Urinary System Overview and Anatomy

Urinary System Overview

• The urinary system is responsible for removing wastes, hormones, and regulating blood pressure, ion levels, and acid/base balance

Kidney Functions

• Filters blood
• Removes wastes, hormones, and excess water
• Regulates blood pressure and ion levels
• Produces calcitriol (important for calcium absorption) and erythropoietin (stimulates red blood cell production)
• Makes glucose from non-carbohydrates (gluconeogenesis) - only during starvation

Kidney Anatomy

• Renal cortex: Outer layer
• Renal medulla: Inner layer, contains renal pyramids
• Renal columns: Extensions of cortex into the medulla
• Renal pelvis: Funnel-shaped structure that collects urine
• Minor calyx: Collects urine from the renal pyramids
• Major calyx: Collects urine from the minor calyces
• Ureter: Tube that carries urine to the bladder
• Renal sinus: Cavity in the kidney
• Renal artery: Carries blood to the kidney
• Renal vein: Carries blood away from the kidney
• Renal pyramids: Triangular structures in the medulla
• Renal papilla: Tip of the renal pyramid
• Nephron: The functional unit of the kidney. It has two main parts: Renal corpuscle Renal tubule

Nephron Structure and Function

• Renal Corpuscle:

  • Contains glomerulus (a capillary network).
  • Glomerular capsule (Bowman's capsule): Surrounds the glomerulus.

• Renal Tubule:

  • Proximal convoluted tubule (PCT): Reabsorption of water, glucose, amino acids, and other valuable substances into the blood.
  • Loop of Henle: Responsible for water reabsorption and concentrating urine
    • Descending limb. (Permeable to water but not solutes)
    • Ascending limb (Permeable to solutes but not water)
  • Distal convoluted tubule (DCT): Reabsorption of essential substances (water, salts), and actively secretes waste products
  • Collecting duct: Collects urine from many nephrons and carries it to the renal pelvis. ADH (antidiuretic hormone), aldosterone (regulates reabsorption of Na+ and K+), parathyroid hormone (regulates calcium balance) play roles in this part.

Blood Vessels in the Kidney

• Afferent and efferent arterioles (supply blood to glomerulus).
• Peritubular capillaries (surround nephron tubules)
• Vasa Recta (part of peritubular capillary network, close to loop of Henle, important in concentrating urine)

Glomerular Filtration

• Specialized filtration membrane between glomerulus and Bowman's capsule
• Filtering blood to create filtrate
• Selectively permeable, allowing small molecules to pass through while blocking larger molecules and blood cells

Tubular Reabsorption

• Recovers valuable substances (water, ions, glucose) from filtrate.
• Movement of substances from filtrate into blood

Tubular Secretion

• Movement of substances from blood into filtrate (secretion)
• Active process, requiring energy

Net Filtration Pressure (NFP)

• Forces that promote filtration and forces that oppose filtration must be balanced
• NFP is the difference between hydrostatic pressure in glomerular capillaries and hydrostatic pressure in Bowman’s capsule (HPg - HPc).

Glomerular Filtration Rate (GFR)

• The volume of filtrate formed per minute by all glomeruli in both kidneys

Factors Affecting GFR

• Blood pressure
• Blood colloid osmotic pressure
• Glomerular hydrostatic pressure
• Capsular hydrostatic pressure
• Surface area of glomeruli.
• Renal blood flow

Regulation of Acid-Base Balance

• Intercalated cells (A and B cells) play a role in maintaining acid/base balance.

Hormones Affecting Kidney Function

• Renin/Angiotensin II
• Aldosterone
• Atrial Natriuretic Peptide (ANP)
• Antidiuretic Hormone (ADH)
• Parathyroid Hormone

Micturition (Urine Formation)

• The process of urination, controlled by the nervous system
• Storage reflex (prevent urination).
• Micturition reflex (stimulate urination).

Loop of Henle

• A U-shaped structure within the nephron
• Crucial for concentrating urine by creating a concentration gradient in the medulla
  • Countercurrent multiplier system
  • Countercurrent exchange system

Explore the essential functions and structure of the urinary system, focusing on the kidneys. This quiz covers kidney functions such as waste removal, hormone regulation, and the anatomy of the kidney components. Test your understanding of how these elements work together to maintain homeostasis.