Download Urinary Physiology - El Camino College

Physiology 31 Lecture
Chapter 19 - Urinary Physiology
I.
Overview
A. Functions of the Urinary System
B. Anatomy of the Urinary System
C. Overview of Kidney Function
1. Filtration
2. Reabsorption
3. Secretion
D. Micturation
II. Functions of the Urinary System
A. The ___________ system, along with the respiratory, digestive, & integumentary
systems, excretes wastes from the body
B. Major ____________ of the Urinary (renal) System are:
1. _______ balance – blood and ECF volume are regulated by water retention or
excretion
2.
3.
Regulation of blood ____________ at about 290 mOsM
4.
5.
Blood ____ is regulated via excretion of H+ and HCO3-
6.
Regulates blood _________ via the renin-angiotension pathway, which increases
blood pressure
_____________ balance – ions, such as Na+, K+, and Ca2+ are maintained within a
normal range
____________ of toxic nitrogenous compounds (e.g.: urea, uric acid, & creatinine),
other wastes, & drugs
C. ____________ produced by the kidneys include
1. ___________ (vitamin D), formed in cooperation with the skin and liver, helps to
regulate blood Ca2+ levels
2.
3.
__________________ for erythrocyte production
_________ – involved in Na+ balance and blood pressure homeostasis
III. Anatomy of the Urinary System
A. Major components of the urinary system are the _________, ureters, urinary bladder and
urethra
1.
2.
3.
Blood enters the kidneys via the renal ________, is filtered, then exits via the renal
________
Kidney _________ intertwine with vascular networks to enable urine formation
Urine moves from kidneys to _________ to the urinary bladder for storage
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4.
____________ is the voiding of urine from the bladder through the urethra
B. The ___________ is the functional unit of the kidney
1. A __________ consists of an outer cortex and an inner medulla
a.
Renal __________ – outer, lighter colored area
1) Contains many _________ vessels intertwined with
2) Renal _________, which consist of glomerulus capillaries within a Bowman’s
capsule of epithelial tissue and CT
b. Renal ____________ – darker colored, inner region
1) Contains 5-11 renal ___________
2) Renal __________ pass down the renal pyramids to the
3) Minor _______, which converge into major calyces, which converge into the
renal pelvis, which becomes the _______
2. Each kidney contains about 1 million _________, the functional units of the kidney.
3. A nephron consists of a renal corpuscle, renal tubules, and associated blood vessels.
Three _________ of the nephron are
a. _____________ of solutes from blood plasma
b. ______________ of needed solutes back into the bloodstream
c. ____________ of waste products from the bloodstream
4. ______________ elements of a nephron
a. Blood enters the kidney via the renal ______, which branches into smaller arteries
until it reaches the
b. ___________ arterioles, which lead into the
c. _____________ capillaries, which reunite to form the
d. _________ arterioles that drain blood out of the glomerulus, then divide to form
the
e. _____________ capillaries that surround the proximal convoluted tubule and
___________ that surround the loop of Henle
f. Peritubular capillaries converge into venules and ______, then exit the kidney via
the
g. Renal ________, which converges with the inferior vena cava
2.
Two major ___________ beds are found in the kidneys
a.
b.
In _____________ capillaries, water, wastes and other solutes are __________
from the blood into nephron tubules
In ____________ capillaries (and vasa recta)
1) Water and substances needed by the body are __________ from the tubules
back into the blood
2) Waste materials are ___________ from the capillaries into the tubules
3. ____________ elements of the nephron consist of two main portions: the renal
corpuscle and the renal tubule.
a. Renal ____________ - found in the cortex, consists of a porous glomerulus
surrounded by a Bowman’s capsule; area of plasma __________
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b.
Renal _____ - collects blood plasma filtrate from Bowman’s capsule; filtered
water, glucose, amino acids, salts are __________, while excess H+, K+, and
NH4+ are ______ by peritubular capillaries. The tubule is composed of 3 regions:
1) ____________ Convoluted Tubule (PCT) - in the cortex; wall consists of
simple cuboidal epithelium with microvilli for _____________; from here,
filtrate goes to the
2) Descending & ascending Loop of __________ - located mostly in the
medulla; filtrate then goes to the
3) ____________ Convoluted Tubule (DCT) - in the cortex; remaining filtrate
with wastes passes to a _________ duct, to the minor and major calyces, to
renal pelvis, into the ureter.
c.
Two types of __________ are found in the kidneys
1) _________ – 85% of nephrons, have their glomeruli in the outer 2/3 of the
cortex
2) ______________ - have their glomeruli in the inner 1/3 of the cortex; loops of
Henle extend farther into the medulla
IV. Urine Formation I: Glomerular Filtration
A. The first step of urine formation is blood plasma ___________ in the glomerulus
1. Blood enters the ____________ capillaries, which are fenestrated
2. Water and small solutes form a glomerular filtrate that passes into the glomerular
capsule through the filtration ___________, which consists of
a. Fenestrated _____________ of the glomerular capillary walls
b. ___________ membrane of collagen and glycoprotein
c. Flitration _______ formed by the pedicels of __________ wrapped around the
glomerular capillaries
3. ___________ in the plasma filtrate include glucose, amino acids, electrolytes, fatty
acids, vitamins, and nitrogenous wastes
4. Larger molecules, such as __________, and blood cells are too large to pass through the
filtration membrane, thus remain in the glomerulus
5. Relatively high ___________ pressure in the glomeruli is what forces the filtrate
through the filtration membrane, due to
a. A wide ________ arteriole and narrow efferent arteriole causes a glomerular blood
pressure of about 55 mm Hg
b. Colloid ______ pressure in the glomerulus averages 30 mm Hg
c. _____________ hydrostatic pressure averages 15 mm Hg
d. _____ hydrostatic pressure forces fluids out of glomerulus
6. ______________ ruptures the glomerular capillaries, leading to scarring
(nephrosclerosis) and eventual renal failure
7. The glomerular filtration rate (____) is the amount of plasma ___________ formed
per minute by both kidneys, which averages about 125 mL/min in men and 105 mL/min
in women
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B. Regulation of Glomerular Filtration
1. Renal _____________ is the ability of the kidneys to maintain a stable GFR, despite
MAP changes, without nervous or hormonal control via the following mechanisms
a. ___________ mechanism occurs in the __________ arteriole; as MAP increases, it
stretches the arteriole, which causes it to constrict, reducing blood flow into the
glomerulus
b. Tubuloglomerular feedback is accomplished by the _____________ apparatus
1) Juxtaglomerular (___) cells in the afferent arteriole dilate or constrict the
arteriole when stimulated by the macula densa. They also secrete ______ to raise
BP when BP drops
2) Macula _______ cells in the distal convoluted tubule sense changes in filtrate
______ and ___________.
a) With _____ flow or low osmolarity, JG cells are signaled to vaso_______
b) With ______ flow or high osmolarity, JG cells are signaled to
vaso_________
2. Sympathetic control – during strenous exercise or circulatory shock, sympathetic
nerves and ____________ constrict the afferent arteriole, reducing GFR and urine
production
3. Renin-Angiotensin mechanism
a. When BP drops, sympathetic nerves stimulate JG cells to release ________ into the
bloodstream
b. Renin converts angiotensinogen to ______________
c. In the lungs and kidneys, angiotensin-converting enzyme (____) converts
angiotensin I to angiontensin ___, which increases BP by
1) Stimulates vaso____________ throughout the body
2) Constricts afferent and efferent _________
3) Stimulates secretion of _____, promoting water reabsorption
4) Stimulates the adrenal gland to secrete ____________, promoting sodium and
water retention
5) Stimulates _________ and water intake
V. Urine Formation II: Tubular Reabsorption and Secretion
A. ___________ Convoluted Tubule – ___________ about 70% of the glomerular filtrate
back into the peritubular capillaries, and removes other substances from the blood to
secrete into the tubule for excretion in the urine
1. Substances the body needs, such as ________, glucose, lactate, amino acids, and
varying amounts of ions (65% Na+) are __________, mostly by active transport across
the tubule walls
2. Products not needed by the body, such as _________, uric acid, ammonia, creatinine,
H+ or HCO3-, and some drugs are _______ into the tubule from the peritubular
capillaries
3. If a solute, such as ________, is filtered by the glomerulus faster than the PCT can
reabsorb it, the excess will pass out in the urine (e.g., __________ occurs in diabetes
mellitus)
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B. The Loop of _________
1. Primary function is to generate a ________ gradient that enables the collecting duct to
concentrate the urine and conserve water
2. The __________ thin segment allows _______ to flow out to surrounding peritubular
capillaries (or vasa recta)
3. The __________ thick segment is impermeable to water, but allows Na+, K+, and Clto be transported out, increasing ______ of the surrounding medulla tissues (which
increases osmosis out of the descending segment)
4. About 25% of ___, K+. and Cl- and 15% ______ are reabsorbed by the loop
C. ___________ Convoluted Tubule & Collecting Duct
1. ___________ cells in the walls of both tubes have hormone receptors and are involved
in the reabsorption of water and ____
2. ______________ cells reabsorb K+, secrete H+ into the tubule, and are involved in
_____-base balance
3. ____________ involved include the following
a. ___________ stimulates the DCT to reabsorb Na+ and secrete K+
b. Atrial natriuretic peptide (____) increases salt and ______ excretion by
decreasing ___ and GFR, and inhibiting NaCl reabsorption by the collecting duct
c. Parathyroid hormone (____) acts on the nephron loop and DCT to promote ____
reabsorption, and acts on the PCT to promote phosphate excretion
VI. Urine Formation III: Water Conservation in the collecting ducts
A. The __________ duct (CD) reabsorbs varying amounts of _______ to leave the urine as
dilute as 50 mOsm/L or as concentrated as 1,200 mOsm/L, depending upon the body’s
state of hydration
B. The CD is permeable to _______, but not to NaCl. As the CD passes through the medulla,
it loses water to surrounding tissues, and urine becomes more concentrated
C. ______ controls the rate of water loss by the CD
1. ADH stimulates the installation of _________ water transporters in CD cells,
increasing CD permeability to water
2. High ADH causes urine to be scanty and highly ____________
3. Low ADH causes increased dilute urine (_________)
VII. Urine & Renal Function Tests
A. ____________ is the examination of the physical and chemical properties of urine, which
is a valuable diagnostic procedure
B. Composition & Properties of Urine
1. Appearance – varies from colorless to ________, depending on the body’s state of
hydration. Cloudiness might indicate ___________ growth
2. ________ – fresh urine should have a distinctive, but not repulsive, smell. As urine
stands, bacteria degrade urea to ___________, producing a more pungent odor
3. Specific _______, the ratio of the ______ (g/mL) of a substance to the density of water
(1.000 g/mL); urine SG ranges from 1.001 when dilute to 1.028 when concentrated
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4. ___________, concentration of dissolved solutes, varies from 50 mOsm/L in a
hydrated person, to 1,200 mOsm/L in a dehydrated person
a. Excess urine concentration can lead to renal __________ (kidney stones) that can
block the ureter
5. ___ ranges from 4.5-8.2, but is usually about 6.0 (mildly acidic)
6. Chemical composition – urine averages 95% water and 5% _______ by volume.
Components include
a. _______, NaCl, KCl are in greatest concentration
b. _____________, uric acid, phosphates, sulfates, and traces of Ca 2+, Mg2+, and
sometimes HCO3- are found in lesser amounts
c. Biliruben or __________, breakdown products of hemoglobin, may be found
d. It is abnormal to find _________, hemoglobin, albumin, or ketones in urine. Their
presence may indicate kidney dysfunction
C. Urine Volume in an average adult is __-__ L per day. Abnormally high output is
__________; low output is _________.
D. ___________ is any chronic polyuria of metabolic origin. Forms of diabetes include
1. Type __ (juvenile or insulin dependent) diabetes mellitus – pancreatic ___ cells are
destroyed and no longer produce insulin
2. Type ___ (adult-onset or insulin independent) diabetes mellitus – beta cells may still
produce insulin, but insulin __________ on effector organs are deficient
3. The above types of diabetes are characterized by ___________ (glucose in the urine),
poly______ (extreme thirst), poly_____ (excess urination), poly________ (excessive
hunger)
4. Diabetes _________ – characterized by polydipsia and polyuria due to a deficiency of
____
E. __________ are chemicals that increase urine output. Some examples are
1. _________ – inhibits the release of ADH, reducing tubular reabsorption
2. ___________ – dilates the afferent arteriole and increases GFR
3. Diuretic drugs are used to treat ____________ and congestive heart failure because
they reduce the body’s fluid volume and blood pressure
F. Renal ___________ Tests are performed to diagnose and monitor kidney diseases. Two
frequently used methods are
1. Glomerular Filtration Rate (_____) is the amount of plasma _______ formed per
minute (about 125 mL/min) by both kidneys.
a. GFR can be measured by injecting a substance that is not ________ nor ________
(e.g., inulin), then measuring the rate of urine output and concentrations of the
substance in the blood and urine.
2. Renal _________ (RC) – the volume of blood ________ from which a particular
substance is completely ______________ in 1 minute. It is calculated by: RC = UV/P,
where
a. U = concentration (mg/ml) of the substance in the ______
b. V = the ______ rate of urine formation (ml/min)
c. P = the concentration of the same substance in the _________
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d. Example: _______ RC can be used to calculate GFR
1) Inulin (a polysaccharide) is not ___________, stored, or secreted by kidneys
2) If inulin is __________ so that P = 1 mg/dl, then U = 125 mg/mL, and V = 1
mL/min, so RC = _____ mL/min
e. A normal renal clearance value for _____ is about 70 mL/min, meaning of the 125
mL/min GFR, 70 mL is ________ of urea, while the remaining 55 mL is
___________ into the plasma
f. A renal clearance of ____ (as with glucose in a healthy person) means that
____________ is complete or the substance is not __________ (as with hemoglobin
in a healthy person)
g. A renal clearance greater than inulin, as with ___________ and most drugs, means
the tubules are secreting the substance into the filtrate
VIII. Urine Storage and Excretion
A. ___________ (urination) – is the process by which urine passes from bladder through
urethra. Events include:
1. The urinary bladder becomes ___________ with urine
2. ________ receptors in the bladder wall send sensory impulses to the spinal cord, then
to the micturation center in the _____
3. Parasympathetic impulses from the pons go to the _________ muscle & internal
urethral __________
4. The detrusor muscle contracts & internal sphincter ________
5. The need to urinate is sensed as ________
6. Urination is prevented by voluntary contraction of the ________ urethral sphincter
(voluntary skeletal muscle)
7. When urinating, the _________ sphincter is relaxed, the ______ muscle contracts, &
urine is expelled through the urethra
8. Neurons of the micturation center are ___________, the detrusor muscle relaxes, & the
urinary bladder fills again.