Back
Vertebral column, spinal cord and meninges, and the intrinsic and extrinsic back muscles.
23 entriesVertebral column: 9Muscles of the back: 6Spinal cord & meninges: 5Suboccipital region: 3
Bones (6)
- Atlas and axis (C1 and C2) HYThe first two cervical vertebrae, specialized for head movement. The atlas (C1) has no body; the axis (C2) carries the dens, around which the atlas rotates. Their fractures and instability are high-yield.
- Cervical vertebrae HYSeven small vertebrae of the neck with transverse foramina for the vertebral arteries. Cervical radiculopathy, myelopathy and trauma clearance are the key clinical topics.
- Lumbar vertebrae HYFive large weight-bearing vertebrae of the lower back. Spondylolysis, spondylolisthesis and lumbar spinal stenosis are their key clinical problems.
- Sacrum and coccyx The fused sacral vertebrae form the posterior wall of the pelvis and articulate with the ilia at the sacroiliac joints; the coccyx is the vestigial tail. The sacral hiatus is the route for caudal epidural block.
- Thoracic vertebrae HYTwelve vertebrae that articulate with the ribs. They are the common site of osteoporotic compression fractures, metastases and spinal tuberculosis.
- Vertebral column HYColumn of 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, about 4 coccygeal) with four curvatures. It supports the trunk, protects the spinal cord, and is the site of scoliosis, kyphosis and inflammatory back disease.
Muscles (5)
- Erector spinae HYMain extensor of the vertebral column, running in three columns beside the spine. It is supplied by the dorsal rami of spinal nerves and is the usual site of mechanical low back strain.
- Latissimus dorsi Broad flat muscle of the lower back that extends, adducts and medially rotates the arm. It is supplied by the thoracodorsal nerve and forms the posterior axillary fold.
- Levator scapulae Strap-like muscle from the upper cervical transverse processes to the superior angle of the scapula. It elevates the scapula and is a frequent source of neck and shoulder stiffness.
- Rhomboid major and minor Two flat muscles between the upper thoracic spine and the medial border of the scapula that retract the scapula. They are supplied by the dorsal scapular nerve (C5).
- Trapezius HYLarge superficial triangular muscle of the upper back and neck that elevates, retracts and rotates the scapula. It is supplied by the spinal accessory nerve (CN XI), whose injury causes a drooping shoulder and lateral winging.
Nerves (3)
- Cauda equina HYBundle of lumbar and sacral nerve roots descending in the lumbar cistern below the end of the spinal cord. Compression causes cauda equina syndrome, a surgical emergency.
- Greater occipital nerve Medial branch of the dorsal ramus of C2 that supplies the skin of the back of the scalp. Its irritation causes occipital neuralgia, which responds to nerve block.
- Spinal nerves and roots HYThe 31 pairs of mixed nerves formed from dorsal (sensory) and ventral (motor) roots. Knowing where each root exits and what it supplies lets you localize radiculopathy.
Arteries (1)
Veins (1)
Organs (1)
Joints (2)
- Intervertebral disc HYFibrocartilaginous joint between vertebral bodies, made of a tough anulus fibrosus around a gel-like nucleus pulposus. Lumbar disc herniation at L4–L5 or L5–S1 causes sciatica.
- Zygapophysial (facet) joints Paired synovial joints between the articular processes of adjacent vertebrae. Their orientation determines spinal motion at each level, and facet arthropathy is a common cause of axial back and neck pain.
Ligaments (1)
Spaces & regions (3)
- Spinal meninges and spaces HYThree membranes (dura, arachnoid, pia) and the spaces between them surrounding the spinal cord. The epidural space is the target of epidural anesthesia, and the lumbar cistern is sampled by lumbar puncture.
- Suboccipital triangle Small triangle deep in the back of the neck, bounded by three suboccipital muscles. It contains the vertebral artery and the suboccipital nerve, and the greater occipital nerve emerges just below it.
- Triangle of auscultation and lumbar triangle Two gaps in the superficial muscles of the back. The triangle of auscultation lets breath sounds be heard clearly; the lumbar (Petit) triangle is a rare site of lumbar hernia.