Connective Tissue

• Connective tissues provide support, protection, and structure to the body.

Types of Connective Tissues

Loose Connective Tissue

Areolar Tissue

• Structure: Contains a loose arrangement of fibers and various cell types.
• Location: Widely distributed under epithelia, surrounds capillaries.
• Function: Provides cushioning, binds tissues, and allows for nutrient diffusion.

Adipose Tissue

• Structure: Comprised mainly of adipocytes filled with fat droplets.
• Location: Under the skin (subcutaneous layer), around kidneys and eyeballs, within the abdomen, and in breasts.
• Function: Stores energy insulates against heat loss, and cushions organs.

Reticular Tissue

• Structure: Network of reticular fibers with supportive cells.
• Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).
• Function: Provides a supportive framework for soft organs.

Dense Connective Tissue

Regular Connective Tissue (Dense)

• Structure: Parallel collagen fibers with a few elastic fibers; major cell type is fibroblasts.
• Location: Tendons, ligaments, and aponeuroses.
• Function: Attaches muscles to bones or to muscles and bones to bones; withstands great tensile stress in one direction.

Irregular Connective Tissue (Dense)

• Structure: Irregularly arranged collagen fibers with some elastic fibers; major cell type is fibroblasts.
• Location: Dermis of the skin, submucosa of digestive tract, fibrous capsules of organs and joints.
• Function: Withstands tension exerted in many directions; provides structural strength.

Elastic Connective Tissue

• Structure: Dense regular connective tissue containing a high proportion of elastic fibers.
• Location: Walls of large arteries, within certain ligaments associated with the vertebral column, within the walls of the bronchial tubes.
• Function: Allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration.

Specialized Connective Tissues

Cartilage

Hyaline Cartilage:

• Structure: Amorphous but firm matrix with collagen fibers; chondrocytes lie in lacunae.
• Location: Embryonic skeleton ends of long bones in joint cavities, costal cartilages of the ribs, nose, trachea, and larynx.
• Function: Supports and reinforces; serves as a resilient cushion; resists compressive stress.

Elastic Cartilage:

• Structure: Similar to hyaline cartilage, but more elastic fibers in matrix.
• Location: External ear (pinna), epiglottis.
• Function: Maintains the shape of a structure while allowing great flexibility.

Fibrocartilage:

• Structure: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate.
• Location: Intervertebral discs, pubic symphysis, discs of knee joint.
• Function: Tensile strength allows it to absorb compressive shock.

Bone (Osseous Tissue):

• Structure: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized.
• Location: Bones
• Function: Supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis).

Blood:

• Structure: Red and white blood cells in a fluid matrix (plasma).
• Location: Contained within blood vessels.
• Function: Transports respiratory gases, nutrients, wastes, and other substances.

Structure

• Connective tissues have fewer cells and more extracellular matrix than other tissues.
• The extracellular matrix consists of protein fibers (collagen, elastin, reticular) and ground substance.

Location

• Connective tissue proper: Beneath the skin, around organs, tendons, ligaments, and bone marrow.
• Specialized connective tissue: Joints, rib cage, ear, and skeletal system.
• Fluid connective tissue: Blood vessels and lymphatic vessels.

Functions

• Support: Connective tissues bind and support other tissues and organs.
• Protection: They protect and cushion organs.
• Insulation: Adipose tissue stores energy and insulates the body.

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