Excretion Flashcards
Excretion:
The removal of the waste substances of metabolic reactions from the body
Skin excretes:
Water, Mineral Ions
Lungs excrete:
Carbon Dioxide, Water
Kidneys excrete:
Water, Mineral Ions, Urea
Role of the Kidney:
Regulate water (and salt) content of blood
Excrete toxins and nitrogenous wastes
Osmoregulation:
The process of maintaining water and salt concentrations across membranes within the body
Kidney Explanation:
Two bean-shaped organs that filter the blood
Ureter Explanation:
Tube connecting the kidney to the bladder
Bladder Explanation:
Organ that stores urine produced by the kidney
Urethra Explanation:
Tube that connects the bladder to the exterior, where urine is released.
Urine is composed of:
Water, salts(ions) and urea
Renal Pelvis:
Links the kidney to the ureter
Cortex contains
What occurs:
- Tiny blood vessels 2. Nephrons
Ultrafiltration
Medulla contains
What occurs:
Connects to:
- Nephrons 2. Capillaries
Osmoregulation
Renal Pelvis
Parts of the Nephron in order
Glomerulus (Ball of Capillaries)
Bowman’s Capsule (Ultrafiltration)
Proximal Convoluted Tubule
Loop of Henle
Distal Convoluted Tubule
Collecting Duct
Ultrafiltration:
The capillaries in the glomerulus get narrower further on, forcing blood through under high pressure
This forces smaller molecules carried in the blood out of the capillaries and into the Bowman’s capsule (Glomerular filtrate)
Substances forced out: Glucose, water, urea, salts
Substances remaining: Cells and large proteins
Water is reabsorbed at:
Loop of Henle, Collecting Duct
Salts are reabsorbed at:
Loop of Henle
Glucose is reabsorbed at:
Proximal Convoluted Tubule (via active transport)
Less water means urine is more:
Concentrated
Adaptation of the nephron for glucose:
Many mitochondria to provide energy for active transport
Diabetes:
At a normal blood glucose level, there are enough gates in the PCT to remove all the glucose from the filtrate
People with diabetes cannot control their blood glucose levels and they are often very high
Hence, not all the glucose can be filtered out, and it continues in the filtrate and ends up in the urine
This is why doctors test urine for presence of glucose to check for diabetes
Role of ADH
Negative Feedback
The Hypothalamus detects low water content, stimulating the pituitary gland
The pituitary gland secretes increased amounts of ADH
ADH is carried in the blood
ADH arrives at the collecting duct, and causes it to become more permeable to water
More water is reabsorbed into the blood, less urine is produced, more concentrated
