 excretion  the removal of metabolic wastes from the body  kidneys are the primary organ of...

Download  Excretion  The removal of metabolic wastes from the body  Kidneys are the primary organ of this process

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  • ExcretionThe removal of metabolic wastes from the body Kidneys are the primary organ of this process

  • 1. Excretion of Metabolic WastesRemoving metabolic waste products, notably nitrogenous waste from breakdown of amino acids (aa):UreaBreakdown 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 CreatinineUric acidif too much uric acid crystals can form in jointsThis is known as gout

  • 2. Maintenance of Water-Salt BalanceBlood volume is associated with salt balance in bodySalt (NaCl) can cause water diffusion into blood salt = blood volume = blood pressure

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

  • 4. Secretion of HormonesReninLeads to secretion of aldosteroneReabsorption of sodium ionsErythropoetinStimulates red blood cell productionActivates vitamin D from the skinHelps promote calcium absorption from the digestive tract.

  • 16-*Fig. 16.1

  • KidneysTwo bean-shaped organsLocated near lumbar region on either side of vertebral columnHas a depression called the hilum where the Renal artery Renal vein are located

  • UretersConduct urine from the kidneys to the bladderSmall, muscular tube 25cm long, 5 mm thick

  • Urinary Bladder Stores urine until it is expelled from the bodyLocated in the pelvic cavity 3 openings (orifices): 2 for the ureters1 for urethera

  • Urinary Bladder cont... ExpandableDetrusor Muscle bladder wall Sphincter Muscles surround bladder neck and urethra

  • 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


  • UrethraSmall tube that extends from the urinary bladder to an external openingfemales 4 cm longIncreases likelihood of urinary tract infectionNot connected to reproductive systemMales20 cm longCommon pathway for reproductive and urinary tracts

  • 16-*Micturition When the bladder fills to 250mlStretch 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 reflexPresent in infants and young children

  • In older children and adults the brain can control this reflex and delay urination until a suitable timeStretch receptors in the bladder send a sensory signal to micturition center in the ponsIf not appropriate it will send an inhibitory signal to keep the sphinter closedThis is called a voluntary responsehttps://www.youtube.com/watch?v=US0vNoxsW-k

    Not the same as defecation elimanting waste (undigested food and bacteria via feces) *Urea is main part of urine (makes up most part of it)Creatinine by product of creatine phosphate breakdown in muscles

    Uric acid is produced in the body through breakdown of purines- chemiacls found in foods meat, poultry, alcohol (high rich foods) if too much uric acid crystals form in jointsPainful called gout

    **Again urinate help remove water and Nacl from body so we have balance *We eat foods with certain ph eliminate in body *Kidneys secrete: renin, erythropoetin**To locate your kidneys, put your hands on your hips, then slide your hands up until you can feel your ribs. Now if you put your thumbs on your back, you will know where your kidneys are. You can't feel them, but they are there. Lie behind peritoneum & gets some protection from rib cage

    *******Voluntary reflex *


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