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The Excretory System
The Kidneys and the Nephron
| Question | Answer |
|---|---|
| What is excretion? | Excretion is the removal of metabolic wastes made by the body. |
| What do we call organisms that get their body heat from their external environment? | Ectotherms (cold blooded) |
| What do we call organisms that generate their own heat from metabolic reactions? | Endotherms (warm blooded) |
| What are the 3 main layers of human skin? | The epidermic, the dermis and adipose tissue |
| What are the 3 layers of the epidermic? | 1: The outer layer called the cornified layer made up of dead skin cells. 2: The middle layer: the granular layer where skin cells grow and mature. 3: The bottom layer called the malpigian layer that produces melanin. |
| What is the function of melanin? | Melanin is produced in response to UV light. It protects us from the dangerous effects of UV light in sunlight. |
| What is the function of adipose tissue? | Adipose tissue consists of a layer of fat used for insulation and food storage. |
| What is the function of the dermis? | The dermis is made up of connective tissue called collagen and contains blood vessels, nerves, sweat glands and hair folicles, |
| What is the function of the sebaceous gland? | The sebaceous gland secretes a material called sebum. Sebum is essential for healthy hair and skin. During puberty the increased production of hormones like testosterone cause an overproduction of sebum which can cause acne. |
| How does our body respond to cold temperatures? | The hair erector muscles contract causing the hair to stand upright which traps a layer of air that acts as an insulator. Blood vessels in the skin contract to reduce heat lost from the skin (vascoconstriction).Our nervous system causes our body to shiver |
| How does our body respond to warm temperatures? | Our bodies produce sweat as temperature rises. This keeps our body cool by latent heat. Blood vessels in the skin dilate and release heat out through our skin which gives us a flushes appearance. |
| What are the main organs of excretion? | 1: Our lungs excrete carbon dioxide and water vapour. 2: Our skin excretes sweat. 3: Our kidneys excrete urine which contains salt, water and urea. |
| What role does the liver have in excretion? | The liver breaks down proteins and nucleic acid to form urea and uric acid. These are then sent to the kidney for excretion. |
| What is the function of the adrenal glands? | The adrenal glands are found on top of each kidney. Their function is to produce adrenalin. Adrenalin is produced to prepare the body for extreme pressure, fight fright and flight. |
| How is blood brought to and from the kidneys? | Blood is brought to the kidneys by the renal artery which is a branch of the aorta. Blood leaves from the kidney by the renal vein which is a branch of the vena cava. |
| What is the main function of the kidneys? | The kidneys filter waste products like urea from our blood and control the pH of our blood. |
| What is the basic unit of the kidney? | The nephron. |
| What are the 2 blood vessels that bring blood into and out of the nephron? | The afferent and efferent arteriole. There is a large pressure difference between the 2 arterioles die to the fact that the afferent arteriole is wider than the efferent arteriole and that the afferent arteriole is a branch of the aorta/renal artery |
| What is pressure filtration? | The high pressure in the glomerulus forces plasma out. This is aided by the fact that the walls of the glomerulus are only one cell thick. This liquid is called glomerular filtrate. |
| Why does glomerular filtrate not contain protein or blood cells? | Protein and blood cells are to large to pass through the walls of the glomerulus. |
| What adaptations does the Proximal Convoluted Tubule have to help it reabsorb 80% of the salt and water that passes through it? | 1: It is very long. 2: Its walls are only one cell thic. 3: It has microvilli for increased surface area. 4: It has lots of mitochondria to help with active transport. |
| What are the functions of the descending and ascending limbs of the loop of Henle? | The descending limb is permeable to water and impermeable to salt and urea. The ascending limb is permeable to salt and urea but impermeable to water. |
| What are the main functions of the Distal Convoluted Tubule? | The Distal Convoluted Tubule controls the precise amount of water, salt and pH concentration in our blood. |
| How does the Distal Convoluted Tubule control the pH of our blood? | It controls our bloods pH by absorbing H+ ions in or out of the plasma to make it more or less acidic. |
| What is the control of water levels in our body called? What part of the body controls this? | It is known as osmoregulation. The level of water in our body is monitored by the hypothalamus. The hypothalamus controls the production of Anti-Diuretic Hormone from the Pituitary Gland. |
| By what other name is ADH known as? How does it control the level of water in our bodies? | ADH is also known as vasopressin. ADH causes the walls of the DCT to become more permeable to water, so more water will be absorbed. ADH is produced when we don't drink enough water, lose too much sweat of have a high salt diet. |
| What do we call a chemical that can switch off the production of ADH? Give 2 examples of these chemicals. | They are known as diuretics. Examples include caffeine and alcohol. |
| What effect does a high protein diet have on the volume, concentration and colour of urine produced? | A high protein diet has no effect on the volume of urine produced. The urine produces would be high in urea concentration and therefore darker in colour. |
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