Loose Connective Tissue (Areolar Tissue)

Connective Tissue

• Loose connective tissue (areolar tissue) is the most widely distributed connective tissue type in the vertebrate body.
• It consists of various cells, including fibroblasts, macrophages, mast cells, leukocytes, and fat cells.
• All three types of fibers are found in this tissue, which are loosely arranged and wavy in nature.
• This tissue binds epithelia and the underlying tissue, holding organs in place.
• It is found under the skin and throughout the body.

Fibrous Connective Tissue (Dense Connective Tissue)

• This tissue is densely packed with collagen fibers.
• The matrix is relatively reduced and contains fewer cells (fibrocytes).
• It is found in tendons (attaching muscle to bones) and ligaments (connecting bones and joints) where tensile strength is required.

Adipose Tissue

• This tissue is packed with adipose cells, each containing a large fat droplet.
• It is a specialized type of loose connective tissue that pads and insulates the body and stores fuel as fat molecules.
• It is found under the skin, where it acts as a thermal insulator and energy store.

Blood Tissue

• This tissue is a specialized connective tissue where the matrix is not secreted by the cells and fibers are formed only during blood clotting process.
• The extracellular matrix of the blood is liquid, known as plasma.
• Plasma contains salts, water, and dissolved proteins.
• Red blood cells (transport respiratory gases), white blood cells (defense), and platelets (blood clotting) are suspended in the blood plasma.
• Main functions of blood tissues include transport of materials, protection, and osmoregulation.

Cartilage

• This tissue consists of a matrix composed of chondroitin sulphate, a rubbery protein-carbohydrate complex.
• Collagen fibers and chondrocytes are embedded in the matrix.
• Chondrocytes secrete chondroitin sulphate and collagen fibers.
• This tissue provides support and flexibility in places such as the trachea, intervertebral discs.

Bone

• It is a mineralized connective tissue.
• The matrix consists of collagen fibers and inorganic salts, such as calcium, magnesium, and phosphate ions.
• Cells are osteoblasts (bone-forming cells) and osteocytes (mature bone cells that maintain bone tissue).
• Osteocytes are enclosed within lacunae.
• The mammalian hard bone has repeating units called osteons.
• Each osteon has a concentric layer of mineralized materials.
• At the center of the osteon is a central canal containing blood vessels and nerves.
• This tissue forms the endoskeleton of most vertebrates and provides support and strength to the body.

Muscle Tissue

• Muscle tissue is responsible for movement.
• The cells in the muscle tissue are composed of actin and myosin proteins.
• This tissue is able to contract and relax.
• There are three basic types of muscle tissues found in the vertebrate animal body: smooth muscle, skeletal muscle, and cardiac muscle tissues.

Smooth Muscle Tissue

• The cells of the smooth muscle tissue are spindle-shaped and uninucleated.
• Cells lack striations.
• This tissue is responsible for involuntary body functions (e.g., churning of stomach, constriction of arteries).
• It is found in the digestive tract, urinary bladder, arteries, and other internal organs.