Epithelial tissue. Connective tissue

Learning Objectives Identify the four major tissue types and describe their functions. Describe the relationship between form and function for each tissue type. Discuss the types and functions of epithelial tissues. Compare the structure and function of connective tissues.

Learning Objectives Explain the structure and function of the four types of membrane. Describe the three types of muscle tissue and the structural features of each. Discuss the basic structure and role of neural tissue.

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 Tissues of the Body: An Introduction Tissues and tissue types

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

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

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

The Polarity of Epithelial Cells

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

Intercellular connections Animation: check tutorials

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

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

Squamous Epithelia

Cuboidal Epithelia

Transitional Epithelium

Columnar Epithelia

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

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

Mechanisms of Glandular Secretion Animation: Mechanisms of glandular secretion (check tutorial)

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

A Structural Classification of Exocrine Glands

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 Connective Tissues Connective tissue functions:

A Classification of Connective Tissues

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

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

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

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

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 Connective tissue proper

The Cells and Fibers of Connective Tissue Proper

Connective Tissue in Embryos

Adipose and Reticular Tissues

Dense 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 Fluid connective tissues

Formed Elements of the Blood

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 Supporting connective tissues

The Perichondrium and Types of Cartilage

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

Bone

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

Membranes

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

Line sealed internal cavities Form transudate Serous membranes

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

Network of connective tissue proper consisting of –Superficial fascia –Deep fascia –Subserous fascia The Connective Tissue Framework of the Body Organs and systems are interconnected