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A&P LECTURE CH 25 URINARY PART B
Terms in this set (27)
when does Tubular reabsorption begin?
as soon as the filtrate enters the proximal convoluted tubule
what is Secondary active transport responsible for? occurs when?
-absorption of glucose, amino acids, vitamins, and most cations
-occurs when solutes are cotransported with Na+ when it moves along its concentration gradient
what is Transport maximum (Tm)? what determines this? levels above Tm?
-sets the maximum for amount reabsorbed
-for substances requiring a carrier is determined by the number of specific receptors,
-Amounts above the Tm will not be reabsorbed, and thus will be lost through the urine
what happens to Substances that are not reabsorbed or incompletely reabsorbed? examples?
remain in the filtrate due to a lack of carrier molecules, lipid insolubility, or large size
(urea, creatinine, and uric acid)
what are the 2 categories of Water reabsorption?
1) Obligatory reabsorption
2) Facultative reabsorption
what is obligatory reabsorption? takes place where?
that reabsorption which must take place to meet minimum requirements
takes place in the PCT
what is Facultative reabsorption? takes place where? influenced by? accomplished due to?
-the adjustable portion applies primarily to water and ions
-takes place in the DCT and CD
-strongly influenced by the body's hydration level -accomplished due to response to hormonal signals (especially ADH & aldosterone
what is the absorptive capability of the proximal convoluted tubule? selectivity?
is most active in reabsorption
most selective reabsorption occurring here
what is the absorptive capability of The descending limb of the loop of Henle? ascending limb?
-is permeable to water
-the ascending limb is impermeable to water but permeable to electrolytes.
The distal convoluted tubule and collecting duct is permeable to? regulated by?
-Na+ and water regulated by the hormones aldosterone, antidiuretic hormone, and atrial natriuretic peptide (details to follow in chapter 26)
what is the function of Tubular secretion (5)? most active where? but can also occur?
-disposes of undesirable solutes that were reabsorbed, rids the body of excess K+ , and controls blood pH, and remove certain toxins, such as penicillin.
-most active in the proximal convoluted tubule
-but occurs in the collecting ducts and distal convoluted tubules as well
how is urine concentration and volume regulated?
-The countercurrent mechanism
-involves interaction between filtrate flow through the loops of Henle (the countercurrent multiplier) of juxtamedullary nephrons and the flow of blood through the vasa recta (the countercurrent exchanger)
how does the descending limb of nephron loop (Loop of Henle) contribute to regulation of urine concentration and volume?
-Freely permeable to H2O
-Because water is freely absorbed from the descending limb of the loop of Henle, filtrate concentration increases and water is reabsorbed.
-Filtrate osmolality increases
what is Renal clearance? what is used as a clearance standard? why?
-refers to the volume of plasma that is cleared of a specific substance in a given time
-Inulin is used as a clearance standard to determine glomerular filtration rate because it is not reabsorbed, stored, or secreted
If the clearance value for a substance is less than that for inulin?
if the clearance value is greater than the inulin clearance rate?
A clearance value of zero indicates?
-then some of the substance is being reabsorbed
-then some of the substance is being secreted
-the substance is completely reabsorbed.
what is the pH of urine?
around pH 6 but can vary from about 4.5- 8.0
specific gravity of urine?
Urine has a higher specific gravity than water, due to the presence of solutes
what is the chemical composition of urine?
about 95% water and 5% solutes, the largest solute fraction devoted to the nitrogenous wastes urea, creatinine, and uric acid
what are the 3 layers of the ureters?
(innermost) mucosa, muscularis, adventitia
what are the 3 layers of the bladder?
-mucosa: transitional epithelium (highly folded to allow distention of the bladder without a large increase in internal pressure)
-Thick detrusor muscle
-Outer layer: fibrous adventitia
How long is the urethra in males and females?
3-4 cm (2 inches) long in females
20 cm (5-6 inches) in males
what are the two sphincter muscles associated with the urethra? voluntary or involuntary? formed of?
-the internal urethral sphincter, which is involuntary and formed from smooth muscle
-the external urethral sphincter, which is voluntary and formed by the skeletal muscle at the urogenital diaphragm
where can the external urethral orifice be found in males and females?
-lies between the clitoris and vaginal opening in females
-occurs at the tip of the penis in males.
what are the Three simultaneous events during micturition? what is each controlled by?
1. Contraction of detrusor muscle by ANS
2. Opening of internal urethral sphincter by ANS
3. Opening of external urethral sphincter by somatic nervous system
where does Voluntary initiation of voiding reflexes come from? what does this do?
-signals parasympathetic motor neurons that stimulate contraction of the detrusor muscle and relaxation of the urinary sphincters
what are Renal calculi? made of what?
-Kidney stones form in renal pelvis
-Crystallized calcium, magnesium, or uric acid salts
what is the most common cause for UTI?
E. coli bacteria responsible for 80% of all UTIs
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