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HAN 202 > Chapter 25: Urinary System > Flashcards

Chapter 25: Urinary System Flashcards

1
Q

Kidneys

A

major excretory organs

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2
Q

Urinary Bladder

A

the temporary storage reservoir for urine

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3
Q

Ureters

A

transport urine from the kidneys to the bladder

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4
Q

Urethra

A

transports urine out of the body

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5
Q

Kidney functions

A
  • removal of toxins, metabolic wastes, and excess ions from the blood
  • regulation of blood volume, chemical composition, and pH
  • Gluconeogenesis during prolonged fasting
  • Endocrine functions:
  • Renin
  • Erythropoietin (EPO)

-Activation of vitamin D

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6
Q

Endocrine functions

A
  • Renin: regulation of blood pressure and kidney function

- Erythropoietin (EPO): regulation of RBC production

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7
Q

Internal Anatomy: Renal Cortex

A

A granular superficial region

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8
Q

Internal Anatomy: Renal Medulla

A

-The cone-shaped pyramids separated by renal columns

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9
Q

Internal Anatomy: Renal pelvis

A

The funnel-shaped tube within the renal sinus, continuous with the ureter

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10
Q

Nephrons

A

-Structural and functional units that form urine

  • Two main parts:
    1. Renal Corpuscle: capsule (Bowman’s) and glomerulus
  1. Renal Tubule: proximal and distal convoluted tubule, nephron loop & collecting duct
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11
Q

Nephrons: 2 types

A

-> Cortical nephrons:
85% of nephrons; almost entirely in the cortex

  • > Juxtamedullary nephrons: *Long loops of Henle deeply invade the medulla
  • Important in the production of concentrated urine
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12
Q

Nephron Capillary beds:

1. Glomerulus

A

Afferent arteriole-> glomerulus-> efferent arteriole (only place in body)

  • Specialized for filtration. Blood pressure is high bc:
  • Arterioles are high pressure
  • afferent arterioles are larger in diameter than efferent arterioles
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13
Q

Nephron capillary beds:

2. Peritubular capillaries

A
  • low pressure, porous, meandering

- associated with cortical nephron

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14
Q

Nephron capillary beds:

3. Vasa recta

A
  • long and straight vessel loops of Henle
  • juxtamedullary nephrons
  • formation of concentrated urine
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15
Q

Cortical nephron

A
  • has short loop of henle and glomerulus

- efferent arteriole supplies peritubular capillaries

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16
Q

juxtamedullary nephron

A
  • has long loop of henle and glomerulus

- efferent arteriole supplies vasa recta

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17
Q

Renal tubule

A
  • glomerular capsule
  • proximal convoluted tubule: functions in reabsorption and secretion
  • Loop of henle: descending and ascending limbs
  • distal convoluted tubule: secretion
  • collecting ducts: receives filtrate from many nephrons
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18
Q

juxtaglomerular complex (JGC)

A
  • 1 per nephron
  • important in regulation of filtrate formation and blood pressure
  • involves modified portions of the
  • distal portion of the ascending limb of the loop of henle
  • afferent (sometime efferent) arteriole
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19
Q

juxtaglomerular complex (JGC): GRANULAR CELLS

A
  • wall of afferent arteriole
  • mechanoreceptors (monitor BP)
  • secrete enzyme renin
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20
Q

juxtaglomerular complex (JGC): MACULAR DENSA CELLS

A
  • cells in ascending limb of tubule

- chemoreceptors monitor NaCl of filtrate entering the distal convoluted tubule

21
Q

filtration membrane

A

-porous membrane between the blood and the capsular space

  • consists of:
    1. fenestrated endothelium (pores) of the glomerular capillaries
  1. visceral membrane of the glomerular capsule (podocytes with foot processes and filtration slits)
  2. basement membrane
    * negatively charged basement membrane repels large plasma proteins
22
Q

mechanisms of urine formation

A
  1. glomerular filtration (“clean out closet”)
    * passive, nonselective
  2. tubular reabsorption
    * returns all glucose and amino acids, 99% of water, salt, and other component TO THE BLOOD
  3. tubular secretion
    * reverse of reabsorption; selective addition to urine
23
Q

mechanisms of urine formation:

Step 1: Glomerular filtration

A
  • passive, nonselective process (no ATP)
  • filtration membrane (efficient)
  • large plasma proteins are not filtered and function to maintain colloid osmotic pressure of the blood
  • net filtration pressure (NFP)= pressure responsible for filtration
  • glomerular filtration rate due to 3 factors:
  • net filtration pressure
  • total surface area (large)
  • membrane permeability
24
Q

Pressure drives filtration

A

true

25
Q

Regulation of glomerular filtration rate

A
  • GFR is tightly regulated to serve 2 crucial needs:
    1. kidneys need a constant GFR to make filtrate
  1. body as a whole needs a constant BP
    - the 2 are closely related, if GFR increases, urine output increases which reduces blood volume and BP
26
Q

Regulation of glomerular filtration

A

GFR is tightly controlled by 2 types of mechanisms

  • Intrinsic controls (renal autoregulation)
  • act locally within the kidney
  • extrinsic controls
  • nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function
27
Q

intrinsic controls

A

-maintains a nearly constant GFR when MAP (mean arterial pressure) is in the range of 80-180 mm Hg

  • 2 types of renal autoregulation:
  • Myogenic mechanism- stretch
  • Tubuloglomerular feedback mechanism, which senses changes in Na concentration of filtrate
28
Q

INtrinsic controls: myogenic mechanism

A

increased systemic BP stretches vascular smooth muscle-> constriction of afferent arterioles

  • prevents glomerular BP from rising
  • protects glomeruli from damaging high BP

decreased systemic BP-> dilation of afferent arterioles
-helps maintain normal GFR

29
Q

Intrinsic controls: tubuloglomerular feedback mechanism

A
  • > macula densa cells (in walls of ascending limb, salt monitoring)-flow dependent
  • If GFR increases, filtrate flow rate increases in the tubule
  • NaCl concentration in filtrate will be high because of insufficient time for reabsorption
  • macula densa cells respond to increased NaCl by releasing a chemical that vasoconstricts the afferent arteriole-> decreases GFR (slows down rate of flow)
  • the opposite occurs if GFR decreases and causes vasodilation of afferent arteriole
30
Q

tubuloglomerular mechanism of autoregulation

A
  1. GFR increases
  2. Increased filtrate flow
  3. Flow past macula densa increases (in JGC)
  4. Release of vasoactive chemicals
  5. Afferent arteriole constricts
  6. Resistance in afferent arteriole increases
  7. Hydrostatic pressure in glomerulus decreases
  8. GFR decreases
31
Q

Extrinsic controls: sympathetic nervous system

A
  • > under normal conditions at rest:
  • renal blood vessels are dilated
  • renal autoregulation (intrinsic) mechanisms prevail
  • > under extreme stress (low BP-hypovolemic shock-need to maintain BP):
  • norepinephrine and epinephrine are released
  • both cause constriction of afferent arterioles which inhibits filtration and renin is released
  • Goal: restore blood volume and pressure
32
Q

summary of intrinsic control

A
  • > myogenic mechanism:
  • if increased BP, stretches arteriole wall, causes constriction and decreases BP
  • > tubuloglomerular feedback:
  • if GFR increases, will have increased flow rate, NaCl will be high, macula densa cells (ascending limb) will detect and release a chemical for constriction
33
Q

Extrinsic controls renin-angiotensin-aldosterone

A
  • main mechanism for raising BP
  • low BP causes granular cells to release renin
  • renin assists in changing angiotensinogen to angiotensin II
34
Q

effects of angiotensin II

A
  1. constricts arteriolar smooth muscle, causing MAP to rise
  2. triggers aldosterone secretion from adrenal cortex
    * stimulates the reabsorption of Na+ (Na moves into blood, water follows, conserves blood volume)
  3. stimulates the hypothalamus to release ADH (anti-diuretic hormone) and activates the thirst center
35
Q

Step 2: tubular reabsoprtion

A
  • A selective process that begins in prox convoluted tubule
  • All organic nutrients are reabsorbed
  • Water and ion reabsorption are hormonally regulated
  • Includes active (requires ATP) and passive transport
  • Different areas of the tubules have different absorptive capabilities
36
Q

reabsorption of nutrients, water, and ions

A

Na+ reabsorption – active transport

  • Organic nutrients (glucose, AA, vitamins) -by secondary active transport (carriers)
  • When the carriers are saturated, excess of that substance is excreted (glucose in urine sign of DM)
  • Water – reabsorbed by osmosis
  • Aided by pores called aquaporins
37
Q

reabsorptive capabilities of renal tubules and collecting ducts

A

Proximal convoluted tubule (PCT):

  • site of most reabsorption
  • ions, water, nutrients

loop of henle:

  • descending limb: H2O
  • ascending limb: Na+, K+, Cl-

DCT & collecting duct:

  • hormonally regulated
  • Na+ - aldosterone
  • water - ADH
  • Ca+ - parathyroid hormone
38
Q

Step 3: tubular secretion

A
  • Eliminates undesirable substances (e.g., urea and uric acid)
  • Disposes of substances such as drugs
  • Rids the body of excess K+
  • Controls blood pH by altering amounts of H+ or HCO3– in urine
  • These solutes move from peritubular capillaries into filtrate
39
Q

regulation of urine concentration and volume

A

-Kidneys make adjustments to keep solute concentration constant, whether dehydrated or overhydrated.

  • Osmolality of body fluids
  • The kidneys maintain osmolality of plasma at ~300mOsm, using countercurrent mechanisms

*Allow the kidneys to vary urine concentration

40
Q

countercurrent mechanism

A

Occurs when fluid flows in opposite directions in two adjacent segments of the same tube

  • Filtrate flow in the loop of Henle
  • Blood flow in the vasa recta
41
Q

countercurrent multiplier: loop of henle

A

Descending limb:

  • freely permeable to H2O
  • Filtrate osmolality increases

Ascending limb:

  • selectively permeable to solutes
  • filtrate osmolality decreases
42
Q

diuretics

A
  • Chemicals that enhance the urinary output
  • Osmotic diuretics: substances not reabsorbed, (e.g., high glucose in a diabetic patient, water follows glucose)
  • ADH inhibitors such as alcohol
  • Substances that inhibit Na+ reabsorption and obligatory H2O reabsorption such as caffeine and many drugs
43
Q

physical characteristics of urine

A

color and transparency:

  • Clear, pale to deep yellow
  • Cloudy urine may indicate a urinary tract infection
  • Pink urine = blood

Odor:

  • Slightly aromatic when fresh
  • Develops ammonia odor upon standing
  • May be altered by some drugs and vegetables
  • Diabetics = fruity smelling
44
Q

ureters

A

-Convey urine from kidneys to bladder

  • Enter the base of the bladder through the posterior wall
  • As bladder pressure increases, distal ends of the ureters close, preventing backflow of urine
45
Q

urniary bladder

A
  • Muscular sac for temporary storage of urine
  • Collapses when empty; rugae (folded walls) appear
  • Trigone (inferior portion of bladder)
  • Infections tend to persist in this region
46
Q

urethra

A

Sphincters:

  • Internal urethral sphincter
  • Involuntary (smooth muscle) at bladder-urethra junction
  • Internal sphincter opens
  • External urethral sphincter
  • Voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor
47
Q

micturition

A
  • Urination or voiding
  • Three simultaneous events:
    1. Contraction of detrusor muscle by ANS
  1. Opening of internal urethral sphincter by ANS
  2. Opening of external urethral sphincter by somatic nervous system
48
Q

micturition

A

Reflexive urination in infants
-Distension of bladder activates stretch receptors

  • Excitation of parasympathetic neurons in reflex center of spinal cord
  • Contraction of the detrusor muscle
  • Opening of internal sphincter
  • Inhibition of somatic pathways to external sphincter, allowing its relaxation (opening)
49
Q

micturition

A
  • Pontine control centers mature between ages 2 and3
    1. Pontine storage center inhibits micturition:
  • Inhibits parasympathetic pathways
  • Excites sympathetic and somatic efferent pathways
  1. Pontine micturition center promotes micturition:
    * Excites parasympathetic pathways
    * Inhibits sympathetic and somatic efferent pathways

HAN 202 (13 decks)

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