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A & P Lecture > Urinary System > Flashcards

Urinary System Flashcards

1
Q

Excretion

A

removal of organic waste products from
body fluids

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2
Q

Regulation

A

maintenance of homeostasis in volume and solute concentration of plasma

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3
Q

Elimination

A

discharge of waste products into environment

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4
Q

The Kidneys

A

• Paired, retroperitoneal organs (behind abdominal wall)

• Surrounded by:
- Fibrous capsule
- Fat capsule
- Renal fascia

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5
Q

The Nephron

A

• Functional unit of the kidney
• ~1.25 million per kidney
Juxtamedullary nephron
• Consists of a renal corpuscle and a renal tubule
• Surrounded by capillary network

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6
Q

Renal corpuscle

A

•Site where filtration of
plasma occurs
•Blood pressure pushes fluid
out of capillaries into
capsular space
- Continuous with renal tubule

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7
Q

Glomerulus

A
  • Capillary network
  • Blood arrives via afferent arteriole (in)
  • Blood leaves via efferent arteriole (out)
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8
Q

Glomerular capsule has 2
layers

A
  • Outer capsular epithelium
  • Inner visceral epithelium
  • Capsular space between
  • Podocytes: large cells in visceral epithelium
    • Wrap around capillaries
    . “Feet” called pedicels
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9
Q

Renal tubule

A

•Proximal convoluted tubule (PCT)
- Simple cuboidal epithelium w/microvilli
• Nephron loop
- Thin segment: simple squamous; thick:
simple cuboidal
• Distal convoluted tubule (DCT)
- Simple cuboidal epithelium
•Empties into collecting duct

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10
Q

Nephron structure

A

• 85% are cortical nephrons
- Almost entirely within cortex
- Nephron loops surrounded by peritubular capillaries
• 15% are juxtamedullary nephrons
- Nephron loops extend into medulla
- Surrounded by vasa recta

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11
Q

Filtration

A
  • BP forces H2O and small solutes from plasma into
    nephron
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12
Q

Reabsorption

A
  • Removal of water & solutes from filtrate into blood
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13
Q

Secretion

A

Addition of solutes to filtrate from blood

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14
Q

Nitrogenous wastes

A

• Urea: breakdown of amino acids
• Creatinine: breakdown of creatine phosphate
• Uric acid: breakdown of RNA nitrogenous bases
• Others: ammonia, urobilin, bilirubin…

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15
Q

Glomerular Filtration

A

• Filtration membrane
- Capillary membrane
• fenestrated (has holes)
• Prevents movement of blood cells
- Dense layer
• Only allows small proteins, nutrients and ions through
- Filtration slits
• Prevent passage of most proteins

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16
Q

Filtration Pressures

A

• Glomerular Hydrostatic Pressure (GHP)
- Blood pressure in capillaries
- 50 mmHg

• Capsular Hydrostatic Pressure (CsHP)
- Resistance in nephron
- 15 mmHg

• Net Hydrostatic Pressure (NHP)
- Difference between GHP and CsHP
- 50 mm Hg - 15 mm Hg = 35 mm Hg

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17
Q

Colloid osmotic pressure (COP)

A

-Osmotic pressure resulting from suspended proteins
- Tends to draw water back into plasma
- 25 mm Hg

18
Q

Filtration pressure

A
  • Difference between NHP and COP
  • 35 mm Hg - 25 mm Hg = 10 mm Hg
19
Q

If blood pressure goes up then filtration pressure increase which

A

Results in more filtrate produce

20
Q

Glomerular Filtration Rate (GFR)

A

• Amount of filtrate produced by the kidneys each minute
• Averages 125 mL/min
• Glomeruli generate 180 L filtrate per day
- 99% reabsorbed in renal tubules

21
Q

Autoregulation

A

• Decline in glomerular blood pressure triggers:
- Dilation of afferent arteriole and glomerular capillaries
- Constriction of efferent arteriole (increases pressure)

22
Q

Hormonal Regulation

A

• Renin-angiotensin system
• Renin produced in nephrons at the juxtaglomerular complex (JGC)

23
Q

Juxtaglomerular complex (JGG)

A
  • Epithelial cells of DCT near renal corpuscle (macula densa)
  • Smooth muscle fibers in afferent arteriole
24
Q

Renin released due to:

A
  • Decline in BP at glomerulus
  • Decline in osmotic concentration (ie. solute concentration) of tubular fluid at macula densa

•no enough solutes, not enough filtration so increases solutes for more filtration

25
Q

Release of renin results in production of angiotensin |I in the blood

A
  • Causes constriction of efferent arteriole
  • Secretion of aldosterone by adrenal glands
    • Increases Na+ reabsorption in DCT & CD
  • Triggers sensation of thirst
  • Release of antidiuretic hormone (ADH)
    • Increases water reabsorption in DCT & CD
  • Widespread peripheral vasoconstriction
26
Q

Reabsorption & Secretion at PCT

A

• Reabsorbs 60-70% of filtrate
- “bulk reabsorber”
- Organic nutrients: sugar, amino acids
- Ions: Sodium
- Water
- Urea
- Requires channels or carrier proteins

27
Q

Transport Maximum

A

• Carrier proteins can be saturated
• Determines the renal threshold
- Plasma concentration at which substance of interest begins to appear in urine
- Renal threshold for glucose: 180 mg/dL
• Glycosuria: presence of glucose in urine

28
Q

The Nephron Loop

A

Reabsorbs ½ of remaining water, 2/3 remaining sodium & chloride

29
Q

Thin segment of descending limb

A

impermeable to solutes, permeable to water

30
Q

Thick segment of ascending limb

A
  • impermeable to solutes and water
  • Has proteins that pump sodium & chloride into peritubular fluid
31
Q

Countercurrent multiplication

A

• Na+ & CI- pumped out of thick ascending limb into peritubular fluid, increasing osmotic concentration
• Water flows out of thin descending limb into peritubular fluid, increasing osmolarity in thin descending limb

32
Q

The Nephron Loop

A

Fluid arrives at DCT with concentration of 100 mOsm/L
- Waste products make up more of the concentration at this point

33
Q

Reabsorption at DCT

A

• Calcium reabsorption is regulated by parathyroid hormone
• Na+ reabsorption is regulated by aldosterone
• Stimulates synthesis of ion pumps and channels
• Water reabsorption is regulated by antidiuretic hormone
(ADH)
- Stimulates synthesis of aquaporins
- Also occurs in collecting duct

34
Q

Secretion at DCT

A

• Potassium
• Hydrogen lons

• Both are “traded” for sodium ions
- Sodium ions are reabsorbed from the DCT

35
Q

Regulation of urine volume & concentration

A

• Obligatory water reabsorption
- Occurs in PCT & nephron loop
- Recovers 85% of filtrate volume

• Facultative water reabsorption
- Occurs in DCT & collecting duct
- ADH & aldosterone allow for precise control of urine volume & concentration
(Can be fine tuned, adjusted)

36
Q

No antidieuric

A

Not retaining water

37
Q

With antidiueric

A

• able to reabsorb water
•More concentrated urine, less volume

38
Q

Ureters

A

• Transport urine from kidneys to bladder
• Three layers
- Transitional epithelium
- Smooth muscle
- Outer connective tissue layer

(No modification of urine)

39
Q

Urinary bladder

A

• Urine storage
• Lined with transitional epithelium
- Folds called rugae
• Three layers of smooth muscle
- Detrusor muscle

40
Q

After Kidneys:

A
  1. Ureters
  2. Bladder
  3. Urethra
41
Q

Urethra

A

• Transports urine from bladder to outside
• Lined with stratified squamous epithelium

• The Male Urethra
- from neck of urinary bladder to tip of penis
(18-20 cm; 7-8 in.)

• The Female Urethra
- Is very short (3-5 cm; 1-2 in.)> reason why women get more UTIs than men
- External urethral orifice is near anterior wall of vagina

42
Q

Urination

A

• Micturition reflex
- Stretch receptors in wall of bladder detect increased pressure caused by urine volume
(200mL or more)
• Info sent to spinal cord, brain (awareness)
- Wall of bladder contracts, further increasing
pressure
- Brain sends signal to external urethral sphincter to relax (voluntary)
• internal urethral sphincter then relaxes (involuntary)

A & P Lecture (7 decks)

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