Download Structure of The Kidney - Fundamentals of Physiology - Notes | BMS 360 and more Study notes Biology in PDF only on Docsity! 27 April Introduction The concentration and only the concentration determines whether a substance is a toxin (Paracelsus) Steady-state level of any chemical in the body is based on input (production, ingestion, administration) and output (metabolism, elimination) The liver and kidneys play major roles in input/output and regulate homeostasis of soluble molecules Table 14 – 1 The kidneys are located retroperitoneally at the level of the lower ribs Structure of the Kidney Massive parallel processing of blood Renal arteries take blood to the cortex Afferent arterioles and glomeruli are all found in the cortex Juxtamedullary boundary – between cortex and medulla There are about 1 million nephrons in each kidney The Nephron (basic unit of the kidney) A nephron is comprised of Renal corpuscle = glomerulus + Bowman’s capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule The glomerulus is the capillary network within the renal corpuscle Structures associated with but not part of the nephron Afferent and efferent arteriole Peritubular capillaries Collecting ducts (multiple nephrons feed into a duct) Each nephron has two arterioles and two sets of capillaries associated with it The diameter of the afferent arteriole is larger than the efferent arterioles, increasing blood pressure within the glomerulus capillaries to promote filtration 20% of the plasma from the afferent arteriole is filtered into Bowman’s capsule Figure 14 – 5 The macula densa cells in the distal tubule plus the juxtaglomerular cells (secretes renin) within the afferent arterioles forms the juxtaglomerular apparatus Similar to fig 14 – 3 overview Blood Flow and Glomerular Filtration Resting cardiac output approximately 5 L/min 20% of cardiac output goes to two kidneys (1 L/min) GFR is normally about 180 L/day (70 kg person) GFR will be affected by factors that alter arterial flow and pressure Glomerular Filtration Glomerular capillary endothelial cells have pores Basement membrane forming outside wall of capillary is leaky connective tissue
