URINARY SYSTEM

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Kidneys maintain the purity and constancy of internal fluids
Kidneys filter fluid from the bloodstream, allowing waste to leave the body in urine
Kidneys eliminate nitrogenous wastes, toxins, and drugs
Other regulatory functions of kidneys include controlling blood pressure and fluid balance, stimulating red blood cell production, and converting vitamin D to its active form

Kidneys are located against the dorsal body wall in the superior lumbar region
Each kidney is about 12cm long, 6cm wide, and 3cm thick
Kidney has a renal hilum, where blood vessels and nerves enter and exit
Sitting atop each kidney is an adrenal gland
Kidney has three protective layers: fibrous capsule, perirenal fat capsule, and renal fascia

Ptosis can cause problems if the ureters become kinked, leading to hydronephrosis (swelling of the kidney due to a build-up of urine)

When the kidney is cut lengthwise, three distinct regions become apparent: renal cortex, renal medulla, and renal pyramids
Renal cortex is the outer portion responsible for filtration of urine
Renal medulla is the interior portion responsible for filtering waste materials and eliminating fluid
Renal pyramids transport urine from the outer part of the kidney
Renal columns allow the cortex to be better anchored
Renal pelvis is a funnel for urine flowing to the ureter

Approximately one-quarter of the total blood supply in the body passes through the kidneys each minute
Blood supply to the kidneys includes renal artery, segmental arteries, interlobar arteries, arcuate arteries, cortical radiate arteries, cortical radiate veins, arcuate veins, and interlobar veins

Nephrons are the structural and functional units of the kidneys responsible for forming urine
Each nephron consists of a renal corpuscle and a renal tubule
Renal corpuscle includes a glomerulus and a cup-shaped structure called Bowman's capsule
Podocytes are highly modified cells in the inner layer of the capsule that support the structure and function of the glomerulus
Renal tubule is about 3cm long and consists of different regions, including the proximal convoluted tubule and the nephron loop

Receives urine from the glomerulus.
Secretion of wastes and ions takes place in the DCT.
Cortical nephrons, glomeruli, proximal and distal convoluting ducts, and loops of Henle stay limited to the cortex.
Juxtamedullary nephrons extend into the medulla.
- Most nephrons are cortical nephrons located within the cortex.
- Filtrate passes through the thick ascending limb of Henle and enters the DCT.
- DCT reabsorbs calcium, sodium, and chloride and regulates urine pH by secreting protons and absorbing bicarbonate.
- Juxtamedullary nephrons are situated close to the cortex medulla junction and their nephron loops dip deep into the medulla.

Final component of the kidney that influences the body's electrolyte and fluid balance.