Excretory+system

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 * EXCRETORY SYSTEM by Nick Pekas and Gabe Sexton**

**//1.//** **//Structures of the Renal (Excretory) System://**
 * Kidneys (Main Organs of the Excretory System)**

-Shaped like a kidney bean, with renal blood vessels entering & exiting the concave side.


 * Structures of the Kidney:**

-Renal Pyramids are fan shaped structures made up of thousands of nephrons.

-Nephron (Main Component of the Kidney)

-Glomerulus (AKA renal corpuscle) – portion of a nephron that begins the process of filtration · Blood enters the glomerulus by the renal artery


 * Function(s)of the Kidney**:

a. After a nephron filtrates the blood, it empties the waste into a collecting duct
 * Collects and excretes nitrogen waste
 * · Regulates blood pressure
 * · Activates Vitamin D (regulates calcium absorption)
 * · Controls erythropoiesis (blood cell creation) using the hormone erythropoietin (which activates when the kidney recognizes low Oxygen conditions)
 * · Osmoregulation (control of ions and water balance in the body)

b. Collecting Ducts –Small tubes in a nephron that carry nitrogen waste

c. Minor Calyx - Many collecting ducts empty into the Minor Calyx (a larger duct) d. Major Calyx – Many Minor Calyces empty into a Major Calyx

e. Renal Pelvis – All Major Calyces empty into the renal Pelvis where the nitrogen waste enters the ureters.



1. [|Renal pyramid] • 2. [|Interlobular artery] • 3. [|Renal artery] • 4. [|Renal vein] 5. [|Renal hilum] • 6. [|Renal pelvis] • 7. [|Ureter] • 8. [|Minor calyx] • 9. [|Renal capsule] • 10. [|Inferior renal capsule] • 11. [|Superior renal capsule] • 12. [|Interlobular vein] • 13. [|Nephron] • 14. [|Minor calyx] • 15. [|Major calyx] • 16. [|Renal papilla] • 17. [|Renal column]


 * Ureters:**

-Long tubes that carry urine from the kidneys to the urinary bladder


 * Urinary Bladder:**


 * -Storage sack for urine. Has nerves within that create the urge to urinate when it is filled to 25% capacity.
 * Two muscles that control urination are the internal and external sphincter. The internal sphincter is involuntary, and the external one is voluntary.
 * If the Urinary Bladder ever reaches 100% capacity, the external sphincter is opened automatically, and urination takes place.

-Carries urine out of the body
 * Urethra:**


 * //2. Enzymes/Hormones//**

Antidiuretic Hormone (ADH)
 * Controls the reabsorption of water into the blood
 * Released by the pituitary gland in the brain
 * Low fluid levels in blood - Increased production of ADH, more water is reabsorbed
 * High fluid levels in blood - Decreased production of ADH, less water is reabsorbed

Aldosterone
 * Controls passage of sodium ions from nephron to blood
 * Also affects water transfer, since "solute sucks"
 * The sodium ion has a positive charge, so negatively charged ions will also follow it into the blood

Renin (the only enzyme in this list)
 * Stimulates production of Angiotensin I, which is converted to Angiotensin II
 * Released by afferent arteriole cells (inside nephron)

Angiotensin II The co-operation of Renin, Angiotensin and Aldosterone is known as the Renin-Angiotensin-Aldosterone System (RAAS). Its overall effect is to regulate blood pressure and fluid balance.
 * Stimulates release of Aldosterone
 * Increases blood pressure by causing blood vessels to constrict

**//3.//** **//Regulation of the Urinary System//**
 * · Adrenal Gland
 * sits on top of kidneys produces hormones that help control osmoregulation by determining how many sodium and chloride ions are reabsorbed into the bloodstream.

o This controls water balance because water follows the greatest concentration of solute i.e. “solute sucks”


 * · Antidiuretic Hormone (ADH), which is also known as Vasopressin
 * Is secreted by the pituitary gland and controls the amount of water absorption by nephron tubules (controls the amount of urine produced)

//**4. Communication**//

With Excretory cells/organs: Explained in section 2

With rest of body/other body systems: The Nervous System is constantly communicating with all systems via nervous impulses.

The Circulatory System can communicate with the Excretory system through **//Atrial Natriuretic Hormones//**
 * Inhibits release of Aldosterone and ADH
 * Produced by the heart when there is excess blood in the body
 * Inhibition of Aldosterone and ADH means more ions and water are excreted in urine, decreasing blood volume

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