Urinary system

Functions: Major Organs: -Kidneys -Bladder -Ureters -Urethra Removes waste from the blood. Regulates water and pH of blood Controls red blood cell production Major Organs: -Kidneys -Bladder -Ureters -Urethra © Gnature with Gnat 2018

Urinary system Bean-shaped organs located on either side of the spine The kidneys are the most important organs in the excretory system. Bean-shaped organs located on either side of the spine Protected and held in place by perirenal fat tissue Right kidney is slightly lower to make space for liver © Gnature with Gnat 2018

Kidney structure Outer cortex Inner medulla made of renal pyramids Surrounded by a renal capsule made of connective tissue Cross-section of a kidney: Outer cortex Inner medulla made of renal pyramids The renal pyramids are the site of urine production. © Gnature with Gnat 2018

After formation in the renal pyramid, urine drains into a tube called the minor calyx (plural: calyces), then into the major calyx. The major calyces converge at the renal pelvis, which then forms the ureter, ultimately removing the urine from the kidney and passing it to the bladder. © Gnature with Gnat 2018

Nephrons extend into both the cortex and medulla. The functional unit of the kidney is a nephron, which is a tubular network of blood vessels, nerves, and lymph vessels. Nephrons extend into both the cortex and medulla. Each kidney contains about 1.3 million nephrons. © Gnature with Gnat 2018

Nephron structure The renal artery brings blood to the kidney for filtration. The filtration occurs in a collection of capillaries called the glomerulus. The Bowman’s capsule is a sac-like projection that surrounds the glomerulus. © Gnature with Gnat 2018

Nephron Function © Gnature with Gnat 2018 Filtration: Secretion: 3 Fluid from blood plasma (minus proteins & blood cells) leaves the blood capillaries through filtration membrane Location: Bowman’s capsule Additional substances are actively removed from the blood (H+, drugs, steroids) Location: Distal (far) Convoluted Tubule Urine Formation: 4 -Fine-tuning of K+ and H+ in the urine to regulate levels in blood -Urine is transported to renal pelvis Location: Collecting duct 2 Reabsorption: Most of the water (80%) and many ions and nutrients are reabsorbed into the blood Location: Proximal (near) Convoluted Tubule & Loop of Henle © Gnature with Gnat 2018

From the kidneys, urine enters the tube-like ureters and empties into the elastic urinary bladder for storage. From the bladder, the urine passes through the urethra and is released from the body by 2 sphincter muscles. Just as in the rectum, there is an internal (involuntary) sphincter and an external (voluntary) sphincter. Loss of control (often with age) in the external urethra sphincter is the cause of incontinence. ureters Urinary bladder urethra © Gnature with Gnat 2018

urine 95% water, 5% solutes Urea, from metabolism of proteins, is the most common solute. Urinalysis (urine testing) can provide a lot of information about the body’s processes. Drugs and bacteria can also be found in urinalysis A high intake of water helps the kidneys to function efficiently. This is why doctors recommend lots of fluids during an infection. © Gnature with Gnat 2018

Kidney stones High protein and calcium diets can lead to the concentration of calcium oxalate in the renal pelvis, causing kidney “stones”. These often pass through the ureter on their own (painfully), but some large ones can be broken apart by ultrasound. © Gnature with Gnat 2018

Kidney dialysis When kidneys are not filtering blood correctly, dialysis may be used. In dialysis treatments, blood is removed from the body, passes through porous tubing that acts like nephrons, then returned to the body. Alternatively, a kidney transplant may be required. © Gnature with Gnat 2018

Images courtesy of: By CNX OpenStax - http://cnx.org/contents/GFy_h8cu@10.53:rZudN6XP@2/Introduc tion, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=49935734 By OpenStax College [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons © Gnature with Gnat 2018