Kidney, Ureter, and Suprarenal GlandKidney
- Is retroperitoneal and extends from T12 to L3 vertebrae in the erect position. The right kidney lies a little lower than the left because of the large size of the right lobe of the liver. The right kidney usually is related to ribs 10 and 11 posteriorly, whereas the left kidney is related to ribs 11 and 12 posteriorly.
- Is invested by a firm, fibrous renal capsule and is surrounded by the renal fascia, which divides the fat in two regions. The perirenal (perinephric) fat lies in the perinephric space between the renal capsule and renal fascia, and the pararenal (paranephric) fat lies external to the renal fascia.
- Has an indentation at the hilus on its medial border, through which the ureter, renal vessels, and nerves enter or leave the organ.
- Consists of the medulla and the cortex , containing 1 to 2 million nephrons , which are the anatomic and functional units of the kidney. Each nephron consists of a renal corpuscle, a proximal convoluted tubule called Henle's loop , and a distal convoluted tubule.
- Has arterial segments including the superior, anterosuperior, anteroinferior, inferior , and posterior segments , which are of surgical importance.
- Filters blood to produce urine ; reabsorbs nutrients, essential ions, and water; excretes urine (by which metabolic waste products are eliminated) and foreign substances; regulates the salt ion (electron, and water balance) and produces vasoactive substance (angiotensin II) that regulates blood pressure.
- Also produces renin by juxtaglomerular (JG) cells, which converts plasma angiotensinogen to angiotensin which is converted to angiotensin II by enzymes in the lungs. Angiotensin II, a vasoconstrictor, increases blood pressure and stimulates aldosterone production by the suprarenal cortex, thereby regulating the salt ion, and water balance between the blood and urine.
- Forms the outer part of the kidney and also projects into the medullary region between the renal pyramids and renal columns.
- Contains renal corpuscles and proximal and distal convoluted tubules. The renal corpuscle consists of the glomerulus (a tuft of capillaries) surrounded by a glomerular (Bowman's) capsule.
- Forms the inner part of the kidney and consists of 8 to 12 renal pyramids (of Malpighi), which contain tubules (Henle's loops ) and collecting tubules. An apex of the renal pyramid, the renal papilla , fits cup-shaped minor calyx on which the collecting tubules open (10 to 25 openings).
- Receive urine from the collecting tubules and empty into two or three major calyces , which in turn empty an upper dilated portion of the ureter, the renal pelvis.
Suprarenal (adrenal) gland
- Is a muscular tube that begins with the renal pelvis, extending from the kidney to the urinary bladder.
- Is retroperitoneal, descends on the transverse processes of the lumbar vertebrae and the psoas muscle, crossed anteriorly by the gonadal vessels, and crosses the bifurcation of the common iliac artery.
- May be obstructed by renal calculi (kidney stones) where it joins the renal pelvis (uretero-pelvic junction) where it crosses the pelvic brim over the distal end of the common iliac artery, or where it enters the wall of the urinary bladder (ureterovesicular junction ).
- Receives blood from the aorta and from the renal, gonadal, common and internal iliac, umbilical, superior inferior vesical, and middle rectal arteries.
- Is innervated by the lumbar (sympathetic) and pelvic (parasympathetic) splanchnic nerves.
- Is a retroperitoneal organ lying on the superomedial aspect of the kidney. It is surrounded by a capsule of renal fascia.
- Is pyramidal on the right and semilunar on the left.
- Has a cortex that is essential to life and produces three types of steroid hormones. The outer zona glomerulosa produces mineralocorticoids, mainly aldosterones; the middle zona fasciculata produces glucocorticoids, mainly cortisol and corticosterone; and the inner zona reticularis produces androgens; thus, the mnemonic is SEX. Aldosteron controls electrolyte (sodium, potassium, etc.) and water balance; cortisol controls glucose regulation and suppresses immune response; and androgen controls sexual development (maleness).
- Has a medulla that is derived from embryonic neural crest cells, receives preganglionic sympathetic nerve fibers directly, and secretes epinephrine and norepinephrine.
- Receives arteries from three sources: the superior suprarenal artery from the inferior phrenic artery , the middle suprarenal artery from the abdominal aorta , and the inferior suprarenal artery from the renal artery.
- Is drained via the suprarenal vein, which empties into the IVC on the right and the renal vein on the left.
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