The circulatory system Endocrine system

25 Source: US Federal Government via Wikimedia commons Figure 2.4 - Major endocrine glands Male on the left, female on the right 1. Pineal gland, 2. Pituitary gland, 3. Thyroid gland, 4. Thymus, 5. Adrenal gland, 6. Pancrease, 7. Ovary, 8. Testes. Pharmaceutical workers handling endocrine drugs like oestrogen in the pill or thyroxin used for thyroid treatment are at risk of upsetting their own endocrine balance and diethylstilboestrol DES has led to tumours in the children of workers of both sexes. Anaesthetic gases female anaesthetists and vinyl chloride exposure while pregnant have been linked to stillbirth or birth defects. Ionizing radiation can damage gonads reducing fertility or increasing risks of congenital malformations and cancer in the offspring.

2.4.1 The circulatory system

The circulatory system moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH. This system may be seen strictly as a blood distribution network, but some 26 consider the circulatory system as composed of the cardiovascular system, which distributes blood, and the lymphatic system, which distributes lymph. The main components of the human circulatory system are the heart, the blood and the blood vessels. The circulatory system includes:  Pulmonary circulation: where blood is passed through the lungs and becomes oxygenated.  Systemic circulation: where the oxygenated blood is passed through the rest of the body. An average adult contains 4.7 to 5.7 litres of blood, which consists of plasma, red blood cells, white blood cells and platelets. Also, the digestive system works with the circulatory system to provide the nutrients the system needs to keep the heart pumping. The lymphatic system is responsible for the removal of interstitial fluid from tissues as well as the absorption and transport of fats and fatty acids. The lymphatic system is also responsible for the transport of antigen presenting cells APCs. The cardiovascular system is exposed to any agent carried in the blood. Carbon monoxide and many metals including chromium, manganese and lead are thought to cause damage to heart muscle, but the only proven link is with cobalt. Chlorinated hydrocarbons like CFCs, trichloroethylene and 111- trichloroethane can induce arrhythmias abnormal heart rhythms due to defects in electrical conduction in the heart. Trichloroethylene has caused sudden death this way. Carbon disulphide viscose rayon industry speeds up atherosclerosis hardening of the arteries. High or low temperature work affects the peripheral circulation and can strain the heart. 27

2.5 The Blood