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The epithelium serves the purpose to...
separate a space (the lumen) from the underlying tissue
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What are the 5 defining characteristics of epithelium?
- 1. Close apposition of cells.
- 2. Free surface of epithelial cells is adjacent to the space that is limited
- 3. Basal surface (bottom) is adjacent to connective tissue
- 4. Sheets of epithelial cells may be modified to glands
- 5. Absence of blood vessels within epithelial layer
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6 functions of epithelium.
- 1. Protection against abrasion, desiccation
- 2. Lubrication
- 3. Secretion
- 4. Absorption
- 5. Sensory reception
- 6. Gas transfer
- 7. Ion transport
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Surface of the cell adjacent or attached to the basement membrane.
Basilar or basolateral surface
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Surface of the cell farthest away from the basement membrane.
Apical surface
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Three characteristics used to classify epithelium.
number of layers of cells, shape of cells, function (glandular/non-glandular)
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Three classifications of epithelium based upon numbers of cells.
- Simple- one layer of cells.
- Stratified- two or more true layers (only cells at the basal surface have attachment to the basement membrane).
- Pseudostratified- Cells have nuclei arranged at different levels, giving a stratified appearance, but all cells make contact with basal lamina.
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4 classifications of epithelium based on cellular shape.
- Squamous- flattened in the plane of the epithelium.
- Cuboidal- height and width are equal.
- Columnar- height is much more than width.
- Transitional- capable of changing shape (only in urinary tract).
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Epithelial type cells that do not produce and secrete extracellular products.
Non-glandular
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5 body tissues where non-glandular epithelial cells are found.
skin, urinary bladder, oral mucosa, esophagus, vasculature
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Skin is an example of ______, _______ epithelium.
stratified, squamous
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Epithelial lined structures that produce a chemical that is secreted extracellularly.
Glands
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Glands can be ______ or ______.
endocrine (secrete into bloodstream) or exocrine (secrete into duct)
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3 mechanisms for glandular secretions.
- 1. Merocrine- exocytosis of secretory vesicles to the lumen of the gland.
- 2. Holocrine- death of an entire cell within a gland releases content into the lumen of the gland.
- 3. Apocrine- release of budding vesicles off the epithelial cells into the lumen of the gland (an actual piece of the cell blebs off, unlike merocrine, which releases vacuoles from the cytoplasm)
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Sweat glands are _____.
apocrine
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Sebaceous glands are _____.
holocrine
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Cell surface modifications which increase surface area of a cell, while keeping the size of the cell relatively small.
microvilli
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Microvilli are seen in organs where _________ is a primary function, such as ______ and _______.
absorption of molecules; small intestine; kidneys
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Modifications of epithelium that are projections and type of organelle that are seen on the apical surface of epithelial cells, beat in a coordinated fashion, and assist in the movement of material over the epithelial surface.
Cilia
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Cilia are always found on the _______ of epithelial cells.
apical surface
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Tight junctions ________, and hen present in a sheet, they allow ______________ [functions].
hold cells together; epithelium to form a barrier between two compartments
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Tight junctions are aka ______.
zona occludens
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Gap junctions serve as a _____________, and they allow _________ [functions].
connection between cells which joins their cytoplasms; the passage of molecules freely between the cells
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Desmosomes join _______ to ________.
cells to other cells.
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Hemidesmosomes join ________ to _________.
cells to the basement membrane
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Desmosomes and hemidesmosomes bind __________ across cells and are anchored by __________ within a cell.
cell surface proteins; filaments
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Single layer of flat cells that can be continuous or discontinuous and is permeable to the passage of molecules.
simple squamous epithelium
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Simple squamous epithelium is particularly important inside of ______.
blood vessels
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The outer membrane that covers internal organs.
serosa
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The serosa and cells forming it.
mesothelium
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The most inner wall of the blood vessels.
endothelium
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The endothelium is _____, ______ epithelium.
simple, squamous
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Simple squamous epithelium that has small openings; common in the liver.
fenestrated
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Simple squamous epithelium that has large spaces.
Sinusoidal
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A single layer of cuboidal epithelium lining a basement membrane.
simple cuboidal epithelium
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Simple cuboidal epithelium provide ______ and ______ functions.
secretory, absorptive
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Epithelium in which the length if greater than the width and the nuclei are located at the base of the cell; often has a modification (cilia or microvilli).
simple columnar epithelium
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A single layer of cells similar to columnar epithelium, except the nuclei are arranged at different levels and every cell is attached to the underlying basement membrane.
pseudostratified columnar epithelium
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Pseudostratified columnar epithelium have _______ and ________ functions.
absorptive and secretory
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Pseudostratified columnar epithelium is common in the _____.
respiratory tract
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Epithelium arranged in layers; superficial cells are flat, but deeper layers may be cuboidal.
Stratified squamous epithelium
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Stratified squamous epithelium is common in regions where ___________ is necessary.
protection against abrasions
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Stratified squamous epithelium is common in _______.
oral mucosa
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Layers of this type of epithelium can be shed and regrown.
stratified squamous epithelium
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Intracellular filament which provides structure to cells.
keratin
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A tough waterproof barrier is formed through cornification (keritinization), which is...
cells int he uppermost layer of stratified squamous epithelium lose their nuclei and organelles, leaving behind a dead cell with keratin and other inert structural elements
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Unique type of stratified epithelium in which the cells can change shape in response to stretching of the organ.
urothelium (transitional epithelium)
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All types of connective tissue are composed of... (2)
cells and extracellular matrix
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__________ is the primary structural component of connective tissue.
Extracellular matrix
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Material formed from glycoproteins and glycosaminoglycans in connective tissue; holds water and acts as a space filler.
ground substance (extrafibrillar matrix)
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The fiber component of extracellular matrix can be... (3)
collagen, reticular fibers, or elastic fibers (elastin)
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Describe the structure of collagen.
AA sequence--> triple helix (tropocollagen) --> fibrils --> fibers
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Fibrils are cross-linked with each other in collagen to form ________.
fibers
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Type I collagen
most abundant; tendons, dermis, arterial walls
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Type II collagen
hyaline cartilage
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Type III collagen
reticulin fibers, granulation tissue
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Type IV collagen
basil lamina, ocular membranes, basement membrane of glomerular capillaries
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Type V collagen
interstitial connective tissue (fine/in between cells)
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New vascular tissue in granular form on an ulcer or the healing surface of a wound.
granulation tissue
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subtype of collagen that are delicate and unorganized and easily identified by silver staining.
reticulin fibers
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Reticulin fibers are present in...
lymphatic organs and bone marrow
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Provide connective tissue with the ability to stretch.
Elastin
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3 examples of tissues with high elastin content.
tendons, ligaments, arteries
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Cellular components of connective tissue. (5)
fibroblasts, macrophages, neutrophils, eosinophils, lymphocytes
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The most common cells in connective tissue.
fibroblasts
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Fibroblasts are _________ and ________-shaped with _________ of cytoplasm.
elongated; spindle-shaped; a small amount
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Fibroblasts are distinguished from fibrocytes because they are...
metabolically active and larger
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Derived from blood monocytes; function to phagocytose debris and act as surveillance for the immune system.
macrophages
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Cells that store lipids and are often interspersed between collagen bundles.
Adipocytes
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The microscopic appearance of connective tissue is divided into two forms:
embryonic connective tissue and fibrous connective tissue
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This type of tissue is found in the developing embryo and in the umbilical cord.
embryonic connective tissue
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Loosely arranged fibers of ground substance containing interspersed stellate cells.
mesenchymal tissue
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A loose network of type I collagen and reticulin fibers with interspersed ground substance, cells, and vasculature.
loose (areolar) connective tissue (type of fibrous connective tissue)
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Closely packed collagen fibers with interspersed fibroblasts an fibrocytes; primary component of tissue that need to be tough yet pliable.
dense fibrous connective tissue
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dense fibrous connective tissue is found in... (2)
tendons and ligaments
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Connective tissue that acts as a skeleton for organs with a high parenchymal component (liver, spleen, kidney).
reticulin fibrous connective tissue
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The 2 main roles of adipose tissue.
store energy in the form of lipid, insulation
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Predominant type of adipose tissue in most animals.
white adipose tissue
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Adipose cells appear like....
clear, circular structures with flattened nuclei on one edge
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Brown adipose tissue is seen in...
neonates or animals that hibernate
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Brown adipose tissues appear...
to have smaller cytoplasmic vacuoles and eosinophilic cytoplasm; nuclei are not flattened to the side of the cell.
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Cartilage is composed of _________ embedded in extracellular matrix, composed of... (3)
chondrocytes; collagen, ground substance; elastic fibers
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Three major types of cartilage.
hyaline cartilage, fibrocartilage, elastic cartilage
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In hyaline cartilage, chondrocytes are arranged in...
clusters of linear arrays
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Hyaline cartilage is found primarily on ________ and provides...
joint surfaces (articular cartilage); a compressible surface
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Elastic cartilage is found... (3)
ear, nose, and trachea
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Fibrocartilage has higher ________ content than hyaline cartilage, causing it to...
collagen; be tougher yet remain flexible
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Fibrocartilage is found... (2)
intervertebral discs, symphasis between certain bones
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