Classification of Tissues (Lab 6A)
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mistyblue17 on February 21, 2011
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47 terms
Terms | Definitions |
|---|---|
 Histology | - The study of tissues. |
| Epithelial Tissue (Epithelium) | - Covers Surfaces - Covers external body surface - Lines cavities and tubules - Generally marks off our insides from our outsides - Endocrine and exocrine glands develop from epithelial cells - Glands are classified as epithelium |
| Epithelial Functions | - Protection - Absorption - Filtration - Excretion - Secretion - Sensory reception |
| Characteristics of Epithelial Tissues | - Polarity - Cellularity and specialized contacts - Supported by connective tissue - Avascularity - Regeneration |
| Polarity | - Membranes always have one free surface (apical surface), and typically that surface is significantly different from the basal surface |
| Apical Surface | - Free surface |
| Basal Surface | - Opposite the free surface |
| Cellularity and Specialized Contacts | - Cells fit closely together to form membranes and are bound together by specialized junctions |
| Supported by Connective Tissue | - Cells are attached to and supported by an adhesive basement membrane |
| Basement Membrane | - An amorphous material secreted partly by the basal lamina and reticular lamina that lie adjacent to each other |
| Basal Lamina | - Part of the basement membrane that is secreted by the epithelial cells |
| Reticular Lamina | - Part of the basement membrane that is secreted by the connective tissues |
| Avascularity | - Epithelial tissues have no blood supply of their own - Instead depend on diffusion of nutrients from the underlying connective tissue - Glandular epithelia are vascular |
| Regeneration | - Epithelial cells can easily regenerate themselves if well nourished - Important because many epithelia are subjected to a great deal of friction |
| Simple Epithelia | - Consisting of one layer of cells attached to the basement membrane |
| Stratified Epithelia | - Consisting of two or more layers of cells |
| Squamous Epithelial Cells | - Scale-like in shape |
| Cuboidal Epithelial Cells | - Cube-like in shape |
| Columnar Epithelia Cells | - Column-like in shape |
| Pseudostratified Epithelium | - A simple columnar epithelium but because the cells vary in height and nuclei lie at different levels above the basement membrane, it fives the false appearance of being stratified - Often ciliated |
| Transitional Epithelium | - Stratified squamous epithelium formed of rounded cells with the ability to slide over one another to allow the organ to be stretched - Found in organs subjected to periodic distension - Superficial cells are flatened when the organ is distended and rounded when the organ is empty |
| Endocrine Glands | - Lose their duct (surface connection) as they develop; ductless - Secretions (all hormones) are released into the extracellular fluid, from which they enter the blood or the lymphatic vessels that weave through the glands |
| Exocrine Glands | - Retain their ducts - Secretions empty through these ducts to an epithelial surface - Both external (sweat and oil glands) and internal (liver and pancreas glands) |
| Simple Squamous Epithelium - Description | - Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm - Simplest of the epithelia |
| Simple Squamous Epithelium - Function | - Allows passage of materials by diffusion and filtration in sites where protection is not important - Secretes lubricating substances in serosae |
| Simple Squamous Epithelium - Location | - Kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lymphatic vessels, lining of ventral body cavity (serosae) |
| Simple Cuboidal Epithelium - Description | - Single layer of cube-like cells with large, spherical nuclei |
| Simple Cuboidal Epithelium - Function | - Secretion - Absorption |
| Simple Cuboidal Epithelium - 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) |
| Simple Columnar Epithelium - Function | - Absorption - Secretion of mucus, enzymes, and other substances - Ciliated type propels mucus (or reproductive cells) by ciliary action |
| Simple Columnar Epithelium - Location | - Nonciliated type lines most of the digestive tract, gallbladder, and excretory ducts of some glands - Ciliated type lines small bronchi, uterine tubes, and some regions of uterus |
| Pseudostratified Columnar Epithelium - Description | - Single layer of cells of differing heights, some not reaching the free surface - May contain mucus-secreting cells and bear cilia |
| Pseudostratified Columnar Epithelium - Function | - Secretion, particularly of mucus - Propulsion of mucus by ciliary action |
| Pseudostratified Columnar Epithelium - Location | - Nonciliated type in male sperm-carrying ducts and ducts of large glands - Ciliated type lines 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 - In the keratinized type, the surface cells are full of keratin and are dead - Basal cells are active in mitosis and produce the cells of more superficial layers |
| Stratified Squamous Epithelium - Function | - Protects underlying tissues in areas subjected to abrasion |
| Stratified Squamous Epithelium - Location | - Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina - Keratinized type forms the epidermis of the skin |
| Stratified Cuboidal Epithelium - Description | - Generally two layers of cube-like cells |
| Stratified Cuboidal Epithelium - Function | - Protection |
| Stratified Cuboidal Epithelium - Location | - Largest ducts of sweat glands, mammary glands, and salivary glands |
| Stratified Columnar Epithelium - Description | - Several cell layers - Basal cells usually cuboidal - Superficial cells elongated and columnar |
| Stratified Columnar Epithelium - Function | - Protection - Secretion |
| Stratified Columnar Epithelium - Location | - Rare in the body - Small amounts in male urethra and in large ducts of some glands |
| Transitional Epithelium - Description | - Resembles both stratified and squamous cuboidal - Basal cells cuboidal or columnar - Surface cells dome shaped or squamous-like, depending on degree of organ stretch |
| Transitional Epithelium - Function | - Stretches readily and permits distension of urinary organ by contained urine |
| Transitional Epithelium - Location | - Lines the ureters, urinary bladder, and part of the urethra |
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