Connective tissues

• The special tissues which link and support other tissues/organs of the body are called connective tissues.
• Connective tissues include cartilage, bone, adipose, and blood.
• In all connective tissues except blood, the cells secrete fibres of structural proteins called collagen or elastin.
• Connective tissues are classified into three types
• Loose connective tissue
• Dense connective tissue and
• Specialized connective tissue
• Loose connective tissue has cells and fibres loosely arranged in a semi-fluid ground substance.

For example-

Areolar tissue present beneath the skin contains fibroblasts, macrophages.

Fig. Areolar tissue

 Adipose tissue is located mainly beneath the skin, which is specialized to store fats.

Fig. Adipose tissue

• Fibres and fibroblasts are compactly packed in the dense connective tissues.
• Orientation of fibres shows a regular or irregular pattern and are called dense regular and dense irregular tissues, respectively.
• In the dense regular connective tissues, the collagen fibres are present in rows between many parallel bundles of fibres.

Examples –

• Tendons which attach skeletal muscles to bones
• Ligaments which attach one bone to another.

Fig. Tendons and ligaments

• Dense irregular connective tissue has fibroblasts and many fibres oriented differently and are present in the skin.
• Cartilage, bone and blood are types of specialized connective tissue.

Cartilage

• The intercellular material of cartilage is solid and pliable and resists compression.
• Cells of this tissue called as chondrocytes are enclosed in small cavities within the matrix secreted by them.
• Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, etc.

Fig. Cartilage

Bone

• Bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres which give bone its strength.
• Bones support and protect softer tissues and organs.
• The bone cells (osteocytes) are present in the spaces called
• They interact with skeletal muscles attached to them to bring about movements.
• The bone marrow in some bones is the site of production of blood cells.

Fig. Bone

Blood

• Blood is a fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets.
• Blood is the main circulating fluid that helps in the transport of various substances.

Fig. Blood