Anatomy & Physiology Chapter 18 Urinary System Organisms in the Urinary System Two kidneys, two ureters, urinary bladder, urethra Functions 1. Urine formation and excretion 2. Blood pressure control 3. blood pH regulation 4. fluid and electrolyte balance 5. Erythropoiesis – kidneys secrete this hormone which causes the red bone marrow to make more Red blood cells. Retroperitoneal – structures behind the peritoneum, like the kidneys Renal capsule – layer of connective tissue that surrounds each kidney Hilum – location where renal artery and nerves enter and where the renal vein, ureter, and lymphatic vessels exit the kidney Renal sinuses – cavity in the kidneys which contains blood vessels, adipose tissue, and part of the urine collection system Cortex – outer part of the kidney Medulla – inner part of the kidney that surrounds the renal sinus Renal pyramids – cone shaped structures that contains the tubules that transport urine from the nephrons to the calyx Renal columns – masses of blood vessels, tubes, and connective tissue that separate the renal pyramids Papillae – apex of a renal pyramid Renal Calyx – spaces that collect urine inside the kidney Minor calyces – any calyx that surround the apex of the renal pyramids Major calyces – when two or three minor calyces merge they form this structure Renal pelvis – funnel like part of the kidney, which collects urine before exiting through the ureter. The major calyces drain into this structure. Ureter – duct through which urine is moved from the kidney to the urinary bladder

Nephron – functional unit of the kidney Renal corpuscle – blood filtering component of the nephron of the kidney Two parts: Bowman’s capsule (glomerular capsule) and Glomerulus – group of capillaries composed of endothelial cells Proximal convoluted tubule – segment of the nephron which begins at Bowman’s

capsule and ends at the loop of Henle Loop of Henle – segment of the nephron tubule which forms a long loop in the medulla

from which water and minerals are reabsorbed into the blood Distal convoluted tubule – segment of the nephron tubule between the loop of Henle

and the collecting duct. Collecting duct – long, narrow tubule in the kidney that concentrates and transports urine from the nephrons to the minor calyces Vasa recta – a series of straight capillaries net to the loop of Henle in which reabsorption into the blood occurs Juxtamedullary nephrons – these nephrons are completely in the cortex Cortical nephrons – these nephrons have a longer loop of Henle that reaches from the cortex to deeper in the medullar. Bowman’s capsule – a cup-like sack at the beginning of the tubular component of a nephron in which filtration of blood occurs Glomerulus – a cluster of capillaries around the end of a kidney tubule where wastes are filtered from the blood. Podocytes – cells in Bowman’s capsule that wrap around the capillaries of the glomerulus. Plasma – fluid portion of blood Filtrate – fluid that has passed from the blood into Bowman’s capsule Urine – filtrate that has passed into the collecting ducts Renal arteries – arteries that branch off the abdominal aorta and enter the kidneys Interlobar arteries – the renal arteries divide into these arteries which pass between the renal pyramids and branch into the arcuate arteries Arcuate arteries – the interlobar arteries branch into these arteries which project into the cortex

Afferent arterioles – branches of the arcuate arteries that extend to the glomerulus as well as surround the nephron tubules Vasa recta – specialized portions of the capillaries that surround the loops of Henle and collecting ducts where reabsorption occurs The vasa recta drains into the interlobar veins. Three processes of urine formation

1. Filtration 2. Tubular Reabsorption 3. Tubular secretion

Filtration Nonspecific – materials are separated by size or charge Force that causes the separation – blood pressure Cells are too large, some of the larger proteins also cannot pass through the glomerulus Filtration pressure: Blood pressure in the glomerulus à forcing fluids into the capsule Capsular pressure (pressure of fluid already in capsule) à Preventing fluid from entering the capsule Colloid osmotic pressure – osmotic pressure is the movement of water through a Membrane to the side that has more particles concentration/less Water concentration. Cells/large proteins left in blood create a high osmotic pressure à Pressure to return water to the blood à blocks fluid leaving blood Filtration Pressure= Glomerular capillary pressure – capsular pressure – colloid osmotic pressure How is filtration pressure controlled? Afferent and efferent arterioles dilate or constrict to control blood pressure in glomerulus

The diagram below shows a cortical nephron. The arrows pointing away from the tubule show things that are being reabsorbed by the blood (they leave the tubule and enter interstitial space and then cross into the vasa recta capillaries. The numbers represent osmotic pressure. osmosis causes water to travel from low osmotic pressure to high osmotic pressure.

- Adding water to the filtrate or interstitial fluid decreases the osmotic pressure - Adding solids (such as salts) to the filtrate or interstitial fluid increases the osmotic pressure

Parts of the nephron do NOT allow the passage of water. The proximal convoluted tubule and descending loop of Henle are permeable to water The ascending tubule is NOT permeable to water but solutes diffuse out. The distal convoluted tubule and collecting duct are permeable to water if a hormone ADH (antidiuretic hormone) is present but NOT as permeable if ADH is not present. In proximal convoluted tubule – 65% of water leaves the tubule and enters the interstitial fluid because the fluid is very dilute compared to the interstitial fluid. End of proximal convoluted tubule – filtrate pressure = interstitial fluid pressure – water does not move As the filtrate descends into the cortex – interstitial fluid has much greater pressure – this is due to salts and ions either diffusing or being actively transported into the interstitial fluid. Water leaves filtrate. As the filtrate ascends – the ascending tubule is not permeable so the water does not leave but solutes do. The pressure and volume do not change but by the time the water returns to the cortex, so many particles have left that the filtrate is very dilute. Distal convoluted tubule – although the osmotic pressure in the cortex has not changed from 300 mOsm, the filtrate has become so dilute that water leaves again. The collecting duct – the fluid is now called urine These are controlled by the hormone ADH ,which allow water to leave if present Since the collecting duct

descends into the more concentrated part of the medulla, Almost 19% more of the original volume can be reabsorbed at this point.

If ADH is not present, no water is reabsorbed

Major Hormone Control of Kidney The pituitary gland releases Antidiuretic Hormone (ADH) ADH allows the collecting duct to be permeable to water

The heart can release Atrial natriuretic hormone (ANH) when blood pressure in the right atrium increases above normal. ANH causes the kidney to decrease Na+ reabsorption (Na+ stays in the filtrate in the tubules and does not enter interstitial space) This causes the osmotic pressure of the filtrate to increase. This means the osmotic pressure number inside the filtrate is higher. This means less water leaves the filtrate and more stays to become urine. The lower amount of water in the blood reduces blood pressure.

Ureters – only function is to transport urine from the kidney to the urinary bladder. Urinary bladder – stores urine – (a few milliliters to 1 Liter of urine) Urethra – tube that carries urine from the urinary bladder to the outside of the body Internal urinary sphincter – only found in males, it is a muscle that contracts to keep semen from entering the urinary bladder during sexual intercourse. Eternal urinary sphincter – muscle that surrounds the urethra and allows voluntary control of the flow of urine through the urethra. Trigone – triangle created by the three holes in the urinary bladder – the entry of the two ureters and the exit to the urethra Order fluids move through the urinary system : Blood plasma in the glomerulus à filtrate in bowman’s capsule à proximal convoluted tubule à descending loop of Henle à ascending loop of Henle à distal tubule à collecting duct à Minor calyx à joins with 2 other minor calyces for a total of 3 à major calyx à renal pelvis à Ureter à urinary bladder à urethra Order blood flows through the urinary system: Abdominal aorta à renal artery (1 per kidney) à interlobar arteries à arcuate arteries à afferent arteries à afferent arterioles àglomerulus capillaries à efferent venules à efferent veins à arcuate veins à interlobar veins à renal vein à inferior vena cava Know these for the test – this is for those people who actually read the notes! Please do not tell everybody because if everybody gets the extra credit I will know! Regular Credit

Is all urine formed in the cortex? True What happens in the medulla? The ONLY nephrons that extend in the medulla are the cortical nephrons and the ONLY part in the medulla is the loop of Henle and the ONLY thing that happens there is water resorption

Extra Credit Mrs. Johnson’s favorite superhero is the Tick and favorite avenger is the Hulk. There must be something about large, oddly colored superheroes.