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M101 > W23 Urinary system (Renal) > Flashcards

W23 Urinary system (Renal) Flashcards

1
Q

What does the urinary system consist of? (4)

A

Kidneys- renal pelvis (into which urine is drained). It is a pressure filter prdoucing urine from blood

Ureters- transport urine to the urinary bladder

Bladder- stores urine until convenient to void

Urethra- tube between the bladder and external environment. Transports urine outside of the body.

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2
Q

What are the main functions of the kidneys? (3)

A

Filtration (blood)
Reabsorption (selection)
Homeostasis

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3
Q

What are the substances filtered and reabsorbed by the kidneys? (6)

A
  1. Water Glomerular filtrate (180-200 l/day approx)
  2. Sodium Chloride (nearly all Na+ and Cl- is reabsorbed to maintain internal O.P)
  3. Glucose (Reabsorbed as long as plasma glucose < 200mg/100ml)
  4. Hydrogen ions (Normal diet generates H+ ions and kidney eliminates them)
  5. Urea ( End product of protein metabolism, 2/3 of that filtered is passed out in urine, the remainder is reabsorbed)
  6. Toxic substances ( Body metabolites drugs and drug metabolites, some of these may be actively secreted (removed)
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4
Q

Kidney Facts and Figures

Kidneys are ? % of body weight
How many nephrons in kidney? How long are they in length and diameter?How much plasma does the kidney process in a day?

A
  1. Kidneys are < 1% of body weight
    * Yet receive about 25% of Cardiac Output
    * ¼ of all ‘work’ performed by the heart is to perfuse kidneys
  2. Functional unit is the nephron
    * Approx 2.5 million
    * Each approx 5 cm in length about 50 μm in diameter
    * Approx 125 km tubing (not including blood vessels)
  3. Processes 180 L plasma/day
    * Only about 1.5 drops per nephron
    * Of which ~ 1% ends up as urine
    * About 600g of sodium reabsorbed per day
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5
Q

What is contained in urine? (5)

A

Relatively high concentrations of:
- Urea
- Uric acid
- Creatinine
- K+
- Other toxic substances
- Rest is reabsorbed

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6
Q

What does the gross structure of a kidney contain?

A

Renal cortex, renal medulla, Renal pelvis, Renal pyramid, Ureter

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7
Q

What is Hematuria?
What is this a sign of?

A

Red blood cells in urine (not normal)

Sign of damage (to barrier)
Maybe from outside or inside kidney

Outside
-Kidney stones, tumours (renal pelvis, ureter, urinary bladder, prostate, urethra)
-UTI (inflammation of urinary bladder, urethra, prostate)
-May also get WBC in urine

Inside
-Inflammation of glomeruli (eg glomeruli nephritis) – affects filtration
-Infarct – necrosis of kidney

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8
Q

What is the nephron?
What are the features of the nephron?
What are the 2 components?

A

The functional unit of the kidney (renal corpuscle and tubule)
* Each nephron has two components
* Vascular (blood)
* Tubular (filtered fluid)

Some of the nephron is in renal cortex
* outer region
* granular

Some of the nephron is in renal medulla
*inner region,
* made up of triangles (renal pyramids)

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9
Q

What makes up the vascular component of the nephron?

A

Blood travels to the Interlobular artery- afferent arteriole (aa)
Splits the glomerulus (g)
- A ball of capillaries
- Responsible for filtration
Rejoin- Efferent arteriole (ea)
- In other beds (a venule)

Splits- peritubular capillaries
- A secondary capillary bed!
- Supply renal tissue with blood
- Receives compounds reabsorbed by tubule
- Source of compounds secreted by tubule

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10
Q

The Nephron: Tubular component
What are they composed of?
What are the 5 components?

A

The Nephron: Tubular component
Composed of epithelial cells
1. Bowman’s capsule (BC)
* encloses glomerulus in cortex
* where filtration occurs
2. Proximal Convoluted Tubule (PCT)
* in cortex
* responsible for most reabsorption/secretion
3. Loop of Henle (LH)
* cortex/medulla
* responsible for osmotic gradient in medulla
4. Distal Convoluted Tubule (DCT)
* in cortex
* ‘fine-tuning’ of solute/water reabsorption
5. Collecting Tubules/Ducts (CD)
* in cortex/medulla
* “fine-tuning’ of urine concentration

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11
Q

What is the function of the Afferent arteriole?
Takes blood to the glomerulus

A

Takes blood to the glomerulus

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12
Q

What is Proteinuria?

Is this healthy?

A

Protein in urine

-Why?
CHARGE, SIZE
-Albumin slightly < 7nm (urine minute amounts)
-Some protein hormones are smaller but actively reabsorbed
V little protein found in the urine of healthy people
Question
- Haemoglobin smaller than albumin
- V little passes from the blood to filtrate – v little found infiltrate?
- Why?

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13
Q

What are Podocytes?

A

Highly specialised cells of the kidney glomerulus that help form a filtration barrier (with endothelial cells)

Podocytes are found in epithelium of BC and surround capillaries (filtration)

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14
Q

What are the different ways of ‘Fine-tuning’ urine osmolarity? (DCT and CD)

A

Hormonal mechanisms:
- Renin-angiotensin-aldosterone (RAAS) mechanisms
- Antidiuretic hormone (ADH) mechanism
- Atrial natriuretic peptide (ANP) mechanisms
- RAAS and ANP: more sensitive to changes in BP
- ADH: more sensitive to blood concentration

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15
Q

Low Blood Pressure
Angiotensin (RAAS)

A

 Macula Densa cells sense low Na in filtrate in dct
 JG cells also detect reduced stretch in
afferent arteriole
 Renin release from kidney (from JGC)
 Converts angiotensinogen (found in plasma) into angiotensin I
 ACE (pulmonary capillaries) converts
angiotensin I into angiotensin II
 Angiotensin II: vasoconstrictor
 Increases TPR
 Stimulates release of aldosterone (and thirst)

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16
Q

Low BP: Aldosterone

A

 Steroid hormone / Released from adrenal cortex
 Travels to DCT and CD
 Bind to receptors
 Stimulates Na+ reabsorption from CD into capillaries
 Cl- co-transported
 Water follows
 Increases Blood Volume
 Increases BP

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17
Q

ADH effect on dct and collecting duct

A

 Anti-Diuretic Hormone (ADH)
 Released from posterior pituitary
 Release sensitive to…
 Osmoreceptors (hypothalamus) –
 sense when body fluids become concentrated
 Volume stretch receptors (right atrium) (decrease)
 High osmolarity or low blood pressure cause
vasopressin (ADH) release
 ADH release:
 Increases permeability of dct and collecting ducts to
water
 Increases reabsorption in collecting ducts
 Small volume concentrated urine

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18
Q

What is the function of Atrial Natriuretic Peptide?

Where is it released from and when?

A

Opposite effect (of ADH): Na+ excretion increased!
- ANP released from right atrium when blood volume increases
- Leads to increased loss/excretion of Na+
- Decreases Na+ reabsorption
- Na + remains in tubules
- Water moves towards Na +
- Increases Urine volume while reducing blood volume and BP
- Can inhibit ADH

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19
Q

Urine analysis:
- Would you expect cells in the urine?
- Would you expect proteins in the urine?
- Would you expect glucose in the urine?

A

No
Yes
No- sign of diabetes

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20
Q

Somatic vs Autonomic:
Voluntary or Involuntary?

A

Somatic- voluntary
Autonomic- Involuntary (fight or flight)
- Consists of sympathetic and parasympathetic

21
Q

What are the Features and Functions of Ureters?

A
  • Tubes that carry urine FROM each kidney TO the bladder
  • Surrounded by smooth muscle which contracts
  • Urine passed down ureters by peristalsis.
  • 25–30 cm long & ~3-4 mm in diameter
  • Pass urine by peristaltic waves (smooth muscle)
  • Enter the back of the bladder
  • Urine backflow - prevented by ureterovesical valves
22
Q

Structure of the bladder:
What is the muscular wall made of?

A
  • Hollow smooth muscle organ
  • Bladder can be divided into two parts:
    1) Body (lying above ureteral orifices)
    2) Base (Consisting of trigone and bladder neck
  • Its muscular wall is formed of smooth muscle cells (detrusor)
  • The only involuntary organ in the body under voluntary control
  • All humans are incontinent at birth
  • Activation of numerous neurologic reflexes are learned in early life to control the bladder
  • 35+ reflexes coordinate activities of bladder smooth muscle, plus striated & smooth muscle of the urethra
23
Q

Bladder filling and voiding

A

The filling and voiding cycle is complex and requires coordination between contractile motions of the bladder and reciprocal motions of the bladder neck.

Filling:
The detrusor is relaxed
The bladder neck is closed

Voiding
The detrusor contracts
The bladder neck opens

24
Q

What occurs during the micturition reflex?
( 2 phases)

A

Activated when the urinary bladder
stretched= Results in micturition

Storage phase- As the bladder fills, the pressure stays low (due to highly elastic nature)
1. Voluntary signals relax the external sphincter (somatic)
2. Autonomic contraction of detrusor muscle

25
Q

What are the muscarinic receptors which are part of the parasympathetic system and affect the bladder

A
  1. M2
    - Cardiac
    - Acts via G protein
    - Inhibits Ca2+ channels & efflux K
  2. M3
    - Glandular smooth muscle
    - Acts via Gq
26
Q

Micturition reflex

A
  • Activated by stretch of urinary bladder
    (trigone)
  • Eventually Action potentials travel along
    sensory nerves in pelvic nerve to sacral
    region of spinal cord
  • Integrated at spine - AP travel Along
    parasympathetic nerve to urinary
    bladder
    – Bladder contracts
  • External sphincter normally contracted
    as result of somatic motor nervous
    system
    – Decreased AP cause Urethral sphincter to
    relax
  • Can also be activated by irritation from
    bacterial infections – in urinary bladder
    – Desire to void
    – Occurs when bacteria pass up along urethra
    and enter and multiply within the bladder,
    causing inflammation
    – Usually caused by bacteria from the GI tract,
    eg E.coli
    – WBC and RBC in urine
27
Q

What is micturition?

A

The voiding of urine.

28
Q

Kidney facts and figures (info only)

A
  1. Kidneys are < 1% of body weight
    * Yet receive about 25% of Cardiac Output
    * ¼ of all ‘work’ performed by heart is to perfuse kidneys
  2. Functional unit is the nephron
    * Approx 2.5 million
    * Each approx 5 cm in length about 50 μm in diameter
    * Approx 125 km tubing (not including blood vessels)
  3. Processes 180 L plasma/day
    * Only about 1.5 drops per nephron
    * Of which ~ 1% ends up as urine
    * About 600g of sodium reabsorbed per day
29
Q

What is the main function of the kidneys?
What is the name of the ball of capillaries?
What is the name of the tubular structure that surrounds this^?

A

Homeostasis (filtration)
Glomerulus
Bowman’s capsule

30
Q

What are the names of the arterioles that take blood to and from the glomerulus?

A

Afferent and Efferent arterioles

31
Q

What are the different components of the nephron called?

A

PCT, Loop of Henle, DCT, Collecting duct, Renal corpuscle?

32
Q

Albumin passes into the filtrate but with Haemoglobin, but very little passes from blood to filtrate, why?

A

Size and Charge barrier

Haemoglobin is comprised of large proteins. It is bound to RBCs which are too large to pass through the glomerular filtration barrier.

33
Q

Where is renin secreted from?
What stimuli results in the secretion of renin?

A

JG/ Juxtaglomerular cells
Hypotension/Low BP

34
Q

What effect does the RAAS system have on Na+ (eventually)?

A

Reabsorption

35
Q

What are the 2 branches of autonomic NS called?

A

Sympathetic and Parasympathetic

36
Q

How many neurones are there in series?
What neurotransmitter does the first neurone of both branches secrete?

A

2
Acetycholine

37
Q

What neurotransmitter does the second in the sympathetic NS secrete on effector organ?

A

Noradrenaline

38
Q

Calculating how much the kidney excretes (of a compound) :

A

Exreted= Filtered + Secreted- Reabsorbed

39
Q

Polycystic kidney disease

A

Fluid-filled cysts
Nephrons destroyed
Reduced renal function
= loss of functional renal mass
-Less filtration, retention of salt and water, expanded blood volume, increased BP

Renal failure leads to:
- Accumulation of the substances normally eliminated

40
Q

What is GFR?

A

Total amount of filtrate formed per minute by the kidneys

41
Q

What are the 3 layers of the filtering membrane?

A
  1. Endothelial layer (flat cells-fenestrated cytoplasm)
  2. Basement membrane
  3. Epithelial layer
42
Q

Which of the following factors affect GFR?
A. Changes in Renal Blood Flow
B. Changes in glomerular filtration SA
C. Inc glucose in plasma
D. Large decrease in systolic BP (as in haemorrhage)
E. Obstruction of ureters

A

All except C

43
Q

Renal tubules of the nephrons absorb and secrete electrolytes to maintain the body’s internal environment : Which are re -absorbed by renal tubules?
Ammonia
Chloride
Drugs/toxins
H ions
Nutrients
Potassium
Sodium
Water

A

Chloride, Nutrients, Nutrients, Sodium, water

44
Q

Renal tubules of the nephrons absorb and secrete electrolytes to maintain the body’s internal environment : Which are secreted ?
Ammonia
Chloride
Drugs/toxins
H ions
Nutrients
Potassium
Sodium
Water

A

Ammonia, Drugs/toxins, H ions, Potassium

45
Q

Where does most reabsorption take place? (of ions)

A

PCT

46
Q

Which molecule is most important in the reabsorption of water

A

Sodium

47
Q

Sodium and water retention can lead to

A

Hypertension

48
Q

What causes the anemia that is often seen in chronic renal disease?
Lack of iron
Lack of EPOI
Lack of Vitamin B12

Anaemia- Impaired cell metabolism and feelings of coldness

A

Lack of EPO

Dec blood oxygen
Kidneys release EPO into the general circulation
Stimulates red blood cell production in the red bone marrow
Inc blood oxygen levels

M101 (41 decks)

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