Urinary System 2010
In addition to web sites already suggested, you may want to visit:
personally think the SIUSOM web site is the best for the renal system.
Do not forget
that the kidneys have been called the “the brain” below the diaphragm, but we know
much more about the kidneys than we do about the brain, but it is very complex and
involves much physiology.
I have a textbook on renal pathology from 1966 which has
45 pages on renal anatomy and histology.
If this book was written today, instead of
800+ pages, it would be 1600 pages and the anatomy and histology section would be
expanded to 90 or more pages.
In these notes, I have tried to give you some basic
information about the physiology of the kidney as well as the histology. "The
composition of the body is determined not by what the mouth takes in but by what the
kidney keeps." (Homer Smith, renal physiologist)
The urinary system consists of paired kidneys and ureters, the urinary bladder, and
1. Regulation of volume and composition of body fluid which
includes salt and water balance, preservation of nutrients, excretion of wastes
(urea), acid-base balance.
2. Filtration of
(at a rate of 120 ml per
minute), reabsorption of 99% of this filtrate which includes all glucose, amino
acids, most of the water and salts, and secretion of K
results in approximately 1500 ml of urine per day after the kidney has filtered
nearly 200,000 ml of blood
per day; 3. Endocrine function includes secretion of
rennin, erythropoietin, and Vitamin D (calcitriol, the active form of Vit D).
the functional and structural unit of the kidney is the
consisting of renal corpuscle (Bowman's capsule and the glomerulus), proximal
convoluted tubule, loop of Henle, and distal convoluted tubule which lead to collecting
tubules which join to form collecting ducts. Each nephron consists of vascular
elements and tubular elements.
Each kidney has over a million nephrons and the
simple tubular epithelium measures approximately 25 miles. The kidneys are covered
by a capsule, but within the parenchyma of the kidney, there is very little CT unlike
most other glands.
The kidney is divided into an outer
and a thicker inner
the renal glomeruli reside in the cortex but the bulk of the substance in
the cortex are the proximal and distal convoluted tubules.
The medulla has no
glomeruli and consists mostly of renal tubules, the pars recta of the proximal tubule,
loop of Henle, the pars recta of the distal tubule, and collecting ducts and blood
vessels, capillaries, associated with these tubules. These tubules lie very close