Anatomy of the Spine Ligaments, Bones, & Disc

By: Ehren Allen, DPT, COMT

Anatomy of the Spine or Back 

Please watch this video on why Back Pain Can't Wait.

The spine is made up of numerous structures which support the body.  It includes 

  • bones
  • nerves
  • muscles
  • tendons
  • ligaments.  

There are over 25 bones called vertebrae which are stacked on top of each other to make up the spine.  It starts in the pelvis and ends at the head.  

Image of the spine with anatomy labelled and the cervical, thoracic, lumbar, sacrum, and coccyx specifically labelled.  Anatomy of the Spine

Spine Anatomy

The vertebrae are separated by a cushion called the intervertebral disk.  The disc is kind of like a jelly donut. The outer portion is made of thick connective tissue and attaches to the body of the vertebrae. 

 It is called the annulus fibrosis.  The inner portion is a thick gel material called the nucleus pulposus.  To learn more about spinal disks, please watch this educational video about disks.

There is a joint on each side of the vertebrae at each level.  These are called facet joints.  Facet joints provide stability but allow movement of the vertebrae on each other.  

MRI image of the lumbar spine with labelled arrows pointing to herniated discsMRI Image of Lumbar Disc

In the center of the vertebrae there is a large hole called the vertebral foramen. The spinal cord is housed within the foramen of the vertebrae.  It begins at the base of the skull at the bottom of the brain and runs down to the L2 level.  Nerves branch off of the spinal cord between every vertebrae.

The muscle anatomy of the back Includes many small muscles that control the small movements at each spinal level.  There are also large muscle that control posture and movement of the spine as a unit.  Many other large muscle attach to the spine which control extremity and trunk movements.

To learn more about the spine, please watch this video about the Anatomy of the Spine.

What are the Five Parts of the Spine?

The spine can be divided into 5 parts.  They include:

  • Cervical: the neck
  • Thoracic: the chest and anything with a rib attached to it
  • Lumbar: the low back
  • Sacrum: the part that sits between the pelvic bones in the back
  • Coccyx: the pointy part at the bottom

Image of the components of the spine

What Does C3 Spine Control?

C3 is a key level in the spine because injuries to the spinal cord at or above this level can impair the ability to breath.  This is because the Phrenic nerve branches off of the C1, 2, and 3 spinal levels. The phrenic nerve is the nerve which controls the  Diaphragm muscle which draws air into the lungs during breathing.  

What Part of the Spine Controls the Arms?

The quick answer is that most of the nerves that supply the arms come from the neck.  Nerves exit the neck from C3 to T1 and join together to give nerve supply to the arms. An injury to the neck or a disk issue between the vertebrae in the neck can cause problems in the arms. These problems may include weakness, loss of sensation, or pain. Problems in the neck can also cause pain under the shoulder blades. 

What Part of the Spine Controls the Legs?

The quick answer is that the lower part of the spine controls the legs.  The nerves that exit the spinal cord in the lower portion travel through the spaces between the lumbar and sacral segments. They join to form the lumbosacral plexus, which is a network of nerves.  

Low Back Nerves

The nerves separate in the low back and pelvic regions in to several large nerves. These include the:

  • Femoral Nerve
  • Obturator Nerve
  • Sciatic Nerve

If you have back or neck problems, you need to have a thorough examination.  With expert surgeons, physical therapists and physical medicine physicians, JOI can help you get back to the activities of daily living.

For physical therapy appointments, please call 904-858-7045To schedule an appointment with an Orthopedic Spine Specialist, please call 904-JOI-2000, schedule online or click the link below.



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