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Connective Tissue – Definition, Functions, Types, Examples

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  • Last Updated : 13 Jun, 2022

In unicellular organisms, a single cell performs all necessary tasks such as digesting, respiration, and reproduction. The same basic duties are well-organized by distinct groups of cells in the complex body of multicellular organisms. A basic organism’s body, such as Hydra, is made up of many types of cells, with thousands of cells in each category. A group of identical cells, combined with intercellular signalling, fulfill a specialized role in multicellular creatures. This type of organization is known as tissue.

It may surprise you to learn that all sophisticated animals are made up of only four fundamental types of tissues. These tissues are arranged in a certain proportion and pattern to form an organ such as the stomach, lung, heart, or kidney. When two or more organs interact physically and/or chemically to perform a common function, they form an organ system, for as the digestive system or respiratory system. Cells, tissues, organs, and organ systems divide the job to promote the division of labor and contribute to the overall survival of the body.

Functions of Connective Tissue

  1. Connective tissue’s job is to either connect biological components like bones and muscles together or to hold tissues like muscles, tendons, and even organs in their right location in the body. 
  2. Reinforcing joints also strengthen and supports the articulations connecting bones.
  3. Connective tissue also transports nutrients and metabolic wastes from the bloodstream to the tissues to which it clings. 
  4. Connective tissue is composed of proteins such as collagen, elastin, and intercellular fluid, and while its shape can range from a thin sheet to a rope of fibers, its structure is relatively stable throughout the body.

Animal Tissues- The structure of cells varies depending on their role. As a result, the tissues differ and can be generically categorized into four types:

  1. Epithelial 
  2. Connective 
  3. Muscular 
  4. Neural

Connective Tissue

Connective tissues are ample and widely distributed in the bodies of complex animals. Connective tissues are so named because they connect and support other tissues/organs in the extracellular matrix. They include soft connective tissues as well as specialized forms such as cartilage, bone, fat, and blood. Cells secrete structural proteins known as collagen or elastin in all connective tissues except blood. The fibers give the tissue strength, elasticity, and flexibility. These cells also release modified polysaccharides, which collect between cells and fibers and serve as a matrix (ground substance). 

There are three types of connective tissues

  1. Loose connective tissue
  2.  Dense connective tissue
  3.  Specialized connective tissue

Loose Connective Tissue

Loose connective tissue is composed of cells and fibers that are dispersed in a semi-fluid ground substance, such as areolar tissue found beneath the skin layer. It frequently serves as a scaffolding for the epithelium. It is made up of fibroblasts (cells that make and secrete fibers), macrophages, and mast cells. Adipose tissue is a form of loose connective tissue that is mostly found beneath the skin. This tissue’s cells are specialized in fat storage. Excess nutrients that are not immediately utilized are turned into lipids and stored in this tissue.

Loose Connective Tissue

 

Loose Connective Tissue Functions

  • Collagen fibers give other tissues and organs strength and structural support.
  • It serves as a cushion.
  • Elastic fibers give elasticity to tissues and organs.
  • Blood supply is provided to surrounding epithelial tissue.
  • Responds immediately to epithelial damage or antigen interaction.
  • Adipose tissue aids in lipid storage.

Dense Connective Tissue

The dense connective tissues are densely packed with fibers and fibroblasts. The orientation of fibers produces a regular or irregular pattern, resulting in dense regular and dense irregular tissues. Collagen fibers are found in rows between several antiparallel bundles of fibers in dense regular connective tissues. Tendons, which connect skeletal muscles to bones, and ligaments, which connect two bones, are examples of this tissue.
Dense irregular connective tissue contains fibroblasts and many fibers (mainly collagen) that are orientated in diverse directions.

Dense Connective Tissue Functions

  • The primary function of dense connective tissue is to protect the body from mechanical stress. In this manner, irregular dense connective tissue may counterbalance multidirectional pressures, whereas regular dense connective tissue can only do so in one direction (in the sense that its collagen fibers are parallelly orientated).
  • Highly resistant to one-way traction, dense regular collagenous connective tissue. However, because this tissue is present in ligaments and capsules, it also serves as structural support for the organs in which it is found.
  • As the name implies, regular elastic dense connective tissue provides elastic characteristics to the organ in which it is found, allowing it to stretch and generate a certain degree of flexion when coupled with rigid parts.
  • This tissue, which is part of the dermis of the skin, serves as the second line of protection against injuries.
  • It gives the skin suppleness and, because it contains multiple types of cells, it aids in the defense against bacteria and other substances, forming a physical and chemical barrier that protects essential organs.
  • The presence of thick regular elastic connective tissue in big blood arteries allows tension to build up in the vessel wall during cardiac systolic ejection, and the release of this tension keeps vascular blood flow going during the diastole phase.

Specialized Connective Tissue

This tissue can be found in the skin. Specialized connective tissues include cartilage, bones, and blood. Cartilage’s intercellular substance is solid and malleable, and it resists compression. This tissue’s cells (chondrocytes) are encased in small cavities within the matrix that they secrete. In adults, most cartilages in vertebrate embryos are replaced by bones. In adults, cartilage can be found in the tip of the nose, and outer ear joints, between adjoining spinal column bones, limbs, and hands.

Bone’s hard, the non-pliable ground substance is rich in calcium salts and collagen fibers, which give bone its strength. It is the primary tissue that supplies the body with structural support. Soft tissues and organs are supported and protected by bones. Lacunae are niches that contain bone cells (osteocytes). Weight-bearing limb bones, such as the long bones of the legs, are present. They also interact with the skeletal muscles that are linked to them to produce movement. Some bones create blood cells in their bone marrow. Blood is a connective fluid that contains plasma, red blood cells (RBC), white blood cells (WBC), and platelets. It is the primary circulating fluid involved in the transportation of numerous chemicals.

Connective Tissue

 

 Specialized Connective Tissue Functions

  • These are connective and support tissues that have no other purpose except to fill the body. 
  • The adipose tissue is made up primarily of lipids and/or fats.
  • In Cartilaginous connective tissue where Cartilage is an elastic material that serves as a cushion between the bones.
  • Woven Bone is composed of mineralized tissues called bone.
  • The lymphatic system that connects the glands and serves as a conveyance for the body’s defenses as part of the lymphatic system.
  • Tissue made of blood. The blood and the cells that make it up.

Conceptual Questions

Question 1: How tissues are formed in the human body?

Answer: 

The human body is made up of billions of cells that work together to execute numerous jobs. A group of identical cells, combined with intercellular chemicals, fulfill a specialized role in multicellular creatures. This type of organization is known as tissue.

Question 2: What are connective tissues and their types?

Answer:

In the bodies of sophisticated animals, connective tissues are most plentiful and widely dispersed. Because of their unique ability to connect and support other tissues/organs in the body, connective tissues are so named. Soft connective tissues, as well as specialized forms such as cartilage, bone, fat, and blood, are examples. Cells secrete structural proteins called collagen or elastin in all connective tissues except blood. The fibers give the tissue strength, elasticity, and flexibility.
These cells also release modified polysaccharides, which collect between cells and fibers and serve as a matrix (ground substance).

There are three types of connective tissues:

  1. Loose connective tissue
  2. Dense connective tissue
  3. Specialized connective tissue

Question 3: Write about loose connective tissue?

Answer: 

Loose connective tissue is made up of cells and fibers that are loosely distributed in a semi-fluid ground substance, such as areolar tissue found beneath the skin. It frequently serves as a scaffolding for the epithelium. It is made up of fibroblasts (cells that make and secrete fibers), macrophages, and mast cells. Adipose tissue is a form of loose connective tissue that is mostly found beneath the skin. This tissue’s cells are specialized in fat storage. Excess nutrients are converted into lipids and stored in this tissue if they are not immediately used.

Question 4: In what tissue collagen fiber is present?

Answer: 

Collagen fiber is mostly found in dense connective tissue.

Question 5: Discuss specialized connective tissue?

Answer: 

This tissue can be found in the skin. Cartilage, bones, and blood are examples of specialized connective tissues. Cartilage’s intercellular substance is solid and malleable, and it resists compression. This tissue’s cells (chondrocytes) are encased in small cavities within the matrix that they secrete. In adults, most cartilages in vertebrate embryos are replaced by bones. In adults, cartilage can be found in the tip of the nose, and outer ear joints, between adjoining spinal column bones, limbs, and hands. Bone’s hard, non-pliable ground substance is rich in calcium salts and collagen fibers, which give bone its strength. It is the primary tissue that supplies the body with structural support. Soft tissues and organs are supported and protected by bones. Lacunae are niches that contain bone cells (osteocytes). There are weight-bearing limb bones present, such as the long bones of the legs. To produce movement, they also interact with the skeletal muscles that are attached to them. In the bone marrow, some bones produce blood cells. Blood is a fluid composed of plasma, red blood cells (RBC), white blood cells (WBC), and platelets. It is the primary circulating fluid involved in the transportation of numerous chemicals.

Question 6: What are the structural proteins that are secreted by cells?

Answer: 

Cells secrete structural proteins called collagen or elastin in all connective tissues except blood. 


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