•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