Anatomy
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Abdomen
A patient presents with a superficial stab wound to the rectus sheath. Which of the following muscles is contained within the rectus sheath:
Answer:
The rectus sheath encloses the rectus abdominis and pyramidalis muscles, the superior and inferior epigastric vessels, the termination of intercostal nerves T7 - T11 and the 12th thoracic nerve and the accompanying vessels.Rectus Sheath
Anatomy / Abdomen / Anterior Abdominal Wall
Last Updated: 11th April 2019
The rectus sheath is formed by the aponeuroses of the three flat anterior abdominal wall muscles.
Derivation
- The anterior wall of the sheath is formed by the aponeurosis of the external oblique and half of the aponeurosis of the internal oblique (which splits at the lateral margin of the rectus abdominis).
- The posterior wall of the sheath is formed by the other half of the aponeurosis of the internal oblique and by the aponeurosis of the transversus abdominis.
The rectus sheath completely encloses the upper three-quarters of the rectus abdominis in the above formation but only covers the anterior surface of the lower one-quarter of the muscle. At this point (midway between the umbilicus and the pubic symphysis), the anterior wall is formed by the aponeuroses of all three muscles, there is no posterior wall to the rectus sheath and the rectus abdominis muscle is in direct contact with the transversalis fascia. Marking this point of transition is the arcuate line.
![By Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/02/Rectus-sheath-1.png)
Rectus Sheath (enclosing upper three-quarters of rectus abdominis muscle). (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/02/Rectus-sheath-2.png)
Rectus Sheath (covering lower one-quarter of rectus abdominis muscle). (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Contents
In addition to the rectus abdominis muscle, the rectus sheath also encloses:
- the pyramidalis muscle
- the superior and inferior epigastric vessels
- the termination of intercostal nerves T7 - T11
- the 12th thoracic nerve and the accompanying vessels
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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 |
