- 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.
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.
- 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.
- 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.
- 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.
- 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.