Urinary System Histology and Anatomy

Urinary System Histology

• The urinary system includes the kidneys, ureters, urinary bladder, and urethra.
• The kidneys are responsible for maintaining the optimal properties of the blood.
• Key functions of the kidneys include:
  • Balancing water, electrolytes, and acid-base balance.
  • Removing metabolic wastes, excess water, and electrolytes.
  • Eliminating bioactive substances (drugs).
  • Secreting renin and erythropoietin.
  • Converting vitamin D to active calcitriol.
  • Carrying out gluconeogenesis during starvation.

Kidney Anatomy

• The kidney has a hilum, renal artery, renal vein, renal pelvis, ureter. Major and minor calyces, renal cortex, renal medulla, renal papillae, renal pyramids, renal columns, and a fibrous capsule.

Blood Flow Through the Kidney

• Blood flows from the renal artery to segmental arteries, interlobar arteries, arcuate arteries, interlobular arteries, afferent arterioles, glomerular capillaries, efferent arterioles, peritubular capillaries (or vasa recta), interlobular veins, arcuate veins, interlobar veins, segmental veins, and finally the renal vein.

Renal Corpuscle & Blood Filtration

• The renal corpuscle consists of the glomerulus and Bowman's capsule.
• The glomerulus is a network of capillaries where filtration occurs.
• The Bowman's capsule surrounds the glomerulus and collects the filtered fluid.
• The filtration process involves glomerular capillaries, the glomerular basement membrane, and podocyte filtration slit diaphragms.
• The filtration membrane must be crossed for filtration to occur.

Nephron Structure

• A nephron consists of the renal corpuscle and a renal tubule.
• The renal tubule is composed of:
  • Proximal convoluted tubule (PCT)
  • Loop of Henle
  • Distal convoluted tubule (DCT)
  • Collecting duct

Proximal Convoluted Tubule

• The PCT is responsible for the reabsorption of nutrients, water, and electrolytes.
• Also involved with secretion of organic anions and cations (hydrogen and ammonium)
• Other functions include vitamin D hydroxylation and erythropoietin production.

Loop of Henle

• The loop of Henle plays a crucial role in creating a concentration gradient in the kidney medulla.
• The descending limb is permeable to water, but not solutes
• The ascending limb is impermeable to water, but permeable to solutes.

Distal Convoluted Tubule and Juxtaglomerular Apparatus

• The DCT regulates electrolyte balance.
• The Juxtaglomerular apparatus, which includes the macula densa and juxtaglomerular cells, regulates glomerular blood flow.

Collecting Ducts

• The collecting ducts are involved in water reabsorption (with ADH).
• Reabsorption of sodium along with water in response to aldosterone effects.
• The ducts concentrate urine.

Functions of the Mesangium

• Providing structural support to capillaries.
• Regulating contractions in response to blood pressure.
• Phagocytosis of protein aggregates if they occur.
• Producing cytokines and immune factors.

Other Components: Ureters, Bladder, and Urethra

• The ureters transport urine from the kidneys to the bladder.
• The bladder stores urine.
• The urethra carries urine outside the body.

This quiz covers the histology and anatomy of the urinary system, focusing on kidney structure and functions. Participants will explore blood flow through the kidneys and the roles they serve in maintaining body balance. Test your knowledge on key concepts and terminologies associated with renal physiology.