CONNECTIVE TISSUE

Other tissues & internal organs rely on this tissue for support, protection, and structure. Additionally, connective tissue stores fat, aids in the movement of nutrients as well as other substances among tissues and organs, also aids in the repair of injured tissue. Bones, cartilage, fat, blood, & lymphatic tissue are all examples of connective tissue.

It develops from the mesoderm in embryology. The three membranes that surround the brain & spinal cord (meninges) are made up of dense, inert connective tissue. 

Fibers (elastic and collagen fibers), ground substance, and cells are the three basic components of connective tissue. Everyone is submerged in bodily water. Adipocytes, fibroblasts, macrophages, mast cells, and leukocytes are connective tissue cells.

Johannes Peter Müller coined the phrase “connective tissue” in 1830. In the 18th century, the tissue was already classified as a different class.

TYPES OF CONNECTIVE TISSUE:

Connective tissue is divided into two types: connective tissue proper and connective tissue special. There are two types of connective tissue: loose connective tissue and thick connective tissue (which is subdivided into dense regular and dense irregular connective tissues.) 

Dense connective tissue contains a lot more ground material and a lot less fibrous tissue, whereas loose connective tissue has a lot more ground substance and a lot less fibrous tissue. Collagen fibers are arranged in an orderly parallel pattern in dense regular connective tissue, which gives it tensile strength in one direction and is seen in structures such as tendons and ligaments. 

Reticular connective tissue, adipose tissue, bone, cartilage & blood are all examples of special connective tissue. Fibrous, elastic, and lymphoid connective tissues are examples of other connective tissues. Fibro areolar tissue is made up of a combination of fibrous & areolar tissue. Fibrous and muscular tissue combine to form fibromuscular tissue. Granulation tissue is a type of 

CARTILAGE:

• Cartilage is a type of connective tissue wherein the ground substance is plentiful and has a firmly gelled consistency, giving it extraordinary rigidity and compression resistance. The cartilage cells, or chondrocytes, are isolated in minute lacunae within the matrix.
• Despite the fact that cartilage is avascular, gaseous metabolites and nutrients can enter the cells via the aqueous phase of the gel-like matrix. The perichondrium, a dense fibrous layer bordered by cells capable of secreting a hyaline matrix, surrounds cartilage. 
• Cartilage grows by forming a new matrix and incorporating new cells from the perichondrium’s inner chondrogenic layer. Furthermore, even after becoming separated in lacunae, immature chondrocytes retain their ability to divide.
• The most common type of cartilage is hyaline cartilage, which has a pearl-gray semi translucent matrix with randomly arranged collagen fibrils but minimal elastin. It’s usually present on joint surfaces as well as in the cartilage that makes up the fetal skeleton. 
• The number of elastic fibers contained in the matrix of elastic cartilage, on the other hand, gives it a pale-yellow look. This type of cartilage is more flexible from hyaline cartilage and can be found in the external ear, larynx, and epiglottis. 
• The third form, fibrocartilage, has a high proportion of parallel-oriented thick collagen bundles. Its cells live in lacunae, which are commonly placed in rows between coarse collagen bundles. It can be present in intervertebral discs, tendons’ attachment points to bone, and the articular discs of some joints. Calcification foci can occur in any cartilage type.

BONE:

• Bone is made up of cells, fibers, and ground substance, just like other connective tissues, but the extracellular components are also impregnated with minute calcium phosphate crystals in the form of the mineral hydroxyapatite. 
• The mineralization of matrix determines the toughness of the bone. It also stores a substantial amount of calcium which can be used to address unexpected calcium requirements somewhere else in the body. 
• Bone’s structural organization has evolved to provide maximum strength for its own weight-bearing purpose while weighing as little as possible. There are bones strong enough even to support an elephant’s weight, and others that are light enough to provide internal support & leverage to a bird’s wings.

DERMIS:

• The dermis, also known as the corium, is a thicker, deeper layer of skin made up of connective tissue that lies underneath the epidermis.
• It can be found in various stages of development in different vertebrate taxa, ranging from thin and simple in aquatic animals to thicker and more complex in terrestrial mammals.

TENDON:

• A tendon is a piece of tissue that connects a muscle to other body parts, most commonly bones. Tendons are connective tissues that carry the mechanical power of muscle contraction to the bones; they are securely attached to muscle fibers on one end and to bone components on the other. 
• Tendons are among the toughest soft tissues in the body, with one of the ultimate tensile strengths. The hierarchical organizational structure, parallel orientation, and tissue composition of tendon fibers are responsible for their tremendous strength, which is required to endure the forces caused by muscular contraction.

FIBROBLAST:

• The major active cell of connective tissue is the fibroblast. Fibroblasts are huge, elongated (spindle-shaped), flat cells with processes that extend out from the cell body’s ends. The nucleus of a cell is flat & oval. 
• Tropocollagen, a precursor to collagen, plus ground substance, an amorphous mucilaginous matrix which fills the gaps between cells & fibers in connective tissue, are both produced by fibroblasts.

CHARACTERISTICS:

The ground substance is a clear, colorless, viscous fluid with glycosaminoglycans and proteoglycans that allow Collagen fibers to be fixed in intercellular spaces. Adipose tissue (fat) and blood are examples of non-fibrous connective tissue. Among other things, adipose tissue provides “mechanical cushioning” to the body.

Although there is no thick collagen network in adipose tissue, collagen fibers and collagen sheets bind groups of adipose cells together to keep fat tissue under compression in place (for example, the sole of the foot). The matrix for connective tissue is made up of both the ground substance and proteins (fibers).

FUNCTIONS:

1. Connective tissue has a wide range of functions that are dependent on the cell types and fiber classes involved. Loose and thick irregular connective tissue, primarily composed of fibroblasts and collagen fibers, plays a crucial role in allowing oxygen and nutrients to pass from capillaries to cells and carbon dioxide and waste products to diffuse back into circulation.
2.  They also enable organs to withstand tearing and stretching forces. Dense regular connective tissue is a main functional element of tendons, ligaments, and aponeuroses, as well as highly specialized organs like the cornea. Elastic fibers, which are made of elastin & fibrillin, also resist stretch forces.
3. They can be present in the walls of big blood arteries as well as some ligaments, especially the ligamentum flavum.
4. The stroma—or structural support—for the parenchyma—or functional part—of the organ is provided by reticular fibers generated by reticular cells in hematological and lymphatic tissues.
5. Mesenchyme is a type of connective tissue that can differentiate into any type of mature connective tissue and is found in the developing organs of embryos. Wharton’s jelly, a mucous connective tissue found inside the umbilical cord, is another kind of relatively undifferentiated connective tissue.
6. The spectrum of connective tissue encompasses a wide range of specialized tissues and cells, including white & brown adipose tissue, blood, cartilage, and bone. Immunological cells like macrophages, mast cells, plasma cells, and eosinophils are dispersed throughout loose connective tissue providing the foundation for initiating inflammatory and immune responses in response to antigen recognition.

CONCLUSION:

Connective tissue is a set of tissues in the body which keep the body as well as its organs in shape while also providing cohesion & internal support. Bone, ligaments, tendons, cartilage, & adipose (fat) tissue are all kinds of connective tissue that differ only in density and cellularity, as well as more specialised and recognized varieties like bone, ligaments, tendons, cartilage, including adipose (fat) tissue.