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urinary anatomy
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Lecture notes of 6 pages for the course Anatomy at (urinary anatomy)
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Urinary System1. List the functions of the kidneys.
The kidneys maintain the purity and constancy of fluids in our internal
environment. They filter gallons of fluid from the bloodstream, ridding the
body of metabolic wastes, toxins, and excess ions, while returning needed
substances to the blood.
Major Functions:
a. Eliminating nitrogenous wastes, toxins, and drugs from the body.
b. Regulating the volume and chemical makeup of the blood.
c. Maintaining the balance between water and salts and between acids
and bases.
Other Functions:
a. Producing renin to help regulate blood pressure and kidney function.
b. Producing the hormone erythropoietin (stimulates red blood cell
production).
c. Metabolizing vitamin D to its active form.
2. List the organs of the urinary system.
kidneys, ureters, urinary bladder, urethra
3. Describe the kidney structure and how urine flows from kidney
to outside the body.
Kidneys are bean-shaped and lie in a retroperitoneal position in the superior
lumbar region. They receive some protection from the lower rib cage. The
right kidney is crowded by the liver and lies slightly lower than the left. The
medial surface contains a cleft (hilus). The ureters, renal blood vessels,
lymphatics, and nerves enter or exit the kidney at the hilus.
Three layers of supportive tissue surrounds each kidney:
a. transparent renal capsule - closest, provides a strong barrier that
prevents infection from surrounding regions from spreading to the kidneys.
b. adipose capsule - middle layer, fatty tissue which helps protect
kidneys and hold them in place.
c. renal fascia - dense fibrous connective tissue, anchors kidneys to
surrounding structures.
Internal anatomy:
a. cortex - outer region, contains the nephrons
b. medulla - middle region, contains the renal pyramids
c. pelvis - flat, funnel-shaped tube continuous with the ureter, branching
sections form the major calyces, each of which subdivides further
, The calyces collect urine, which drains from the papillae (tips of renal
pyramids) and empties into the pelvis. Urine then flows through the pelvis
and into the ureter which transports it to the bladder to be stored. The walls
of the calyces, pelvis, and ureter contract rhythmically and propel the urine
along by peristalsis.
4. Describe the structure and general function of the nephron.
Each kidney contains over one million tiny blood processing units called
nephrons which carry out the process of urine formation.
Parts of the nephron and processes that occur:
a. glomerulus - tuft of capillaries; filtration
b. Bowman's capsule - enlarged, cup-shaped capsule which surrounds
the glomerulus; collects filtrate
c. proximal convoluted tubule - tubular reabsorption
d. loop of Henle - sodium and water balance
e. distal convoluted tubule - tubular secretion
Each region of the tubule (proximal convoluted, loop of Henle, and distal
convoluted) has a special filtrate-processing function as listed above.
5. Describe the general process of urine formation.
The filtrate reaching the distal convoluted tubule empties into the collecting
tubules, each of which receives filtrate from many nephrons. The collecting
tubules run through the medullary pyramids. As the collecting tubules
approach the renal pelvis, they fuse to form larger papillary ducts which
deliver urine into the minor calyces via the papillae of the pyramids. The
kidneys process about 47 gallons of fluid daily. Of this amount, only about
1.5 liters actually leaves the body as urine. The process of urine formation
and adjustment of blood composition involves three processes: glomerular
filtration, tubular reabsorption, and tubular secretion.
6. Describe glomerular filtration. (fenestrated capillaries, net
filtration pressure, three factors of GFR and which is most
important, regulation of GFR by macula densa cells)
Glomerular filtration is the beginning of urine formation. It is a passive,
non-selective process in which fluids and solutes are forced through a
membrane by hydrostatic pressure. The glomerulus has special
characteristics which make it an efficient filter: (1) fenestrated capillaries
and very permeable to water and solutes (which allows free passage of
everything except blood cells and plasma proteins) and (2) the glomerular
blood pressure is higher resulting in a higher filtration pressure.
Net Filtration Pressure is the pressure that favors the forming of renal
filtrate from plasma. Its numerical value is the result of opposing forces -
those that would force fluid into the Bowman's capsule against those that
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