Navigation Links
Cartilage


Cartilage is type of dense connective tissue. Cartilage is composed of cells called chondrocytes which are dispersed in a firm gel-like ground substance, called the matrix. Cartilage contains no blood vessels and nutrients are diffused through the matrix. Cartilage is found in the joints, the rib cage, the ear, the nose, in the throat and between intervertebral disks. There are three main types of cartilage: hyaline, elastic & fibrocartilage.

Contents

Composition

Much like other connective tissue, cartilage is composed of cells, fibers and a matrix.

Cells

Chondrocytes are the only cells found in cartilage. They are responsible for the secretion and maintenance of the matrix. The matrix immediately surrounding the chondrocytes is referred to as the territorial matrix and stains darker than the interstitial matrix. Chondrocytes lie in a cavity called a lacuna. During slide preparations, chondrocytes often shrink and appear smaller than the lacunae but in live tissue, they occupy the entire area.

Fibers

Cartilage is composed of collagen and elastic fibers. In hyaline cartilage, Type II collagen make up 40% of its dry weight and are arranged in cross-striated fibers, 15-45nm in diameter that do not assemble into large bundles. Elastic cartilage also contains elastic fibers and fibrocartilage contains more collagen than hyaline cartilage.

Matrix

The matrix is mainly composed of proteoglycans, a special type of glycosaminoglycans. The most common type is chondroitin sulfate and keratan sulfate .

Types of Cartilage

There are three different types of cartilage, each with special characteristics adapted to local needs.

Hyaline Cartilage

This is the most abundant type of cartilage. The name hyaline is derived from the greek word hyalos, meaning glass. This refers to the translucent matrix or ground substance. Hyaline cartilage is found lining bones in joints (articular cartilage) . It is also present inside bones, serving as a center of ossification or bone growth.

Elastic Cartilage

Elastic cartilage (also called yellow cartilage) is found in the pinna of the ear and several tubes, such as the walls of the auditory and eustachian canals and larynx. Cartilage is present to keep the tubes permanently open. Elastic cartilage is similar to hyaline cartilage but contains elastic bundles (elastin) scattered throughout the matrix. This provides a tissue which is stiff yet elastic.

Fibrocartilage

Fibrocartilage (also called white cartilage) is a specialised type of cartilage found in areas requiring tough support or great tensile strength, such as between intervertebral disks, the pubic symphisys and at sites connecting tendons or ligaments to bones. There is rarely any clear line of demarcation between fibrocartilage and the neighboring hyaline cartilage or connective tissue. The fibrocartilage found in intervertebral disks contains more collagen compared to hyaline. Fibrocartilage lacks a perichondrium.

Perichondrium

The perichondrium is a tissue layer that lines most types of cartilage. There are two distinct layers, an outer fibrous layer and inner chondrogenic layer. The fibrous layer contains fibroblasts which can produce collagen fibers while the inner layer contains undifferentiated or osteogenic cells capable of forming chondrocytes. If cartilage is transformed to bone, the perichondrium becomes the periosteum.

Growth / Development

Chondrification

Most of the skeletal system is derived from mesoderm tissue. Chondrification is the process in which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondrocytes and begin secreting the materials that form the matrix.


Two types of growth can occur in cartilage: appositional and interstitial.

Appositional

Appositional growth results in the increase of the diameter or thickness of the cartilage. The new cells derive from the perichondrium and occur on the surface of the cartilage model.

Interstitial

Interstitial growth results in an increase of cartilage mass and occurs from within. Chondrocytes undergo mitosis within their lacuna but remain imprisoned in the matrix, which results in clusters of cells called isogenous groups.

Cartilage in fetal development

In the fetus, at an early period, the greater part of the skeleton is cartilaginous; as this cartilage is afterward replaced by bone, it is called temporary, in contradistinction to that which remains unossified during the whole of life, and is called permanent.

It has been said that the cartilage in ears and noses continues to grow in size throughout adult life; however, this seems to be an urban myth which is not substantiated by research.

Diseases / Medicine

There are several diseases which can affect the cartilage. Chondrodystrophies are a group of diseases characterized by disturbance of growth and subsequent ossification of cartilage. Some common diseases affecting/involving the cartilage are listed below.

  • Arthritis: The cartilage covering bones in joints (articular cartilage) is degraded, resulting in limitation of movement and pain.
  • Achondroplasia: Reduced proliferation of chondrocytes in the epiphyseal plate of long bones results in a form of dwarfism.
  • Costochondritis: Inflammation of cartilage in the ribs which causes chest pain
  • Herniated disk: Asymmetrical compression of a disk ruptures the cartilage ring, causing tissue to herniate into the spinal canal.

The matrix of cartilage acts as a barrier, preventing the entry of lymphocytes or diffusion of immunoglobins . This property allows for the transplantation of cartilage from one individual to another without fear of tissue rejection.

Bioengineering techniques are being developed to generate new cartilage, using a cellular "scaffolding" material and cultured cells to grow artificial cartilage.

See also

External links


'"/>


(Date:7/11/2014)... the marginal division of the striatum is also ... impact degree of substance P in the striatal ... Yu and his team, College of Biophotonics, South ... that substance P receptor, neurokinin 1 was highly ... of normal rats. Unilateral or bilateral injection of ...
(Date:7/11/2014)... exists that cannabinoid receptor type 1 can ... influx, and reduce neurotransmitter release. However, some ... can increase extracellular Ca2+ influx and increase ... team, Tongji Hospital Affiliated to Tongji Medical ... China used whole cell voltage-clamp and calcium ...
(Date:7/11/2014)... that let nerve cells send out electrical signals, Johns ... tactic that may offer a new way to protect ... responsible way. , Their findingthat naturally occurring insect ... for a closely related onesuggests that insecticides can be ... like bees. A summary of the research, led by ...
Breaking Biology News(10 mins):Potent spider toxin 'electrocutes' German, not American, cockroaches 2Potent spider toxin 'electrocutes' German, not American, cockroaches 3
... and Low Power ... Consumption, ... an intelligent high-performance module designed for connecting,devices that require low power ... mobile OEM applications that need,WLAN connectivity with minimal power usage, such ...
... with things like trout and salmon would be good for the ... it would be natural to assume that more fish would mean ... journal of Ecology by the Ecological Society of America says that ... the area has not been good for the birds, demonstrating that ...
... human-caused climate change has made an impact on a ... plants blooming earlier across Europe, and lakes declining in ... Goddard Institute for Space Science in New York and ... biological impacts since 1970 with rises in temperatures during ...
Cached Biology News:New Silex SX-560 Enables Enterprise 802.11 Wireless Connectivity for Battery Operated Devices 2Restoring fish populations leads to tough choice for Great Lakes Gulls 2NASA study links Earth impacts to human-caused climate change 2
Other biology definitionOther Tags