Ch04 Histology

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Human Anatomy, First EditionMcKinley & O'Loughlin

Chapter 4 Lecture Outline:

Tissue Levelof Organization


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Tissue Level of OrganizationTissues are groups of similar cells andextracellular products that carry out acommon function.


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Epithelial TissueLines every body surface and all bodycavities.

Forms both the external and internal lining of many organs.Constitutes the majority of glands.Composed of one or more layers of closelypacked cells that form a barrier between twocompartments having different components.Little to no extracellular matrix.No blood vessels penetrate an epithelium.


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Characteristics of Epithelial

Tissue: CellularityComposed almost entirely of cellsbound closely together by differenttypes of cell junctions.


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Tissue: Polarity Apical surface (free, or top, surface)Intercellular junctionsBasal surface (fixed, or bottom, surface)


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Tissue: AttachmentThe basal surface of an epithelium isbound to a thin basement membrane.


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Tissue: AvascularityLack blood vessels.Nutrients obtained either directly acrossthe apical surface or by diffusion acrossthe basal surface.


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Tissue: InnervationSome epithelia are richly innervated todetect changes in the environment atthat body or organ surface.Most nervous tissue is in the underlyingconnective tissue.


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Tissue: Regeneration CapacityFrequently damaged or lost by abrasion and is replaced via high regenerationcapacity.Continual replacement occurs throughthe divisions of the deepest epithelialcells (called stem cells) near its base.


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Functions of Epithelial TissueProtectionRegulation of materials into and out of the organ or tissueProduce secretions

Endocrine glandsExocrine glands


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Functions of Epithelial TissueNerve endings detect changes in theexternal environment at their surface.Continuously supply information to thenervous system concerning touch,pressure, temperature, and pain.


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JunctionsThere are four types of cell junctions:

tight junctionsadhering junctionsdesmosomes

gap junctions


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Exocrine GlandsUsually maintain their contact with theepithelial surface by means of a duct.

Duct secretes materials onto the surface of the skin or onto an epithelial surface liningan internal passageway.


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Classification of Exocrine

GlandsForm and structure (morphology)

simple glands vs. compound glands

Type of secretiontubular vs. acinar ducts

Method of secretiontubuloacinar gland


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Secretion TypesSerous glands produce and secrete a nonviscous,watery fluid, such as sweat, milk, tears, ordigestive juices.Mucus glands secrete mucin, which forms mucuswhen mixed with water.Mixed glands , such as the two pairs of salivaryglands inferior to the oral cavity, contain both

serous and mucus cells, and produce a mixture of the two types of secretions.


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Merocrine Glands Also called eccrine glands, package theirsecretions in structures called secretory

vesicles which travel to the apical surfaceof the glandular cell and release theirsecretion by exocytosis.The glandular cells remain intact and arenot damaged in any way by producing thesecretion.


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Holocrine GlandSecretion is produced through thedestruction of the secretory cell.

Lost cells are replaced by cell division atthe base of the gland.


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Apocrine GlandSecretion occurs with the decapitation of the apical surface of the cell and thesubsequent release of secretory productand some cellular fragments.

Examples: the mammary glands and some

sweat glands in the axillary and pubicregions


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Basic Components of CT All CT share three basic components:

cellsprotein fibersground substance


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Components of CT: Cellsconnective tissue proper containsfibroblasts,

fat contains adipocytes,cartilage contains chondrocytes, andbone contains osteocytes.

Many CTs contain white blood cells suchas macrophages, which phagocytizeforeign materials.


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Components of CT: Protein

FibersMost contains protein fibers throughoutthe tissue.

Strengthen and support connectivetissue.Type and abundance of these fibersvaries depending on function.


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Components of CT: Protein

FibersThree basic types of protein fibers:

collagen fibers are strong and stretch-resistantelastic fibers are flexible and resilientreticular fibers form an interwoven

framework


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Components of CT: Ground

SubstanceCells and the protein fibers reside within amaterial called ground substance .

Nonliving material produced by theconnective tissue cells.Primarily consists of molecules composed of protein and carbohydrate and variable

amounts of water.May be viscous (blood), semisolid (cartilage),or solid (bone).


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Functions of Connective TissuePhysical protectionSupport and structural framework Binding of structuresStorage

Transport


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Classification of Connective

TissueThe connective tissue types presentafter birth are classified into threebroad categories:

connective tissue propersupporting connective tissue

fluid connective tissue


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The Resident Cells of the

Connective Tissue ProperFibroblasts

Adipocytes

Fixed macrophages Mesenchymal cells


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The Wandering Cells of the

Connective Tissue ProperMast cellsPlasma cells

B-lymphocytesMacrophagesLeukocytes


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2 Broad Categories of CTLoose connective tissueDense connective tissue

based on the relative proportions of cells,fibers, and ground substance


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Supporting Connective TissueCartilage and boneForm a strong, durable framework thatprotects and supports the soft bodytissues.Extracellular matrix contains manyprotein fibers and a ground substancethat ranges from semisolid to solid.


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Fluid Connective TissueBlood is a fluid connective tissue composed of cells called formed elements .

erythrocytes (red blood cells)leukocytes (white blood cells)platelets

erythrocytes transport oxygen and carbon dioxide

between the lungs and the body tissuesleukocytes mount an immune responseplatelets are involved with blood clotting


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Muscle TissueResponds to stimulation from thenervous system causing them toshorten.Produce voluntary and involuntarymovement.


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Nervous TissueSometimes termed neural tissue.Consists of neurons, or nerve cells, andglial cells that support, protect, andprovide a framework for neurons.


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NeuronsDetect stimuli, process information quickly,and rapidly transmit electrical impulses from

one region of the body to another.Prominent cell body functions in control;information processing, storage, andretrieval; internal communication.


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NeuronsProcesses extend from the nerve cellbody.

Dendrite Axon


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Ch04 Histology

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