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Epithelium Tissue
| Term | Definition |
|---|---|
| Simple Epithelium | Consists of a single layer of cells(apical surface and attach to the basement membrane. (diffusion, filtration, absorption, secretion) |
| Stratified Epithelium | Protection, consist of two or more layers of cells. Not all cells have an apical surface, nor do all cells attach to the basement membrane (found in skin, esophagus, vagina) constant regeneration |
| Pseudostratified | Appears to have multiple layers but only has one. All cells are attached to basement, but not all are attached to apical |
| Squamous | flat, wide, irregular in shape. |
| Cuboidal | as tall as they are wide, circular |
| Columnar | tall and thin, columns, nuclei are oval and located in the basal region. |
| Transitional | cells change shape depending on degree of stretch of epithelium - oval on the apical surface (polyhedral (relaxed state) squamous (stretched state), - ex. bladder wall - binucleated cells |
| Simple squamos | Single layer of flat cells - allows for rapid exchange - delicate and found in moist regions -Ex: lining lung air sacs, lining blood vessels |
| simple cuboidal | -Single layer of cells as tall as they are wide - allows for absorption and secretion - Very thin layer that creates a protective layer - In Kidneys and ducts of exocrine glands |
| simple columnar | Single layer of tall, narrow cells - Allows for absorption and secretion - Ciliated and nonciliated forms |
| pseudostratified Columnar | Single layer of cells with varying heights - appears stratified but is simple -All cells touch basement but not apical surface - nasal cavity, trachea, bronchi |
| stratified squamos | Multiple layers; upper layers of flattened cells - cells in basal layers appear cuboidal, cels in apical appear squamous. |
| stratified cuboidal | Two or more layers; cells about as tall as wide - forms walls of most exocrine glands - protects and strengthens walls |
| stratified columnar | Two or more layers of tall, narrow cells only in apical surface - rare - found in membranous segment of male urethra and salivary glands |
| Endothelium | Epithelium lining blood and lymphatic vessels. Inside our blood supply |
| mesothelium | simple squamous epithelium of a serous membrane that lines internal walls of the pericardial, pleural, and peritoneal cavities. |
| Microvilli | Brush border (fuzzy border), tiny, cytoplasmic projection on the apical surface that increase the surface area for secretion and absorption. |
| Goblet Cells | Secrete mucin, unicellular - Only in simple columnar, pseudostratified epithelial - enclosed in a capsule - most common type of unicellular exocrine |
| Ciliated | uterine tube (moving, grass) - Covered in mucus that moved by cilia - Goblet cells are throughout the epithelium |
| Nonciliated | Most of digestive tract from stomach to anal canal - microvilli(brush border)More surface area - Big peaks and valleys |
| Epithelial Tissue | Covers/ lines every body surface and all body cavities. - Forms external and internal lining of many organs - majority of glands - little to no extracellular matrix - No blood vessels |
| Epithelium | One or more layers of closely packed cells between two compartments having different components |
| Extra Cellular Matrix | - Produced by the cells and surrounds them - Composed of water, protein Fibers, dissolved molecules |
| Characteristics of Epithelial Tissue | Cellularity, polarity, attachment to a basement membrane, avascularity, innervation, high regeneration capacity. |
| Cellularity | Made entirely of cells bound closely together through intercellular junctions, little extracellular matrix between cells |
| Polarity | Apical, basal and lateral surfaces |
| Apical Surface | top surface of tissue exposed to external environment or some internal body surface. May include cilia or microvilli |
| Lateral surfaces | has intercellular junctions |
| Basal surface | bottom surface, epithelium is attached to connective tissue. |
| Attachment to a basement membrane | At the basal surface, epithelial layer is bound to a thin basement membrane( a molecular structure produced by epithelium and connective tissue) |
| Avacularity | Lack of blood vessels in epithelial tissue. Receive nutrients through apical surface or diffusion from basal surface. |
| Innerevation | Epithelia are innervated to detect changes in the environment(externally or internally) |
| High regeneration capacity | Apical surface is frequently damaged, so epithelium has a high regeneration capacity |
| Function of Epithelial Tissue | Physical protection, selective permeability, secretion, sensation |
| Physical protection | Epithelial tissues protect from dehydration, abrasion, and destruction by physical, chemical or biological agents. |
| Selective permeability | Regulates passage of molecules in or out of certain regions of the body("gatekeepers") lets somethings pass through while restricting others. |
| Secretion | Secrete substances for use in the body or for elimination from the body. uses exocrine glands and other glands through the cell. |
| Sensation | possess nerve endings that can detect light, taste, sound, smell, hearing |
| Basement membrane | specializes structure found between epithelium and connective tissue. - lamina lucida, lamina densa, and reticular lamina - provides physical support - anchors the epithelium to the connective - acts as barrier to regulate movement of lare molecules |
| Basal Lamina/ Two lamina | Closest to epithelium, contains collagen fibers and specific protein fibers and carbohydrates secreted by the epithelial cells |
| Reticular lamina | Cells in underlying connective tissue, contain protein fibers and carbohydrates, |
| Intercellular Junction | strongly binds epithelial cells by their lateral surfaces(tight, adhering, desmosomes, gap) |
| Tight Junction(zipper) | encircle epithelial cells near their apical surface and completely attach each cell to its neighbor - Ensure molecules go through epithelial cells rather than in between them - Prevents mixing of membrane proteins and lipids to maintain polarity. |
| Adhering Junctions | (Support)Form around the cell deep to the tight junctions. - microfilaments are anchored to membrane, and membrane proteins link cells together - stabilize the apical surface |
| Desmosomes (button or snap) | appear at mechanical stress between cells - protein plaque on cell membranes with a fine network of proteins spanning intercellular space - Intermediate filaments attach to plaques provide support and stability - some have hemidesmosomes |
| Gap Junction | (Conjoined twins)Span the intercellular space between neighboring cells - connexon(door) proteins that forms a pore - pore connects cytoplasm of cells - allows cells to communicate and flow ions and molecules. |
| Classification of Epithelial | - number of cells(first) - shape of apical cells(second) |
| Keratinized | Superficial cells are dead(hair) |
| Nonkeratinized | Superficial cells are living |
| Glands | Individual cells or multicellular organs composed of epithelial tissue - produce mucin, hormones, enzymes, waste products |
| Endocrine glands | No ducts; secrete hormones into blood stream - hormones are chemical messengers |
| Exocrine glands | Has ducts; secret products into their ducts |
| Classification of exocrine glands | 1. form and structure 2. type of secretion 3. method of secretion |
| Serous glands | watery fluid (sweat, milk, tears) |
| Mucous gland | secrete mucin (mucous) |
| Mixed glands | mix of watery or mucous secretion |
| tubular | secretory portion and the duct are of uniform diameter |
| simple glands | single, unbranched duct |
| acinar | round and bulbous, secretory cells form an expanded sac |
| Compound gland | branched duct |
| Tubuloacinar gland | both secretory tubules and secretory acini |
| Merocrine | secrete products from vesicles using exocytosis |
| Apocrine | produces stored apical part of cell that pinches of (smells)axillary, anus, ariola |
| Holocrine | (whole) cell accumulates oily glands, then dies |
| keratinized stratified squamous epithelium | multiple layers of cells, basal cells typically are cuboidal, apical cell are squamous, outer cells are dead and filled with protein keratin which makes them strong. - epidermis of skin |
| Nonkeratinized Stratified Squamous | Multiple layers of cells, basal cells are cuboidal, apical cells are squamous, surface cells are alive and moist - vagina, oral cavity, - lack keratin |
| Duct | epithelium- lined tube, secretions of the gland are discharged onto the surface of the skin or internal passageway. |
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