L26 - Kidney Structure and Blood Filtration

• What are the functions of the kidneys?

  - regulate water, salt, pH- remove metabolic waste- remove foriegn chemicals- gluconeogenesis- produce hormones/enzymes (eg erythropoietin, renin)

  
• What does erythropoietin contol?

  Erythrocyte production
• What does renin control?

  Blood pressure and Na+ levels
• Describe the anatomy of the kidney

  capsule, cortex, medulla, renal pelvis, ureterTubular organ - tubes connecting renal pelvis to ureter and nephrons

  
• What's the functional unit of the kidney?

  The nephron

  
• Describe the nephron- How is it adapted for its function?- (describe the journey of filtrate)

  Highly vascularised for reabsorptionafferent and efferent arterioles, glomerulus in bowman's capsule, proximal convoluted tubule (PCT), loop of Henle (ascending and descending), distal convoluted tubule (DCT), collecting duct, then filtrate goes to renal pelvis

  
• Where is the nephron?

  At interface between cortex and medulla

  
• What are the two main arterioles?

  Afferent - blood going TO nephron. Before glomerulusEfferent - blood going away FROM nephron. After glomerulus

  
• What are the 3 main functions of the nephron?

  1. Glomerular filtration2. Tubular secretion3. Tubular reabsorption

  
• What are podocytes?

  specialised cells between blood vessels and nephron. Allow filtration from blood to nephron- have "feet" - tiny projections that gab onto blood vessels to create sieve structure

  
• How are blood vessels adapated for filtration in the glomerulus?

  undulated, high density, bundled - fast and effective filtration

  
• Describe how glomerular filtration occurs.Active or passive process?

  Passive- podocytes surround glomerular blood vessels- podocyte 'feet' create sieve-like structure- allows passage of small molecules from blood to kidney tubules.

  
• What molecules can be filtered by glomerular filtration? What can't?

  Filtered = Small molecules eg glucose, water, salt, amino acids, small drugsNot filtered = large molecules eg proteins. Too big to pass through sieve-like structures of podocytes

  
• Define Glomerular Filtration Rate

  GFR = Volume of fluid filtered from glomerulus to bowman's space per unit time
• How is GFR regulated?

  By control of blood pressure either side of glomerulus(constrict/dilate blood vessels)- this regulates force applied across podocyte 'sieve'. more force = more filtration

  
• How can GFR maintain water and salt balance?

  By regulating rate at which fluid is filtered through nephrons
• How can we reduce GFR?What effect does this have on water and salt excretion?

  Constrict AfferentDilate Efferent= blood pressure across glomerulus lowered, so GFR lowered- decreases water and salt excretion

  
• How can we increase GFR?What effect does this have on water and salt excretion?

  Dilate AfferentConstrict Efferent= higher pressure across glomerulus, so more blood flows in and GFR increased- increases water and salt excretion