Lecture 32 Flashcards
What are the two types of nephron?
There are two types of nephrons the cortical nephrons lie mainly in the cortex and the juxtamedullary nephrons (extend deep into the medulla, important for formation of concentrated urine). They mainly only differ in location.
What do nephrons function to do and what are the main parts?
Nephrons function to selectively filter blood, return to blood anything to be kept, carry waste away for storage and expulsion. Each is comprised of a Bowman’s capsule (where nephron meets blood supply), renal tubules (electively reabsorbs what the body needs and actively secretes in to filtrate what the body does not need anymore) and collecting ducts. They are association with the glomerulus and peritubular capillaries.
What are the two types of capillaries? What properties?
Glomerular cpillaries are thin walled, single layer, fenestrated endothelial cells which are fed and drained by arterioles, they are high pressure and tightly regulated to increase or decrease flow. Peritubular capillaries are specialised for reabsorption of materials which have came from the nephron. They are adjacent to the renal tubules and arise from efferent arterioles which drain from the glomerul, they are low pressure and porous. Vasa Recta are long straight vessels which come off these peritubular capillaries and are typically associated with the loop of Henle in Juxtamedullary nephrons. Blood will be viscous and protein/cell rich once filtered.
What is the renal corpuscle, what layers? What cells can be found in the glomerulus.
The renal corpuscle is the site where the blood and nephron meet, it is the glomerulus being enclosed by the two layers of the bowman’s capsule. It is the site of filtration. The Bowman’s capsule has two layers, the outer parietal layer of simple squamous cells and the inner visceral layer of podocytes. Between these two is the Bowman’s space. Mesangial cells are inside the glomerulus, they regulart filtration flow and produce extracellular matrix.
What are podocytes and what do they do?
Podocytes are specialised epithelial cells which surround the glomerular capillaries, thhey are very branched with the branches forming intertwining foot processes called pedicels, the spaces between which are known as filtration slits , filtered blood goes through into the Bowman’s space.
What layers does the filtration barrier consist of?
The filtration barrier consists of three layers, the fenestrated endothelium of glomerular capillary, a fused basement membrane behind to stop the capillar and nephron from coming apart and then before this the filtration slits between the pedicels of the podocytes.
What are the key points on the loops of Henle
The loop of Henle is the only prt of the tubule which penetrates the medulla, it has a thick descending limb (similar to PCT structure), then a thin descending limb (simple squamoud epithelium which is permeable to water and impermeable to sodium chloride). The thin ascending limb is simple squamous epithelium and impermeable to water and permeable to codiium chloride. It then has a thick ascending limb similar to DCT structure. The length is important for production of highly concentrated or very dilute urine (via use of countercurrent multiplier system and the hyperosmotic medullary gradient.)
Compare the proximal conoluted tubules and distal convoluted tubules.
The proximal convoluted tubules (PCT) are closest to the Bowman’s capsule, they are for bulk absorption and have a structure of: cuboidal epithelial cells with dense microvilli (brush border) on the luminal membrane, a highly folded basolateral membrane and with many mitochondria for active transport.
The distal convoluted tubule (DCT) is located between the loop of Henle and collecting duct, it has cuboidal epithelium which are thinner than those in the PCT, it has few microvilli and hence no bruch border with fewer mitochondria and reabbsorption influenced by aldosterone.
What does the collecting duct do and what cells does it have?
The collecting duct recieves filtrate from several DCTs, this thhen emptys at the papilla. It has a wall of simple cuboidal epithelium with principal cells for reabsorption and intercalated cells (found between principal cells) for the acid/base balance. Reabsorption is influennced by antidiuretic hormone.
What is the juxtaglomerular apparatus? What does it do?
The juxtaglomerular apparatus is a special zone in eaver neuron which is found next to the glomerulus where the DCT lies against the afferent arteriole, for the afferent arteiole the function is mechanoreceptors which release renin in response to blood pressure to stimulat angiotensin II, chemoreceptors sense sodium chloride concentration.
