| 100 mm Hg| Partial pressure of O2 in the alveoli. | 40 mm Hg| Partial pressure of O2 in the venous blood entering the pulmonary capillaries and partial pressure of CO2 in the alveoli.
| 46 mm Hg| Partial pressure of CO2 in the blood entering the pulmonary capillaries.
| 20 | Number of seconds after which loss of consciousness can occur in severe hypoxia (PO2 less than 20 mmHg).
| 200 | Number of times more affinity CO has for Hb than O2. | 3% | Percentage of O2 physically dissolved in plasma. | 97% | Percentage of O2 chemically combined with hemoglobin (Hb).
| 4 | Number of molecules of O2 each molecule of hemoglobin carries.
| 19.4 ml /100 ml| Total O2 content in arterial blood. | 14.4 ml / 100 ml| Total O2 content in venous blood. | 5 ml O2/min| Amount of O2 taken by tissues per minute. | 5% | Percentage of CO2 physically dissolved in plasma and percentage of CO2 in carbamino compounds.
| 90% | Percentage of CO2 transported as bicarbonate. | 4 ml | Normal value of tidal CO2 (volume of CO2 released from tissues as a result of metabolism). | 5 gm/100ml| Abnormal increase in reduced Hb in the blood above this value causes cyanosis. | 80% | Normal ratio of forced expiratory volume in the first second (FEV1) to forced vital capacity (FVC).
| 4 seconds| Normal time for air of FVC to be completely expired.
3. Gastrointestinal System
| 3 | Number of main pairs of salivary glands (parotid, submandibular, and sublingual).
| 1-1.5 liters/day| Amount of saliva produced per day. | 6.6- 7.1 | Slightly acidic pH of saliva. | posterior 1/3| Area of the tongue where mechanical stimulation can cause vomiting. | 3 liters /day| Amount of gastric juice produced per day. | first few centimetres| Area of the duodenum that is a frequent site of peptic ulcer.
| 2| Number of feedback control mechanisms that ensure complete neutralization of gastric secretion in the duodenum.
| 10 times | How much bile can be concentrated in the gall bladder. | 2 mg/dl | Increased serum bilirubin above this value causes jaundice. | 0.2 – 0.8 mg/dl| Normal value of serum bilirubin. | Three | Physiologically, the number of parts the large intestine can be divided into (proximal colon, distal colon, and rectum/anal canal).

4. Endocrine System
| Two| Number of main coordinating and integrating systems of the body (endocrine and nervous) and divisions of the pituitary gland (anterior and posterior).
| 1 | Number of thirds of individuals with hyposecretion of GH during childhood who are sexually mature. | Two| Number of thirds of individuals with hyposecretion of GH during childhood who are sexually immature.
| four | Number of parathyroid glands. | 9-11 mg/dl| Normal value of blood calcium level. | 7 mg/dl| Plasma calcium level below which manifest tetany occurs spontaneously. | 7 mg /dl| Approximate plasma calcium level in latent tetany.