Connective Tissues: Types, Components, Functions & Disorders

Connective tissue is a type of tissue which acts as a connection between several organs and various parts of the body. Several connective tissues are blood, bones, muscles, tendons, etc. 

• The major function of connective tissue includes binding and supporting different parts of the body. 
• It is responsible for tying organs and parts of the body.
• Cells and homogeneous fluids are two components of tissues.
• Homogenous fluids are also called matrices.
• The cells are embedded in the matrix. 
• Connective tissues are mostly developed in the area of mesoderm.
• It is made of two proteins, namely collagen and elastin.
• Ground substance is another component of the tissue.
• There are more than 200 disorders that cause harm to connective tissues.
• These tissues combine to form different parts like skin and kidneys.

Read More: Tissue culture

Key Terms: Connective Tissues, Collagen, Elastin, Protein, Tissues, Organs, Fibres, Fibroblasts, Macrophages, Areolar Tissues, Adipose Tissues

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What are Connective Tissues?

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Connective tissues are type of tissues which acts as a connection link between several organs and various body parts. These are made up of cells which are present in the intercellular framework of protein fibres, which are secreted by the cells, known as collagen or elastin.

• The cells secrete a layer of gel of polysaccharides.
• Polysaccharides, together with fibres, will make a matrix or ground substance. 
• The connective tissues' elasticity, flexibility, and strength are because of the presence of fibres. 
• Blood and lymph are special fluids of tissues.
• Fibroblasts, Macrophages, Mast Cells and leucocytes are special cells of connective tissues.
• The functions of tissues are dependent on the type of the intercellular substance. 
• The tissues have high tensile strength.
• For example, macrophages act as scavengers.

Read More: Difference Between Cell and Tissue

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Components of Connective Tissues

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The connective tissues comprise of three main components, which are as follows:

Fibroblasts

Fibroblasts are found in developing tissues and play a crucial part in wound-healing and new tissue formation. They are spindle-shaped and are present in between collagen fibres. They secrete tropocollagen and other substances which are found in the matrix.

Macrophages

Macrophages are also known as scavenger cells. They wander through connective tissues, clean up debris and waste material, and remove bacteria and other antigens (disease-causing microbes) by phagocytosis (engulfing the antigens and then digesting them).

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Ground Substance

Ground substance is a type of transparent material found in the connective tissues. It has the properties of a viscous solution and a highly hydrated thin gel. The main components of ground substance include carbohydrates like mucopolysaccharides and complex proteins. It acts as a barrier to particulates found in the tissues.

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Connective Tissues Fibres

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Connective tissues comprise three types of fibres, namely collagen, elastic and reticular fibres.

Collagen Fibres

They are the most common and widespread fibres present in the connective tissues. They are made up of a fibrous protein called collagen. Collagen fibres are highly flexible and have high tensile strength (even comparable to steel), i.e., they are elastic.

Elastic Fibres

Elastic fibres form a network and a mesh-like structure. They can be stretched like a rubber band and have high elasticity. They are formed of the protein elastin. They regain their original shape and size once the force is removed; this proves their high elasticity.

Reticulate Fibres

Reticulate fibres consist of collagen and glycoproteins. They are thin and together form a delicate network. Their major function is to join connective tissues to neighbouring tissues.

Read More: Genes

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Types of Connective Tissues

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Connective Tissues are widely classified into three categories which are as follows:

Loose Connective Tissues

Loose Connective Tissues are present all over the body, at the areas requiring support and elasticity. Blood vessels, nerves and muscles, have a loose connective tissue wrapping them.

• They also form the subcutaneous layer under the skin along with adipose tissues.
• It plays a crucial role in attaching muscles and other organs to the skin.
• The fibres and cells are loosely arranged in the fluid polysaccharide matrix in the loose connective tissue.
• They are found in-between several organs acting as a filling to fill in the space.
• They also act as a shock absorber, and a reservoir for salt and fluid.

Read More: Reproduction in Organisms

Loose Connective Tissues present in the body are classified into three categories, which are as follows:

Areolar Tissues

Areolar Tissue is present right below the skin and supports the epithelium of the skin. It contains a randomly distributed network of fibres, fibroblasts, mast cells, and macrophages. Its major functions include supporting the organs in the abdominal cavity, filling the space between muscle fibres, and wrapping around blood and lymph vessels.

Adipose Tissues

Adipose Tissues are located under the skin and store fat. It acts as a shock absorber and helps maintain body temperature in colder environments to a constant. White adipose tissues protect kidneys and are found at the back of the eye, in the hump of camels, blubber of whales, etc.

• Brown adipose tissue is found only in infants, penguins, polar bears, and other animals found in cold climates.
• It contains more mitochondria and thus generates 20 times more heat as compared to the other fat. It releases metabolic heat.

Reticular Connective Tissues

Reticular Connective Tissues are made up of reticular fibres. It supports the internal framework of organs such as the liver, lymph nodes and spleen.

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Dense Connective Tissues

In dense connective tissues, fibroblast cells and fibres are compactly packed, i.e., densely packed. Their main function is to support and transfer the mechanical forces. Dense Connective Tissue is less flexible than loose connective tissue due to the compact nature of fibres and cells.

Based on the arrangement of collagen fibres, they are further divided into two types:

Dense Regular Tissues

In this type of tissue, the orientation of fibres is in a regular manner. The collagen fibres are present in between the parallel packs of fibres. The regular arrangement increases the tensile strength.

• It results in resistance to stretching in the direction of the orientation of fibre. 
• Examples of some dense regular tissue are ligaments and tendons. 
• Tendons stick bones to skeletal muscles. 
• Ligaments attach one bone to another.

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Dense Irregular Tissues

Here, the fibres are arranged in an irregular manner. There are many fibres which are oriented irregularly or randomly. The irregular arrangement of these fibres gives uniform strength across all directions. Fibres may form a mesh-like network. This type of tissue is present in the dermis of the skin.

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Specialised Connective Tissues

Specialised Connective Tissues help in maintaining the correct posture and support internal organs, e.g. cartilage and bone. It is considered one of the four cells found in the body of animals. Blood and lymph are fluid connective tissues that circulate in the body and result in communication among all the organs.

Cartilage

Cartilage is mostly present in the embryonic stages and acts as a supporting skeleton. Most of the cartilage is solidified and replaced by bones in adults. However, it supports some structures in adults, too.

• The cartilage consists of chondrocyte cells.
• They secrete collagen fibres, which provide additional strength to the structure.
• Chondrocytes lie in the lacunae cavities, in a group of 2-4 cells or as a single cell.
• Cartilage possesses elasticity but is firm, too.
• They lack nerves, blood and lymph vessels.

Read More: Diagram of Mitochondria

Bones

Bone is the hardest connective tissue in the body and helps maintain the body's shape and posture; it protects all the internal organs. They are rich in collagen fibres and calcium, which gives it strength.

• The cells of bones are called osteocytes. 
• They are also present in lacunae and secrete the matrix.
• There is a presence of blood supply in bone tissues.
• The cytoplasmic extension of osteocytes forms tiny channels called canaliculi.
• These channels assist in the communication process between osteocytes and capillaries.
• Spongy bone is present in the core and is surrounded by compact bone.
• Osteons are the spindle-shaped units present in the compact bone.
• Osteocytes are present in the concentric layers of the matrix in each osteon, called lamellae. 
• Capillaries and nerves pass through a central channel known as the Haversian canals. 

Blood

Blood is made up of a variety of cells present in the plasma. The blood contains RBC, WBC, plasma and platelets. Red Blood Cells are rich in haemoglobin and transport oxygen.

• White Blood Cells form a defence system and protect the body from foreign antigens.
• Platelets are essential for blood clotting.
• Plasma contains proteins, water, hormones, salts, etc., to transport to various parts of the body.

Lymph

Lymph is a fluid which drains into the blood and transports absorbed fat to the blood, which cannot enter the bloodstream directly. It possesses white blood cells in the liquid matrix.

• They help in the reduction of toxins and waste materials.
• They contain WBCs assisting in fighting foreign infection.

Read More: Uremia

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Connective Tissues Disorder

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Connective tissues disorder arises due to faulty genes or mutation of genes. Epidermolysis bullosa (EB) and Marfan syndrome are two main disorders of connective tissues. 

Epidermolysis Bullosa (EB)

Epidermolysis Bullosa (EB) is a type of skin oversensitivity that causes fragile and blistering skin. The blistering of skin arises due to minor injury or by rubbing, scratching or heat. The disorder is inherited and mostly found in infants or young children.

Marfan Syndrome

Marfan Syndrome is responsible for affecting the tissues that provide support to your body. It also affects your heart, blood vessels, skin, eyes, bones, tendons, cartilage and lungs. It occurs equally in both men and women and can be inherited from one of the parents.

Autoimmune

Autoimmune is another type of connective tissue disorder that starts attacking the healthy tissues in the human body. It will affect the normal function of the body and can be life-threatening.

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Things to Remember

• Connective tissue is a type of tissue that supports organs and various parts of the body. 
• It consists of fibrous tissues that vary in density and cellularity.
• Fibroblasts, Macrophages and Ground Substances are three main components.
• Loose connective tissues, Dense connective tissues and Specialized connective tissues are three types of connective tissues.
• Disorder in connective tissues arises due to mutation of genes.

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