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94 Cards in this Set
- Front
- Back
tissues: definition
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organized aggregation of cells with same structure, same origin, perform same function
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4 basic types of tissues
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1.epithelial
2.connective 3.muscle 4.nervous |
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3 main locations of epithelial tissue
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1.cover exterior surfaces (barrier epithelium)
2.line internal cavities (barrier epithelium 3.form secretory portion of glands and their ducts (glandular epithelium) |
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main structural difference of epithelial tissue
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exposed free surface in external body surface (skin) and luminal surface (linine of the intestine) --> much adaptation to deal with environment
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cellular composition of epithelial tissue & key difference
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closley aggregated cells, adhesion between cells is very strong (strongest of all tissues)
key difference: little to no extracellular matrix |
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Epithelial tissue is vascular or avascular?
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avascular- no blood supply.
get rid of waste via diffusion because cells line the walls of blood vessels`` |
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morphological polarity
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Epithelial cells have distinctive orientation. Possible to identify 3 main surfaces
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3 main surfaces present in epithelial cell
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1.apical
2. lateral 3. basal |
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apical domain
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forms the external or luminal surface of the cell
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3 modifications found on apical surface
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1.microvilli
2. stereocilia 3. cilia |
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function and location of microvilli
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function- increase surface area
location- where absorption is important, small intestine or kidney |
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3 characteristics of microvilli
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1. size- 0.01 µm
2. actin core 3.amorphous apex formed by villin |
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villin
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protein into which actin filaments are anchored by myosin I
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actin core
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actin filaments bound together by fimbrin and fascin, anchored into membrane by myosin I
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fimbrin and fascin
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actin-binding protiens
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myosin I
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latera anchoring protien, attaches actin filaments to membrane
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stereocilia vs cilia
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Stereocilia are modified microvilli. They are NOT RELATED to cilia.
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stereocilia
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long, sometimes branching projections of actin filaments of microvilli's core.2
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2 roles of stereocilia
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1. epididymis-absorption of fluid
2. inner ear cochlea- sensory receptors |
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function and location of cilia
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function-move substances along the surface of epithelium (mucus)
location-areas where transport is necessary (respiratory tract or ovum |
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axoneme
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20 pairs of microtbles forming the core of a cillium
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basal body
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centriole, attached to base of cilium, formed by 9 triplets of microtubules WITHOUT A CENTRAL PAIR
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primary ciliary dyskinesia
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(immotile ciliary syndrome)
genetic defects ---> maformation of the skeleton of cilia --->uncoordinated or absent ciliary beating. dextrocardia, impaired development of sinuses, no mucus removal/infections, infertility |
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lateral domain
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characterized by the presence of cell junctions that allow the tissue to function as a whole
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3 major classes of cellular junctions
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1.occluding
2.anchoring 3.communicating |
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terminal bars
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many junctions occuring together ina group or complex, visualized in light microscope
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occluding junctions
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(tight junctions)
mostly present toward apical portion, represented by a single type, zonula occludens |
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zona occludens
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belt-like junction formed by sealing starnds of trasmembrane proteins that bind membranes of two adjacent cells
virtually impermeable main function is to prevent diffusion |
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What type of cells are occluding/tight junctions found in?
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Cells with a secretory role (stomach epithelia) or absorptive role (kidney tubule cells)
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How does the zona occludens preent diffusion?
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By blocking the paracellular pathway.
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anchoring junction
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connect cytoskeleton of one cell to that of an adjacent cell or extracellular matric
designed to provide stability and mechanical strength to the tissue and allow it to function as one unit 4 types: 2 in lateral, 2 in basal |
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4 types of anchoring junctions
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1. zonula adherens (lateral)
2. macula adherens (lateral) 3. focal contact (basal) 4. hemidesmosome (basal) |
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zonula = x
macula = y |
zonula = belt
macula = spot |
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zonula adherens
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belt like junction that connects actin filaments of one cell to actin filaments of another cell
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macula adherens
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(desmosome)
spot-like junction that connects intermediate filaments of two cells (stronger because intermediate filaments >> actin filaments) |
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composition of zonula adherens
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composed of actin, actin binding protein viniculin, peripheral protein which links viniculin to transmembrane protein cadherin, and cadherin which binds to itself on the next cell.
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composition of macula adherens
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composed of intermediate filaments that go through an intracellular plaque made of desmoplakin, and transmembrane cadherin proteins
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pemphigus
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condition in which body produces too many antibodies to proteins forming desmosome junctions---> poor adhesion--> space finns up and creates blister in mouth and skin
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communicating junctions
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(gap junctions)
allow for diffusion of small molecules and ions between cytoplasms of adjacent cells allow communication between cells and have a role in the control of cell proliferation and differentiation |
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composition of communicating/gap junctions
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intercellular channels- allow for diffusion. composed of a pair of connexons allinghed with each other
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connexon
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forms intercellular channel in gap junctions
made up of 6 protein subunits called connexins |
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Gap junctions typically occul in groups called ___________.
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patches
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4 common location of gap junctions
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1. epithelium
2. cardiac muscle 3. smooth muscle 4. embryonic tissue |
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basal domain
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epithelial cell domain which faces the basement membrane and is important for interactions with the underlying (connective) tissue
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basement membrane
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seperates epithelium from the underlying connective tissue, formed by 2 layers
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2 layers of basement membrane
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1. basal lamina
2. reticular lamina |
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basal lamina
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most external layer of the basement membrane, belongs to the epithelium
composed of sheets of collagen type IV and laminin |
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reticular lamina
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deeper layer of basement membrane, belongs to connective tissue
composed of thin collagen fibers |
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2 types of anchoring junctions in the basal domain
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1.focal adhesions
2. hemidesmosomes |
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focal adhesions
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(focal contacts)
attach actin cytoskeleton of a cell to the extracellular matrix |
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key difference in composition of basal domain and lateral domain anchoring junctions
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lateral = cadherin transmembrane protein
basal= integrin transmembrane protein |
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integrin is Ca 2+ _____________
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independent
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composition of focal adhesions
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microfilaments attach to actin binding protiein vinculin,peripheral protein talin connectis vinculin to the integrin transmembrane protein.
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hemidesmosome
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connects intermediate filaments in cell cytoskeleton to the extracellular matrix
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key difference in hemidesmosome vs desmosome
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intermediate filaments go through a desmosome.
intermediate filaments end on plaque in hemidesmosome. |
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composition of hemidesmosome
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intermediate filaments end on intracellular plaque made of desmoplakin, integrin transmembrane proteins attach to the extracellular proteins
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3 ways to classify epithelial tissue
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1.By layers
2. By cell shape 3. By apical cell surface modifications |
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simple
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single cell layer in the epithelium
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pseudostratified
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all cells of the tissue rest on the basement membrane, but not
all of them reach the surface. |
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stratified
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more than one layer of cells in the epithelium.
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squamous
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flat cells
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cuboidal
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if the transverse diameter of the cell is roughly equal to the cell height
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columnar
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if the cell height is considerably greater than the transverse diameter.
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ciliated vs non-ciliated
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cilia present vs cilia not present, even if microvilli or stereocilia are
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location of simple squamous epithelium
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lining of the cardiovasuclar sytem, body cavities, parietal layer of the Bowman's capsule of the kidney, alveoli of the lung
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2 major functions of simple squamous epithelium
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1. barrier
2. diffusion of oxygen and carbon dioxide |
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endothelium
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special type of simple squamous epithelium that lines inner walls of blood vessels and heart
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mesothelium
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special type of simple squamous epithelium that covers internal organs within the plueral, pericardial and peritoneal cavities.
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common locations of simple cuboidal epithelium
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walls of ducts of various glands, kidney tubules, germinal epithelium of the ovary, thyrouid follicles
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3 main functions of simple cuboidal epithelium
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1.barrier (ducts)
2.secretion (thyroid) 3.absoption (kidney) |
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Individual microvilli cannot be seen in the light microscope but densely packed microvilli form a thin layer called the ______________.
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striated or microvillar border
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non-ciliated simple columnar epithelium
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found in the lining of the GI tract and in the walls of the gallbladder
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ciliated simple columnar epithelium
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found in the lining of the oviduct
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4 main functions of simple columnar epithelium
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1. absorption
2. secretion 3. lubrication 4. transport (if cilia are present) |
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basal cells
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bells in psuedostratified columnar epithelium which rest on the basement membrane and serve as the replacement/progenitor cells in this epithelium
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metaplasia
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reversible replacement of one differentiated cell type with another mature differentiated cell type
in heavy smokers, normally psuedostratified ciliated columnar epithelium goes to startified squamous non-ciliated. |
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keratinized stratified squamous epithelium
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characterized by the presence of the dead cornified layer on the surface, found in the epidermis of the skin.
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non- keratinized stratified squamous epithelium
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does not have the dead layer of keratin on the surface, found in the beginning of the GI tract (oral cavity, esophagus) and in the female reproductive system (vagina).
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stratified cuboidal epithelium
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rather rare, found in ducts of glands, most common in the ducts of sweat glands of the skin
consists of two layers of cells that are cuboidal in shape. |
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2 functions of stratified cuboidal epithelium
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1. barrier
2. conduit. |
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stratified columnar epithelium,
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even rarer, can be found in the larger ducts of several glands, including the parotid and submandibular salivary glands. The basal layer of this epithelium is composed of cuboidal cells, while the surface cells are columnar.
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2 functions of stratified columnar epithelium
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1. barrier
2. conduit |
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transitional epithelium
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(urothelium)
restricted to the urinary system (urinary bladder, ureter, and in the pelvis and calyces of the kidney) cannot be classified as squamous, cuboidal, or columnar. It is composed of multiple layers of cells of different shape. The surface layer often contains large rounded “dome” cells that are often binucleated. The most important feature of the transitional epithelium is its ability to stretch enormously: bladder full= flat bladder empty= cuboidal |
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glandular epithelium
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formed as a result of invagination of the epithelial tissue
epithelial cells then start secreting various materials, such as mucins, steroids, etc. |
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endocrine glands
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secrete their product into the intercellular space or underlying
connective tissue and the product diffuses into blood (NO DUCTS) Cells within endocrine glands are usually arranged in cords that follow the capillaries that supply the gland. |
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exocrine glands
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maintain their connection to the originating epithelium and secrete into ducts, or spaces lined with the originating epithelium.
Cells within the exocrine glands are usually arranged into acini or tubules. |
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3 major mechanisms of secretion
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1. merocrine
2. apocrine 3. holocrine |
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merocrine gland
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secretory product is delivered in membrane-bound
vesicles to the apical surface, where the vesicles fuse with the plasma membrane to release their content via exocytosis. |
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3 types of merocrine glands
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1. serous
2. mucous 3. mixed |
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serous glands
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secrete a thin, watery, protein-rich secretion. The secretory vesicles are small and densely-staining. These cells have better developed rough ER than mucous cells, and consequently their cytoplasm stains more basophilic. The rough ER occupies the basal part of the cell, and as a result the nuclei are shifted towards the middle of the cell. These cells are usually pyramidal in shape and as a result serous acini are rounded in shape. Examples: pancreas and parotid salivary gland.
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mucous glands
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produce mucins that consist of long chains of negatively charged carbohydrates attached to a small protein core. Mucins are viscous and are important for lubrication and protection. The secretory granules are large and stain very lightly with hematoxylin and eosin. The rough ER is not well developed. The nuclei are heterochromatic and occupy basal position in the secretory cells of mucous glands. Mucous cells are usually columnar in shape and mucous acini typically have tubular shape. Examples: goblet cells, glands of the soft palate, Brunner’s glands.
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mixed/ seromucous glands
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have both serous and mucous cells. Mucous cells form tubules, capped by serous cells that form serous demilunes. Example: submandibular salivary gland.
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apocrine
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secretion involves pinching of the apical cytoplasm with the formation of secretory vesicles. This mechanism is found in the mammary gland, where it is responsible for releasing large lipid droplets into milk.
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holocrine
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secretion involves the whole cell, rather than its parts. As the cell accumulates the secretory product, it goes through apoptosis (programmed cell death), and both the cellular content and cell debris are released into the lumen of the gland. This type of secretion is typical for sebaceous glands of the skin.
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