Body Tissues Tissues Groups of cells with similar

Body Tissues • Tissues – Groups of cells with similar structure and function – Four primary types • • Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue

Epithelial Tissues • Locations – Body coverings – Body linings – Glandular tissue • Functions – Protection – Absorption – Filtration – Secretion

Epithelium Characteristics • Cells fit closely together and often form sheets • The apical surface is the free surface of the tissue • The lower surface of the epithelium rests on a basement membrane • Avascular (no blood supply) • Regenerate easily if well nourished

Apical surface Basal surface Simple Apical surface Basal surface Stratified (a) Classification based on number of cell layers Figure 3. 17 a

Classification of Epithelia • Number of cell layers – Simple—one layer – Stratified—more than one layer

Apical surface Basal surface Simple Apical surface Basal surface Stratified (a) Classification based on number of cell layers Figure 3. 17 a

Classification of Epithelia • Shape of cells – Squamous • flattened – Cuboidal • cube-shaped – Columnar • column-like

Figure 3. 17 b

Simple Epithelia • Simple squamous – Single layer of flat cells – Location - usually forms membranes • Lines body cavities • Lines lungs and capillaries – Functions in diffusion, filtration, or secretion in membranes

Air sacs of lungs Nucleus of squamous epithelial cell Basement membrane (a) Diagram: Simple squamous Nuclei of squamous epithelial cells Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (185×). Figure 3. 18 a

Simple Epithelia • Simple cuboidal – Single layer of cube-like cells – Locations • Common in glands and their ducts • Forms walls of kidney tubules • Covers the ovaries – Functions in secretion and absorption; ciliated types propel mucus or reproductive cells

Simple cuboidal epithelial cells Nucleus of simple cuboidal epithelial cell Basement membrane Connective tissue (b) Diagram: Simple cuboidal Photomicrograph: Simple cuboidal epithelium in kidney tubules (250×). Figure 3. 18 b

Simple Epithelia • Simple columnar – Single layer of tall cells – Often includes mucus-producing goblet cells – Location - lines digestive tract – Functions in secretion and absorption; ciliated types propel mucus or reproductive cells

Simple columnar epithelial cell Nucleus of simple columnar epithelial cell Goblet cell Basement membrane Connective tissue Basement membrane (c) Diagram: Simple columnar Photomicrograph: Simple columnar epithelium of the small intestine (430×). Figure 3. 18 c

Simple Epithelia • Pseudostratified columnar – Single layer, but some cells are shorter than others – Often looks like a double layer of cells but all cells rest on the basement membrane – Location - respiratory tract, where it is ciliated – Functions in absorption or secretion

Cilia Pseudostratified epithelial layer Basement membrane (d) Diagram: Pseudostratified (ciliated) columnar Basement membrane Connective tissue Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (430×). Figure 3. 18 d

Stratified Epithelia • Stratified squamous – Cells at the apical surface are flattened – Functions as a protective covering where friction is common – Locations - lining of the: • Skin • Mouth • Esophagus

Nuclei Stratified squamous epithelium Basement membrane (e) Diagram: Stratified squamous Photomicrograph: Stratified squamous epithelium lining of the esophagus (140×). Basement membrane Connective tissue Figure 3. 18 e

Stratified Epithelia • Stratified cuboidal—two layers of cuboidal cells; functions in protection • Stratified columnar—surface cells are columnar, cells underneath vary in size and shape; functions in protection • Stratified cuboidal and columnar – Rare in human body – Found mainly in ducts of large glands

Stratified Epithelia • Transitional epithelium – Composed of modified stratified squamous epithelium – Shape of cells depends upon the amount of stretching – Functions in stretching and the ability to return to normal shape – Location - lines organs of the urinary system

Basement membrane Transitional epithelium Connective tissue (f) Diagram: Transitional Photomicrograph: Transitional epithelium lining of the bladder, relaxed state (215×); surface rounded cells flatten and elongate when the bladder fills with urine. Figure 3. 18 f

Glandular Epithelium • Gland – One or more cells responsible for secreting a particular product – Secretions contain protein molecules in an aqueous (water-based) fluid

Glandular Epithelium • Two major gland types – Endocrine gland • Ductless since secretions diffuse into blood vessels • All secretions are hormones – Exocrine gland • Secretions empty through ducts to the epithelial surface • Include sweat and oil glands

Terms to understand • • • Simple Stratified Cell shapes Microvilli Cilia Goblet cells

Workbook #17, page 45 • Find all illustrations of epithelium

Workbook #20, page 47 • Think of 3 -4 more identification statements

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1. (arrow) what is this structure at the free surface? 2. (arrow) name the specific cell 3 What specific tissue is this?

4. Name specific tissue. 5. Where is it located?

6. Name specific tissue lining the tubule 7. What is the dark black line? 8. Name the blue-stained tissue.

Epithelium: identify by function Protection Modified for excellent absorption Secretion Can distend, then return to original shape/layers • Fabulous for diffusion • •

Epithelium: identify by location • • Lines air sacs of lungs: Lines respiratory passages: Lines bladder & urinary passages: Lines mouth, throat, anal canal, vagina: Forms outer layer of skin: Lines digestive tract: Forms most glands:

This tissue has cells that are flat, and all cells touch the basement membrane. – Simple cuboidal – Simple squamous – Stratified squamous – Transitional

List 5 general characteristics of epithelial tissue.