Physiology
Cardiovascular
Regarding the heart, which of the following statements is CORRECT:
Answer:
The annulus fibrosis prevents electrical conduction between the atria and the ventricles, except at the atrioventricular node. The inner surface of the heart is covered by the endocardium which provides an anti-thrombogenic surface, the outer surface is covered by epicardium, a layer of mesothelial cells. The walls of the heart are formed from myocardium, and the left side has more muscle than the right (as the systemic circulation has greater resistance to flow, the left ventricle requires more force). Blood flows from the left atrium into the left ventricle via the mitral atrioventricular valve, and from the left ventricle into the aorta via the aortic semilunar valve.Functional Anatomy of Heart
Physiology / Cardiovascular / Cardiac Output
Last Updated: 26th July 2024
Heart Chambers
The heart consists of four chambers - two thin-walled atria and two muscular ventricles. The atria are separated from the ventricles by a band of fibrous connective tissue called the annulus fibrosus, which provides a skeleton for the attachment of muscle and cardiac valves, and prevents electrical conduction between the atria and ventricles (except at the atrioventricular node).
Heart Valves
Blood flows from the right atrium into the right ventricle via the tricuspid atrioventricular valve and from the left atrium into the left ventricle via the mitral atrioventricular valve.
Blood is ejected from the right ventricle through the pulmonary semilunar valve into the pulmonary artery and from the left ventricle via the aortic semilunar valve into the aorta.
Sectional Anatomy of the Heart. (Image by Blausen Medical Communications, Inc. [CC BY 3.0 , via Wikimedia Commons)
Heart Wall
The walls of the heart are formed from myocardium, and the left side has more muscle than the right (as the systemic circulation has greater resistance to flow, the left ventricle requires more force).
The inner surface of the heart is covered by the endocardium which provides an anti-thrombogenic surface. The outer surface is covered by epicardium, a layer of mesothelial cells. The whole heart is enclosed in a thin fibrous sheath, the pericardium.
Heart Wall. (Image by OpenStax College [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)])
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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 |
