Urinary System The eye

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2.9 Urinary System

The kidney plays an important role in the maintenance of fluid and electrolyte balance by filtration and selective re-absorption of them into the blood. It excretes via urine unwanted waste products including toxins, made water- soluble by metabolism in the liver. Source: US Federal Government via Wikimedia commons Figure 2.9 – Urinary System 1. Kidneys, 2. Ureter, 3. Bladder, 4. Urethra Toxins can damage the kidney which in turn affects calcium metabolism, acid- base balance and re-absorption of water. In acute renal failure, urine flow may cease altogether. lonising radiation can cause renal cell damage and fibrosis. Because urine is concentrated and delayed within the bladder, exposure to this organ is far longer than to the rest of the urinary tract. It is thus far more susceptible to industrially induced cancers.

2.10 The eye

The eyes need no explanation as to their functions. It is also clear that they are relatively fragile. Eyes are protected to an extent by the frontal bones above them and the eyelids, together with the blink reflex. Eyelashes keep 34 dust particles away and tears provide a dilution factor for intruding chemicals and sterilisation against infecting agents. Due to their fragile construction eyes are particularly susceptible to injury. Penetrating wounds can lead to corneal damage, cataract and retinal detachment, any of which can cause blindness. Damage to the iris can provoke a sympathetic reaction in the other eye and total blindness. Acids and alkalis will burn the cornea. Alkalis are especially dangerous as they sting less, and by the time the victim realises and washes them away, the front of the eye can have been dissolved. Any irritant gases, like sulphur dioxide and ammonia can cause conjunctivitis characterised by redness, discomfort and watering of the eyes. Allergens like plants and dyes sometimes produce a similar reaction. An extremely painful conjunctivitis including photophobia unwillingness to look at light follows a few hours after exposure to ultra-violet radiation used in welding. The condition is known as arc eye and usually involves the cornea as well as conjunctiva keratoconjunctivitis. Cataracts lens opacities result from trauma a penetrating wound or severe blow, heat glass workers eye and irradiation lasers and microwaves. Retinal burns can be caused by infra-red radiation and lasers. Cataracts can be removed and replaced by artificial lenses or contact lenses. Retinal burns and tears produce irrevocable damage to that area of vision blind spots. Source: Wikimedia commons Figure 2.10 - The Eye 35 3 FUNDAMENTALS OF TOXICOLOGY

3.1 Introduction