Chapter 3 Body Tissues He he he he he…

Body Tissues Cells are specialized for particular functions Tissues - Groups of cells with similar structure and function Four primary types Epithelium Connective tissue Nervous tissue Muscle

Epithelial Tissues Locations Functions Characteristics Body coverings Body linings Glandular tissue Functions Protection Absorption Filtration Secretion Characteristics Cells close together Cells have free apical surface Bottom surface is basement membrane Avascular – no blood supply Regenerate easily

Classification of Epithelium 1. Based on # of cell layers Simple – one layer Stratified – more than one layer 2. Shape of cells Squamous – flattened Cuboidal – cube-shaped Columnar – column-like

Simple Epithelium 1. Simple squamous Single layer of flat cells Usually forms membranes Lines body cavities Lines lungs and capillaries

2. Simple cuboidal Single layer of cube-like cells Common in glands and their ducts Forms walls of kidney tubules Covers the ovaries

3. Simple columnar Single layer of tall cells Often includes goblet cells, which produce mucus Lines digestive tract

4. Pseudostratified Single layer, but some cells are shorter than others Often looks like a double cell layer Sometimes ciliated, such as in the respiratory tract May function in absorption or secretion

Stratified Epithelium 1. Stratified squamous Cells at the free edge are flattened Found as a protective covering where friction is common Locations Skin Mouth Esophagus

Rare in human body 2. Stratified cuboidal 3. Stratified columnar Two layers of cuboidal cells 3. Stratified columnar Surface cells are columnar, cells underneath vary in size and shape Both are: Found mainly in ducts of large glands

Glands Gland – one or more cells that secretes a particular product 2 types 1. Endocrine gland Ductless Secretes hormones 2. Exocrine gland Empty through ducts to surface Include sweat and oil glands

4. Transitional epithelium Shape of cells depends upon the amount of stretching Lines organs of the urinary system

Connective Tissue Most abundant and widely distributed Some have good blood supply (vascularized) Some don’t (avascular) All have extracellular matrix – nonliving material surrounding cells Functions Binds tissues together Supports Protects

Extracellular Matrix Two parts Ground substance – mostly water along with adhesion proteins and polysaccharide molecules Fibers Produced by the cells 3 types Collagen fibers Elastic fibers Reticular fibers

Connective Tissue Types 1. Bone (osseous tissue) Bone cells in lacunae (cavities) Hard matrix of calcium salts A lot of collagen fibers Protect & supports body

Connective Tissue Types 2. Hyaline cartilage Most common cartilage Lots of collagen fibers Rubbery matrix Fetal skeleton & ribs

Connective Tissue Types 3. Elastic cartilage Provides elasticity found in external ear, epiglottis, & trachea

Connective Tissue Types 4. Fibrocartilage Highly compressible forms cushion-like discs between vertebrae

Connective Tissue Types 5. Dense Main matrix element is collagen fibers Cells are fibroblasts Tendon – muscle to bone Ligaments – bone to bone

Connective Tissue Types 6. Areolar Most widely distributed Soft, pliable tissue Contains all fiber types Can soak up excess fluid Think “airy”

Connective Tissue Types 7. Adipose Similar to areolar with fat globules Many cells contain large lipid deposits Functions Insulates body Protects organs Fuel storage

Connective Tissue Types 8. Reticular Delicate network of fibers Forms network of lymphoid organs Lymph nodes Spleen Bone marrow

Connective Tissue Types 9. Blood cells & fluid matrix Fibers visible during clotting Transports materials

Muscle Tissue Function = produce movement 3 types Skeletal muscle move muscles of skeleton Cardiac muscle only found in heart Smooth muscle found in organs & vessels

Muscle Type Type of Control? Striations? How many nuclei? Skeletal Voluntary Yes Many per cell Cardiac Involuntary Yes & intercalated disks 1 per cell Smooth No

Nervous Tissue Neurons and nerve support cells Function = send impulses to other areas of the body Irritability – able to respond to stimuli Conductivity – conducts messages