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► Med - Anatomy & Physiology > Urinary System > Flashcards

Urinary System Flashcards

1
Q

Functions of kidneys

A
  • Filters ~180-200 liters of fluid from the blood daily
  • Removal of toxins, metabolic wastes, and excess ions from the blood
  • Regulation of blood volume, chemical composition, and pH
  • Gluconeogenesis during prolonged fasting
  • Activation of vitamin D
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2
Q

Endocrine function of kidneys

A

–Renin: regulation of blood pressure

–Erythropoietin: regulation of RBC production

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3
Q

Major excretory organs

A

Kidneys

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4
Q

Transport urine from kidneys to urinary bladder

A

Ureters

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5
Q

Temporary storage reservoir for urine

A

Urinary bladder

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6
Q

Transports urine out of body

A

Urethra

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7
Q

Ureters, renal blood vessels, lymphatics, and nerves enter and exit kidney at …

A

Hilum

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8
Q

Prevents spread of infection to kidney

A

Fibrous capsule

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9
Q

Granular-appearing superficial region of kidney

A

Renal cortex

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10
Q

–Composed of cone-shaped medullary (renal) pyramids

–Pyramids separated by renal columns

A

Renal medulla

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11
Q

Tip of pyramid; releases urine into minor calyx

A

Papilla

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12
Q

Medullary pyramid and its surrounding cortical tissue

A

Lobe

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13
Q

Funnel-shaped tube continuous with ureter

A

Renal pelvis

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14
Q

Drain pyramids at papillae

A

Minor calyces

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15
Q

–Collect urine from minor calyces

–Empty urine into renal pelvis

A

Major calyces

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16
Q

Urine flow

A

Renal pyramid –> minor calyx –> major calyx –> renal pelvis –> ureter

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17
Q
  • Structural and functional units that form urine

* > 1 million per kidney

A

Nephrons

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18
Q

Two main parts of a nephron

A
  1. Renal corpuscle

2. Renal tubule

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19
Q

Two parts of the renal corpuscle

A

–Glomerulus

–Glomerular capsule (Bowman’s capsule)

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20
Q

Tuft of capillaries, highly porous, allows filtrate formation, specialized for filtration

A

Glomerulus

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21
Q

Cup-shaped, hollow structure surrounding glomerulus

A

Glomerular capsule (Bowman’s capsule)

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22
Q

Porous membrane between blood and interior of glomerular capsule

A

Filtration membrane

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23
Q

Three layers of the filtration membrane

A

–Fenestrated endothelium of glomerular capillaries
–Basement membrane
–Foot processes of podocytes with filtration slits

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24
Q

Blood pressure in glomerulus hight because …

A

–Afferent arterioles larger in diameter than efferent arterioles
–Arterioles are high-resistance vessels

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25
Q

Glomerular filtration

A
  • Passive process
  • No metabolic energy required
  • Hydrostatic pressure forces fluids and solutes through filtration membrane
  • No reabsorption into capillaries of glomerulus
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26
Q

Three parts of renal tubules

A

–Proximal convoluted tubule (closest to renal corpuscle)
–Nephron loop
–Distal convoluted tubule (farthest from renal corpuscle)

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27
Q

–Functions in reabsorption and secretion

–Confined to cortex

A

Proximal convoluted tubule (PCT)

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28
Q
  • Descending thin limb, freely permeable to water

* Thick ascending limb

A

Nephron loop (Loop of Henle)

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29
Q

–Functions more in secretion than reabsorption

–Confined to cortex

A

Distal convoluted tubule (DCT)

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30
Q
  • Receive filtrate from many nephrons
  • Run through medullary pyramids - striped appearance
  • Fuse together to deliver urine through papillae into minor calyces
A

Collecting duct

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31
Q

Two classes of nephrons

A
  • Cortical nephrons

* Juxtamedullary nephrons

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32
Q

85% of nephrons; almost entirely in cortex

A

Cortical nephrons

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33
Q

–Long nephron loops deeply invade medulla
–Ascending limbs have thick and thin segments
–Important in production of concentrated urine

A

Juxtamedullary nephrons

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34
Q

–Low-pressure, porous capillaries adapted for absorption of water and solutes
–Arise from efferent arterioles
–Cling to adjacent renal tubules in cortex
–Empty into venules

A

Peritubular capillaries

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35
Q

–Long, thin-walled vessels parallel to long nephron loops of juxtamedullary nephrons
–Arise from efferent arterioles serving juxtamedullary nephrons
–Function in formation of concentrated urine

A

Vasa recta

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36
Q
  • One per nephron

* Important in regulation of rate of filtrate formation and blood pressure

A

Juxtaglomerular complex (JGC)

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37
Q

Three cell populations of the juxtaglomerular complex

A
  • Macula densa
  • Granular cells (juxtaglomerular, or JG cells)
  • Extraglomerular mesangial cells
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38
Q

Chemoreceptors; sense NaCl content of filtrate

A

Macula densa

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39
Q

–Secretory granules contain enzyme renin

–Mechanoreceptors; sense blood pressure in afferent arteriole

A

Granular cells (juxtaglomerular, or JG cells)

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40
Q

May pass signals between macula densa and granular cells

A

Extraglomerular mesangial cells

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41
Q

Three processes in urine formation and adjustment of blood composition

A
  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion
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42
Q

Produces cell and protein-free filtrate

A

Glomerular filtration

43
Q

Selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts

A

Tubular reabsorption

44
Q

Selectively moves substances from blood to filtrate in renal tubules and collecting ducts

A

Tubular secretion

45
Q

Kidneys filter, consume, produce …

A

Filter body’s entire plasma volume 60 times each day; consume 20-25% oxygen used by body at rest; produce urine from filtrate

46
Q

Blood plasma minus proteins

A

Filtrate

47
Q

–<1% of original filtrate

–Contains metabolic wastes and unneeded substances

A

Urine

48
Q

Volume of filtrate formed per minute by both kidneys (normal = 120–125 ml/min)

A

Glomerular filtration rate (GFR)

49
Q

Glomerular filtration rate directly proportional to …

A
  1. NFP (Net Filtration Pressure)
  2. Total surface area available for filtration
  3. Filtration membrane permeability
50
Q

Pressure responsible for filtrate formation

•Main controllable factor determining glomerular filtration rate (GFR)

A

Net filtration pressure (NFP)

51
Q

•Maintains nearly constant GFR when MAP in range of 80–180 mm Hg
- Act locally within kidney to maintain GFR

A

Intrinsic controls (renal autoregulation)

52
Q

–Nervous and endocrine mechanisms that maintain blood pressure; can negatively affect kidney function
–Take precedence over intrinsic controls if mean arterial BP < 80 or > 180 mm Hg

A

Extrinsic controls

53
Q

Two types of renal autoregulation

A
  1. Myogenic mechanism

2. Tubuloglomerular feedback mechanism

54
Q
  • Smooth muscle contracts when stretched
  • Increased BP –> muscle stretch –> constriction of afferent arterioles –> restricts blood flow into glomerulus
  • Decreased BP –> dilation of afferent arterioles
  • Both help maintain normal GFR despite normal fluctuations in blood pressure
A

Myogenic mechanism

55
Q
  • Flow-dependent mechanism directed by macula densa cells; respond to filtrate NaCl concentration
  • If GFR increases –> filtrate flow rate increases –> decreases reabsorption time –> high filtrate NaCl levels –> constriction of afferent arteriole –> decreased NFP & GFR –> more time for NaCl reabsorption
  • Opposite for decreased GFR
A

Tubuloglomerular feedback mechanism

56
Q

Under normal conditions at rest

A

–Renal blood vessels dilated

–Renal autoregulation mechanisms prevail

57
Q

Sympathetic nervous system control

A

If extracellular fluid volume extremely low (blood pressure low) –> Norepinephrine released by sympathetic nervous system; epinephrine released by adrenal medulla –> Systemic vasoconstriction –> increased blood pressure

58
Q

•Main mechanism for increasing blood pressure •Triggered when the granular cells of the JGA release renin

A

Renin-angiotensin mechanism

59
Q

Three effects of angiotensin II

A
  1. Constricts arteriolar smooth muscle, causing blood pressure to rise
  2. Stimulates the reabsorption of Na+
  3. Stimulates the hypothalamus to release ADH and activates the thirst center
60
Q

Provides energy and means for reabsorbing most other substances

A

Na+ reabsorption by primary active transport

61
Q

Creates electrical gradient

A

Passive reabsorption of anions

62
Q

Reabsorbed by secondary active transport; co-transported with Na+

A

Organic nutrients

63
Q

Movement of Na+ and other solutes creates …

A

Osmotic gradient for water

64
Q

Water reabsorbed by osmosis, aided by water-filled pores called …

A

Aquaporins

65
Q

Aquaporins always present in PCT –>

A

Obligatory water reabsorption

66
Q

Aquaporins inserted in collecting ducts only if ADH present –>

A

Facultative water reabsorption

67
Q

Reflects number of carriers in renal tubules available

A

Transport maximum (Tm)

68
Q

When transport carriers are saturated …

A

Excess excreted in urine

69
Q

Site of most reabsorption
•All nutrients, e.g., glucose and amino acids
•65% of Na+ and water
•Many ions
•~ All uric acid; ½ urea (later secreted back into filtrate)

A

PCT

70
Q

Site of most reabsorption
•All nutrients, e.g., glucose and amino acids
•65% of Na+ and water
•Many ions
•~ All uric acid; ½ urea (later secreted back into filtrate)

A

PCT

71
Q

H2O can leave; solutes cannot

A

Descending limb of nephron loop

72
Q

H2O cannot leave; solutes can

A

Ascending limb of nephron loop

73
Q

Four hormones that regulate reabsorption in the DCT and collecting duct

A
  • Antidiuretic hormone (ADH) – increases water reabsorption
  • Aldosterone – increases Na+reabsorption (therefore water as well)
  • Atrial natriuretic peptide (ANP) – decreases Na+ reabsorption
  • PTH – increases Ca2+ reabsorption
74
Q

–Released by posterior pituitary gland

–Causes principal cells of collecting ducts to insert aquaporins in membranes –> water reabsorption

A

ADH

75
Q

Reabsorption in reverse; almost all in PCT

A

Tubular secretion

76
Q

Five functions of tubular secretion

A
  1. K+, H+, NH4+, creatinine, organic acids and bases move from peritubular capillaries through tubule cells into filtrate
  2. Disposes of substances (e.g., drugs) bound to plasma proteins
  3. Eliminates undesirable substances passively reabsorbed (e.g., urea and uric acid)
  4. Rids body of excess K+ (aldosterone effect)
  5. Controls blood pH by altering amounts of H+ or HCO3– in urine
77
Q

–Number of solute particles in 1 kg of H2O

–Reflects ability to cause osmosis

A

Osmolality

78
Q

Overhydration –> decreased ADH =

A

Dilute urine

79
Q

Dehydration –> increased ADH =

A

Concentrate urine

80
Q

Three chemicals that enhance urinary output

A

–ADH inhibitors, e.g., alcohol
–Na+ reabsorption inhibitors (and resultant H2O reabsorption), e.g., caffeine, drugs for hypertension or edema
–Osmotic diuretics - substance not reabsorbed so water remains in urine, e.g., high glucose of diabetic patient

81
Q

Volume of plasma kidneys clear of particular substance in given time

A

Renal clearance

82
Q

Renal clearance tests used to determine GFR

A
  1. To detect glomerular damage

2. To follow progress of renal disease

83
Q

Measures blood nitrogen that is part of the urea resulting from catabolism and deamination of amino acids

A

Blood urea nitrogen (BUN)

84
Q

Results from catabolism of creatine phosphate in skeletal muscle – measure of renal function

A

Plasma creatinine

85
Q

pH of urine

A

Slightly acidic (~pH 6, with range of 4.5 to 8.0)

86
Q

Chemical composition of urine

A

•95% water and 5% solutes
•Nitrogenous wastes
–Urea (from amino acid breakdown) – largest solute component
–Uric acid (from nucleic acid metabolism)
–Creatinine (metabolite of creatine phosphate)

87
Q

As bladder pressure increases …

A

Distal ends of ureters close, preventing backflow of urine

88
Q

Renal calculi formed in renal pelvis

A

Kidney stones

89
Q

Percentage of all women who get urinary tract infections

A

40%

90
Q

Inflammation or infection of the urethra

A

Urethritis

91
Q

Inflammation or infection of the urinary bladder

A

Cystitis

92
Q

Inflammation or infection of the kidneys

A

Pyelonephritis

93
Q

–Smooth triangular area outlined by openings for ureters and urethra
–Infections tend to persist in this region

A

Trigone

94
Q

Expands and rises superiorly during filling without significant rise in internal pressure

A

Urinary bladder

95
Q

Three layers of bladder wall

A

–Mucosa - transitional epithelial mucosa
–Thick detrusor muscle - three layers of smooth muscle
–Fibrous adventitia (peritoneum on superior surface only)

96
Q
  • Involuntary (smooth muscle) at bladder-urethra junction

* Contracts to open

A

Internal urethral sphincter

97
Q

Voluntary (skeletal) muscle surrounding urethra as it passes through pelvic floor

A

External urethral sphincter

98
Q

Three regions of the male urethra

A
  • Prostatic urethra (2.5 cm)—within prostate gland
  • Membranous urethra (2 cm)—passes through urogenital diaphragm from prostate to beginning of penis
  • Spongy urethra (15 cm)—passes through penis; opens via external urethral orifice
99
Q

Urination or voiding

A

Micturition

100
Q

Three simultaneous events that must occur for urination

A
  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
101
Q

Usually from weakened pelvic muscles

A

Incontinence

102
Q

Five steps of reflexive urination (in infants)

A
  1. Distension of bladder activates stretch receptors
  2. Excitation of parasympathetic neurons in reflex center in sacral region of spinal cord
  3. Contraction of detrusor muscle
  4. Contraction (opening) of internal sphincter
  5. Inhibition of somatic pathways to external sphincter, allowing its relaxation (opening)
103
Q

Increased intra-abdominal pressure forces urine through external sphincter

A

Stress incontinence (eg. laughing, coughing)

104
Q

Urine dribbles when bladder overfills

A

Overflow incontinence

► Med - Anatomy & Physiology (130 decks)

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