Kidney & Osmoregulation: Excretion and Regulation of Waste

1. Topic 11.3 The Kidney & Osmoregulation

2. Excretory System • Function is to rid the body of toxic waste through excretion • Excretion: the removal of waste products of metabolic processes in the body

3. Types of Regulation • Osmoconformers: maintain solute concentrations in their body tissues that are isotonic to the surrounding environment. • Saltwater fish (sharks etc.) • Osmoregulators: have adaptations to live in aquatic environments that are not isotonic to their body tissues. • Freshwater fish

4. Types of regulation Cont. • Malpighian Tubules: osmoregulation by insects • Absorb salt, water and waste • Mammals: osmoregulation by mammals using the kidneys • use nephrons to regulate concentration of substances

5. The Human Excretory System • Consists of the following parts • Kidneys • Ureters • Urinary Bladder • Urethra • Kidneys carry out Both excretion and Osmoregulation The filtrate eventually Becomes urine

7. Parts of the Kidney • Outside is called the renal cortex • Middle is called the renal medulla • Inner funnel shaped section is called the renal pelvis • Renal artery brings blood into the kidneys • Renal vein takes blood away from the kidneys

9. The Nephron • The functional unit of the kidney • Ultrafiltration • Selective reabsorption • Secretion • excretion

10. Functions of the Nephron

11. The Glomerulus • Helps with ultrafiltration • 3 parts • Fenestration: pores between cells in the wall of capillaries that allow fluid to escape, but not blood cells • The basement membrane: covers and supports the wall of capillaries. Prevents plasma proteins from being filtered out. • Podocytes: form inner wall of Bowman’s capsule (foot like projections) prevents small molecules from being filtered out of the blood

12. Glomerulus

13. The Proximal Convoluted Tubule • Selectively reabsorbs useful substances by active transport • Most filtrate from glomerulus is reabsorbed • Most happens in the PCT • By the end of the PCT all glucose and amino acids & 80% of the water, sodium and other mineral ions have been reabsorbed

14. The Loop of Henle • Maintains hypertonic conditions in the renal medulla • Sodium ions are pumped out of the filtrate to the fluid between the cells in the medulla and the interstitial fluid • The Ascending limb is permeable to salts, but impermeable to water; water is retained • The descending limb is permeable to water but impermeable to sodium ions • Longer loops of Henle are found in animals that need to conserve more water • Then moves to DCT Distal convoluted tubule

15. Loop of Henle

16. Role of ADH • ADH = Antidiuretic Hormone • Filtrate in the DCT concentration is lower than that of normal body fluids (hypertonic) • If the solute concentration of blood is too low litter water is reabsorbed • If the solute concentration of the blood is too high they hypothalamus causes the pituitary to secrete ADH. • ADH causes the walls of the DCT and collecting duct to become more permeable to water

17. Protein, Glucose & Urea Filtration

18. Glucose in Urine & Diabetes • Presence of glucose in the urine is the main identifying feature of diabetes • High level of glucose present in glomerular filtrate and enters the PCT

19. Nitrogenous Waste • Organisms have evolved to excrete ammonia, urea or uric acid • Directly related to the environment in which they live • Freshwater organisms can easily secrete ammonia into their environment • Terrestrial animals need to convert ammonia to urea or uric acid

20. Renal Arteries Vs. Renal Veins • Composition of Blood in the Renal Artery & Renal Vein

21. Stuff to Know Afferent: Going towards, moving into Efferent: Going away from, moving out