Anatomy
Upper Limb
You are part of the trauma team caring for a 23 year old tree surgeon who has fallen approximately 7 metres from a tree. He tells you that as he fell he tried to grab a branch and his right arm was hyperextended. He now has a weakness to the hand muscles on the right side. The trauma team leader suspects a brachial plexus injury. The brachial plexus is formed by the union of which of the following spinal nerves:
Answer:
The brachial plexus is formed by the union of the anterior rami of spinal nerves C5 - T1.Brachial Plexus
Anatomy / Upper Limb / Axilla
Last Updated: 8th April 2019
![By Brachial_plexus.jpg:Mattopaedia at en.wikipedia derivative work: Captain-n00dle (talk), MissMJ (Brachial_plexus.jpg) [Public domain], from Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/12/Brachial-Plexus.png)
Brachial Plexus. (Image by Mattopaedia at en.wikipedia derivative work: Captain-n00dle (talk), MissMJ (Brachial_plexus.jpg) [Public domain], from Wikimedia Commons)
ROOTS:
The brachial plexus is formed by the union of the anterior rami of spinal nerves C5 - T1.
TRUNKS:
In the inferior neck, the roots of the brachial plexus unite to form three trunks:
- A superior trunk (from the union of the C5 and C6 roots)
- A middle trunk (which is a continuation of the C7 root)
- An inferior trunk (from the union of the C8 and T1 roots)
DIVISIONS:
Within the posterior triangle of the neck, the trunks divide into anterior and posterior divisions.
CORDS:
Within the axilla, the divisions reunite to form three cords (named by their relation to the axillary artery):
- The lateral cord (from the anterior divisions of the superior and middle trunks)
- The medial cord (a continuation of the anterior division of the inferior trunk)
- The posterior cord (from the posterior divisions of all three trunks)
NERVES:
The cords give rise to the major branches of the brachial plexus.
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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 |
