Exercise 6 Classification of Tissues

What is a tissue? Group of cells Group of cells Similar structure & function Similar structure & function

4 Major Tissue Types Epithelial Epithelial Connective Connective Muscle Muscle Nervous Nervous

Epithelial Tissues Cover surfaces Cover surfaces Simple or stratified? Simple or stratified? Simple = 1 layer of cells attached to basement membrane Simple = 1 layer of cells attached to basement membrane Stratified = 2 or more layers Stratified = 2 or more layers Named by “shape” of top layer (apical layer), not bottom (basal layer) Named by “shape” of top layer (apical layer), not bottom (basal layer)

Epithelial Tissues Shapes of Epithelial Cells Shapes of Epithelial Cells Squamous Squamous Flattened Flattened Cuboidal Cuboidal Cubelike Cubelike Columnar Columnar Column-shaped Column-shaped Simple squamous Stratified squamous Simple cuboidal Stratified cuboidal Simple columnar Stratified columnar

Epithelial Tissues Simple squamous epithelium Simple squamous epithelium

Epithelial Tissues Simple cuboidal epithelium Simple cuboidal epithelium Fig 4-4

Epithelial Tissues Simple columnar epithelium Simple columnar epithelium

Epithelial Tissues Pseudostratified columnar epithelium Pseudostratified columnar epithelium Actually simple columnar: nuclei are at different levels so there appears to be more than one layer Actually simple columnar: nuclei are at different levels so there appears to be more than one layer Fig 4-5

Epithelial Tissues Stratified squamous epithelium Stratified squamous epithelium

Epithelial Tissues Stratified cuboidal epithelium Stratified cuboidal epithelium

Epithelial Tissues Stratified columnar epithelium Stratified columnar epithelium Fig 4-5

Epithelial Tissues Fig 4-4 Transitional epithelium Transitional epithelium Stratified squamous epithelium formed of rounded cells that can slide over one another, allowing the organ to stretch: urinary system only Stratified squamous epithelium formed of rounded cells that can slide over one another, allowing the organ to stretch: urinary system only

CONNECTIVE TISSUES Embryonic connective tissue Embryonic connective tissue mesenchyme mesenchyme Loose connective tissue Loose connective tissue Areolar, adipose, reticular Areolar, adipose, reticular Dense connective tissue Dense connective tissue Dense irregular, dense regular Dense irregular, dense regular Supportive connective tissue Supportive connective tissue Hyaline, elastic, fibrocartilages; bone Hyaline, elastic, fibrocartilages; bone Fluid connective tissue Fluid connective tissue Blood, lymph Blood, lymph

CONNECTIVE TISSUES Differing proportions of cells & fibers to “matrix” Differing proportions of cells & fibers to “matrix” Matrix Matrix noncellular, nonliving material between connective tissue cells noncellular, nonliving material between connective tissue cells Different proportions  strength of tissue Different proportions  strength of tissue

Classification of Connective Tissues Fig. 4-8 Many cell types Syrupy ground substance Distinct cell types Watery matrix Less diverse cell types More fibrous matrix

Embryonic Connective Tissue Mesenchyme Mesenchyme Many star-shaped stem cells Gives rise to all other connective tissues Not present in adults Fig. 4-10

Loose Connective Tissue: Areolar

Adipose Connective Tissue Adipose connective tissue Adipose connective tissue (fat) Insulation for the body’s tissues Food storage Little matrix Fig. 4-11

Reticular Connective Tissue Reticular connective tissue Reticular connective tissue Reticular fibers form a soft internal skeleton for support

Dense Irregular Collagenous Connective Tissue

Dense Irregular Elastic Connective Tissue

Dense Regular Collagenous Connective Tissue Dense regular connective tissue Dense regular connective tissue Fibers in one direction Tendons, ligaments of body’s joints Fig. 4-12

Dense Regular Elastic Connective Tissue

Hyaline Cartilage Connective Tissue

Elastic Cartilage Connective Tissue Elastic Cartilage Elastic Cartilage Maintains shape, but flexible Many elastic fibers

Fibrocartilage Connective Tissue Fibrocartilage Fibrocartilage Strength, shock absorption Dense network of collagen fibers

Osseous Connective Tissue Osseous Connective Tissue (Bone) Osseous Connective Tissue (Bone) Support, protection

Blood Connective Tissue

Lymph Connective Tissue Lymph Lymph Fluid of the lymphatic system Like plasma without the big proteins Immune defense

MUSCLE TISSUES Skeletal Skeletal Cardiac Cardiac Smooth Smooth

Skeletal Muscle Tissue

Cardiac Muscle Tissue Only in the heart Only in the heart Striated tissue Striated tissue Under involuntary control Under involuntary control Branching, uninucleate cells with intercalated discs Branching, uninucleate cells with intercalated discs

Smooth Muscle Tissue Found in the walls of hollow organs (digestive, urinary tracts; blood vessels) Found in the walls of hollow organs (digestive, urinary tracts; blood vessels) 2 layers at right angles for contraction/dilation of the organ cavity Not striated tissue Uninucleate, spindle-shaped cells

Muscle typeCellsstriationsVoluntary? Cardiacbranched Uninucleate Intercalated discs yesno SkeletalLong fibers multinucleate yes SmoothSpindle shaped 1 nucleus no

NERVOUS TISSUE Brain, spinal cord, nerves Brain, spinal cord, nerves 2 basic cell types: 2 basic cell types: Neuroglia cells Protect, support, insulate neurons Neurons Receive stimuli & conduct nerve impulses