Where is the embryological origin of nucleus pulposus?
embryonic notochord
Over 60 years ago, the embryonic nucleus pulposus was postulated to form from the embryonic notochord (Walmsley, 1953) and studies in rat have supported this hypothesis (Rufai et al., 1995).
What is the notochord derived from?
The notochord arises from axial mesoderm at about 16 days and is completely formed by the beginning of the fourth week. It defines the longitudinal axis of the embryo, determines the orientation of the vertebral column, and persists as the nucleus pulposus of the intervertebral disks.
What forms the vertebrae embryology?
Paraxial mesoderm is responsible for the formation of the vertebrae as well as the dermis of the skin, striated skeletal muscle, muscles of the head and connective tissue [4].
What are the two main early embryonic development roles of the notochord?
The notochord is widely regarded to have two main roles in embryology: 1. Secreting signaling molecules (namely hedgehog proteins, such as sonic hedgehog (Shh)) to promote the development of the surrounding tissue and 2.
What does nucleus pulposus mean?
The nucleus pulposus is the soft, gelatinous central portion of the intervertebral disk that moves within the disk with changes in posture. The ability of the nucleus pulposus to resist compression is related to the ability of its proteoglycan composition to retain water.
How does the notochordal process form?
The notochord derives during gastrulation (infolding of the blastula, or early embryo) from cells that migrate anteriorly in the midline between the hypoblast and the epiblast (inner and outer layers of the blastula). These cells coalesce immediately beneath the developing central nervous system.
What is the nucleus pulposus made of?
The semifluid nucleus pulposus is composed of a loose network of cells of notochordal origin interspersed within a collagen and proteoglycan matrix. Nuclear proteoglycans have a strong affinity for water, giving the nucleus a positive swelling pressure or turgor.
How do vertebrae develop spinous process?
The spinous process of a typical cervical vertebra is short and bifid posteriorly. It is bifid because it develops from two separate secondary centers of ossification. This morphology is unique to cervical spinous processes.
Which structure is the main postnatal remnant of the embryonic notochord?
A postembryonic vestige of the notochord is found in the nucleus pulposus of the intervertebral discs.
What is the nucleus pulposus do?
What are the properties of the nucleus pulposus?
The nucleus pulposus is a highly hydrated gel with important material properties that include swelling pressure, compression modulus, permeability, and shear modulus. The nucleus has a large water and proteoglycan content.
What causes nucleus pulposus to protrude into spinal canal?
This leads to focal areas of annular wall weakness, which allow the nucleus pulposus to protrude into the spinal canal or against pain-sensitive structures (Fig. 149.5 C). Such protrusions are focal in nature and are easily seen on both T1- and T2-weighted MRI ( Fig. 149.7 ).
What makes up the nucleus of the anulus fibrosus?
The centrally located nucleus pulposus consists of collagenous and reticular fibers enmeshed in mucoid material. The anulus fibrosus, composed of concentric layers of fibrous connective tissue and fibrocartilage, retains the mucoid nucleus.
What happens to the nucleus when the disc annulus degenerates?
As the disc annulus and nucleus pulposus continue to degenerate, the ability of the annulus to completely contain and compress the nucleus pulposus is lost and with it the incompressible nature of the nucleus pulposus.