This damage can occur from both acute trauma and chronic degeneration. Each disc is made up of two parts:. On either side of the disc is a cartilaginous end plate that acts as connection between the disc and the vertebral body. Together with the annulus fibrosis, the nucleus pulposus helps reduce and cushion stress and weight from vertebra to vertebra.
The structural components of the nucleus pulposus are similar to the annulus fibrosus. It is a collection of molecules combined to form matrix consisting of:. The difference between the nucleus and the annulus is the concentration of each of these substances. The nucleus contains more water than the annulus — the more water, the more cushioning or shock absorbing ability a disc will have and the more height each disc will maintain.
This water will cause the discs to appear bright white on a T2 MRI image. Damage to a disc can cause water to leave or leak out of the disc and appear the disc to appear dark on MRI see below — Pathology for causes of DDD.
This lack of water will decrease the height of the disc and increase stress, as well as the amount of weight transmitted to the vertebra of the spine — also known as Degenerative Disc Disease DDD Annulus Fibrosus The annulus is a sturdy tire-like structure that encases a gel-like center, the nucleus pulposus. The intervertebral discs are the largest structures in the body without a vascular supply.
As mentioned above, the discs depend on osmosis to get the nutrients they need to survive and maintain their health. The annulus contains water, although less than the nucleus. It also contains layers of sturdy elastic collagen fibers. These fibers are oriented at different angles horizontally, similar to the construction of a radial tire. The collagen within these fibers is comprised of fibrous bundles made of protein bound together by proteoglycan gel.
The annulus fibrosis consists of an outer dense circumferential fibrous band and an inner fibrocartilaginous layer. The cartilaginous end plate is composed of hyaline cartilage that tightly adheres to the vertebral end plate. These are typically a consequence of trauma and can be exquisitely painful.
Larger tears, perforations or weaknesses within the annulus can break containment of the nucleus, causing it to bulge or herniate beyond the confines of the annulus leading to a disc bulge or disc herniation.
Endplates The top superior and bottom inferior of each vertebral body is coated with an endplate. Endplates are complex structures that blend into the intervertebral disc and help hold the disc in place. By injecting a small amount of contrast dye into the disc, your doctor can see whether it is damaged or abnormal, and further assess whether or not it is the disc causing pain.
Microdiscectomy This is a highly advanced, minimally invasive procedure proven to reduce pain caused by disc herniations sciatica that are unresponsive to conservative, non-surgical therapy. The sensory component of intervertebral discs is complex and actually differs depending on their location within the spinal column.
In contrast, the cartilage in the joints remains permanently unossified during life. Once damaged, cartilage has limited repair capabilities because chondrocytes are bound in lacunae and cannot migrate to damaged areas. Also, because cartilage does not have a blood supply, the deposition of new matrix is slow.
Damaged hyaline cartilage is usually replaced by fibrocartilage scar tissue. Over the last few years, surgeons and scientists have elaborated a series of cartilage repair procedures that help to postpone the need for joint replacement.
These include marrow stimulation techniques, including surgeries, stem cell injections, and grafting of cartilage into damaged areas. However, due to the extremely slow growth of cartilage and its avascular properties, regeneration and growth of cartilage post-injury is still very slow. Privacy Policy. Skip to main content.
Skeletal System. Search for:. Learning Objective Differentiate among the types of cartilage. Key Takeaways Key Points Cartilage is a flexible connective tissue that differs from bone in several ways; it is avascular and its microarchitecture is less organized than bone. Cartilage is not innervated and therefore relies on diffusion to obtain nutrients. This causes it to heal very slowly. The main cell types in cartilage are chondrocytes, the ground substance is chondroitin sulfate, and the fibrous sheath is called perichondrium.
There are three types of cartilage: hyaline, fibrous, and elastic cartilage. Hyaline cartilage is the most widespread type and resembles glass. In the embryo, bone begins as hyaline cartilage and later ossifies. Fibrous cartilage has many collagen fibers and is found in the intervertebral discs and pubic symphysis. Elastic cartilage is springy, yellow, and elastic and is found in the internal support of the external ear and in the epiglottis.
Key Terms chondroitin sulfate : An important structural component of cartilage that provides much of its resistance to compression. Chondrocytes : Cells that form and maintain the cartilage. Learning Objective Describe cartilage growth and repair.
Key Takeaways Key Points The division of cells within cartilage occurs very slowly. Articular cartilage function is dependent on the molecular composition of its extracellular matrix ECM. The remodeling of cartilage is predominantly affected by changes and rearrangements of the collagen matrix in response to forces experienced by the cartilage.
Cartilage growth mainly refers to matrix deposition, but can include both growth and remodeling of the extracellular matrix. It is part of the skin dermis area and in the joint capsules of the limbs. The main fibers that form this tissue are elastic in nature. These fibers allow the tissues to recoil after stretching. This is especially seen in the arterial blood vessels and walls of the bronchial tubes.
This is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes, and the intervertebral discs. Cartilage is composed of specialized cells called chondroblasts and, unlike other connective tissues, cartilage does not contain blood vessels. Cartilage is classified in three types: 1 elastic cartilage, 2 hyaline cartilage, and 3 fibrocartilage, which differ in the relative amounts of these three main components.
This is similar to hyaline cartilage but is more elastic in nature. Its function is to maintain the shape of the structure while allowing flexibility. It is found in the external ear known as an auricle and in the epiglottis. This is is the most abundant of all cartilage in the body. Its matrix appears transparent or glassy when viewed under a microscope. It provides strong support while providing pads for shock absorption. It is a major part of the embryonic skeleton, the costal cartilages of the ribs, and the cartilage of the nose, trachea, and larynx.
This is a blend of hyaline cartilage and dense regular connective tissue. Because it is compressible and resists tension well, fibrocartilage is found where strong support and the ability to withstand heavy pressure are required.
It is found in the intervertebral discs of the bony vertebrae and knee meniscus. Bone tissue is also called the osseous tissue. The osseous tissue is relatively hard and lightweight in nature. It is mostly formed of calcium phosphate in the chemical arrangement termed calcium hydroxyapatite, which gives bones their rigidity.
It has relatively high compressive strength, but poor tensile strength, and very low shear stress strength. The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. Filling the interior of the bone is the trabecular bone tissue an open cell porous network also called cancellous or spongy bone , which is composed of a network of rod and plate-like elements that make the overall organ lighter and allow room for blood vessels and marrow.
This is considered a specialized form of connective tissue. Blood is a bodily fluid in animals that delivers necessary substances, such as nutrients and oxygen, to the cells and transports metabolic waste products away from those same cells. It is an atypical connective tissue since it does not bind, connect, or network with any body cells.
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