Tissues

• Connective tissues are the most abundant tissues of complex animals.
• All connective tissues except blood tend to secrete structural proteins called collagen or elastin.
• There are different types of connective tissues like Loose Connective tissue, Dense Connective tissue, and Specialized Connective tissue.

Structure:

• The cells of connective tissue are living, separated from each other i.e. loosely spaced and low in number.
• The cells of connective tissue are loosely spaced and embedded in an intercellular matrix.
• The matrix may be jelly like, fluid, dense or rigid.
• The space between cells is filled with a non-living matrix which may be solid as in bone and cartilage and fluid as in the blood.
• Fibrous connective tissue is strong and is found in areas like ligaments, which basically connects bones to one another.

Types of Connective Tissue:

In animals, there are following five types of connective tissues:

Blood:

• Blood has a fluid (liquid) matrix called plasma, in which red blood corpuscles (RBCs), white blood corpuscles (WBCs) and platelets are suspended.  The plasma contains proteins, salts and hormones.

Functions:

• Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.

Bones:

• It forms the framework that supports the body.
• It is a strong and nonflexible tissue. Bone cells are composed of calcium and phosphorus compounds.

Ligaments and Tendons:

• Tendons connect muscles to bones. Tendons are fibrous tissue. They have great strength but limited flexibility.

• Ligaments are elastic structures which connect bones to bones. This tissue is highly elastic. It has considerable strength.

Differences between tendon and ligament

Cartilage

• Cartilage has widely spaced cells. It is composed of proteins and sugars. Cartilage smoothens bone surfaces at joints.
• Occurrence: They are present in the nose, ear, trachea and larynx.

Areolar or Loose Connective Tissue

• It is the simplest and most widely distributed connective tissue.
• It is found between the skin and muscles,
• It fills spaces inside organs and is found around muscles, blood vessels and nerves.

Functions:

• It acts as a supporting and packing tissue between organs lying in the body cavity.
• It helps in repair of tissues after an injury.
• It also helps in combating foreign toxins.
• It fixes skin to underlying muscles.

Adipose Tissue

• Adipose tissue is basically an aggregation of fat cells.
• Each fat cell is rounded or oval in shape and contains a large droplet of fat that almost fills it.
• Adipose tissue is found below the skin and between internal organs.
• The cells of this tissue are filled with fat globules.

Functions:

• Serves as a fat reservoir
• Keeps visceral organs in position
• Forms shock-absorbing cushions around kidneys and eye balls
• Provides shape to the limbs and the body
• Acts as an insulator being a poor conductor of heat, it reduces heat loss from body.