Renal function and test

• loop of henle is found in the renal medulla
• glomerulus is found in the renal cortex.
• ultra filtration is done in the renal cortex.
• reabsorption= tubules to blood
• filtration= blood through the glomerulus
• secretion= blood to tubules
• difference between secretion and reabsorption is osmosis
• each kidney contains 1-1.5 million nephrons and an average of 1.3 million.
• nephron is the basic structural unit of the kidney.
• two parts of nephron: glomerulus and tubules
• two types of nephron: cortical and juxta medullary nephrons
• cortical nephrons is for the removal of the waste and reabsorption of nutrients; they are 85% of the nephrons
• juxta medullary nephron is for the concentration of urine; have longer loops of Henle
• hydrostatic pressure drives ultrafitration.
• vasa recta is for the major exchanges of water and salt
• part of blood vessel that maintains osmotic gradient of concentration is the vasa recta.
• renal blood flow: Afferent arterioles, Efferent arterioles, Peritubular capillaries, and Vasa recta
• the varying sizes of the arterioles help create to create the hydrostatic pressure differential important for glomerular filtration and to maintain consistency of glomerular capillary pressure and renal blood flow within the glomerulus.
• efferent arteiole has smaller size.
• peritubular capillaries surrounds the proximal and distal convoluted tubules.
• vasa recta is located adjacent to the ascending and descing loop of henle
• glomerulus is where the urine formation begins.
• forms the beggining of the vein: vasa recta
• kidney receives 20-25% of the blood
• glomerulus is also known as Renal corpuscle
• glomerulus is consist of coils of capillary lobes
• bowman's capsule forms the beginning of the renal tubule
• glomerular filtration barriers - walls of glomerulus; non selective filter; chemical filtration
• capillary filtration barrier

  1. capillary wall membrane
  2. basement membrane
  3. visceral epithelium of bowman's capsule
• podocytes are foot like processes that has a shield of negativity that repels the negative charge proteins.
• glomerulus only allows less than 70KD, size: </= 8nm
• the only difference of filtrate (glomerular) and plasma is protein,
• factors influencing glomerular filtration:

  1. structure of capillary walls and bowman's capsule
  2. hydrostatic and oncotic pressure
  3. feedback mechanism of RAAS
• juxtamglomerular apparatus maintains the glomerular blood pressure at a relatrively constant rate regardless of fluctuations in systemic blood pressure; by increasing or decreasing the size of the afferent and efferent arterioles
• RAAS regulates the flow of the blood to and within the glomerulus and respond to the changes in blood pressure and plasma sodium
• juxtaglomerular apparatus is consists of:

  1. juxtaglomerular cells
  2. macula densa
• juxtaglomerular cells produces Renin (enzyme and protein)
• macula densa senses change in BP
• in RAAS: Angiotensin II will dilate the afferent arteriole and constrict the efferent areteriole and will trigger the release of aldosterone (ADRENAL CORTEX) and ADH (HYPOTHALAMUS)
• glomerular filtration test is not a valuable detector of early renal disease (but protein) but is used to know the extent of nephron damage of known cause of renal disease