Anatomy
Upper Limb
Question 24 of 239
A 72 year old man is brought to the ED by his daughter. He is complaining of a numbness in his right arm. On examination you note he has lost sensation to the posterior forearm. The skin over the posterior forearm is supplied by which of the following nerves:
Answer:
The posterior cutaneous nerve of the forearm, branch of the radial nerve, supplies the skin over the posterior forearm.Cutaneous Innervation of Upper Limb
Anatomy / Upper Limb / Innervation of Upper Limb
Last Updated: 1st November 2022
Table: Cutaneous Innervation of the Upper Limb
| Cutaneous Nerve | Origin | Skin Supplied |
|---|---|---|
| Lateral supraclavicular nerve | Cervical plexus (C3, C4) | Upper half of deltoid muscle |
| Superior lateral cutaneous nerve of the arm | Axillary nerve | Lower half of deltoid muscle |
| Inferior lateral cutaneous nerve of the arm | Radial nerve | Lateral arm below deltoid muscle |
| Medial cutaneous nerve of the arm | Brachial plexus (C8, T1) | Medial arm |
| Intercostobrachial nerve | Second intercostal nerve (T2) | Axilla |
| Posterior cutaneous nerve of the arm | Radial nerve | Posterior arm |
| Medial cutaneous nerve of the forearm | Brachial plexus (C8, T1) | Medial forearm |
| Posterior cutaneous nerve of the forearm | Radial nerve | Posterior forearm |
| Lateral cutaneous nerve of the forearm | Musculocutaneous nerve | Lateral forearm |
| Superficial branch of radial nerve | Radial nerve | Lateral dorsum of hand and lateral three and a half digits |
| Palmar cutaneous branch of ulnar nerve | Ulnar nerve | Medial half of palm |
| Dorsal cutaneous branch of ulnar nerve | Ulnar nerve | Medial dorsum of hand and medial one and a half fingers |
| Superficial branch of ulnar nerve | Ulnar nerve | Palmar surface of medial one and a half digits |
| Palmar cutaneous branch of median nerve | Median nerve | Lateral half of palm |
| Palmar digital branch of median nerve | Median nerve | Palmar surface and fingertips of lateral three and a half digits |
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/12/Cutaneous-Innervation-1.png)
Cutaneous Innervation of Upper Limb. (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Cutaneous Innervation of Arm
- The lateral supraclavicular nerve, branch of the cervical plexus, supplies the skin over the upper half of the deltoid muscle.
- The superior lateral cutaneous nerve of the arm, branch of the axillary nerve, supplies the skin over the lower half of the deltoid muscle (regimental badge area).
- The inferior lateral cutaneous nerve of the arm, branch of the radial nerve, supplies the skin over the lateral side of the arm below the deltoid muscle.
- The medial cutaneous nerve of the arm, branch of the brachial plexus, supplies the skin over the medial arm.
- The intercostobrachial nerve, branch of the second intercostal nerve, supplies the skin of the axilla.
- The posterior cutaneous nerve of the arm, branch of the radial nerve, supplies the skin over the posterior arm.
Cutaneous Innervation of Forearm
- The medial cutaneous nerve of the forearm, branch of the brachial plexus, supplies the skin over the medial aspect of the forearm.
- The posterior cutaneous nerve of the forearm, branch of the radial nerve, supplies the skin over the posterior forearm.
- The lateral cutaneous nerve of the forearm, branch of the musculocutaneous nerve, supplies the skin over the lateral aspect of the forearm.
Cutaneous Innervation of Hand
- The superficial branch of the radial nerve supplies the skin over the lateral dorsum of the hand and the dorsum of the lateral three and a half digits (except for the fingertips).
- The palmar cutaneous branch of the ulnar nerve supplies the skin over the medial half of the palm.
- The dorsal cutaneous branch of the ulnar nerve supplies the skin over the medial dorsum of the hand and the dorsum of the medial one and a half fingers.
- The superficial branch of the ulnar nerve supplies the skin over the palmar surface of the medial one and a half fingers.
- The palmar cutaneous branch of the median nerve supplies the skin over the lateral half of the palm.
- The palmar digital branch of the median nerve supplies the skin over the palmar surface and the fingertips of the lateral three and a half digits.
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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 |
