Anatomy
Head and Neck
A 28 year old climber falls from a steep rock wall and sustains significant injuries to his back. Imaging shows injuries that impinge on the posterior rami of several spinal nerves. Which of the following muscles is most likely to be affected in this patient:
Answer:
The intrinsic back muscles, including the erector spinae muscles, are innervated by the posterior rami of spinal nerves. The extrinsic back muscles (including the trapezius, latissimus dorsi, rhomboid major and minor, and levator scapulae muscles) are innervated by the anterior rami of spinal nerves.Vertebral Column Muscles
Anatomy / Head and Neck / Vertebral Column
Last Updated: 11th April 2019
Movements by the vertebral column include flexion, extension, lateral flexion and rotation. Rotation occurs predominantly in the thoracic column. Flexion of the vertebral column is provided predominantly by the rectus abdominis muscle assisted for rotation by the obliques.
Back Muscles
Muscles of the back are organised into superficial, intermediate and deep groups.
- Extrinsic muscles (innervated by anterior rami of spinal nerves)
- The superficial group consists of muscles related to and involved with movements of the upper limb.
- The intermediate group consists of muscles attached to the ribs and involved in respiratory function.
- Intrinsic muscles (innervated by posterior rami of spinal nerves)
- The deep group consists of muscles directly related to movements of the vertebral column and head.
Deep Muscles
The deep muscles of the back include:
- the splenius capitis and cervicis (extensors and rotators of the head and neck)
- the erector spinae and transversospinalis (extensors and rotators of the vertebral column)
- the short segmental muscles.
Erector Spinae
The erector spinae is the largest group of intrinsic back muscles, lying posterolaterally to the vertebral column between the spinous processes medially and the angles of the ribs laterally. The muscles in the erector spinae group are the primary extensors of the vertebral column and head. Acting bilaterally, they straighten the back, returning it to the upright position from the flexed position, and pull the head posteriorly. Acting unilaterally, they bend the vertebral column laterally.
![Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/07/back-muscles.png)
Erector Spinae Muscles. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
