In the last lecture we started talking about the joints in the vertebral column, and we said that there are two types of joints between adjacent vertebrae: 1. Between the bodies of the vertebrae; which is the intervertebral disc (cartilaginous) and we talked about it in the last lecture. 2. Between the superior articular facet of the lower vertebra and the inferior articular facet of the upper vertebra. The type of this joint is plane synovial and the movement in this joint is gliding. Ligaments of the vertebral column: There are TWO ligaments between the bodies of the vertebrae: 1. Anterior longitudinal ligament 2. Posterior longitudinal ligament Those were mentioned in previous lectures. And 4 types of ligaments between the arches of the vertebrae: 1. Supraspinous ligament: Connects the tips of all spinous processes. 2. Interspinous ligament: Connects the spinous processes of adjacent vertebrae. 3. Intertransverse ligaments: connects the transverse processes of adjacent vertebrae. 4. Ligamentum flavum: Connects the laminae of adjacent vertebrae. It could be torn while performing Laminectomy. In the cervical spine, the interspinous and supraspinous ligaments thicken and combine to form Ligamentum nuchae; which is a triangular shaped ligament connects the external occipital protuberance (remember from the skull lab: it is the elevated area in the surface of the occipital bone) and the tip of the spinous
process of 7th cervical vertebra (which is the first cervical vertebra that can be felt). Curves of the vertebral column: First of all, we need to know two definitions: Kyphosis: is the concavity of the vertebral column anteriorly. Lordosis: is the convexity of the vertebral column anteriorly. - In the fetus, the vertebral column is concave anteriorly, but after birth, when the child becomes able to raise his head (4-5 months) the cervical part of the vertebral column becomes convex anteriorly (cervical Lordosis), and when the child begins to walk (1 year), the lumbar part of the vertebral column becomes convex anteriorly (lumbar Lordosis), while the thoracic area remains concave (thoracic kyphosis). Clinical application: abnormal curves: There are three different abnormalities in the vertebral column: 1. Kyphosis: there are several types of kyphosis: a. Acute: and it might be due to fractures or the destruction of the vertebrae by tuberculosis.
b. Senile: this type is mainly age-related and it might be caused by muscular weakness, osteoporosis or the degeneration of intervertebral discs. c. Round-shouldered: it is mild thoracic kyphosis caused by sitting for a long time. d. Congenital kyphosis: this type will be discussed later. 2. Lordosis: it can be caused by an increase in abdominal weight (due to pregnancy, tumor etc.) or a disease of the vertebral column (such as spondylolisthesis; in which case one vertebra slips over another). 3. Scoliosis: which is a lateral deviation of the vertebral column. It can be caused by Paralysis of muscles caused by poliomyelitis or it can be congenital which will be discussed later. Dislocations of the Vertebral Column: As with any other joint in the body, the vertebral column can be dislocated and this dislocation can be due to a fracture or without a fracture (the last occur ONLY in cervical vertebrae) and it can be unilateral (only one side is dislocated from its original place) or bilateral (where the two sides are dislocated in opposite directions). Unilateral dislocations can cause spinal nerve injury, while bilateral dislocations cause spinal cord injury and if it involves upper cervical vertebrae it can cause death due to injury of phrenic nerves C3 to C5 which will lead to diaphragm paralysis. Muscles of the back:
Muscles of the back are divided to three layers: 1. Superficial layer: the muscles related to the upper limb. 2. Intermediate layer: muscles that on the thoracic region and they help in the respiration. 3. Deep layer: those muscles are connected directly to the vertebral column. the line of gravity passes behind the centers of the hip joints and in front of the knee and ankle joints; so, most of the muscles are located behind the line and that what make us stand on our feet. (note that the gluteus maximus is not a gravity muscle because the line of gravity passes behind the hip joint). *The doctor said that you don t need to memorize the names of the muscles in the back.* Movement of the vertebral column: Flexion Extension Lateral flexion rotation Circumduction
Note that the most movable region is the cervical region. Venous plexus of the vertebrae: -located in the epidural space (which is the space between dura mater and the bone). - they are valve-less veins. -it is connected to many regions in the body; so, it is common to cancer to metastasize via those veins. - it is connected to a vein called the basivertebral vein which is located in the bodies of the vertebrae.
Special joints in the vertebral column: 1. Atlanto-Occipital Joints: are the joints between the occipital condyles of the occipital bone (remember from the skull lab that those are located around the foramina magnum) and the superior articular surface of the atlas (the 1st cervical vertebra, which is ring-shaped and has two lateral masses connected by an anterior arch and a posterior arch). Type: Synovial condylar joints. Movements: They allow extension, forward and lateral flexion (note that there is no rotation here). Ligaments: Anterior Atlanto-occipital membrane: connects the anterior arch of the atlas to the anterior margin of the foramen magnum. Posterior Atlanto-occipital membrane: connects the posterior arch of the atlas to the posterior margin of the foramen magnum. 2. Atlanto-axial Joints: are the joints between atlas and axis (it is the 2 nd cervical vertebra, it has dens called the odontoid process). They are three joints; one median and two laterals. Dislocation of this joint causes injury to vital centers responsible for respiration, resulting in death. A: Median atlanto-axial Joint: it is the joint between the odontoid process and the anterior arch of the atlas. Type: Pivot synovial joint Movement: Rotation Ligaments: a. Apical ligament: connects the apex of the odontoid process to the anterior margin of foramen magnum. b. Alar ligaments: connect the odontoid process to the occipital condyles. c. Cruciate ligament: It consists of a transverse and a vertical part. -The transverse part is attached to the lateral mass of the atlas. -The vertical part runs from the body of the axis to cranial aspect of occipital bone.
B: Lateral atlanto-axial Joints: they are the joints between the Inferior atlantal and the superior axial articular facets (this joint is just like other vertebral articular facets joints is plane synovial). 3. Sacroiliac Joints: Type: plane synovial joint, allows gliding movement. Functions: It transmits the body weight from lumbar spine to the hip bones. Ligaments: a. The ventral sacroiliac ligament b. The interosseous sacroiliac ligaments. c. The dorsal sacroiliac ligament. The development of the vertebral column: The development of the vertebral column started from the paraxial somite 33 pairs of cube-shaped parts that is originated from mesoderm and the notochord. This event is divided into 3 stages: 1- Mesenchymal stage: it occurs at the 4 th week, in which the 33 pairs of somites and the notochord between them are formed. 2- Chondrification stage: it occurs at the 6 th week, in which each somite divides into 3 parts; dermatome (that forms the epidermis), sclerotome (forms bone and cartilage) and myotome (forms the muscles of the back). 3- Ossification stage: it occurs at the 8 th week, in which each somite is divided into light (cephalic) and dark (caudal) areas. After that, the sclerotome from all somites will fuse together to form the skin and the intersomiter spaces of the notochord form nucleus pulposus and the rest of the notochord fuses with the body of the vertebrae. Finally, the somites extend to form the vertebral canal, the spine, transverse processes and the costal facet (only in the thoracic vertebrae)
Congenital anomalies: Spina bifida: vertebrae didn t fuse. Cause: incomplete fusion of halves of the vertebral arches resulting in midline defect usually in lumbosacral region. It has three types: 1- spina bifida occulta: malformation of one or more vertebrae (bones of the spine). It is sometimes called closed spina bifida, causes no problems. 2- Myelomeningocele: a neural tube defect in which the bones of the spine do not completely form. This results in an incomplete spinal canal. the spinal cords may remain in its place covered by the skin (meningocele), or the spinal cord and meninges (the tissues covering the spinal cord) protrude from (stick out of) the child's back.
Hemivertebra: Cause: failure of one of the chondrification center to appear so failure of half of vertebra to Form. Feature: defective vertebrae produce scoliosis (lateral curvature). Congenital kyphosis: at the junction of the thoracic and lumbar spine. In the first six to eight weeks of embryonic life, a genetic mistake occurs that results in the failure of formation or failure of segmentation on the front part of one or more vertebral bodies and disc.