Urinary system & Excretion

1. Urinary system & Excretion

2. Excretion • The removal of metabolic wastes from the body • Kidneys are the primary organ of this process Urinary system & eXcretion

3. 1. Excretion of Metabolic Wastes • Removing metabolic waste products, notably nitrogenous waste from breakdown of amino acids (aa): • Urea • Breakdown of amino acids releases ammonia which is toxic to cells) • Liver converts the ammonia to urea so it be safely transported in the blood to the kidney where it is eliminated in urine • Creatinine • Uric acid • if too much uric acid crystals can form in joints • This is known as gout Functions of the Urinary System

4. Functions of the Urinary System

5. 2. Maintenance of Water-Salt Balance • Blood volume is associated with salt balance in body • Salt (NaCl) can cause water diffusion into blood • ↑ salt = ↑ blood volume = ↑ blood pressure Functions of the Urinary System

6. 3. Maintenance of Acid-Base Balance • Kidneys regulate acid-base in blood • Excretion of hydrogen ions and reabsorption of bicarbonate to keep pH around 7.4 • Urine often has a pH of 6 Functions of the Urinary System

8. 4. Secretion of Hormones • Renin • Leads to secretion of aldosterone • Reabsorption of sodium ions • Erythropoetin • Stimulates red blood cell production • Activates vitamin D from the skin • Helps promote calcium absorption from the digestive tract. Functions of the urinary system

9. Fig. 16.1 The urinary system

10. Kidneys • Two bean-shaped organs • Located near lumbar region on either side of vertebral column • Has a depression called the hilum where the Renal artery Renal vein are located Organs of the Urinary system

11. Ureters • Conduct urine from the kidneys to the bladder • Small, muscular tube 25cm long, 5 mm thick Organs of the Urinary system

12. Urinary Bladder • Stores urine until it is expelled from the body • Located in the pelvic cavity • 3 openings (orifices): • 2 for the ureters • 1 for urethera Organs of the Urinary system

13. Urinary Bladder con’t... • Expandable • Detrusor Muscle – bladder wall • Sphincter Muscles – surround bladder neck and urethra Organs of the Urinary system

14. While the bladder is filling: • the detrusor muscle is relaxed so the bladder wall can expand and the sphincter muscles are contracted to keep the urethra closed • When the bladder empties: • the detrusor muscle contracts to squeeze the urine out, and the sphincter muscles relax so the urethra can open up http://www.aboutkidshealth.ca/en/howthebodyworks/kidneysandbladderoverview/bladderfillingandemptying/pages/default.aspx Organs of the Urinary system

15. Urethra • Small tube that extends from the urinary bladder to an external opening • females • 4 cm long • Increases likelihood of urinary tract infection • Not connected to reproductive system • Males • 20 cm long • Common pathway for reproductive and urinary tracts Organs of the Urinary system

16. Female & Male Urinary Systems

17. URINATION • Micturition • When the bladder fills to 250ml • Stretch receptors in the bladder wall send sensory impulse to the spinal cord • Motor impulses from spinal cord send a signal the bladder • Bladder contraction and sphinter to relax • This is called an involuntary reflex • Present in infants and young children

18. In older children and adults the brain can control this reflex and delay urination until a suitable time • Stretch receptors in the bladder send a sensory signal to micturition center in the pons • If not appropriate it will send an inhibitory signal to keep the sphinter closed • This is called a voluntary response Urination • https://www.youtube.com/watch?v=US0vNoxsW-k