Anatomy of the back 1 Flashcards
Learning outcomes
- Describe the cutaneous innervation of the back
- Identify the intermediate extrinsic muscles of the back: the serratus posterior superior and serratus posterior inferior muscles; describe the function and innervation of these muscles
- Identify and describe the normal curvatures of the spine
- Describe the anatomical features of the joints of the vertebral bodies
- Identify and describe the anatomical features of the zygapophysial joints (facet joints) of the vertebral column
- Identify the projected bony anatomical landmarks onto the back
Curvatures of spine
We are born with a primary curves- thoracic and sacral regions
As we mature, development of secondary curves-cervical and lumbar regions
C- Convex anteriorly
T- Concave anteriorly
L- Convex anteriorly
S- Concave anteriorly
Curvature of spine
The shape of the vertebral column assists with its functions
Cervical spine – lordosis
Distributing weight of skull
Thoracic spine – kyphosis
Gives more space for the lungs to expand
Lumbar spine – lordosis
Distributing weight of trunk
Scoliosis- left to right or vice versa
Kyphosis- C shape
Lordosis- Reverse C shape
Vertebral column
Series of bones that support the weight of the body
C1-7, T1-12, L1-5, S1-5
Most vertebrae conform to a ‘typical’ design, with regional variations- IN GENERAL Body Pedicles Transverse processes Laminae Spinous process
Some vertebrae are considered ‘atypical’, i.e. they do not conform to ‘normal’ design
Uncovertebral joints
Found in the cervical vertebrae
Uncinate processes form joints with the superior vertebrae (C3-C7)
Zygapophysial joints
-Generally aim to limit movement
Regional variations
-In the cervical spine they project
posterosuperior/anteroinferior
- In the thoracic spine they project posterolateral/anteromedial
- In the lumbar spine they project almost medially and laterally
Intervertebral joints
Shock absorbers for the vertebral column
Found from cervical spine level to lumbar spine
Annulus fibrosus – tough outer layer
Nucleus pulposus – more gelatinous
Compressive weight forces ‘squash’ the nucleus pulposus
Damage or weakness in the discs can lead to back pain
- Slipped discs
- Compressed spinal nerves
- Deformities of the vertebral column
Cutaneous innervation
- Dorsal and ventral roots join to form a spinal nerve
- Spinal nerves contain motor and sensory fibres
- Spinal nerves immediately split into dorsal and ventral rami
- Dorsal and ventral rami are mixed nerves
- The skin and the deep muscles of the back are innervated by the dorsal/posterior rami of the spinal nerves
- In thoracic region, anterior rami are also known as intercostal nerves
- In the cervical, lumbar, sacral and coccygeal regions the anterior rami form plexuses (e.g. the brachial plexus)
Dermatomes
A dermatome is a strip of skin that is innervated by a single spinal nerve
Dermatome maps are used to detect damage or injury to peripheral and/or spinal nerves
Regarding the back:
- Cervical spinal nerves: C3 – C6
- Thoracic spinal nerves: T2 – T12
- Lumbar spinal nerves: L1 – L3
Muscles of the back
Assist in moving the upper limb
Assist in respiration
Assist in stability and support of body
Extrinsic- superficial
- Posterior axioappendicular muscle
- Connect the axial skeleton to the appendicular skeleton
- Act to move the upper limb
- intermediate
-Serratus posterior superior-Deep to the rhomboid muscles
-Serratus posterior inferior- Deep to latissimus dorsi
Connect from the vertebral column to the ribs
Act to move the thoracic cage
SPS – elevates the ribs
SPI – depresses the ribs
Innervated by the ventral/anterior rami
Intrinsic- deep
-iliocostalis, longissimus and spinalis. Together these muscles form a column, known as the erector spinae. The erector spinae is situated posterolaterally to spinal column, between the vertebral spinous processes and the costal angle of the ribs.
Importance of surface anatomy
Positioning of L3-L4 vertebrae- used for performing a lumbar puncture to obtain a sample of CSF from the thecal sac surrounding the spinal cord
