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Tissue Types Overview Tissue Definitions
Epithelial Tissue
• Simple and Stratified
Connective Tissue
• Characteristics
• Bone, Cartilage, Dense
• Connective, Loose Connective
Blood
Muscle Tissue
• Skeletal, Cardiac, and Smooth
Nervous Tissue
Tissue Repair
Tissue Development and Aging
Body Tissues Cells are specialized for particular functions
Tissues
• Groups of cells with similar structure and function
• Four primary types
Epithelium
Connective tissue
Muscle
Nervous tissue
Epithelial Tissues Found in different areas
• Body coverings
• Body linings
• Glandular tissue
Functions
• Protection
• Absorption
• Filtration
• Secretion
Epithelium Characteristics Cells fit closely together
Tissue layer always has one free surface
The lower surface is bounded
by a basement membrane
Avascular (have no blood supply)
Regenerate easily if well nourished
Classification of Epithelium: Layering
Classification of Epithelium: Shape
(a) Simple squamous epithelium
Description: Single layer of flattenedcells with disc-shaped central nucleiand sparse cytoplasm; the simplestof the epithelia.
Function: Allows passage ofmaterials by diffusion and filtrationin sites where protection is notimportant; secretes lubricatingsubstances in serosae.
Location: Kidney glomeruli; air sacsof lungs; lining of heart, bloodvessels, and lymphatic vessels; liningof ventral body cavity (serosae).
Photomicrograph: Simple squamous epitheliumforming part of the alveolar (air sac) walls (125x).
Air sacs oflung tissue
Nuclei ofsquamousepithelialcells
Other important locations:
Endothelium- the lining of lymphatic vessels, blood vessels, and heart
Mesothelium- the epithelium of serous membranes in the ventral body cavity
Figure 4.3b
(b) Simple cuboidal epithelium
Description: Single layer ofcubelike cells with large,spherical central nuclei.
Function: Secretion andabsorption.
Location: Kidney tubules;ducts and secretory portionsof small glands; ovary surface.
Photomicrograph: Simple cuboidalepithelium in kidney tubules (430x).
Basementmembrane
Connectivetissue
Simplecuboidalepithelialcells
Figure 4.3c
(c) 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).
Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.
Location: Nonciliated type lines most of the digestive tract (stomach to anal canal),gallbladder, and excretory ducts of someglands; ciliated variety lines small bronchi, uterine tubes, and some regionsof the uterus.
Photomicrograph: Simple columnar epitheliumof the stomach mucosa (860X).
Simplecolumnarepithelialcell
Basementmembrane
Figure 4.3d
(d) Pseudostratified columnar epithelium
Description: Single layer of cells ofdiffering heights, some not reachingthe free surface; nuclei seen atdifferent levels; may contain mucus-secreting cells and bear cilia.
Function: Secretion, particularly ofmucus; propulsion of mucus byciliary action.
Location: Nonciliated type in male’ssperm-carrying ducts and ducts oflarge glands; ciliated variety linesthe trachea, most of the upperrespiratory tract.
Photomicrograph: Pseudostratified ciliatedcolumnar epithelium lining the human trachea (570x).
Trachea
Cilia
Pseudo-stratifiedepitheliallayer
Basementmembrane
Mucus ofmucous cell
Figure 4.3e
(e) Stratified squamous epithelium
Description: Thick membranecomposed of several cell layers;basal cells are cuboidal or columnarand metabolically active; surfacecells are flattened (squamous); in thekeratinized type, the surface cells arefull of keratin and dead; basal cellsare active in mitosis and produce thecells of the more superficial layers.
Function: Protects underlyingtissues in areas subjected to abrasion.
Location: Nonkeratinized type formsthe moist linings of the esophagus,mouth, and vagina; keratinized varietyforms the epidermis of the skin, a drymembrane.
Photomicrograph: Stratified squamous epitheliumlining the esophagus (285x).
Stratifiedsquamousepithelium
Nuclei
Basementmembrane
Connectivetissue
Stratified Epithelium, Other Types
Stratified cuboidal
Stratified columnar
Mucous gland duct, tongue
•Quite rare in body
•Found in some sweat and mammary glands
•Typically two cell layers thick
•Limited distribution in body
•Small amounts in pharynx, male urethra, and lining some glandular ducts
•Also occurs at transition areas between two other types of epithelia
Figure 4.3f
(f) Transitional epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells domeshaped or squamouslike, depending on degree of organ stretch.
Function: Stretches readily and permits distension of urinary organ by contained urine.
Location: Lines the ureters, urinary bladder, and part of the urethra.
Photomicrograph: Transitional epithelium lining the urinary bladder, relaxed state (360X); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine.
BasementmembraneConnectivetissue
Transitionalepithelium
Glandular Epithelium Gland – one or more cells that secretes a
particular product
Two major gland types
• Endocrine gland
Ductless
Secretions are hormones
• Exocrine gland
Empty through ducts to the epithelial surface
Include sweat and oil glands
Found as unicellular and multicellular types
Unicellular Exocrine Glands: Goblet Cell The only important unicellular gland is the
goblet cell
Figure 4.4
(b)(a)
Microvilli
Secretoryvesiclescontainingmucin
Golgiapparatus
Rough ER
Nucleus
Multicellular Exocrine Glands Multicellular exocrine glands are
composed of a duct and a secretory unit
Classified according to:
• Duct type (simple or compound)
• Structure of their secretory units (tubular, alveolar, or tubuloalveolar)
Figure 4.5
Compound duct structure(duct branches)
Simple tubular
ExampleIntestinal glands
Simple branchedtubular
ExampleStomach (gastric)glands
Compound tubular
ExampleDuodenal glands of small intestine
Compound alveolar
ExampleMammary glands
Simplealveolar
ExampleNo importantexample in humans
Simple branchedalveolar
ExampleSebaceous (oil)glands
Compoundtubuloalveolar
ExampleSalivary glands
Tubularsecretorystructure
Alveolarsecretorystructure
Surface epithelium Duct Secretory epithelium
Simple duct structure(duct does not branch)
Modes of Secretion Merocrine
• Products are secreted by exocytosis (e.g., pancreas, sweat and salivary glands)
Holocrine
• Products are secreted by rupture of gland cells (e.g., sebaceous glands)
Tissue Types Overview Tissue Definitions
Epithelial Tissue
• Simple and Stratified
Connective Tissue
• Characteristics
• Bone, Cartilage, Dense
• Connective, Loose Connective
Blood
Muscle Tissue
• Skeletal, Cardiac, and Smooth
Nervous Tissue
Tissue Repair
Tissue Development and Aging
Connective Tissue Found everywhere in the body
Includes the most abundant and widely distributed tissues
Functions
• Binds body tissues together
• Supports the body
• Provides protection
Connective Tissue Characteristics Variations in blood supply
• Some tissue types are well vascularized
• Some have poor blood supply or are avascular
Extracellular matrix
• Non-living material that surrounds living cells
Extracellular Matrix Two main elements
• Ground substance - Gel like, high water content
Proteoglycans
Glycosaminoglycans (GAGs like hyaluronan), chondroitin sulfate as dietary supplement for osteoarthritis
Glycoproteins
• Fibers
Produced by the cells
Three types
Collagen fibers
Elastic fibers
Reticular fibers
Reticular fibers
Table 4.1
Connective Tissue Types: Areolar Areolar connective tissue
Generic organ packaging tissue, soaks up water
Connective Tissue Types: Bone Bone (osseous tissue)
Has both an organic and a mineral component
Tissue Types Overview Tissue Definitions
Epithelial Tissue
• Simple and Stratified
Connective Tissue
• Characteristics
• Bone, Cartilage, Dense
• Connective, Loose Connective
Blood
Muscle Tissue
• Skeletal, Cardiac, and Smooth
Nervous Tissue
Tissue Repair
Tissue Development and Aging
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