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You are watching: Cartilage is more resilient than bone

StatPearls . Sweetheart Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

Cartilage has numerous functions, including the capability to stand up to compressive forces, boost bone resilience, and administer support ~ above bony locations where there is a need for flexibility. The major cell that renders cartilage is the chondrocyte, which stays within the lacunae. The matrix of cartilage consists of fibrous tissue and various combine of proteoglycans and glycosaminoglycans. Cartilage, as soon as synthesized, lacks lymphatic or blood supply and the activity of waste and also nutrition is chiefly via diffusion to and also from adjacent tissues. Cartilage, favor bone, is surrounded by a perichondrium-like fibrous membrane. This layer is not efficient at regenerating cartilage. Hence, its restore is slow after injury. The lack of energetic blood circulation is the major reason any injury come cartilage bring away a long time to heal. Cartilage has no nerve innervation, and also hence there is no sensation once it is injured or damaged. When there is calcification the cartilage, the chondrocytes die. This is followed by the replacement of cartilage through bone-like tissue. Unequal bone, cartilage walk not have actually calcium in the matrix. Instead, it includes high quantities of chondroitin, i beg your pardon is the material that offers elasticity and also flexibility.


Structure and also Function

Several varieties of cartilage are found in the person body, and also their structure and relevant duty depend on this variation. 

Hyaline Cartilage

Hyaline cartilage is the most copious type that cartilage in the human body.<1> It has a pale blue-white color and also is smooth to the touch. That is mainly composed of type II collagen and proteoglycans. The surface ar is generally moist, however with age, the cartilage i do not care dry, thinner, and more yellow. Hyaline cartilage is usually discovered in the trachea, nose, epiphyseal expansion plate, sternum, and ventral segment of the ribs. Hyaline cartilage produce a durable surface through minimal friction. It likewise has wonderful ability to withstand compressive forces at web page of bone articulation.<2>

Elastic Cartilage

This cartilage appears a dull yellow and also is most commonly found in the larynx, ear, epiglottis, and also eustachian tube. A perichondrium-like layer additionally surrounds it. It provides flexibility and is resilient to pressure.<3>

Fibrocartilage

This is abundant in type 1 collagen and contains significantly less proteoglycan 보다 hyaline cartilage. It have the right to resist high levels of tension and compression. The is frequently found in tendons, ligaments, intervertebral discs, articular surfaces of part bones, and in menisci. Unlike other cartilage, it has actually no perichondrium.<4>


Embryology

Cartilage is developed from the mesoderm germ great by the procedure known as chondrogenesis.<5> Mesenchyme differentiates right into chondroblasts, which space the cells that secrete the significant components that the extracellular matrix—the most important of these materials for cartilage development being aggrecan and form II collagen. When initial chondrification occurs, the immature cartilage grows largely by developing into a an ext mature state due to the fact that it cannot flourish by mitosis. Over there is minimal cell division in cartilage; therefore, the size and mass that cartilage carry out not change significantly after originally chondrification.


Blood Supply and also Lymphatics

Cartilage is avascular. This properties of cartilage is paramount throughout the discussion and also management of illness affecting cartilage. Since there is no direct blood supply, chondrocytes get nourishment via diffusion native the neighboring environment. The compressive pressures that consistently act ~ above cartilage additionally increase the diffusion the nutrients. This indirect procedure of receiving nutrients is a major factor in the slow turnover of the extracellular matrix and lack the repair checked out in cartilage.


Nerves

Cartilage does not contain nerves; the is aneural.<6> If any type of pain is linked with a pathology involving cartilage, it is most generally due to wake up of bordering structures, such together inflammation the the joint and also bone in osteoarthritis.


Muscles

Fibrocartilage is a major component of entheses, characterized as the connective tissue in between muscle tendon or ligament and also bone. The fibrocartilaginous enthesis consists of 4 transition zones together it progresses native tendon come bone.<7> These shift zones are noted in bespeak of progression indigenous muscle come bone. 


Longitudinal fibroblasts and also a parallel plan of collagen yarn are uncovered in the tendinous area
A fibrocartilaginous an ar where the main kind of cells current transitions native fibroblast come chondrocytes
A an ar called the "blue line" or "tide mark" because of an abrupt transition from cartilaginous come calcified fibrocartilage
Bone

Clinical Significance

An immense variety of clinical pathology exists entailing cartilage, such together osteoarthritis, spinal disc herniation, traumatic rupture/detachment, achondroplasia, costochondritis, and also neoplasm, and many others. These an outcome from a selection of degenerative, inflammatory, and congenital causes.

Osteoarthritis is a an illness affecting the totality joint; however, the articular cartilage (a subset that hyaline cartilage) within the joint is the most influenced tissue. Osteoarthritis is well-known as a "wear and tear" phenomenon as result of it largely affecting joints under greater amounts that stress. That results due to articular cartilage gift thinned and wearing away. This eventually results in a decreased range of motion, "bone against bone" contact within the joint, and also pain. The early stage clinical treatment is through anti-inflammatories and corticosteroid injections intraarticularly. Both therapies duty to minimize the inflammation reaction resulted in by the degenerative cartilage"s release of cytokines. Patients might also show innovation by shedding weight, exercising, and efforts come decrease joint stress with rest and using a cane. Eventually, however, many patients will develop pain and symptoms the interfere with day-to-day life. At this point, joint instead of or resurfacing might be recommended. Arthroscopic surgical procedure is no much longer recommended as it walk not enhance outcomes in knee osteoarthritis and can reason harm.

Another usual degenerative condition of cartilage is spinal disc herniation. It is as result of degenerative transforms of the external ring the the intervertebral disc, referred to as the annulus fibrosus. The annulus fibrosus is written of fibrocartilage. Trauma, straining, and lifting injuries are additionally implicated in the weakening of the annulus fibrosis predisposing to disc herniation. As soon as there is structural damage to the annulus fibrosus, the nucleus pulposus consisted of within the disc might herniate into the spinal canal, bring about impingement the 1 or lot of nerves as well as induce inflammatory alters due come the damaged fibrocartilage.<9> Diagnosis is do by history, symptoms, and also physical examination. At some point in the evaluation, imaging studies are usually conducted to dominance out other causes such as tumors, spondylolisthesis, and space-occupying lesions. Although some patients warrant surgery because of the severity of symptoms, most instances do not require surgical intervention as they deal with with conservative procedures such together anti-inflammatories and lifestyle alters for the patient.

In comparison to the degenerative conditions of cartilage, Achondroplasia is a hereditary disorder of cartilage formation and is the many common reason of dwarfism. The pathology viewed is as result of a mutation ~ above chromosome 4 impact the fibroblast growth factor receptor 3 (FGFR3) gene, i m sorry normally features as a an adverse regulator of bone and also cartilage growth. The mutation in achondroplasia results in a truncated dysfunctional protein that is constitutively active. These dysfunctional protein impede cartilage expansion and advance by suppressing chondrocyte proliferation and calcification.

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<10> The diagnosis the achondroplasia is usually during pregnancy via prenatal ultrasound. Over there is currently no known cure because that achondroplasia together it is not affected by a hormone pathway that deserve to be pharmacologically manipulated, and corrective surgery is controversial.<11>