Tissues and tissue types Tissues are: Collections of specialized cells and cell products organized to perform a limited number of functions Histology = study of tissues The four tissue types are: Epithelial Connective Muscular Nervous

Epithelial tissue Includes glands and epithelium Is avascular Glands are secretory Is avascular Forms a protective barrier that regulates permeability Cells may show polarity

Functions of epithelium Physical protection Control permeability Provide sensation Produce specialized secretions

Specializations of epithelium Perform secretory functions Perform transport functions Maintain physical integrity Ciliated epithelia move materials across their surface

The Polarity of Epithelial Cells

Maintaining the integrity of epithelium Cells attach via cell adhesion molecules (CAM) Cells attach at specialized cell junctions Tight junctions Desmosomes Gap junctions

Intercellular connections

Structure of typical epithelium Basal lamina attaches to underlying surface Lamina lucida Lamina densa Germinative cells replace short-lived epithelial cells

Classification of epithelia Number of cell layers Simple Stratified Shape of apical surface cells Squamous Cuboidal Columnar

Squamous Epithelia

Cuboidal Epithelia

Cuboidal Epithelia

Transitional Epithelium

Columnar Epithelia

Columnar Epithelia

Columnar Epithelia

Glandular epithelia Exocrine glands Endocrine glands Secrete through ducts onto the surface of the gland Endocrine glands Release hormones into surrounding fluid

Glandular secretions can be: Merocrine (product released through exocytosis) Apocrine (involves the loss of both product and cytoplasm) Holocrine (destroys the cell)

Mechanisms of Glandular Secretion

Glands Unicellular Multicellular Individual secretory cells Organs containing glandular epithelium Classified according to structure

A Structural Classification of Exocrine Glands

Connective tissue functions: Establishing a structural framework Transporting fluids and dissolved materials Protecting delicate organs Supporting, surrounding and interconnecting tissues Storing energy reserves Defending the body from microorganisms

A Classification of Connective Tissues

Connective tissues contain Specialized cells Matrix Composed of extracellular protein fibers and a ground substance

Connective tissue proper Contains varied cell populations Contains various fiber types A syrupy ground substance

Fluid connective tissue Contains a distinctive cell population Watery ground substance with dissolved proteins Two types Blood Lymph

Supporting connective tissues Less diverse cell population Dense ground substance Closely packed fibers Two types Cartilage Bone

Connective tissue proper Contains fibers, a viscous ground substance, and a varied cell population Fibroblasts Macrophage Adipocytes Mesenchymal cells Melanocytes Mast cells Lymphocytes Microphages

Connective tissue proper Three types of fiber Collagen fibers Reticular fibers Elastic fibers

Connective tissue proper Classified as loose or dense Loose Embryonic mesenchyme, mucous connective tissues Areolar tissue Adipose tissue Reticular tissue Dense Dense regular CT Dense irregular CT

The Cells and Fibers of Connective Tissue Proper

Connective Tissue in Embryos

Adipose and Reticular Tissues

Dense Connective Tissues

Dense Connective Tissues

Dense Connective Tissues

Fluid connective tissues Distinctive collections of cells in a fluid matrix Blood Formed elements and plasma Red blood cells, white blood cells and platelets Arteries carry blood away, veins carry to the heart Capillaries allow diffusion into the interstitial fluid Lymph Interstitial fluid entering the lymphatic vessels

Formed Elements of the Blood

Supporting connective tissues Cartilage and bone support the rest of the body Cartilage Grows via interstitial and appositional growth Matrix is a firm gel containing chondroitin sulfate Cells called chondrocytes Cells found in lacunae Perichondrium separates cartilage from surrounding tissues Three types: hyaline, elastic and fibrocartilage

The Perichondrium and Types of Cartilage

The Perichondrium and Types of Cartilage

The Perichondrium and Types of Cartilage

Bone, or osseus tissue Has osteocytes Little ground substance Depend on diffusion through canaliculi for nutrients Little ground substance Dense mineralized matrix Surrounded by periosteum

Bone

Membranes are simple organs Form a barrier Composed of epithelium and connective tissue Four types Cutaneous Synovial Serous Mucous

Membranes

Mucous membranes Line cavities that communicate with the exterior Contain lamina propria

Serous membranes Line sealed internal cavities Form transudate

Cutaneous membrane Synovial membrane Covers the body surface Incomplete lining within joint cavities

Organs and systems are interconnected Network of connective tissue proper consisting of Superficial fascia Deep fascia Subserous fascia

The Fasciae

Muscle tissue Specialized for contraction Three types Skeletal Cardiac Smooth

Muscle Tissue

Muscle Tissue

Muscle Tissue

Skeletal muscle Cells are multinucleate Striated voluntary muscle Divides via satellite cells

Cardiac muscle Cardiocytes occur only in the heart Striated involuntary muscle Relies on pacemaker cells for regular contraction

Smooth muscle tissue Non-striated involuntary muscle Can divide and regenerate

Neural tissue Conducts electrical impulses Conveys information from one area to another

Neural tissue cells Neurons Neuroglia Transmit information Support neural tissue Help supply nutrients to neurons

Neural Tissue

Neural anatomy Cell body Dendrites Axon (nerve fiber) Carries information to other neurons

Inflammation and regeneration Injured tissues respond in coordinated fashion Homeostasis restored by inflammation and regeneration

Inflammatory response Isolates injured area Damaged cells, tissue components and dangerous microorganisms removed Infection avoided Regeneration restores normal function

An Introduction to Inflammation

Aging and tissue repair Change with age Repair and maintenance less efficient Structure altered Chemical composition altered

Aging and cancer incidence Incidence of cancer increases with age 70-80% of all cases due to exposure to chemicals or environmental factors

Changes in a Tissue under Stress