseudostratified Columnar epithelium
Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia
Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action
Location (nonciliated): Male’s sperm-carrying ducts of large glands
Location (ciliated): Trachea; most of upper respiratory tract
Stratified Squamous epithelium
Description: Thick membrane composed of many cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened; in the keratinized type, surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers
Function: Protects underlying tissues in areas of abrasion
Location (non-keratinized): moist linings of esophagus, mouth, vagina
Location (keratinized): Epidermis of skin (a dry membrane)
Stratified Cuboidal epithelium
Description: Generally two layers of cuboidal cells
Function: Protection
Location: Largest ducts of salivary glands, sweat glands, and mammary glands
Stratified Columnar epithelium
Description: Basal cells usually cuboidal; superficial cells elongated and columnar
Function: Protection; secretion
Location: Small amounts in male urethra; in large ducts of some glands
(Rare in the body)
Transitional epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome-shaped or squamous-like, depending on degree of organ stretch
Function: Stretches readily and permits distension of urinary organs by contained urine
Location: Lines the ureters, urinary bladder, and part of the urethra
Areolar (loose connective) tissue
Description: Gel-like matrix with all 3 fiber types; cells include fibroblasts, macrophages, mast cells, and some white blood cells
Function: Wraps and cushions organs; its macrophages phagocytize bacteria; holds and conveys connective tissue fluid
Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries
Adipose (loose connective) tissue
Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have neuclei pushed to the side by large fat droplets
Function: Provides reserve fuel; insulates against heat loss; protects and supports organs
Location: Under skin; around kidneys and eyeballs; within abdomen; in breasts
Reticular (loose connective) tissue
Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network
Function: Fibers form a soft internal skeleton (stroma) that supports other cell types, including white blood cells, mast cells, and macrophages
Location: Lymphoid organs (lymph nodes, bone marrow, and spleen)
