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•Tissue = A collection of cells that perform related functions, and are similar in structure•Histology = The study of tissues
•The Four Primary Tissue TypesEpithelialConnectiveMuscularNervous
Epithelial TissueEpithelial Tissue
1.1. Epithelium / -a = cell layer (barrier)Epithelium / -a = cell layer (barrier)– Protection: covering or lining—inside and out
– Permeability control: selective secretion and absorption
– Sensation: touch receptors etc. and neuroepithelium of special senses
2. Glands = secretory structure– Specialized secretions
BM
apical
basal
Structural Characteristics Structural Characteristics of Epitheliaof Epithelia
Cellularity
Cell to cell contacts
Polarity
Support by connective tissue
Avascular (esp. skin)
Regeneration/repair
Polarity of Epithelial CellsPolarity of Epithelial Cells
Classification of EpitheliaClassification of Epithelia
The function of the epithelium determines which type.
Typically classified according to1. Number of cell layers
Simple vs. Stratified2. Shape of cell
Squamous, cuboidal, columnar
Simple Squamous EpitheliumSimple Squamous Epithelium
Location:
• Lining of ventral body cavities, e.g. peritoneum
• Lining of blood vessels (endothelium)
• Alveoli
Function of Simple Squamous E.Function of Simple Squamous E.
• Friction reduction (cavity lining)
• Blood vessel permeability control (capillaries)
• Gas absorption and secretion (lung)
• Not very protective—only one cell thick
Simple Cuboidal EpitheliumSimple Cuboidal Epithelium
• Function:Function:
Secretion
Absorption
• Location: Location:
Lining of ductsLining of ducts
Glands (salivary, pancreas, thyroid)
Kidney tubules
Thyroid Follicle
Simple Columnar EpitheliumSimple Columnar Epithelium
• Function:Function:SecretionAbsorption
• Location:Location:GI tractMany excretory
ducts
Pseudostratified Ciliated Pseudostratified Ciliated Columnar EpitheliumColumnar Epithelium
Function:Function:Mucociliary BlanketMucociliary Blanket
Mixture of cell types Mixture of cell types nuclei located at nuclei located at various distances from surface. Yet: all various distances from surface. Yet: all cells contact BMcells contact BM
Location:Location:Respiratory tract except for lungs
StratifiedStratified Squamous Epithelium Squamous Epithelium
• FunctionProtection against abrasion, pathogens, chemicals, heat/cold…
• Keratinized vs. non-keratinized
• Location ? Where we need protection!Location ? Where we need protection!Skin surfaceEntrances/exits of body, e.g. mouth, vagina
Sweat gland
Stratified cuboidal and columnar: quite rare, found in glands and ducts
Transitional EpitheliumTransitional Epithelium
• Function ?Function ?
Extreme expansion & recoil
• Layered appearance due to Layered appearance due to overcrowding. All cells contact BM.overcrowding. All cells contact BM.
• Location ?Location ?
• Bladder, ureters, renal pelvis
stretched
Glandular EpitheliaGlandular Epithelia
• ExocrineExocrine
• Glands have ducts
• Secretion to the “outside” of the body
• Simple or compound
• EndocrineEndocrine
• Glands have no ducts
• Hormones (into the bloodstream)
Types of Glandular Secretions:
Location in the Body
Connective Tissue: Connective Tissue: Supports, protects, binds tissuesSupports, protects, binds tissues
Structural characteristics:
• Specialized cells• Extracellular protein
fibers (collagen)• Ground substance
(fluid-like)
extracellular extracellular matrixmatrix
Functions of C.T.Functions of C.T.
• Structural framework for body (p77)
• Transport of fluids and dissolved materials
• Support and protection for organs
• Energy storage (fat)
• Defense
Classification of Connective Tissue
Connective Tissue ProperConnective Tissue Proper- - viscous matrixviscous matrix
-Includes loose, reticular, dense C.T.-Includes loose, reticular, dense C.T.
Think about dermis
Types of Fibers:
CollagenElasticReticular
Defense:
MacrophagesPlasma CellsMast CellsOther WBC
Fluid C. T.
• Blood (Ch 17)• Lymph (Ch 20)
Supporting C.T.
• Cartilage– Hyaline, cells in lacunae
• Articular cartilage, symphysis pubis
– Elastic• Ear, larynx
– Fibrocartilage• Intervertebral discs
• Bone (Chapter 5)– Mineral matrix
Study individual types of c.t. in labStudy individual types of c.t. in lab
Membranes = Combination of Membranes = Combination of Epithelia & C.T. Epithelia & C.T.
• Mucous membranes,– Lining of cavities that communicate with exterior
• Serous membranes,– Lining of sealed, internal cavities
• Cutaneous membranes,– Skin
• Know special names of serous membranes depending on location
• Also know difference between “parietal” and “visceral”
Membranes, cont’d
Muscle Tissue Muscle Tissue Three types:
Skeletal
Cardiac
Smooth (not striated)
Skeletal Muscle
•Voluntary
•Heavily striated
•Multinucleate
•periphery of the cell
Cardiac Muscle•Heart (Only)
•Involuntary
•Striated
•Intercalated disks
•Heavily branched
•Single central nucleus
Smooth Muscle• Involuntary
• Esp. digestive system
• No striations
• Very slow
• Single central nucleus
Nervous Tissue (ch 12)
• Neurons– Transmit electrical
impulses
• Neuroglia– Supportive cells of the
nervous system
NeNeural Tissue