Tissues Flashcards
group of cells with similar structure and function that have similar extracellular substances located between them
Tissues
microscopic study of tissue structure
Histology
- lines the different organs and used for protection and
covering - covers the body (external and internal surfaces).
- lines cavities, such as the digestive tract, airways, and
blood vessels. - forms most glands
- most epithelia have a free surface and a basal surface
- may consist of a single layer or multiple layers
- classified according to the no. of cell layers and cell shape
AVASCULAR!!! (no blood vessel)
EPITHELIUM/EPITHELIAL TISSUE
Major types of tissues
Epithelial tissue
connective tissue
muscle tissue
nervous tissue
CLASSIFICATION OF EPITHELIAL TISSUE (LAYER)
Simple epithelium
* single layer of cells
* each cell extending from the basement membrane to the
free surface
Stratified epithelium
* more than one layer of cells
* only the basal layer attaches the deepest layer to the
basement membrane.
Pseudostratified epithelium
* special type of simple epithelium
* appears to be stratified but is not.
* one layer of cells attached to the basement membrane
* pseudo- means false
CLASSIFICATION OF EPITHELIAL TISSUE (SHAPE)
- Squamous - cells are flat or scalelike.
- Cuboidal- cells are cube-shaped and about as wide
as they are tall. - Columnar -tall and thin, like a column and the cells tend to
be taller than they are wide
STRUCTURE: Single layer of flat, often hexagonal cells; the
nuclei appear as bumps when viewed in cross section because
the cells are so flat
FUNCTIONS: Diffusion, filtration, some
secretion, and some protection against friction
LOCATION: Lining of blood vessels and the heart,
lymphatic vessels, alveoli of the lungs, portions of the kidney
tubules, lining of serous membranes of body cavities
(pleural, pericardial, peritoneal)
SIMPLE SQUAMOUS EPITHELIUM
STRUCTURE: Single layer of cube-shaped cells; some cells
have microvilli (kidney tubules) or cilia (terminal bronchioles of
the lungs)
FUNCTIONS: Active transport and facilitated diffusion result in
secretion and absorption by cells of the kidney tubules;
secretion by cells of glands and choroid plexuses; movement
of particles embedded in mucus out of the terminal bronchioles
by ciliated cells
LOCATION: Kidney tubules, glands and their ducts,
choroid plexuses of the brain, lining of terminal bronchioles
of the lungs, and surfaces of the ovaries
SIMPLE CUBOIDAL EPITHELIUM
STRUCTURE: Single layer of tall, narrow cells; some cells
have cilia (bronchioles of lungs, auditory tubes, uterine tubes,
and uterus) or microvilli (intestines)
FUNCTIONS: Movement of particles out of the bronchioles of
the lungs by ciliated cells; partially responsible for the
movement of oocytes through the uterine tubes by ciliated
cells; secretion by cells of the glands, the stomach, and the
intestine; absorption by cells of the intestine
LOCATION: Glands and some ducts, bronchioles of lungs,
auditory tubes, uterus, uterine tubes, stomach, intestines,
gallbladder, bile ducts, and ventricles of the brain
SIMPLE COLUMNAR EPITHELIUM
STRUCTURE: Single layer of cells; some cells are tall and thin and reach the free surface, and others do not; the nuclei of these cells are at different levels and appear stratified; the cells are almost always ciliated and are associated with goblet cells that secrete mucus on to the free surface
FUNCTIONS: Synthesize and secrete mucus on to the free surface and move mucus (or fluid) that contains foreign particles over the surface of the free surface and from passages
LOCATION: Lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of lungs
PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
STRUCTURE: Several layers of cells that are cuboidal in the basal layer and progressively flattened toward the surface;
the epithelium can be nonkeratinized (moist) or keratinized; in nonkeratinized stratified squamous epithelium, the surface cells retain a nucleus and cytoplasm; in keratinized stratified epithelium, the cytoplasm of cells at the surface is replaced bya protein called keratin, and the cells are dead
FUNCTIONS: Protects against abrasion, forms a barrier against infection, and reduces loss of water from the body
LOCATION: Keratinized—outer layer of the skin;
nonkeratinized—mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, and corneas
STRATIFIED SQUAMOUS EPITHELIUM
STRUCTURE: consists of more than one layer of cuboidal epithelial cells
FUNCTIONS: absorption, secretion, and protection.
LOCATION: Relatively rare and is found in sweat gland ducts, ovarian follicular cells, and the salivary glands.
STRATIFIED CUBOIDAL EPITHELIUM
STRUCTURE: Consists of more than one layer, but only the surface cells are columnar. The deeper layers are irregular or cuboidal in shape. Relatively rare
FUNCTIONS: Carries out secretion, protection, and some absorption.
LOCATION: Found in the mammary gland ducts, the larynx, and a portion of the male urethra
STRATIFIED COLUMNAR EPITHELIUM
STRUCTURE: Stratified cells that appear cuboidal when the organ or tube is not stretched and squamous when the organ
or tube is stretched by fluid
FUNCTIONS: Accommodates fluctuations in the volume of fluid in an organ or a tube; protects against the caustic effects of urine
LOCATION: Lining of urinary bladder, ureters, and superior urethra
TRANSITIONAL EPITHELIUM
TERMINOLOGIES
Free Surfaces- Epithelia not in contact with other cells and faces away from underlying tissues
* Smooth - reduces frictio (ex. lining of blood vessels)
* Microvilli- increase cell’s surface area
ex. Lining of small intestine
* Cilia - propel materials along the free surface of cells
(move materials over the cell surface)
ex. nasal cavity, trachea
Cell Connections
* Tight junctions - bind adjacent cells together and form a permeability barrier (ex. lining of the intestines)
* Desmosomes - mechanically bind cells together
* Hemidesmosomes - mechanically bind/anchor cells to the basement membrane.
* Gap junctions - small channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one. It allows intercellular communication.
