Handout Renal System

NCM 104 GU-Nsg. Paul Christian P. Santos

Renal System ANATOMY & PHYSIOLOGY The Kidneys -maintain the volume and composition of body fluid by filtration of the blood and selective reabsorption or secretion of filtered solutes. -retroperitoneal organs -situated on the posterior wall of the abdomen on each side of the vertebral column, at about the level of the twelfth rib. -left kidney is lightly higher in the abdomen than the right, due to the presence of the liver pushing the right kidney down. - take their blood supply directly from the aorta via the renal arteries; blood is returned to the inferior vena cava via the renal veins. FUNCTIONS 1) Controls fluid and electrolyte balance(Na & K) 2) Urine formation 3) Excrete end products of body metabolism (urea, uric acid, creatinine) 4) Secrete renin & eryhtropoietin 5) Manufacture & activation of vitamin D for normal calcium balance STRUCTURE Cortex -pale outer region Medulla-darker inner region has 8-18 conical regions, called the renal pyramids *cortex and the medulla are made up of nephrons Renal Pyramids -base of each pyramid starts at the corticomedullary border -apex of each pyramid ends in the renal papilla which merges to form the renal pelvis and then on to form the ureter. Renal Pelvis -is divided into two or three spaces major calyces subdiv. to minor calyces *walls of the calyces, pelvis and ureters are lined with smooth muscle that can contract to force urine towards the bladder by peristalsis. The renal corpuscle is made up of the glomerulus (a capillary network) and Bowman's capsule (the end of the tubule

Nephrons -these are the functional units of the kidney, and each kidney contains about 1.3 million -responsible for “ultrafiltration” of the blood and reabsorption or excretion of products in the subsequent filtrate -made up of: 1} glomerulus -filtering unit- 125ml/min of filtrate is formed by the kidneys as blood is filtered through this sievelike structure. This filtration is uncontrolled 2} proximal convoluted tubule -controlled absorption of glucose, sodium, and other solutes goes on in this region. 3} Loop of Henle -responsible for concentration and dilution of urine by utilizing “countercurrent multiplying mechanism” -it is water-impermeable but can pump sodium out, which affects the osmolarity tissues and will affect the subsequent movement of water in or out of the water-permeable collecting duct. 4} Distal convoluted tubule -responsible, along with the collecting duct for absorbing water back into the body -kidney doesn't produce 125ml of urine every minute. 99% of the water is normally reabsorbed, leaving highly concentrated urine to flow into the collecting duct and then into the renal pelvis. *GLOMERULAR FILTRATION RATE (GFR) is the volume of ultrafiltrate made per minute by both kidneys. The GFR is an important measure of kidney function The Ureters -muscular ducts that propel urine from the kidneys to theurinary bladder. -25–30 cm (10–12 in) long (adult) -arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle -cross the pelvic brim near the bifurcation of the iliac arteries *pelviureteric junction is a common site for the impaction of kidney stones (the 2nd is ureterovesical valve)

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NCM 104 GU-Nsg. Paul Christian P. Santos - URETERS run posteroinferiorly on the lateral walls of the pelvis -then curve anteriormedially to enter the bladder through the back(vesicoureteric) junction, running within the wall of the bladder for a few centimeters Ureterovesical valves -prevents backflow of urine. *In the female, the ureters pass through the mesometrium on the way to the urinary bladder. The Urinary Bladder -midline in the abdominal pelvis -collect and store urine -can hold up to 500 ml ((700 to 1000ml max) of urine -three openings -2 ureteral openings to receive urine from the kidneys -1urethral opening to drain the urine -form the trigone(smooth and triangular) sensitive to expansion

Urethral Sphincter -at the base of the bladder consists of ring like muscles which facilitate its opening and closing -the sphincter relaxes detrusor muscle contract and urination occurs Bladder muscle (detrusor muscle) is capable of distending to accept urine without increasing the pressure inside large volumes can be collected (700-1000ml) without high-pressure damage to the renal system occurring. *When urine is passed, the urethral sphincter at the base of the bladder relaxes, the detrusor contracts and urine is voided via the urethra URINE FORMATION The afferent arteriole brings unfiltered blood to the renal corpuscle flows through the glomerulus. glomerulus and of Bowman’s capsule The fluid and solutes that enter the capsule are called ultrafiltrate. Some water and solutes from the

Detrusor Muscle - smooth muscle of the bladder Blood Supply: O2 vesical obturator uterine gluteal vaginal arteries UnO2 = venous network drains the blood to the abdominal iliac vein The Urethra -urethra is a tube like organ which drains urine from the bladder to the exterior -lined with endothelium and surrounded by involuntary muscles -females it is about 5 to 6 cm long. (Generally it is 6mm wide in healthy patients) -males it is 15 to 22 cm long. It begins at the base of the bladder (surrounded by the prostate gland) and extends to the tip of the penis *Since the female urethra is shorter and located close to the vagina it is subjected to frequent urinary tract infections internal pudendal vaginal arteries urethra in females inferior vesical middle rectal arteries arterial blood in males

O2 supply arterial blood to the

O2 supply the bulk or

blood pass through this filtration membrane

From the renal corpuscle, the blood flows through the peritubular capillaries, and the ultrafiltrate flows through the tubule Water and solutes pass back and forth between the capillaries and the tubule in a highly controlled pattern (early part of tubule) Much of the filtrate gets reabsorbed (leaves the tubule and returns to the blood) before it reaches the end of the nephron over 99% of the water filtered out in the corpuscle is reabsorbed into the blood vessels

(later parts of the tubule) contents of the filtrate are “fine-tuned” Hormones control this process of fine-tuning aldosterone helps the body retain sodium and water ANP hormone (atrial natriuretic peptide) helps the body get rid of excess water

FILTRATE CHANGED INTO URINE Collecting duct Antidiuretic hormone (ADH) works in the collecting duct to regulate urine concentration

MICTURATION *If the body is dehydrated, ADH causes water to leave the collecting duct and return to circulation in the body, the urine will be concentrated *If a person has been drinking a lot of water and the body is well hydrated, ADH causes water to stay in the collecting duct, so it will leave the body in urine. In this case, the urine will be diluted

Nerve Innervation = pudendal nerve

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