Anatomy and Physiology of Renal System

Subject: Medical and Surgical Nursing I (Theory)

Overview

The kidneys discharge urine, which is then collected by the bladder. It stands between the uterus and the rectum. It circulates urine throughout the urethra and serves as a momentary urine reservoir. The bladder presses against the growing uterus during pregnancy, which results in abnormal bladder positioning. The kidney enlarges by 1 cm, the ureter kinks, and the plasma flow of the kidney increases by 50% to 75%. The ureter, renal pelvis, and calyces are all enlarged.

Anatomy and Physiology of Renal System

Function of Renal System

  • Secrete urine,
  • Eliminate urine from body.

Structure of the Renal System

  • Kidneys
    • Located behind peritoneum at level of last thoracic and first three lumbar vertebrae.
    • Receive 20% of cardiac output during rest; reduce to 2% to 4% during physical or emotional stress.
  • Nephron
    • Anatomic and functional unit or kidneys; approximately 1 million per kidney.
    • Function via principles of filtration, reabsorption, and secretion.
    • Glomerulus: urine formation starts with filtration; water and solutes filter out of capillaries through glomerular- capsule.
    • Bowman capsule: filtrate collects here before flow to tubules.
    • Tubular reabsorption and secretion.
    • Proximal tubule.
    • Loop of Henle.
    • Distal tubule.
  • Collecting Tubules: final osmotic reabsorption of most of the remaining water in urine; under antidiuretic hormone influence
  • Urine description / composition
    • 1.5L/day average (30ml/hr).
    • Light yellow to dark amber.
    • Aromatic odor.
    • Specific gravity of 1.005 to 1.030; varies depending on fluid intake and quality of solutes; lower specific gravity the more dilute the urine; higher specific gravity the more concentrated the urine.
    • Acidic PH.
    • Urea/ uric acid.
    • Creatinine.
    • Electrolytes.
    • Hormones and their breakdown products.
    • Abnormal constituents.
    • Urine volume control.

Glomerular Filtration Rates(GFR)

Usually constant in certain pathologic condition GFR may change markedly and alter urine volume

Solutes in Tubular Filtrate

Increase in tubular solute causes decrease osmosis of water from proximal tubule into blood resulting in increase urine volume

Aldosterone Mechanism

Stimulates kidney tubules to reabsorb sodium; water follows the sodium

Antidiuretic Hormone (ADH)

Produce in hypothalamus and secreted into blood by posterior hypothalamus and secreted into blood by posterior pituitary glands

  • Control of amount of blood flow through kidneys.
  • Reduced renal blood flow results in renal excretion of the hormone renin.
  • Renin interacts with blood proteins, producing angiotensinII.
  • Angiotensin II causes vasoconstriction and aldosterone secretion resulting in increased blood pressure and renal blood flow.

Ureters

  • Located behi9nd parietal peritoneum; tube from each kidney connects to urinary bladder
  • Collect urine secreted by kidney and propel it to bladder by peristaltic waves

Urinary Bladder

  • Tube with mucous membrane lining that ends at urinary meatus, it's exterior opening
    • Female: behind symphysis pubis, anterior to vagina
    • Male: extends through prostate gland, fibrous sheet, and penis

Functions

  • Female: passageway for expulsion of urine
  • Male: passageway for expulsion of urine and semen

 

 

 
Things to remember
  • Bladder is the organ which collects urine that is excreted by kidney. 
  • It is temporary reservoir of urine and passes urine throughout the urethra 
  • During pregnancy the enlarged uterus presses bladder. 
  • Kidney is enlarged by 1 cm,
  • Renal plasma flow is increased by 50% to 75%,
  • There is dilation of ureter, renal pelvis, and calyces 
Questions and Answers

Function of Renal System

  • Release urine
  • Remove urine from the body

Structure of The Renal System

Kidneys

  • Located at the level of the final thoracic and first three lumbar vertebrae, behind the peritoneum.
  • When at rest, get 20% of cardiac output; when under physical or emotional stress, this decreases to 2% to 4%.
  • Nephron
  • Kidneys are anatomical and functional units, with one million per kidney.
  • Principles of secretion, reabsorption, and filtrarion
  • Water and solutes filter out of capillaries through the glomerular-capsule to begin the process of urine production in the glomerulus.
  • Before flowing to the tubules, the filtrate gathers in the Bowman capsule.
  • Reabsorption and secretion in the tubules
  • Nearby tubule
  • Henle's loop
  • Proximal tubule
  • Collecting tubules: ultimate osmotic reabsorption of the majority of the leftover urine's water content; influenced by antidiuretic hormone
  • Description and content of urine
  • Average daily fluid consumption is 1.5L (30ml/hr).
  • From pale yellow to deep amber
  • Scented ordor
  • 1.005 to 1.030 specific gravity; varies with hydration and solute quality; Urine that has a lower specific gravity is more diluted than urine that has a higher specific gravity is more concentrated.
  • PH acidic
  • Uric acid and urea
  • Creatinine
  • Electrolytes
  • Hormones and the byproducts of their breakdown
  • Unusual components
  • Control of urine output

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