9.1 - Genitourinary System

LECTURE NOTES

SECTION 1

Functions and Anatomical Structure of Kidney

• Excretion of metabolic products e.g. urea, uric acid, creatinine

• Excretion of foregin substances e.g. drugs

• Homeostasis of body fluids, electrolytes and acid-base balance

• Regulates blood pressure

• Secretes hormones, e.g. erythropoietin and renin

  

• Renal artery brings blood to the kidney and renal vein takes blood away

• Granular part is the cortex

• From the medulla, urine drains into minor calyx. From minor into major calyx and then into the ureter

• Urine is then carried from ureter to bladder and then excreted through urethra

Renal Bloody Supply to the Kidney

• Renal Artery → Segmental Artery → Interlobar Artery → Arcuate Artery → Interlobular Artery → Afferent Arteriole → Glomerular Capillaries

• Afferent arteriole brings the blood to the nephron

• Peritubular capillaries functions

  • Reabsorption - things that are in the nephron are reabsorbed into these capillaries and re-enter blood supply to the body

  • Secretion - some substances in the capillaries need to be gotten rid of, and this is an opportuniy for secretion of these substances

  • Brings nurtrients and oxygen for nephrons to function to allow nephrons to respire and function properly

Bladder and Urethra (Males vs Females)

• Detrusor muscle: contracts to build pressure in the urinary bladder to support urination

• Trigone: stretching of this triangular region to its limit signals the brain aabout the need for urination

• Internal sphincter: Involuntary control to prevent urinaiton

• External sphincter: Voluntary control to prevent urination

  • In urinary incontinence generally there is a malfunctioning of one of these sphincters

• Bulbourethral gland: Located in males, which produces thick lubricant added to watery semen to promote sperm survival

Nephron

• Outline - glomerulus (blood supply), surrounded by the bowman’s capsule. This enters the proximal convoluted tubule → thin descending LOH, then thin ascending to thick ascending LOH, and then distal convoluted tubule, which then leads into the collecting duct.

Mitochondrial Concentrations in the Nephron

• Proximal convoluted tubule - epithelial cells are rich in mitochondria

• Descending and ascending Loop of Henele - low density of mitochondria

• Thick ascneding Loop of Henle - epithelial cells rich in mitochondria

• Distal convoluted tubule - epithelial cells rich in mitochondria

• Collecting duct - principal cells have low density of mitochondria whereas intercalated cells are rich in mitochondria

Types of Nephrons

• There are two types of nephrons - superficial and juxtamedullary

• Based around the length of the Loop of Henle

• Superficial nephron

  • Bowman’s capsule sits to the outer cortex and loop of Henle is shorter, extending to within the outer medulla

• Juxtamedullary nephron

  • Complex sits towards the border of the cortex and medulla

  • Loop of Henle is longer and extends deep within the inner medulla

Cortex vs Medulla

• Cortex is granular whereas medulla has striated appearance

• Tubes such as loop of henle and collecting duct sit within the medulla giving it this striated appearance.

• Complexes like Bowman’s capsule sit within the medulla giving it the lumpy and granular appearance.

Juxtaglomerular Apparatus

• Macula densa

  • Part of distal convoluted tubule, just at the start of DCT

• Extraglomerular mesangial cells

  • Sitting between the DCT and arteriole

• Juxtaglomerular cells.

  • Sit within the afferent arteriole

• Functions: GFR (glomerular filtration regulation) and renin production (bp regulation)

SECTION 2