anatomy of urinary system

urinary system functions

• Filtration of blood plasma to remove waste and produce urine

• Filtration of blood plasma to detoxify (clear hormones and drugs)

• Regulation of blood pressure and blood volume

• Regulation of ion levels (Na+, K+, Ca++, PO4-)

• Regulation of pH (H+ and bicarbonate)

organs of the urinary system

• 2 kidneys (main workers)

• 2 ureters

• bladder

• urethra

kidneys

• retroperitoneal organs that are located posterior to abdominal cavity (behind peritoneum)

• right kidney slightly lower than left due to liver

layers of connective tissue of kidneys (superficial to deep)

1. renal fascia

2. perirenal fat capsule (perinephric fat)

3. fibrous capsule

4. pararenal fat capsule

renal fascia

• Dense irregular fibrous connective tissue

• Attaches kidney to abdominal wall

• Deep to the peritoneum

• Surrounded by fat on two sides…

• clear covering

perirenal fat capsule (perinephric fat)

A brown adipose tissue cushion that holds kidney in place

• yellow covering

fibrous capsule

• Dense irregular CT

  • Collagen and elastic fibers that wrap and protect the kidney

• Collagen fibers extend to the renal fascia to anchor kidneys in place

• inside brown layer

pararenal fat capsule (body)

A white adipose tissue on the posterior side of the kidney

region of kidneys

1. renal cortex

2. renal medulla

3. renal pelvis

renal cortex

• Outer layer of parenchyma (“functional tissue”)

• Appears granular due renal corpuscles of nephrons

renal medulla

• Inner layer of parenchyma facing sinus

• Divided into renal pyramids by columns from cortex (renal columns are part of medulla)

renal pelvis

• Tube-like structure leaving kidney into ureter

• Drains fluid from major calyces

  • Major calyces drain from minor calyces

  • Minor calyces receive fluid from renal papilla of medulla

• Urine drained by peristaltic contraction of smooth muscle

renal pyramid

• in renal medulla

• broad base, and a pointed end called the renal papilla (attached to calyx)

renal columns

• in renal medulla

• Stripped appearance comes from parallel arrangement of collecting tubules and capillaries

renal sinus

region that contains minor + major calyx and renal pelvis

nephrons

functional unit of the kidney, the structure that actually produces urine in the process of removing waste and excess substances from the blood

cortical nephron

Close to surface; short loops; 85% of nephrons

juxtamedullary nephron

long loops extending into renal pyramids; primarily concerned with salt balance/levels

renal corpuscle

enlarged region where filtration occurs

renal tubule

• Tube like portion of nephron

  • PCT, nephron loop, DCT

• Sites of secretion and absorption

glomerular capillary bed

supplied by an afferent arteriole and drained by an efferent arteriole

parietal layer

• surrounds capsule

• Simple squamous epithelium for structure, not diffusion!

glomerulus

• High pressure blood capillaries (central capillaries in corpuscle) where filtration occurs

• A ‘dump’ of contents out of the capillary

• only bed with two arteriole ends

visceral layer

• surrounds capillaries

• Podocytes that wrap around capillaries and interdigitate

• Form filtration slits for passage of solutes

renal tubule

• reabsorbs and secretes various molecules

  • Na+ handling

  • K+ handling

  • Nutrient handling

  • Water handling

• single layer of epithelial cells on basement membrane

• nephron loop (loop of Henle)

• distal convoluted tubule

nephron loops

• proximal straight tubule- thick descending portion of nephron loop

• Thin descending portion of nephron loop

• Thin ascending portion of nephron loop

• Distal straight tubule- thick ascending portion of nephron loop

PCT (proximal convoluted tube)

simple cuboidal epithelium with LOTS of microvilli. Lots of mitochondria

• primary resorptive function: Na+, glucose, amino acids, phosphates, and water

• hormonal influence: angiotensin 2

PST (thick descending segment)

similar to PCT except microvilli fewer and not packed as tightly

• primary resorptive function: water reabsorption

Thin descending segment

simple squamous epithelial cells (water reabsorption specialists)

• primary resorptive function: Water reabsorption; some Na+ reabsorption

Thin ascending segment

simple squamous epithelial cells (ion reabsorption specialists)

• primary resorptive function: Na+, K+reabsorption

DST (thick ascending limb)

simple cuboidal epithelium with few to no microvilli

• primary resorptive function: Na+, K+ reabsorption

• hormonal influence: ADH

DCT (distal convoluted tube)

simple cuboidal epithelium with few to no microvilli

• primary resorptive function: Na+ reabsorption, K+ secretion

• hormonal influence: ADH, aldosterone

collecting duct

Simple cuboidal to columnar epithelium; distinct cell borders

• primary resorptive function: Na+, K+, H+, water reabsorption, K+ secretion

• hormonal influence: ADH, aldosterone

capillary beds in kidneys

• peritubular capillaries

• vasa recta

• glomerulus

peritubular capillaries

• Surround tubules and reabsorbs water and solutes from tubules

• Transport these substances back to venous system

vasa recta

• Specialized capillary bed of juxtamedullary nephrons

• These are peritubular capillaries except these vessels are more “straight”

• Supplies renal medulla with blood (1-2% of total blood)

• Important in establishing and maintain salt concentration in medulla