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Excretory System

Excretory System. An organism’s way of breaking down nitrogenous wastes When proteins are broken down, they form ammonia Birds and reptiles convert ammonia to uric acid and mammals convert it to urea Malpighian tubules are found in arthropods Nephridia are found in earthworms

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Excretory System

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  1. Excretory System • An organism’s way of breaking down nitrogenous wastes • When proteins are broken down, they form ammonia • Birds and reptiles convert ammonia to uric acid and mammals convert it to urea • Malpighian tubules are found in arthropods • Nephridia are found in earthworms • Flame cells are found in flatworms

  2. Human Excretory System • Kidney regulate excretion • Kidneys are made up of nephrons Areas of the nephron Renal cortex • Bowman’s capsule • Proximal convoluted tubule • Collecting duct Renal Medulla • Loop of Henle • Distal convoluted tubule

  3. Cortical nephron Fibrous capsule Renal cortex Collecting duct Renal medulla Renal cortex Proximal convoluted tubule Renal pelvis Glomerulus Ureter Juxtamedullary nephron Distal convoluted tubule Loop of Henle Renal medulla (a) Figure 15.3a

  4. Flow of blood through a nephron • Blood enters at the Bowman’s capsule • The renal artery leads to the kidney and branches into arterioles then into a ball of capillaries called theglomerulus • Blood is filtered and plasma passes from the capillaries into the Bowman’s capsule – it is now called a filtrate

  5. Path of the filtrate • Passes through the B. capsule, through the proximal convoluted tubule, then the loop of Henle, then the distal tubule, and finally the collecting duct. • As it travels, it is modified to form urine. • Then the urine travels through ureters to the bladder, to the urethra

  6. Proximal convoluted tubule (PCT) Peritubular capillaries Glomerular capillaries Distal convoluted tubule (DCT) Glomerular (Bowman’s) capsule Efferent arteriole Afferent arteriole Cells of the juxtaglomerular apparatus Cortical radiate artery Arcuate artery Arcuate vein Cortical radiate vein Collecting duct Loop of Henle (b) Figure 15.3b

  7. How urine is made • Filtration – small substances such as ions, water, nutrients, salts pass from the glomerulus to the Bowman’s capsule, proteins and blood cells are too big • Reabsorption– as the filtrate moves through the proximal convoluted tubule, the small substances are re-absorbed by the blood in the peritubular capillaries (what remains is urine) • Secretion – as the filtrate moves through the remaining tubules, H ions, K ions, ammonium ions are secreted from the capillaries into the tubule

  8. Proximal tubule Distal tubule Glomerular capsule HCO3– Glucose and amino acids NaCl NaCl H2O Blood H+ K+ and some drugs Some drugs and poisons Collecting duct Filtrate Cortex H2O Salts (NaCl, etc.) HCO3– (bicarbonate) H+ Urea Glucose; amino acids Some drugs Medulla H2O Loop of Henle NaCl NaCl H2O K+ Reabsorption Active transport Passive transport Urea Secretion (active transport) NaCl H2O Urine (to renal pelvis) Figure 15.5

  9. Hepatic veins (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Aorta Renal vein Kidney Iliac crest Ureter Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Urethra (a) Figure 15.1a

  10. Hormones of the Kidney • Regulation occurs primarily by hormones • Antidiuretic hormone (ADH) - vasopressin • Prevents excessive water loss in urine • Causes more water re-absorption from the collecting duct • If you are dehydrated, ADH will work to re-absorb the water and urine will be concentrated • If your fluid intake is high, ADH will be low, the body won’t re-absorb most of the water and your urine will be dilute

  11. Hormones cont. • Aldosterone • Regulates sodium ion content of the distal convoluted tubule • Sodium is the electrolyte most responsible for osmotic water flows • Aldosterone promotes reabsorption of sodium ions • Remember, water follows salt!

  12. Skin • Epidermis, dermis, subcutaneous layers • Sweat glands are found in the dermis • Stratum corneum is in the epidermis and forms are barrier against invading microorganisms

  13. Hair shaft Dermal papillae Epidermis Papillary layer Pore Appendages of skin • Eccrine sweat gland • Arrector pili muscle Dermis • Sebaceous (oil) gland Reticular layer • Hair follicle • Hair root Hypodermis (superficial fascia) Cutaneous vascular plexus Nervous structures • Sensory nerve fiber Adipose tissue • Lamellar corpuscle • Hair follicle receptor (root hair plexus) Figure 4.3

  14. Excretory Bingo • Ammonia • Uric acid • Urea • Malpighian tubules • Nephridia • Nephron • Renal cortex • Renal medulla • Bowman’s capsule • Loop of Henle • Renal artery • Glomerulus • Filtrate • Ureters • Bladder • Urethra • Filtration • Reabsorption • Secretion • ADH (vasopressin) • Aldosterone • Epidermis • Dermis • Subcutaneous layer

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