Chp. 6: Classification of Tissues Flashcards
Tissues
Groups of cells that are similar in structure and function
Four Tissue Types
Epithelium, Connective, Nervous, Muscle
Organs
Organized tissues that cumulatively perform body functions. Ex.) Heart, Kidneys, Lungs
Histology
The study of tissues
Epithelial Tissue (epithelium)
A sheet of cells that covers a body surface or lines a body cavity. Occur in the body as 1) covering and lining epithelium and 2) glandular epithelium
Epithelial Functions
Protection, absorption, filtration, excretion, secretion (specialty of glands), and sensory reception.
Apical Surface
The free surface of epithelial tissue
Basal Surface
The attached/bottom surface of epithelial tissue
Basement Membrane
The adhesive membrane that connects the epithelial cells (basal lamina) and connective tissue cells (reticular lamina) via an amorphous material secreted partly by the epithelial cells.
Epithelial tissues are…
Avascular but innervated; supplied by nerves, but have no blood supply of their own. They depend on diffusion of nutrients from underlying connective tissue.
Epithelial Regeneration
If well nourished, epithelial cells can easily divide to regenerate tissue; important because many epithelia are subject to a great deal of friction
Simple Epithelia
One layer of cells attached to the basement membrane
Stratified Epithelia
Consists of two or more layers of cells; named according to the cells at the apical surface of the epithelial sheet.
Squamous Epithelia
Scalelike
Cuboidal
Cubelike
Columnar
Column-like
Pseudostratified Epithelium
Simple columnar epithelium (one layer of cells), but because its cells vary in height and the nuclei lie at different levels above the basement membrane, it gives the false appearance of being stratified; also called ciliated epithelium
Endocrine Glands
Glands that lose their surface connection (duct) as they develop; ductless glands. Secrete hormones into the extracellular fluid, and from the there the hormones enter the blood or the lymphatic vessels that weave through the glands.
Exocrine Glands
Glands that retain their ducts, and their secretions empty through these ducts either to the body surface or into body cavities. A lumen forms in these glands. Includes sweat and oil glands, liver, and pancreas.
Simple Squamous Epithelium
DESCRIPTION: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia.
FXN: Allows materials to pass by diffusion and filtration in sires where protection is not important; secretes lubricating substances in serosae.
LOCATION: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).
Simple Cuboidal Epithelium
DESCRIPTION: Single layer of cubelike cells with large, spherical central nuclei.
FXN: Secretion and absorption
LOCATION: Kidney 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 cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)
FXN: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.
LOCATION: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and 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 goblet cells and bear cilia.
FXN: Secretes substances, particularly mucus; propulsion of mucus by ciliary action.
LOCATION: Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.
Stratified Squamous Epithelium
DESCRIPTION: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.
FXN: Protects underlying tissues in areas subjected to abrasion
LOCATION: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.