Connective Tissue

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Connective tissue

It is one of the four general classes of tissues Connective tissue (CT) is a tissue that

supports, connects, or separates different types of tissues and organs of the body.

Connective tissue is found everywhere including in the central nervous system. It is located in between other tissues

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Connective tissue

All connective tissue except (blood and lymph) consists of three main components:

fibers (reticular, elastic and collagenous fibers), ground substance and Cells (fibroblasts, adipocytes, macrophages, mast cells and

leucocytes)

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MEDICAL APPLICATION

The regenerative capacity of the connective tissue is clearly observed when tissues are destroyed by inflammation or traumatic injury.

In these cases, the spaces left after injury to tissues whose cells do not divide (eg, cardiac muscle) are filled by connective tissue, which forms a scar. The healing of surgical incisions depends on the reparative capacity of connective tissue. The main cell type involved in repair is the fibroblast.

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MEDICAL APPLICATION…

Collagen synthesis depends on the expression of several genes and several posttranslational events. It should not be surprising, therefore, that a large number of pathological conditions are directly attributable to insufficient or abnormal collagen synthesis

Keloid is a local swelling caused by abnormal amounts of collagen that form in scars of the skin

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MEDICAL APPLICATION…

Vitamin C (ascorbic acid) deficiency leads to scurvy, a disease characterized by the degeneration of connective tissue. Without this vitamin, fibroblasts synthesize defective collagen, and the defective fibers are not replaced.

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MEDICAL APPLICATION…

Edema is promoted by the accumulation of water in the extracellular spaces. Water in the extracellular compartment of connective tissue comes from the blood, passing through the capillary walls into the extracellular compartment of the tissue

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CLASSIFICATION OF CT

Classification is based on the density and organization of the connective tissue cells and fibers. The composition of connective tissue also reflects the functions of particular tissues or organs.

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Loose CT

Loose connective (areolar) tissue: Contains more cells than fibers and the fibers are thinner, delicate, sparse and loosely arranged

Areolar connective tissues hold organs in place and attaches epithelial tissue to other underlying tissues. It also surrounds the blood vessels and nerves

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Dense CT

Dense connective tissue is mainly composed of type I collagen. Crowded between the collagen fibers are rows of fibroblasts, fiber-forming cells, that manufacture the fibers.

Dense connective tissue forms strong, rope-like structures such as tendons and ligaments. Tendons attach skeletal muscles to bones; ligaments connect bones to bones at joints. Ligaments are more stretchy and contain more elastic fibers than tendons. Dense connective tissue also make up the lower layers of the skin (dermis), where it is arranged in sheets

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Dense CT…

The specialized connective

Adipose tissue is a special type of connective tissue in which adipose (L. adeps, fat) cells (adipocytes) predominate

Adipose tissue is the largest repository of energy (in the form of triglycerides) in the body. The other organs that store energy (in the form of glycogen) are the liver and skeletal muscle

Subcutaneous layers of adipose tissue help to shape the surface of the body, whereas deposits in the form of pads act as shock absorbers, chiefly in the soles and palms. Because fat is a poor heat conductor, it contributes to the thermal insulation of the body

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Adipose tissue…

Unilocular (yellow) adipose tissue is composed of cells that, when completely developed, contain one large central droplet of yellow fat in their cytoplasm. Multilocular (or brown) adipose tissue is composed of cells that contain numerous lipid droplets and abundant brown mitochondria. Both types of adipose tissue have a rich blood supply

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Adipose tissue…

Yellow adipose tissue is found throughout the human body except for the eyelids, the penis, the scrotum, and the entire auricle of the external ear except for the lobule. Age and sex determine the distribution and density of adipose deposits

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MEDICAL APPLICATION

Obesity in adults may result from an excessive accumulation of fat in unilocular tissue cells that have become larger than usual (hypertrophic obesity). An increase in the number of adipocytes causes hyperplastic obesity

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Cartilage is a specialized form of connective tissue in which the firm consistency of the extracellular matrix allows the tissue to bear mechanical stresses without permanent distortion

Cartilage consists of cells called chondrocytes (Gr. chondros, cartilage, + kytos, cell) and an extensive extracellular matrix composed of fibers and ground substance

Specialized CT: bone and cartilage

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Specialized CT:cartilage

There are three types of cartilage that are distinguished by the light microscope based on the types of fibers it contains, the composition of the ground substance and density and arrangement of cells.

Hyaline cartilage (glass-like) Elastic cartilage Fibrocartilage

Classification of cartilage

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Hyaline cartilage is located in the Wall of the upper airway i.e. nose, larynx,

trachea, bronchi, The sternal ends of ribs, (costal cartilages)

and it also covers the articular surfaces of joints.

Location of hyaline cartilage

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Elastic cartilage is found in the auricle of the ear, the walls of the external auditory canals, the auditory (eustachian) tubes, the epiglottis, and the cuneiform cartilage in the larynx. Elastic cartilage is essentially identical to hyaline cartilage except that it contains an abundant network of fine elastic fibers in addition to collagen type II fibrils

Elastic cartilage

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Fibrocartilage is a tissue intermediate between dense connective tissue and hyaline cartilage.

It is found in intervertebral disks, in attachments of certain ligaments to the cartilaginous surface of bones, and in the symphysis pubis.

Fibrocartilage

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Fibrocartilage…

MEDICAL APPLICATION

Rupture of the annulus fibrosus, which most frequently occurs in the posterior region where there are fewer collagen bundles, results in expulsion of the nucleus pulposus and a concomitant flattening of the disk.

As a consequence, the disk frequently dislocates or slips from its position between the vertebrae

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Specialized CT Bone

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Bone is a specialized connective tissue composed of intercellular calcified material, the bone matrix, and three cell types: osteocytes, which are found in cavities (lacunae) within the matrix; osteoblasts, which synthesize the organic components of the matrix; and osteoclasts, which are multinucleated giant cells involved in the resorption and remodeling of bone tissue

Bone

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Bone…

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