Ch.15: The Urinary System Flashcards
1
Q
Kidneys dispose of waste products in urine, such as:
A
- Nitrogenous wastes
- Toxins
- Drugs
- Excess ions
2
Q
The kidneys’ regulatory functions include:
A
- Production of renin to maintain blood pressure
- Production of erythropoietin to stimulate red blood cell production
- Conversion of vitamin D to its active form
3
Q
What are the organs of the urinary system?
A
- Kidneys
- Ureters
- Urinary bladder
- Urethra
4
Q
What is the location of the kidneys?
A
- The kidneys are situated against the dorsal body wall in a retroperitoneal position (behind the parietal peritoneum)
- The kidneys are situated at the level of the T12 to L3 vertebrae
- The right kidney is slightly lower than the left (because of position of the liver)
5
Q
What is the structure of the kidneys?
A
• An adult kidney is about 12 cm (5 in) long and 6 cm (2.5 in) wide
• An adrenal gland sits atop each kidney
•
6
Q
What is the renal hilum?
A
A medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves)
7
Q
What are the three protective layers that enclose the kidney?
A
- Fibrous capsule encloses each kidney
- Perirenal fat capsule surrounds the kidney and cushions against blows
- Renal fascia is the most superficial layer that anchors the kidney and adrenal gland to surrounding structures
8
Q
What are the three regions that are revealed in a longitudinal section of the kidney?
A
- Renal cortex
- Renal medulla
- Renal pelvis
9
Q
What is the renal cortex of the kidney?
A
Outer region
10
Q
What is the renal medulla of the kidney?
A
- Deeper region
- Renal (medullary) pyramids—triangular regions of tissue in the medulla
- Renal columns—extensions of cortexlike material that separate the pyramids
11
Q
What is the renal pelvis of the kidney?
A
- Medial region that is a flat, funnel-shaped tube
- Calyces form cup-shaped “drains” that enclose the renal pyramids
- Calyces collect urine and send it to the renal pelvis, on to the ureter, and to the urinary bladder for storage
12
Q
What is the supply of blood in the kidneys?
A
- One-quarter of the total blood supply of the body passes through the kidneys each minute
- Renal artery provides each kidney with arterial blood supply
- Renal artery divides into segmental arteries → interlobar arteries → arcuate arteries → cortical radiate arteries
13
Q
What is venous blood flow in the kidneys?
A
- Cortical radiate veins → arcuate veins → interlobar veins → renal vein
- There are no segmental veins
- Renal vein returns blood to the inferior vena cava
14
Q
What are nephrons?
A
- Structural and functional units of the kidneys
* Each kidney contains over a million nephrons
15
Q
Each nephron consists of what two main structures?
A
- Renal corpuscle
2. Renal tubule
16
Q
What does the renal corpuscle consists of?
A
- Glomerulus, a knot of capillaries made of podocytes
- Glomerular (Bowman’s) capsule is a cup-shaped structure that surrounds the glomerulus
• First part of the renal tubule
17
Q
_____ make up the inner (visceral) layer of the glomerular capsule.
A
- Podocytes
- Foot processes cling to the glomerulus
- Filtration slits create a porous membrane—ideal for filtration
18
Q
The _____ extends from the glomerular capsule and ends when it empties into the collecting duct.
A
Renal tubule
19
Q
From the glomerular (Bowman’s) capsule, what are the subdivisions of the renal tubule?
A
- Proximal convoluted tubule (PCT)
- Nephron loop (loop of Henle)
- Distal convoluted tubule (DCT)
20
Q
What are cortical nephrons?
A
- Located entirely in the cortex
* Include most nephrons
21
Q
What are juxtamedullary nephrons?
A
- Found at the cortex-medulla junction
- Nephron loop dips deep into the medulla
- Collecting ducts collect urine from both types of nephrons, through the renal pyramids, to the calyces, and then to the renal pelvis
22
Q
What are the two capillary beds associated with each nephron?
A
- Glomerulus
2. Peritubular capillary bed
23
Q
What is the glomerulus?
A
• Fed and drained by arterioles
*Afferent arteriole—arises from a cortical radiate artery and feeds the glomerulus
*Efferent arteriole—receives blood that has passed through the glomerulus
• Specialized for filtration
• High pressure forces fluid and solutes out of blood and into the glomerular capsule
24
Q
What are peritubular capillary beds?
A
- Arise from the efferent arteriole of the glomerulus
- Low-pressure, porous capillaries
- Adapted for absorption instead of filtration
- Cling close to the renal tubule to receive solutes and water from tubule cells
- Drain into the interlobar veins
25
Urine formation is the result of what three processes?
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
26
Concept Link 1
Recall that filtration, as a passive process, requires a pressure gradient (Chapter 3, p. 78). The capillaries of the glomerulus are under higher pressure compared to the glomerular capsule; as a result, fluids move down the pressure gradient, from the blood into the glomerular capsule.
27
What is glomerular filtration?
• The glomerulus is a filter
• Filtration is a nonselective passive process
*Water and solutes smaller than proteins are forced through glomerular capillary walls
*Proteins and blood cells are normally too large to pass through the filtration membrane
*Once in the capsule, fluid is called filtrate
*Filtrate leaves via the renal tubule
• Filtrate will be formed as long as systemic blood pressure is normal
*If arterial blood pressure is too low, filtrate formation stops because glomerular pressure will be too low to form filtrate
28
What is tubular reabsorption?
• The peritubular capillaries reabsorb useful substances from the renal tubule cells, such as:
*Water
*Glucose
*Amino acids
*Ions
• Some reabsorption is passive; most is active (ATP)
• Most reabsorption occurs in the proximal convoluted tubule
29
What is tubular secretion?
• Reabsorption in reverse
• Some materials move from the blood of the peritubular capillaries into the renal tubules to be eliminated in filtrate
*Hydrogen and potassium ions
*Creatinine
• Secretion is important for:
*Getting rid of substances not already in the filtrate
*Removing drugs and excess ions
*Maintaining acid-base balance of blood
• Materials left in the renal tubule move toward the ureter
30
Concept Link 2
Recall that p H is a measure of hydrogen ion (H+) concentration (see Chapter 2, p. 41 ). When the body experiences a high level of hydrogen ions, which can lower p H, the kidneys help by eliminating excess hydrogen ions from the body via the urine.
31
_____ tend to remain in the filtrate and are excreted from the body in the urine.
* Nitrogenous wastes
* Urea—end product of protein breakdown
* Uric acid—results from nucleic acid metabolism
* Creatinine—associated with creatine metabolism in muscles
32
In 24 hours, about __ to __ liters of urine are produced
* 1.0
| * 1.8
33
How are urine and filtrate different?
* Filtrate contains everything that blood plasma does (except proteins)
* Urine is what remains after the filtrate has lost most of its water, nutrients, and necessary ions through reabsorption
* Urine contains nitrogenous wastes and substances that are not needed
34
What are the characteristics of urine?
• Clear and pale to deep yellow in color
• Yellow color is normal and due to the pigment urochrome (from the destruction of hemoglobin) and solutes
*Dilute urine is a pale, straw color
• Sterile at the time of formation
• Slightly aromatic, but smells like ammonia with time
• Slightly acidic (pH of 6)
• Specific gravity of 1.001 to 1.035
35
What solutes are normally found in urine?
* Sodium and potassium ions
* Urea, uric acid, creatinine
* Ammonia
* Bicarbonate ions
36
What solutes are not normally found in urine?
* Glucose
* Blood proteins
* Red blood cells
* Hemoglobin
* WBCs (pus)
* Bile
37
What are the ureters?
Slender tubes 25–30 centimeters (10–12 inches) attaching the kidney to the urinary bladder
• Continuous with the renal pelvis
• Enter the posterior aspect of the urinary bladder
• Run behind the peritoneum
Peristalsis aids gravity in urine transport
38
What is the urinary bladder and what is its function?
* Smooth, collapsible, muscular sac situated posterior to the pubic symphysis
* Stores urine temporarily
39
What is the trigone?
* Triangular region of the urinary bladder base based on three openings
* Two openings from the ureters (ureteral orifices)
* One opening to the urethra (internal urethral orifice)
40
In males, the _____ surrounds the neck of the urinary bladder.
Prostate
41
What is the structure of the wall of the urinary bladder?
* Three layers of smooth muscle collectively called the detrusor muscle
* Mucosa made of transitional epithelium
* Walls are thick and folded in an empty urinary bladder
* Urinary bladder can expand significantly without increasing internal pressure
42
What is the capacity of the urinary bladder?
* A moderately full bladder is about 5 inches long and holds about 500 milliliters of urine
* Capable of holding twice that amount of urine
43
What is the urethra?
Thin-walled tube that carries urine from the urinary bladder to the outside of the body by peristalsis
44
What is the function of the urethra?
* Females—carries only urine
| * Males—carries urine and sperm
45
Release of urine is controlled by what two sphincters?
1. Internal urethral sphincter
• Involuntary and made of smooth muscle
2. External urethral sphincter
• Voluntary and made of skeletal muscle
46
What is the length of the urethra?
* In females: 3 to 4 centimeters (1.5 inches long)
| * In males: 20 centimeters (8 inches long)
47
What is the location of the urethra?
```
Males—travels through the prostate and penis
• Prostatic urethra
• Membranous urethra
• Spongy urethra
Females—anterior to the vaginal opening
```
48
What is micturition?
* Voiding, or emptying of the urinary bladder
| * Two sphincters control the release of urine, the internal urethral sphincter and external urethral sphincter
49
Bladder collects urine to __ ml.
200
50
_____ transmit impulses to the sacral region of the _____ and impulses travel back to the bladder via the _____ nerves to cause bladder contractions
* Stretch receptors
* Spinal cord
* Pelvic splanchnic
51
When contractions become stronger, urine is forced past the _____ sphincter into the _____.
* Involuntary internal
* Upper urethra
* The external sphincter is voluntarily controlled, so micturition can usually be delayed
52
Blood composition depends on what three factors?
1. Diet
2. Cellular metabolism
3. Urine output
53
The kidneys have what four roles in maintaining blood composition?
1. Excreting nitrogen-containing wastes (previously discussed)
2. Maintaining water balance of the blood
3. Maintaining electrolyte balance of the blood
4. Ensuring proper blood pH
54
What is a normal amount of water in the human body?
* Young adult females = 50%
* Young adult males = 60%
* Babies = 75%
* The elderly = 45%
55
Water occupies what three main fluid compartments?
1. Intracellular fluid (ICF)
• Fluid inside cells
• Accounts for two-thirds of body fluid
2. Extracellular fluid (ECF)
• Fluids outside cells; includes blood plasma, interstitial fluid (IF), lymph, and transcellular fluid
3. Plasma (blood) is ECF, but accounts for 3L of total body water
56
What is the link between water and electrolytes?
* Electrolytes are charged particles (ions) that conduct electrical current in an aqueous solution
* Sodium, potassium, and calcium ions are electrolytes
57
What is the regulation of water intake and output?
• Water intake must equal water output if the body is to remain properly hydrated
• Sources for water intake
*Ingested foods and fluids
*Water produced from metabolic processes (10%)
• Thirst mechanism is the driving force for water intake
58
What is the thirst mechanism?
* Osmoreceptors are sensitive cells in the hypothalamus that become more active in reaction to small changes in plasma solute concentration
* When activated, the thirst center in the hypothalamus is notified
* A dry mouth due to decreased saliva also promotes the thirst mechanism
* Both reinforce the drive to drink
59
What are sources of water output?
* Lungs (insensible since we cannot sense the water leaving)
* Perspiration
* Feces
* Urine
60
_____ are primarily responsible for reabsorption of water and electrolytes by the kidneys.
Hormones
61
_____ prevents excessive water loss in the urine and increases water reabsorption.
* Antidiuretic hormone (ADH)
| * ADH targets the kidney’s collecting ducts
62
Concept Link 3
Remember the concept of interrelationships among organ systems (see Figure 1.3, p. 8), and notice that the interdependent events regulating sodium ion and water balance (see Figure 15.12, p. 528) involve four body systems: urinary, nervous, endocrine, and cardiovascular.
63
Small changes in _____ cause water to move from one fluid compartment to another
Electrolyte concentrations
64
A second hormone, _____, helps regulate blood composition and blood volume by acting on the kidney.
* Aldosterone
* For each sodium ion reabsorbed, a chloride ion follows, and a potassium ion is secreted into the filtrate
* Water follows salt: when sodium is reabsorbed, water follows it passively back into the blood
65
What is the renin-angiotensin mechanism?
* Most important trigger for aldosterone release
* Mediated by the juxtaglomerular (JG) apparatus of the renal tubules
* When cells of the JG apparatus are stimulated by low blood pressure, the enzyme renin is released into blood
* Renin catalyzes reactions that produce angiotensin
* Angiotensin II causes vasoconstriction and aldosterone release
* Result is increase in blood volume and blood pressure
66
Blood p H must remain between __ and __ to maintain homeostasis.
* 7.35
* 7.45
* Alkalosis—p H above 7.45
* Acidosis—p H below 7.35
* Physiological acidosis—p H between 7.0 and 7.35
67
_____ play greatest role in maintaining acid-base balance
Kidneys
68
Other acid-base controlling systems include:
* Blood buffers
| * Respiration
69
What are blood buffers?
Acids are proton (H+) donors
• Strong acids dissociate completely and liberate all of their H+ in water
• Weak acids, such as carbonic acid, dissociate only partially
Bases are proton (H+) acceptors
• Strong bases dissociate easily in water and tie up H+
• Weak bases, such as bicarbonate ion and ammonia, are slower to accept H+
70
Molecules react to prevent dramatic changes in _____ concentrations.
* Hydrogen ion (H+)
* Bind to H+ when p H drops
* Release H+ when p H rises
71
What are three major chemical buffer systems?
1. Bicarbonate buffer system
2. Phosphate buffer system
3. Protein buffer system
72
What is the bicarbonate buffer system?
Mixture of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)
• Carbonic acid is a weak acid that does not dissociate much in neutral or acid solutions
• Bicarbonate ions (H C O3−) react with strong acids to change them to weak acids
• Carbonic acid dissociates in the presence of a strong base to form a weak base and water
73
Respiratory rate can rise and fall depending on changing blood _____ to retain CO2 (_____ the blood pH) or remove CO2 (_____ the blood pH)
* pH
* Decreasing
* Increasing
74
When blood p H rises:
* Bicarbonate ions are excreted
| * Hydrogen ions are retained by kidney tubules
75
When blood p H falls:
* Bicarbonate ions are reabsorbed
| * Hydrogen ions are secreted
76
Urine p H varies from __ to __.
* 4.5
| * 8.0
77
The _____ begin to develop in the first few weeks of embryonic life and are excreting urine by the third month of fetal life
Kidneys
78
Common congenital abnormalities include _____ and _____.
* Polycystic kidney
| * Hypospadias
79
Common urinary system problems in children and young to middle-aged adults include infections caused by _____, microorganisms causing _____, and _____.
* Fecal microorganisms
* Sexually transmitted infections
* Streptococcus
80
Control of the voluntary urethral sphincter does not start until age:
18 months
81
Complete nighttime control may not occur until the child is:
4 years old
82
_____ are the only common problems before old age
* Urinary tract infections (UTIs)
| * Escherichia coli (E. coli), a bacterium, accounts for 80 percent of UTIs
83
_____ is an uncommon but serious problem in which the kidneys are unable to concentrate urine, and dialysis must be done to maintain chemical homeostasis of blood.
Renal failure
84
With age, _____ rate decreases and _____ cells become less efficient at concentrating _____, leading to urgency, frequency, and incontinence.
* Filtration
* Tubule
* Urine
85
In men, _____ is another common problem.
Urinary retention
86
What are urinary problems associated with aging?
* Urgency—feeling that it is necessary to void
* Frequency—frequent voiding of small amounts of urine
* Nocturia—need to get up during the night to urinate
* Incontinence—loss of control
* Urinary retention—common in males, often the result of hypertrophy of the prostate gland
