Urinary system Flashcards
Structures that make up the urinary system
Two kidneys, two ureters, one urinary bladder, and one urethra
Functions of the urinary system
- Excretion 2. Regulation of blood volume and pressure 3. Regulation of blood solute concentration 4. Regulation of extracellular fluid pH 5. Regulation of red blood cells synthesis 6. Regulation of vitamin D synthesis
Location of kidney
between 12th thoracic and 3rd lumbar vertebra and Surrounded by adipose tissue for insulation
The Nephron
is the functional unit of
the kidney. Each kidney has over one million nephrons. It produces filtrate from blood plasma.
The nephron includes
renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.
podocytes
cells that wrap around the glomerular capillaries
afferent arteriole
supplies blood to the glomerulus for filtration
efferent arteriole
transports the filtered blood away from the glomerulus.
Filtrate
the fluid filtered from the
glomerular capillaries. Enters the
lumen inside the Bowman capsule.
Proximal Convoluted tubule
- where filtrate passes first
- Drains Bowman’s capsule
Loop of Henle
- contains descending and ascending loops
- water and solutes pass through thin walls by diffusion
Distal Convoluted tubule
structure between Loop of Henle and collecting duct
Collecting duct
- empties into calyces
- carry fluid from cortex through medulla
Juxtaglomerular cells
specialized smooth muscle cells located where the afferent arteriole enters the renal corpuscle
Macula densa
part of the distal convoluted tubule that lies between the afferent and efferent arterioles next to the renal corpuscle.
Ureters
small tubes that carry urine from
renal pelvis of kidney to bladder (transitional epithelium)
Urinary bladder
in pelvic cavity, stores urine, can hold a few ml to a maximum of 1000 milliliter. (transitional epithelium)
Urethra
Tube that exits bladder and carries urine from urinary bladder to outside of body
Internal urethral sphincter
smooth muscle that surround the urethra at the junction of the urinary bladder and prevent urine from leaving the bladder
External urethral sphincter
- formed of skeletal muscle
surrounding the urethra near the
pelvic floor. - allows a person to voluntarily start or stop the flow of urine out of the urethra
Three processes of urine formation
Filtration, Tubular reabsorption, & Secretion
Filtration
occurs in the renal corpuscle, blood plasma leave glomerulus and enters Bowman space
Tubular Reasborption
involves removing substances from the filtrate and placing them back into the blood
Secretion
involves taking substances from the blood at a nephron area other than the renal corpuscle and putting back into the nephron tubule
Proximal convoluted tubule
the primary site for reabsorption
of solutes and water
Loop of henle
concentrates filtrate
Distal convoluted tubule and collecting duct
Reabsorb water and solutes, but is controlled by hormones
Countercurrent mechanism
fluids in separate structures flow in opposite directions. As they
pass by each other, materials can be exchanged between them
juxtaglomerular apparatus
of the kidneys release the enzyme renin when blood pressure is low
Antidiuretic Hormone
- secreted by the posterior
pituitary gland when the solute
concentration of the blood or
interstitial fluid increases - ADH acts on the collecting ducts of the
kidneys, causing them to absorb more
water (decrease urine volume) - Result is to maintain a normal blood
volume and blood pressure
Atrial Naturectic Hormone
- ANH is secreted from cardiac muscle in the right atrium of the heart when blood pressure increases
- ANH acts on kidneys to decrease Na+ reabsorption
- Sodium ions remain in nephron and enter urine
- Increased loss of sodium and water reduce blood volume and blood pressure
Aldosterone
The juxtaglomerular apparatus of the kidneys release the enzyme renin when blood pressure is low
2. Renin enters the blood and converts angiotensinogen to produce angiotensin I
3. Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II
4. Angiotensin II causes vasoconstriction and raises blood pressure and acts on adrenal cortex to release aldosterone
5. Aldosterone increases rate of water reabsorption in distal convoluted tubules and collecting ducts
6. Volume of water in urine decreases and blood pressure increases
Intracellular Fluid
Includes the fluid cytosol inside all the cells of the body. Two thirds of all the water in the body is in the intracellular compartment.
Extracellular Fluid
Includes all of the fluid outside the cells. includes, interstitial fluid, plasma, lymph, and other special fluids, such as joint fluid, and cerebrospinal fluid.
Na+ in extracellular fluid
sodium ions are the dominant ions in extracellular fluid. About 90 to 95% of the osmotic pressure of the extracellular fluid results from sodium ions and from the negative ions associated with them
Also secreted in sweat
K+ in extracellular fluid
(potassium)
- Electrically excitable tissues, such as muscles and nerves, are highly sensitive to slight changes in the extracellular K+ concentration.
- Controlled by Aldosterone
Ca+ in extracellular fluid
(calcium)
- Increases and decreases in the extracellular concentration of Ca2+ have dramatic effects on the electrical properties of excitable tissues
- Controlled by PTH and Calcitonin
