Week 7 - The Urinary System/pH And Homeostasis
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How does the kidney maintain homeostasis?
• regulating blood electrolytes by secreting excessive ions into urine • regulates blood pH by excreting/conserving H+ or bicarbonate ions • regulating blood volume by conserving or eliminating water • regulating blood pressure (by regulating blood volume) • maintaining blood osmolarity by secreting excessive Na+ into urine • excreting waste products: ammonia, urea, creatinine • producing hormones (EPO, calcitriol, and produced the enzyme renin which leads to the production of angiotensin and aldosterone • regulating blood glucose
What are nephrons?
More than a million microscopic functional units that make up the bulk of each kidney
What are the 2 main regions of the nephrons?
• renal corpuscle - renal tubule
What is formed when fluid is filtered out of the blood of the nephrons?
Forms Filtrate
What are the two parts of the Renal Corpuscle?
• The Glomerulus (a mass of capillaries) - The Glomerular (Bowman’s capsule)
Where does nutrients enter the Renal Corpuscle?
Fed by the Afferent Arteriole
Where do nutrients drain in the Renal Corpuscle?
Excited into the efferent arteriole
What is the blood pathway through the nephron IN ORDER
• renal artery • afferent arterioles • glomerulus • efferent arterioles • peritubular capillaries • renal veins
What are the 3 steps to urine formation?
• Glomerular Filtration • Tubular Reabsorption • Tubular Secretion
What is Glomerular Filtration?
Water and small dissolved solutes move from the blood into the glomerular capsule
What does Glomerular Filtration need to be effective?
A constant blood pressure to force the fluids and solutes across the membranes into the Glomerular capsule
What type of the bodies nutrients are too large to filter into the Glomerular capsule?
Blood cells, plasma proteins, platelets. They remain in the blood
Where does Glomerular filtrate travel?
Into the renal tubules
What are the 3 waste products?
• creatinine (a waste product of muscle metabolism, excreted vis Glomerular filtration) • urea (limited reabsorption in from the convoluted tubule) • some electrolytes (Na+, K+)
What happens is there is a reduction in Glomerular filtration?
A rise in creatinine levels in the blood
The is the Glomerular filtration rate?
The amount of filtrate for are by both kidneys per minute
What is Tubular Reabsorption?
The process of returning important substances from the filtrate back into the blood
How does tubular Reabsorption occur?
• Passive transport (proximal convoluted tubule is ‘leaky’ and allies substances (Na+) to pass through into the capillaries) • water flows by osmosis • Active transport (sodium/potassium pump) • All cells have a decrease in Na+ in the cytosol
What has the greatest level of Reabsorption?
The proximal convoluted tubule
What is completely Reabsorbed?
• glucose - amino acids
What is largely reabsorbed?
• water (99%) • Na+, Cl-, Ca2+, H+, HCO3- Wherever Na+ goes, water will follow
What is reabsorbed somewhat?
• Ca2+ - Mg2+
What is reabsorbed very little
• urea - Unic acid
What happens as solutes are reabsorbed?
Water is reabsorbed via osmosis