Kidney Anatomy and Physiology Study Notes

Kidney Anatomy and Physiology

• Overview

  • Kidney is central to the urinary system; other parts (ureters, bladder, urethra) serve mainly for plumbing.
  • Focus on anatomy: identifying structures such as glomerulus, cortex, medulla, and renal pelvis.

• Kidney Location

  • Located higher in the abdomen than many believe; tenderness upon palpation can indicate infection.
  • Kidneys receive about 20% of blood flow from each cardiac cycle for filtration.

• Key Structures of the Kidney

  • Hilum: Concave portion where renal artery enters and renal vein/ureters exit.
  • Cortex: Outer layer of the kidney, contains a capsule for protection.
  • Medulla: Contains renal pyramids which lead to the renal pelvis.
  • Calyces: Minor calyx drains into major calyx, which drains into the renal pelvis.

• Anatomical Relationships

  • In females, urinary bladder and urethra are anterior to the vagina and uterus, causing increased urinary frequency during pregnancy.
  • Men's urinary systems are impacted by the prostate, which may constrict urethra with aging.

• Urinary Tract Issues

  • Common infections: urinary tract infections (UTIs) occur in the bladder, while kidney infections (pyelonephritis) are more serious.

• Gross Anatomy of the Kidney

  • Kidney includes:
  • Capsule (protective covering)
  • Cortex
  • Medullary pyramids
  • Minor and major calyces
  • Renal pelvis

• Nephron Structure

  • Nephrons consist of:
  • Proximal Convoluted Tubule (PCT): Reabsorbs nutrients, characterized by a brush border.
  • Distal Convoluted Tubule (DCT): Leads into collecting duct, identified by surrounding DCTs.
  • Nephron Loop: Comprises ascending and descending loops.
  • Most nephrons are cortical; juxtamedullary nephrons dip deep into medulla.

• Vasculature

  • Afferent Arteriole: Larger in diameter than efferent arteriole, creating a pressure gradient for filtration.
  • Blood flow: renal artery → afferent arteriole → glomerulus (where filtration happens) → efferent arteriole → peritubular capillaries/vasa recta → renal vein.

Histology

• Identifying Structures on Slides

  • Glomerulus: Distinct appearance on histology slides, characterized by capillaries and filtration spaces.
  • Transitional Epithelium: Found in the ureters and urinary bladder, allows for stretching; identifiable by dome-shaped cells.

• Kidney Capsule & Protection

  • Capsule protects from infection and limits spread of ill effects from kidney infections.

Urine Formation

• Process
  • Begins in glomerulus as filtrate, transforms into urine as it passes through nephron structures.
  • Proteins should remain in blood; presence in urine can indicate kidney damage.

Urinary Bladder and Urethra Anatomy

• Bladder Structure

  • Trigon area: where the ureters enter.
  • Smooth muscle aids in urination control alongside sphincters.

• Identification in Dissections

  • Common questions include identifying major kidney structures, vessels (renal artery and vein), and portions of the bladder (trigon).
  • Students encouraged to correlate textbook images with real structures during labs.

• Important Note: The distinction between various tubes and components of the nephron is critical for understanding kidney function but may not feature heavily in practical exams.