2 ) Helps regulate normal blood hydrogen and bicarbonate ion levels and therefore blood pH.
3) regulates blood calcium, sodium and potassium levels
4) removes urea and ammonia
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I Functions of system
1) Maintains normal blood fluid volume and therefore blood pressure
2 ) Helps regulate normal blood hydrogen and bicarbonate ion levels and therefore
blood pH.
3) regulates blood calcium, sodium and potassium levels
4) removes urea and ammonia
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II. Kidneys: the major excretory organs
A. External Anatomy:
1) renal capsule – adheres directly to the kidney’s surface
- dense irregular connective tissue |
- helps prevent infection
2). Renal Hilus; on the medial, concave surface
- leads into the renal sinus
- the ureters, blood vessels, lymphatics, and nerves enter or exit here
B. Internal Anatomy:
1. renal cortex – the outer region
a) contains the nephron ( renal corpuscles and convoluted tubules) which are
the functional units of a kidney)
2. Renal medulla (inner region)
a)pyramids – cone-shaped tissue masses of the medulla
- contain collecting ducts that empty urine from nephron
into papillary ducts that drain urine into the...
b) calyces –
- drains urine (from the papillary ducts) into the ...
c) renal pelvis
-drains urine (from calyces) into the ureters
C. Microscopic Anatomy: Nephron
1) renal corpuscle = glomerular capillaries+ capsule of renal tubule (Bowman’s
capsule)
- the glomerulus capillaries are very leaky allowing filtration of blood components
into nephron.
2) renal tubule (includes proximal convoluted tubule, loop of nephron, distal convoluted tubule, collecting duct)– meanders through the cortex allowing tubular reabsorption (movement of substance back into blood supply) and tubular secretion (movement of substance from blood supply into urine).
C. Nephrons are the functional units of kidneys.
- functions blood by filtration (red blood cells, white blood cells, platelets
and large proteins are prevented from being filtered into urine so are conserved
by the body. Some filtered substances are then secreted (removing materials
from blood into urine) or reabsorbed (reclaiming materials from urine into blood).
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D. Blood flow
Blood originates at renal Artery, distributed throughout the kidney via a variety
of arteries into the cortex. Blood flows into the "afferent:" arterioles
that regulate flow into the glomerular capillaries (where water and smaller
substances are filtered into the glomerular capsule. Non-filtered blood exits
capillaries into "efferent" arteriole which regulates flow into the
"vasa recta" capillaries. From there blood is drained via a variety
of veins into the renal vein.
Glomerular capillaries allow filtration
Vasa recta capillaries allow reabsorption and secretion.
III. Ureters:
- convey urine from the kidneys to the urinary bladder
- a continuation of the renal pelvis
- enter the posterior wall of the urinary bladder
Three Layers
1. Mucosa; transitional epithelium
2. Muscularis; smooth muscle
3. Adventitia; outer layer, fibrous connective tissue
IV. Urinary Bladder:
Function – holds urine and ejects urine (micturition)
Filled by the paired ureters and ejects urine through opening of the urethra.
Three Layers:
1. Mucosa; transitional epithelium allows stretch to store urine.folded into
rugae for even more stretch.
2. Muscularis; smooth muscle to eject urine.
3. Adventitia; outer layer, fibrous connective tissue or serosa (visceral peritoneum)
V. Urethra:
- drains urine from the urinary bladder and carries it outside of the body
A. Sphincters: two that control the release of urine
1) internal – involuntary
2) external urethral sphincter – voluntary
- surrounds the urethra as it passes through the pelvic floor
- skeletal muscle
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on this image for an audio message
Entire system Urine flow
Blood>Filtrate in glomerular capsule of nephron>nephron tubules>pyramidal
ducts>calyces>renal pelvis>ureter>urinary bladder>urethra
A
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Another
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VI. Urinary hormones
A. ADH
Hypothalamus and Posterior Pituitary – releases ADH
- known as the neurohypophysis
- sits in the sella turcica or sphenoid bone
ADH causes the collecting ducts of the kidneys to reabsorb water more, thereby increasing blood volume and blood pressure. It decreases urine output.
B. Aldosterone
Adrenal cortex-produces Aldosterone
Adosterone promotes Na reabsorption and K secretion at the collecting ducts.So
Na is reclaimed and K is lost into the urine.
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Professor Thomas M. Lancraft
Human Anatomy Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
6/2006