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Understanding the Excretory System: The Role and Structure of the Kidneys

The excretory system plays a crucial role in regulating blood volume and chemical composition while facilitating the metabolism of vitamin D. This overview highlights kidney structure, including the renal pelvis, calyces, cortex, and medulla. The nephron, the kidney's structural unit, comprises Bowman's capsule, glomerulus, and renal tubules, which perform essential functions like filtration and reabsorption of substances. The urinary bladder and its associated structures ensure the efficient removal of urine. Key mechanisms for regulating urine volume, such as hormones from the adrenal cortex and pituitary gland, are also discussed.

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Understanding the Excretory System: The Role and Structure of the Kidneys

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  1. Excretory System

  2. The Kidneys • regulate the volume and chemical make-up of the blood metabolize vitamin D

  3. Kidney Structure • Pelvis: expansion of upper ureter(lies within kidney) • Calyces: divisions of the renal pelvis • Cortex: Outer Layer • Medulla: Inner Portion • Pyramids: triangular divisions of the medulla

  4. Kidney Dissection

  5. Nephron: the structural unit of the kidney • Bowman’s Capsule: cup-shaped top of nephron • Glomerulus: network of capillaries surrounded by Bowman’s capsule • Renal Tubule: • Proximal Convoluted Tubule • Loop of Henle: extension of proximal tubule • Collecting Tubule • Distal Convoluted Tubule:

  6. Nephron Structure

  7. Filtration: in the glomerulus • Blood flows into kidneys and more specifically into the glomerulus • The blood exerts pressure high enough to push water and dissolved substances out of the glomerulus and into the Bowman’s Capsule.

  8. Tubular Reabsorption: in the Loop of Henle • Substances move out of the renal tubules into the capillaries • Those substances reabsorbed include: • Water • Glucose • Sodium

  9. The Urinary Bladder

  10. Ureters: slender tubes that convey urine from the kidneys to the bladder • Bladder: collapsible muscular sac that, in males, is just anterior to the rectum, and in females, is anterior to the vagina and uterus. • Urethra: is a thin-walled muscular tube that drains urine from the bladder and conveys it out of the body.

  11. Mechanisms for Urine Volume Control • Adrenal Cortex: produces aldosternone • Stimulates tubules to absorb salt at a faster rate • Increases tubular reabsporption rates • Posterior Pituitary Gland: produces antidiuretic hormone (ADH) • Makes distal and collecting tubules permeable to water • Decrease amount of urine excreted

  12. Micturition:he act of emptying the bladder • As urine accumulates, the bladder stretches and stretch receptors are activated. • Occurs when about 200 mL of urine has accumulated • impulses are sent to the brain and one begins to feel the urge to urinate • Activation of the micturition center in the pons signals the need to urinate

  13. Simulated Urinalysis Lab

  14. Characteristics of Urine • clear and pale to deep yellow • slightly acidic • around 6. 95% of urine volume is water • largest solute component is urea, a product of protein breakdown • other nitrogenous wastes include creatine and uric acid • In certain diseases, urine composition will change dramatically.

  15. Abnormal urinary constituents can include: • Glucose - due to diabetes mellitus • Proteins - due to hypertension or glomerulunephritis • Ketone bodies - due to starvation or diabetes mellitus • Leukocytes - due to urinary tract infection • Erythrocytes - due to a bleeding urinary tract.

  16. Excretory System Review

  17. Thursday March 17 Excretory Exam

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