Anatomy
Thorax
The sinoatrial node is located at which of the following sites:
Answer:
The sinoatrial node, the cardiac pacemaker, is located at the superior end of the crista terminalis at the junction of the superior vena cava and the right atrium.Cardiac Conduction System
Anatomy / Thorax / Heart and Pericardium
Last Updated: 28th February 2019
The cardiac conduction system initiates and coordinates contraction of the heart.
The sinoatrial node, the cardiac pacemaker, is located at the superior end of the crista terminalis at the junction of the superior vena cava and the right atrium.
Impulses generated by the sinoatrial node are propagated by the atrial myocardium to the atrioventricular node located near the opening of the coronary sinus, close to the attachment of the septal cusp of the tricuspid valve and within the atrioventricular septum. Here the impulse is briefly delayed before being spread to the ventricles.
The atrioventricular bundle (bundle of His) is a direct continuation of the atrioventricular node and continues along the lower margin of the membranous part of the interventricular septum before dividing into the right and left bundles which continue themselves as Purkinje fibres, the final component of the conducting system.
Cardiac Conduction System. (Image by OpenStax College [CC BY 3.0 , 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 |
