Gross and Functional Anatomy of the Urinary System PDF

04/01/24 Gross and functional anatomy of the urinary system: Learning objective: describe the gross anatomy of the kidneys and ureters, including major blood vessels and blood ow through the kidney. Learning objective: de ne what is meant by the nephron, collecting tubules, ducts and juxtaglomerular...

04/01/24 Gross and functional anatomy of the urinary system: Learning objective: describe the gross anatomy of the kidneys and ureters, including major blood vessels and blood ow through the kidney. Learning objective: de ne what is meant by the nephron, collecting tubules, ducts and juxtaglomerular apparatus and what each of their functions are. Learning objective: recognise the basic histology of the kidney and glomerulus. Learning objective: explain basic embryology of the ascent of the kidneys. Gross anatomy: Function: to maintain homeostasis by regulating volume and kidney composition of the blood. ureter Achieved by: Excreted of waste ( urea, creatinine, uric acid ). Regulating water and salt balance in the blood. Bladder Regulate plasma concentrations of Na+, K+, Cl-. urethra Stabilise blood pH. Adrenal glands are not included. Position of the kidneys: They lie on the posterior abdominal wall. They are asymmetrical due to the liver, meaning the left is above the right. They lie bet ween the musculature and peritoneum. Upper right pole is at the transpyloric plane ( T12 ). Upper left pole is at the 11th rib. The kidneys are covered in renal fascia. They are embedded in thick fat pad and fascia. 1. Perinephric fat. 2. Paranephric fat. TA QL PM transversus Quadratus Psoas Major Abdominis cumborum Internal kidney structure: Thin brous capsule. Cortex which extends down to the centre of the kidneys called renal columns. Medulla. Arranged into pyramids. Apices project internally as papillae. Minor calyx major calyx Renal pelvis ureter Renal blood flow: important Ureters: These are a pair of muscular tubes with very small lumen. They begin at the renal pelvis and end at the 29 vesicoureteric junction. 1. Start of the ureter. 14814 441 2. Crosses the pelvic brim/common iliac artery. 3. Vesicoureteric junction. Microanatomy: Nephron: capsule Functional unit of the kidney. Traverses both the cortex and the medulla. Each nephron consists of a renal corpuscle cortex argue and a renal tubule. The renal corpuscle is the glomerulus and Medulla bowman’s capsule. Inter The tubule is the PCT, loop of Henle, DCT and the collecting duct. Mcians segmental arteries fire The Renal Corpuscle: This is the glomerulus and Bowman’s capsule. Glomerulus: Ball of capillary vessels from the afferent arteriole. United by mesangial cells and matrix. Bowman’s capsule: Blind end of renal tubule, invaginated by glomerulus. Juxtaglomerular wall lined by podocytes. Podocytes: Foot processes surround capillary loops. Pedicels are tightly interdigitated that ltrate must pass through. Gaps are covered by diaphragms of cell-surface proteins. Some water and small molecules will pass into Bowman’s capsule. Blood cells/plasma proteins/macro molecules are too large to leave so remain in the blood. Pressure is the main driving force. Glomerular pressure always maintain a matter what the systemic pressure is. Proximal convoluted tubule ( PCT ): This is the rst part of the renal tubule which originates from Bowman’s capsule. Entire tube is lined by single layer of epithelial columnar cells. Brush border of microvilli increases contact with tubular uid. Helps transport of ions and small molecules against steep concentration gradients. Loop of Henle: Has descending and ascending limbs which are connected by an abrupt u-turn. The limb walls are much narrower and thinner when in the medulla. Distal convoluted tubule: Few microvilli, more tubular shape. Tubule wall has a focal thickening near its renal corpuscle. The macula densa is a sensory apparatus concerned with Juhagiomerular blood ow. It regulates GFR as part of a feedback loop. Contains specialised cells which release H+ into ltrate to main pH. cens Collecting duct system: DCT leads into collecting tubule then collecting duct. Cortex Begin in renal cortex and descends through medulla toward papillae. Lined by simple cuboidal or columnar epithelial cells. Medulla Reabsorption of water occurs due to ADH/aquaporins. Papillae Juxtaglomerular apparatus: These are structures within the kidney that regulate nephron activity. 3 cell types: 1. Macula densa. ( affect GFR ). 2. Juxtaglomerular cells ( secrete renin ). 3. Extraglomerular mesangial cells. Mesangial cells: 4 postulated functions: Support capillary loops. Alter GFR via myosin-angiotensin mechanism. Phagocytic function. Maintain the basement membrane. Embryological development of the kidneys: 3 stages of development for excretory system: 1. Pronephros: rudimentary cell groups in the neck region, disappear bet ween the fth week but ducts persist into next stage. 2. Mesonephros: functional week 6 to 10. Form in the thoracolumbar region. Establish connection to future bladder and genitalia. Primitive ltration. 3. Metanephros: nal stage; functional from week 9. Becomes adult kidney. 2 metanephros close together in pelvis. Ascend towards adult position. Rotate medially as they separate, each becoming more lateral. Blood supply changes during ascent. Eventually stop when they come into contact with the suprarenal glands.