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What is a tissue?
A tissue is a group of similar cells and their intercellular matrix functioning together to perform a specialized activity.
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What are the for types of tissues? Briefly define each.
- 1. Epithelial - covers of lines (body surfaces and cavities), forms glands
- 2. Connective - binds and supports
- 3. Muscular - movement
- 4. Nervous - conducts impulses
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What are the three types of junctions between cells in tissues?
- 1. Tight junctions
- 2. Desmosomes
- 3. Gap junctions
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What is the function of a tight junction?
To prevent leakage of molecules from tissue.
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What is the structure of a tight junction?
Proteins in 2 adjacent cell membranes interlock (zipper).
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What is the function of desmosomes?
Hold adjacent cells together for greater stability.
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What is the structure of desmosomes?
Dense mats of microfilaments below cell membrane hold membranes together; with intercellular proteoglycans
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What is the function of gap junctions?
Communication between cells.
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What is the structure of gap junctions?
Protein pores in both cell membranes line up to form continuous channel from one cell to another.
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What is the function of the epithelial tissue and give the 4 types?
- Covering and lining epithelium --> protection and secretion
- 1. skin
- 2. mucus membranes (digestive, respiratory, reproductive tracts)
- 3. endothelium - lines blood vessels
- 4. mesothelium - covers organs, lines cavities
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What is the grandular epithelium?
Manufactures and secretes products into ducts and body.
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Describe the structure of the epithelial tissue.
- 1. closely packed cells with little or no intercellular matrix between cells.
- 2. apical surface - free surface exposed to exterior of body or internal surface of a cavity
- 3. basement membrane - (glycoproteins secreted by epithelium and collagen fibers secreted by underlying connective tissue).
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Is the epithilial tissue vascular or avascular?
Avascular - no blood supply.
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Is the epithilial tissue mitotically active or inactive?
Mitotically active.
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What are the types of lining epithelium?
- 1. by arrangement of layers
- 2. by shape of cell
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What are the 3 layer arrangements of epithelial lining?
- 1. simple
- 2. stratified
- 3. pseudostratified
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What is a simple layer?
Single layer
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What is a stratified layer?
Stacked in layers
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What is a pseudostratified layer?
Appears to be in layers, but all cells are in contact with the basement membrane --> only one layer, not all reach the surface.
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What are the 4 shapes of cells in the epithilial tissue?
- 1. squamous
- 2. cubodial
- 3. columnar
- 4. transitional
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What is squamous tissue?
Flattened, scale-like with a central nuclei
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What is simple squamous?
Good for diffusion, osmosis, filtration. (ie, endothelium and mesothelium)
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What is stratified squamous?
- 1. shape classified by outermost layer
- 2. keratinized (tough and waterproof skin)
- 3. nonkeratinized (inner surfaces)
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What is cuboidal tissue?
Cube or hexagon shape, central nucleus.
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What is simple cubodial?
Kidney tubules, glands
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What is stratified cubodial?
Rare
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What is columnar tissue?
Tall rectangular, nucleus towards base
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What is simple columnar?
Digestive tract, with mircovilli
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What is pseudostratified columnar?
upper respiratory tract, with cilia
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What is stratified columnar?
Rare
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What are goblet cells?
Mucus cells - unicellular gland that secretes mucus.
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What is transitional tissue?
Stratified (only) - can change shape on surface when stretched or relaxed, in bladder and ureter.
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What are the 2 parts to the glandular epithelium?
- 1. endocrine glands
- 2. exocrine glands
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Define an endocrine gland.
- 1. ductless
- 2. secrete product directly into bloodstream
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Define an exocrine gland?
- Exocrine glands secrete products into ducts or directly onto free surface.
- -- unicellular goblet or mucus cells
- -- multicellular glands
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Define what simple/compound means regarding multicellular exocrine gland classification.
Classified by structure of duct.
- Simple - unbranched duct
- Compound - branched duct
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Define what tubular/acinar means regarding multicellular exocrine gland classification.
Classifed by secretory portion structure
- tubular
- acinar = alveolar -flask-shape, sac-like
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Define what mercorine/holocrine/apocrine means regarding multicellular exocrine gland classification.
Classified by mode of secretion (formation)
- merocrine - secretes product only from cell
- holocrine - secretory cell dies and discharged it's contents
- apocrine - outer part of secretory cell pinched off with product in it
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What are the four functions of connective tissue?
- 1. support and protection
- 2. binding together of organs
- 3. insulation
- 4. as blood - transportation
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What is the structure of connective tissue?
- 1. Few widely scattered cells in a large amount of matrix.
- 2. Matrix or intercellular material determines tissue's qualities
- 3. Usually highly vascular
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What is embryonic connective tissue?
Embryonic connective tissue = mesenchyme - give rise to all other connective tissue
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How does connective tissue compare generally to the characteristics of epithelial tissue?
Epithelial tissue is closely packed cells with little or no intercellular matrix. It is avascular, no blood supply.
Connective tissue has few widely scattered cells in a large amount of matrix. Usually highly vascular.
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What are the 5 connective tissue cell types?
- 1. fibroblasts
- 2. macrophages
- 3. mast cells
- 4. plasma cells
- 5. adipocytes
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What is the function of fibroblasts?
Fibroblasts produce intercellular matrix (fibers and ground substances)
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What is the function of macrophages?
phagocytes (fixed and wandering)
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What is the function of mast cells?
allergic mediators (histamine and heparine)
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What is the function of plasma cells?
To produce antibodies.
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What is the function of adipocytes?
Cell surrounds lipid droplets.
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Name the components of the matrix or intercellular material of connective tissue proper.
- 1. hyaluronic acid
- 2. fibers - protein
- a. collagenous
- b. elastic
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Describe collagenous fibers.
- Thick and strong.
- Vitamin C necessary for proper formation.
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Describe elastic fibers.
Very flexible.
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Describe loose connective tissue.
Loose = Areolar connective tissue
- 1. below epithelium and between muscles
- 2. contains all connective type cells
- 3. randomly arranged collagenous and elastic fibers in hyaluronic acid
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Describe dense connective tissue.
- 1. sparse ground substance (hyaluronic acid) with many closely packed collagenous fibers
- 2. fibroblasts between fibers
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Differentiate between dense regular and dense irregular connective tissue and give examples of each.
Dense regular connective tissue - parallel bundles of fibers, ligaments, and tendons.
Dense irregular connective tissue - interwoven fibers, dermis of skin.
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Describe elastic connective tissue.
In walls of elastic arteries, elastic ligaments.
Mainly elastic (yellow) fibers with fibroblasts.
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