Physiology
Basic Cellular
Where does haemopoiesis primarily occur in the foetus at 4 months gestation:
Answer:
Haemopoiesis in the foetus occurs firstly in the yolk sac, and later in the liver and spleen, which are the major haemopoietic organs from about 6 weeks until 6 - 7 months gestation, at which point the bone marrow becomes the most important site. In normal childhood and adult life, haemopoiesis is restricted to the bone marrow.Haemopoiesis
Physiology / Basic Cellular / Blood and Blood Flow
Last Updated: 26th July 2024
Haemopoiesis Sites
Haemopoiesis in the foetus occurs firstly in the yolk sac, and later in the liver and spleen, which are the major haemopoietic organs from about 6 weeks until 6 - 7 months gestation, at which point the bone marrow becomes the most important site. In normal childhood and adult life, haemopoiesis is restricted to the bone marrow.
Haemopoietic Stem Cells
All blood cells develop from haemopoietic stem cells (HSCs). Haemopoiesis occurs when HSCs bind, via cell surface receptors, to adhesion molecules and to fixed or secreted cytokines and growth factors. This binding triggers a cascade of phosphorylation reactions which transmits a signal to the nucleus to upregulate gene transcription. This signal promotes haemopoiesis by activating pathways that lead to cell proliferation, differentiation, maturation, inhibition of apoptosis (programmed cell death) or activation of mature cells.
HSCs give rise to two major lineages, the lymphoid lineage in which a common lymphoid progenitor gives rise to B-cells, T-cells and natural killer (NK) cells, and a myeloid lineage in which a common myeloid progenitor gives rise to erythrocytes, platelets, granulocytes and monocytes.
Haemopoiesis. (Image by unknown [CC-BY-SA-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 |
