[Biology Class Notes] on Connective Tissue Pdf

Connective tissue is one of the four basic types of tissue systems present inside an animal body. It is developed from the mesoderm of the embryo. The connective tissue function is as the name suggests to connect different parts of the body and hold them as one unit. Hence, the connective tissue is found in between other tissue systems as well including specialised systems such as the nervous system. The cell types of connective tissue examples include fibroblasts, macrophages, mast cells, leukocytes, and adipocytes.

So, how did you find the introduction of connective tissues provided by tutors? The matter is prepared by not a single teacher but there is a team to work on various aspects of a single topic. If the topic is connective tissues, then the entire team divides its different parts among them and then they work according to the part assigned to them. Let’s check out how the entire topic has been prepared in detail from definition to the functions of connective tissues.

 

Define Connective Tissue

The term “connective tissue” was coined by Johannes Peter Müller in 1830 even though it was already categorized as a separate tissue system a century before. From the simple attempt to define connective tissue, in the introduction, they can be defined as groups of tissues responsible for maintaining the form of the body and the structural integrity of the organs by providing cohesion and internal support. As given already, it is present all over the body and also in between other tissues. It is also present in the central nervous system within the three outer membranes surrounding and enveloping the brain and spinal cord.

There are three components of connective tissue – the fibres which are both elastic and collagenous, the ground substance of connective tissue, and the specialized connective cells. Some of the scientific authorities also consider the blood and the lymph as connective tissue because they partially hold the connective tissue meaning of connecting the entire body because of their own network of flow within the body. But they are different from typical connective tissues since they do not contain any fibres. 

Key Takeaways about Connective Tissues

• Connectives tissues have different components such as fibres, cells, and the ground substance. Collectively the fibers and ground substance create an extracellular matrix. 

• Connective tissues are the most thoroughly distributed and abundant among the primary tissues. 

• Connective tissues are categorised into two different subtypes named specialised and soft connective tissues. 

• The prime functionality of the connective tissues comprises protection, support & binding, storage of reserving fuel, insulation, and transportation of substances within our body. 

• These tissues are also having different vascularities. If we talk about avascular, then it is a dense connective tissue that has been vascularised poorly. Other such sorts of bone are enriched with the blood vessels supplies.

Types of Connective Tissues

Connective tissue is widely classified into two types – the connective tissue proper and special connective tissue. They are further explained as follows:

Connective Tissue Proper: There are two types of connective tissue proper which are typified as loose connective tissue and dense connective tissue. This classification is based on the ratio of the ground substance of connective tissue to the fibrous tissue. This means that the loose connective tissue proper has more ground substance as compared to the fibrous tissue whereas the dense connective tissue has more fibrous connective tissue than the loose connective tissue. Connective tissue examples of this type include areolar tissue, reticular tissue, and adipose tissue. Examples of dense connective tissue include tendons and ligaments. As a matter of fact, the dense connective tissue is further divided into dense regular and dense irregular connective tissue. The difference is that the dense connective tissue is ordered in a parallel fashion given tensile strength to tendons and ligaments in one direction while the dense irregular connective tissue forms dense fibre bundles providing strength in all directions.

Special Connective Tissue: While talking about connective tissue systems people sometimes ask a general question – is cartilage a connective tissue?. The answer is yes. Cartilage is a special connective tissue. The cartilage connective tissue comes under the classification of special connective tissue along with reticular connective tissue, adipose tissue, bone and blood. Another of the connective tissue examples that are included in this category are the fibrous, elastic and lymphoid tissues. The fibroareolar tissue and fibromuscular tissue is a combination of the fibrous and areolar tissue and fibrous and muscular tissue, respectively.

 

Characteristics & Components of Connective Tissues

Many forms of connective tissue are made up of type I collagen fibres, which make approximately 25% of human protein content and play a primary role in the connective tissue function. These collagen fibres are fixed in the intercellular spaces by the ground substance which is a clear, colourless and viscous fluid containing glycosaminoglycans and proteoglycans.

 

Some of the connective tissue such as the adipose tissue and the blood is different in this sense as they are not made up of fibres. Even though the adipose tissue isn’t made up of collagen fibres they are held together in a group by collagen fibres and sheets. This combination provides mechanical cushioning to the body by keeping the fat tissue under compression and in place. The components of connective tissue – the fibre proteins and ground substance together create the entire matrix for connective tissue.

As part of the components of connective tissue the fibre types are explained below: 

What are the Different Cells of Connective Tissues?

The connective tissues cells include two different types that are named adipose cells and stationary—fibroblasts. And, there are different sorts of mast cells, motile migrating cells, monocytes, macrophages, eosinophils, and plasma cells. The development of all the cells happens at the time of embryonic life via a network of primitive stellate cells, mesenchyme, etc. The primitive cells come with the power to differentiate with diverse lines according to the local conditions. Next to it, the specialised cell is believed to be a small count of stem cells also known as mesenchymal cells that persist via postnatal life within the walls of the smaller blood vessels. Plus, it may preserve the ability to differentiate into adipose cells, fibroblasts, multitude or macrophages and other such cells wherever the requirement arises.

 

Functional and Clinical Importance of Connective Tissue

The connective tissue function varies depending on the cell type and fibrous material present. For example, the loose and dense connective tissue found in the fibroblasts and collagen fibres is responsible for providing a medium for the transfer of oxygen and nutrients from the capillaries to cells and the diffusion of carbon dioxide and waste materials from the cells to back in the circulatory system.

The dense regular connective tissue which as told earlier is responsible for providing tensile strength in organised structures, also provides tear and stretch resistance to the tendons, ligaments, aponeuroses and in specialised organs such as the cornea. The function of elastic fibres made from fibrillin and elastin is also to provide stretch resistance in walls of large blood vessels and particular ligaments (ligamentum flavum).

When asked to name the connective tissue from which the connective tissue of an adult is formed, the answer to be given is the Mesenchyme tissue. It is a type of connective tissue found in the developing organs of the embryo that differentiate into all the mature connective tissues.

Certain specialised cells of the immune system of the kind of macrophages, mast cells, plasma cells, eosinophils are found randomly distributed around the loose connective tissue for starting an immune response upon detection of antigens as soon as possible.

 

There are many kinds of disorders as well related to connective tissue. The name of connective tissue disorders as few examples are shown below:

• Connective tissue neoplasms or connective tissue tumours: Hemangiopericytoma, and Malignant peripheral nerve sheath tumours

• Congenital Diseases: Marfan syndrome, Ehlers-Danlos Syndrome

• Deficiency Diseases: Scurvy caused due to Vitamin C deficiency leads to insufficient collagen production

• Fibromuscular Dysplasia: Abnormal growth in the artery walls

Thus, from the given information in the article, it is clear that the connective tissue plays a vital role in maintaining the structural integrity of the body and performing functions responsible for the diffusion of essential nutrients and substances. The images of certain kinds of connective tissue are shown below:

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