Chapter 4: Tissues. Epithelial Tissue Covers exposed surfaces –Example: The skin Lines internal...
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Transcript of Chapter 4: Tissues. Epithelial Tissue Covers exposed surfaces –Example: The skin Lines internal...
Chapter 4: Tissues Chapter 4: Tissues
Epithelial TissueEpithelial Tissue
Covers exposed surfacesCovers exposed surfaces– Example: The skinExample: The skin
Lines internal passageways Lines internal passageways – Example: The intestinesExample: The 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
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
-respiratory tract, digestive tract-respiratory tract, digestive tract CiliaCilia (ciliated epithelium) move fluids (ciliated epithelium) move fluids
-injury to cilia – smoking, abrasion-injury to cilia – smoking, abrasion
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
Prevents passage Prevents passage of water and solutesof water and solutes
Gap JunctionsGap Junctions
Allow rapid Allow rapid communicationscommunications
Allows ions and Allows ions and small molecules to small molecules to pass throughpass through
Held together by Held together by channel proteinschannel proteins
DesmosomesDesmosomes
CAMsCAMs,, dense dense areasareas, and , and intercellular intercellular cementcement
Ties cells Ties cells together, together, helps to helps to stabilize cell stabilize cell shapeshape
Attachment to Basal LaminaAttachment to Basal Lamina
Hemidesmosomes – half of a desmosome, Hemidesmosomes – half of a desmosome, attaches cell to basal laminaattaches cell to basal lamina
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
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– Tears, milk, enzymes into digestive tract, Tears, milk, enzymes into digestive tract,
perspiration on skinperspiration on skin
Modes of Secretion – Exocrine Modes of Secretion – Exocrine Glands Glands
Merocrine secretion – produced in Golgi Merocrine secretion – produced in Golgi apparatus, released by vesicles (exocytosis)apparatus, released by vesicles (exocytosis)
Modes of SecretionModes of Secretion
Apocrine secretion – produced by Golgi apparatus, Apocrine secretion – produced by Golgi apparatus, released by shedding cytoplasmreleased by shedding cytoplasm
Modes of SecretionModes of Secretion
Holocrine secretion – released by cells burstingHolocrine secretion – released by cells bursting
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