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Chapter 4: The Tissue Chapter 4: The Tissue
Level of OrganizationLevel of Organization
There are 4 types of tissues – We will only study epithelial now.
Epithelial TissueEpithelial Tissue
Covers exposed surfacesCovers exposed surfaces– ExamExample: ple: The skinThe skin
Lines internal passageways Lines internal passageways – Example: Example: The intestinesThe intestines
Forms glandsForms glands– Example: Sweat glandsExample: Sweat glands
KEY CONCEPTKEY CONCEPT
Tissues are collections of cells and cell Tissues are collections of cells and cell products that perform specific, limited products that perform specific, limited functionsfunctions
4 tissue types form all the structures of the 4 tissue types form all the structures of the human body: human body: – epithelial, connective, muscle, and neuralepithelial, connective, muscle, and neural
Epithelial TissuesEpithelial Tissues
EpitheliaEpithelia: : – layers of cells covering internal or external layers of cells covering internal or external
surfacessurfaces
GlandsGlands: : – structures that produce secretionsstructures that produce secretions
What are the special structures and What are the special structures and functions functions
of epithelial tissues?of epithelial tissues?
Characteristics of EpitheliaCharacteristics of Epithelia
1.1. Cellularity (Cellularity (cell junctionscell junctions))
2.2. Polarity (Polarity (apicalapical and and basalbasal surfaces) surfaces)
3.3. Attachment (Attachment (basal laminabasal lamina))
4.4. Avascularity Avascularity
5.5. RegenerationRegeneration
Functions of Epithelial TissueFunctions of Epithelial Tissue
1.1. Provide physical protectionProvide physical protection
2.2. Control permeabilityControl permeability a. Move fluids a. Move fluids overover the epithelium (protection) the epithelium (protection)
b. b. Move fluids Move fluids throughthrough the epithelium (permeability) the epithelium (permeability)
3.3. Provide sensationProvide sensation
4.4. Produce specialized secretions Produce specialized secretions ((glandular glandular epitheliumepithelium))
a. Produce a. Produce secretionssecretions (protection and messengers) (protection and messengers)
Free Surface and Free Surface and Attached SurfaceAttached Surface
Polarity:Polarity: – apical and apical and
basolateral basolateral surfacessurfaces
Increasing Surface AreaIncreasing Surface Area
MicrovilliMicrovilli increase absorption or secretion increase absorption or secretion CiliaCilia (ciliated epithelium) move fluids (ciliated epithelium) move fluids
Effective BarriersEffective Barriers
Physical integrity is maintained by:Physical integrity is maintained by:– intercellular connectionsintercellular connections– attachment to basal laminaattachment to basal lamina– maintenance and repairmaintenance and repair
Intercellular ConnectionsIntercellular Connections
Support and Support and communicationcommunication
Large ConnectionsLarge Connections
CAMsCAMs (cell adhesion molecules): (cell adhesion molecules):– transmembrane proteinstransmembrane proteins
Intercellular cementIntercellular cement::
Cell JunctionsCell Junctions
Form bonds with other cells or extracellular Form bonds with other cells or extracellular material:material:– tight junctionstight junctions– gap junctionsgap junctions– desmosomesdesmosomes
Tight JunctionsTight Junctions
Between 2 cell Between 2 cell membranesmembranes
Gap JunctionsGap Junctions
Allow rapid Allow rapid communicationscommunications
DesmosomesDesmosomes
CAMsCAMs,, dense dense areasareas, and , and intercellular intercellular cementcement
Attachment to Basal LaminaAttachment to Basal Lamina
HemidesmosomesHemidesmosomes
Repairing and Repairing and Replacing EpitheliaReplacing Epithelia
Epithelia are replaced by division of Epithelia are replaced by division of germinative cellsgerminative cells ( (stem cellsstem cells))– Continuous Continuous
Near Near basal laminabasal lamina
Classes of EpitheliaClasses of Epithelia
Based on shape and layersBased on shape and layers
LayersLayers
Simple epitheliumSimple epithelium: : – single layer of cellssingle layer of cells
Stratified epitheliumStratified epithelium::– several layers of cellsseveral layers of cells
Cell ShapeCell Shape
Squamous epitheliaSquamous epithelia::– Thin, flat, irregular shaped (fish scale)Thin, flat, irregular shaped (fish scale)
Cuboidal epitheliaCuboidal epithelia::– square shaped (cube)square shaped (cube)
Columnar epitheliaColumnar epithelia::– tall shaped (column)tall shaped (column)
Simple Squamous EpitheliumSimple Squamous Epithelium
Stratified Squamous EpitheliumStratified Squamous Epithelium
Cuboidal EpitheliaCuboidal Epithelia
Simple cuboidal epithelium: Example – Kidney tubulesSimple cuboidal epithelium: Example – Kidney tubules– secretion and absorptionsecretion and absorption
Cuboidal EpitheliaCuboidal Epithelia
Stratified cuboidal epithelia: Sweat gland ductsStratified cuboidal epithelia: Sweat gland ducts– sweat and mammary ductssweat and mammary ducts
Transitional EpitheliumTransitional Epithelium
Urinary bladderUrinary bladder
Columnar EpitheliaColumnar Epithelia
Simple columnar epithelium: Intestinal LiningSimple columnar epithelium: Intestinal Lining– absorption and secretionabsorption and secretion
Columnar EpitheliaColumnar Epithelia
Pseudostratified columnar epithelium: TracheaPseudostratified columnar epithelium: Trachea– cilia movementcilia movement
Columnar EpitheliaColumnar Epithelia
Stratified columnar epithelium: Salivary Gland DuctStratified columnar epithelium: Salivary Gland Duct– protectionprotection
Glandular EpitheliaGlandular Epithelia
EndocrineEndocrine and and exocrineexocrine glands glands
Endocrine GlandsEndocrine Glands
Release hormones:Release hormones:– into into interstitial fluidinterstitial fluid– no ductsno ducts
Exocrine GlandsExocrine Glands
Produce secretions:Produce secretions:– onto onto epithelial surfacesepithelial surfaces– through through ductsducts
Modes of Secretion – Exocrine Modes of Secretion – Exocrine Glands Glands
Merocrine secretionMerocrine secretion
Modes of SecretionModes of Secretion
Apocrine secretionApocrine secretion
Modes of SecretionModes of Secretion
Holocrine secretionHolocrine secretion
Types of Secretions – Exocrine Types of Secretions – Exocrine GlandsGlands
Serous glandsSerous glands::– watery secretionswatery secretions
Mucous glandsMucous glands::– secrete mucinssecrete mucins
Mixed exocrine glandsMixed exocrine glands::– both serous and mucousboth serous and mucous
Gland Structure – Exocrine GlandsGland Structure – Exocrine Glands
Exocrine glands can be classified as:Exocrine glands can be classified as:– unicellular unicellular glandsglands– multicellularmulticellular glands glands
Unicellular GlandsUnicellular Glands
Goblet cellsGoblet cells are the only unicellular exocrine are the only unicellular exocrine glands:glands:– scattered among epitheliascattered among epithelia– e.g.,e.g., in intestinal lining in intestinal lining
Structure of Multicellular Exocrine Structure of Multicellular Exocrine GlandsGlands
Structural classes of exocrine glandsStructural classes of exocrine glands
Structure of Multicellular Exocrine Structure of Multicellular Exocrine GlandsGlands