Anatomy
Thorax
Regarding the muscles of the thoracic wall, which of the following statements is CORRECT:
Answer:
The internal intercostal muscles lie deep to the external intercostal muscles. They run posteroinferiorly from the rib above to the rib below, and are continuous with the internal oblique muscle inferiorly. The internal intercostal muscles act to move the ribs inferiorly and are most active during expiration.Thoracic Wall Muscles
Anatomy / Thorax / Thoracic Wall
Last Updated: 11th April 2019
The intercostal muscles are three flat muscles found in each intercostal space that pass between adjacent ribs. As a group the intercostal muscles provide structural support of the intercostal spaces during breathing and can also act to move the ribs.
Thoracic Wall Muscles. (Image by CFCF (Own work) [CC BY-SA 4.0 , via Wikimedia Commons)
The neurovascular bundles associated with the intercostal spaces pass around the thoracic wall in the costal grooves in a plane between the layers of the internal and innermost intercostal muscles. The intercostal and transversus thoracis muscles are innervated by the intercostal nerves (T1 - T11).
Table: Function of the Thoracic Wall Muscles
| Muscle | Function |
|---|---|
| External intercostal | Move ribs superiorly, most active in inspiration |
| Internal intercostal | Move ribs inferiorly, most active in expiration |
| Innermost intercostal | Acts with internal intercostal muscles |
| Transversus thoracis | Depresses costal cartilages |
Internal Intercostal Muscles
The internal intercostal muscles lie deep to the external intercostal muscles. They run posteroinferiorly from the rib above to the rib below, and are continuous with the internal oblique muscle inferiorly. The internal intercostal muscles act to move the ribs inferiorly and are most active during expiration.
External Intercostal Muscles
The external intercostal muscles lie in the outer layer. They run anteroinferiorly from the rib above to the rib below, and are continuous with the external oblique muscle inferiorly. The external intercostal muscles act to move the ribs superiorly and are most active in inspiration.
Innermost Intercostal Muscles
The innermost intercostal muscles are the deepest of the intercostal muscles and are very similar to the internal intercostal muscles in terms of structure and function.
Transversus Thoracis Muscle
The transversus thoracis muscle is also part of the innermost layer, and is continuous inferiorly with the transversus abdominis muscle inferiorly.
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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 |
