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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. Regulation of blood ______ at about 290 mOsM
3. ______ balance – ions, such as Na+, K+, and Ca2+ are maintained within a normal range
4. Blood ____ is regulated via excretion of H+ and HCO3-
5. ______ of toxic nitrogenous compounds (e.g.: urea, uric acid, & creatinine), other wastes, & drugs
6. Regulates blood ______ via the renin-angiotension pathway, which increases blood pressure
C. ______ produced by the kidneys include
1. ______ (vitamin D), formed in cooperation with the skin and liver, helps to regulate blood Ca2+ levels
2. ______ for erythrocyte production
3. ______ – 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. Blood enters the kidneys via the renal ______, is filtered, then exits via the renal ______
2. Kidney ______intertwine with vascular networks to enable urine formation
3. Urine moves from kidneys to ______to the urinary bladder for storage
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. In ______capillaries, water, wastes and other solutes are ______ from the blood into nephron tubules
b. 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 ______
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
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)
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 Cl- to 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
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 ______
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 _____