11. Urinary System Flashcards

1
Q

Give urinary system components

A

Two kidneys
Two ureters
One bladder
One urethra

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2
Q

Name urinary system functions

A
  1. Filter/excretion of unwanted substances
  2. Water/electrolyte balance
  3. Body fluid pH regulation
  4. Hormone production (EPO, calcitriol)
  5. Regulation of red blood cell production
  6. Regulation of blood glucose levels
  7. Regulation of blood pressure, volume, osmolarity
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3
Q

What are electrolytes?

A

Electrolytes are charged atoms in solution (they conduct electricity)

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4
Q

What is the optimum blood pH balance?

A

Blood pH must remain between 7.35-7.45 (mildly alkaline)

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5
Q

What is calcitriol?

A

Active form of vitamin D

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6
Q

What is erythropoietin?

A

Protein hormone that stimulates erythropoiesis in the red bone marrow

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7
Q

What is the normal blood glucose level?

A

4-7 mmol/L

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8
Q

How does the amount of urine excreted affect blood volume, pressure, concentration?

A

More water excreted = lower BP
Less water excreted (more conserved in blood) = increased BP

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9
Q

Kidney shape and location

A

Reddish, bean-shaped

Retroperitoneal (behind peritoneum)
Partially protected by 11th and 12th pairs of ribs between vertebral levels T11-L3

Right kidney is lower due to liver on same side

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10
Q

Kidney: external layers

A
  1. Renal capsule (deep layer)
  2. Adipose capsule (middle layer)
  3. Renal fascia (outer layer)
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11
Q

Kidney: internal regions

A
  1. Renal cortex: outer, light red area
  2. Renal medulla: darker area composed of several cone-shaped structures (renal pyramids)
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12
Q

Minor calyces

A

These surround the renal papillae of each pyramid and collects urine from that pyramid

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13
Q

Major calyces

A

Formed where several minor calyces converge

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14
Q

Kidney blood supply

A

Renal artery
20-25% of cardiac output (despite kidney representing 0.5% of body weight!)
1.2L/min

Renal vein
drain deoxygenated blood to Inferior Vena Cava

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15
Q

Nephron: definition

A

Functional unit of the kidney
More than 1 million per kidney
Single epithelial layer throughout

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16
Q

Nephron: regions

A

Renal corpuscle
Renal tubule

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17
Q

Nephron: anatomical labels to know

A

Glomerulus
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Afferent arteriole
Efferent arteriole
Peritubular capillaries

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18
Q

Ureters: function and length

A

Two ureters transport urine from the renal pelvis to the bladder

Each ureter is around 25-30cm long and retroperitoneal

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19
Q

Ureters: layers

A
  1. Inner mucous membrane
  2. Muscularis
  3. Adventitia
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20
Q

Bladder: definition

A

Hollow, muscular organ held in place by folds of peritoneum
Acts as a reservoir for urine

Becomes spherical as it accumulates urine
Collapses when empty

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21
Q

Trigone

A

Small, triangular area on posterior floor of bladder
Bordered by two ureteral openings and the urethral opening

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22
Q

Bladder: layers

A
  1. Inner mucosa layer
  2. Muscularis (detrusor muscle)
  3. Adventitia
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23
Q

Urethra

A

Tube leading from the bladder to the exterior of the body

Between the internal urethral sphincter (involuntary) and the external urethral sphincter (voluntary)

Female urethra = 4cm
Male urethra = 20cm

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24
Q

Urethra: male

A

Around 20cm long

Divided into three sections:

  1. Prostatic
  2. Membranous
  3. Spongy

Passes through the prostate where it receives semen during ejaculation

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25
Q

Urine formation: processes

A
  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular secretion
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26
Q

Blood constituents that CAN pass into the glomerular filtrate

A

Water
Mineral salts (electrolytes)
Amino acids
Glucose
Ketoacids
Hormones
Creatinine
Urea
Uric acid
Toxins

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27
Q

Blood constituents that CAN’T pass into the glomerular filtrate

A

Erythrocytes
Leukocytes
Platelets
Plasma proteins

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28
Q

Renal capsule

A

Deep layer of outer region of kidney

Smooth, transparent sheet of connective tissue

Maintains kidney shape

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29
Q

Adipose capsule

A

Middle layer of outer region of kidney

Mass of fatty tissue

Provides protection and support

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30
Q

Renal fascia

A

Outer layer of outer region of kidney

Thin layer of connective tissue

Anchors kidneys to surrounding structures and keeps them in place

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31
Q

Renal cortex

A

Superficial, light red area of the kidney
The renal corpuscle and both convoluted tubules (proximal and distal) lie in the renal cortex
This means that filtration of blood (in the renal corpuscle) occurs in the renal cortex

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32
Q

Renal medulla

A

Darker area of the inner region of the kidney
Composed of several cone-shaped structures (renal pyramids)
Contains Loop of Henle (part of renal tubules)

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33
Q

How does urine get from the kidneys to the bladder?

A

Peristaltic contractions of the ureters’ muscular walls propel urine towards bladder

Aided by gravity and pressure of urine

1-5 waves per min

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34
Q

Where do the ureters enter the bladder?

A

Through the posterior wall

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35
Q

What prevents the backflow of urine?

A

A physiological valve

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36
Q

Ureter: Inner mucous membrane

A

Transitional epithelium which is able to stretch

Also contains goblet cells which secrete mucous

Provides protection from urine

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37
Q

Ureter: Muscularis

A

Smooth muscle fibres

Produces peristaltic contractions

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38
Q

Ureter: Adventitia

A

Outer coat of connective tissue

Contains blood and lymph vessels, nerves

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39
Q

Bladder: Inner mucosa layer

A

Transitional epithelium supported by connective tissue

The mucosa folds to permit expansion of the bladder

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40
Q

Bladder: Muscularis (detrusor muscle)

A

Middle layer of smooth muscle

At urethral opening, smooth muscle fibres accumulate and form the internal urethral sphincter (involuntary)

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41
Q

Bladder: Adventitia

A

Outer layer of connective tissue

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42
Q

What enables filtration to take place at the golmerular capillaries?

A
  1. The diameter of the efferent arteriole is less than that of the afferent arteriole
  2. Glomerular capillaries are ~50x leakier than normal capillaries
  3. Glomerular capillaries have a large surface area
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43
Q

How is net pressure achieved in golmerular filtration?

A
  1. Blood pressure forces substances through the membrane
  2. Proteins present in blood plasma within the glomerular capillaries oppose filtration (colloid osmotic pressure)
  3. Back pressure of the fluid that’s already filtered opposes filtration (capsular hydrostatic pressure)
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44
Q

What is the glomerular filtration rate (GFR)?

A

The amount of filtrate formed in the renal corpuscles of both kidneys each minute

Normal GFR should be over 90ml/min

GFR males = 125ml/min
GFR females = 105ml/min

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45
Q

How is GFR calculated?

A

Through a blood test

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46
Q

What can the GFR test result determine?

A

The severity of kidney disease

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47
Q

What can affect the GFR?

A

Anything affecting the 3 filtration processes e.g. severe blood loss

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48
Q

What is colloid osmotic pressure?

A

Osmotic pressure exerted by plasma proteins e.g. albumin

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49
Q

What can affect colloid osmotic pressure?

A

Damage to the glomerular capillaries premitting plasma protein loss into urine (albuminuria)

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50
Q

What happens when albumin leaks from blood into the filtrate (urine)?

A

Blood volume decreases and interstitial fluid volume increases causing oedema (note: there are other causes of oedema)

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51
Q

Albuminuria

A

Albumin in urine

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52
Q

Where does most tubular reabsorption happen?

A

In the renal tubules and collecting ducts but mostly in the PCT

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53
Q

What substances are reabsorbed during tubular reabsorption?

A

Water (65% in PCT)
Amino acids
Glucose
Electrolytes

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54
Q

Which mode of transport is used when substances are reabsorbed during tubular reabsorption?

A

Active and passive

Substances pass into peritubular capillaries and return to general circulation

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55
Q

What substances are secreted into the urine during tubular secretion?

A

Waste products - creatinine, ammonium ions, urea
Certain drugs e.g. penicillin
Excess ions e.g. H+ for pH regulation

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56
Q

Which hormones are involved in kidney reabsorption?

A
Angiotensin II
Aldosterone
Antidiuretic hormone
Atrial natriuretic peptide
Parathyroid hormone
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57
Q

What is the Renin-Angiotensin-Aldosterone System (RAAS)?

A

A system of hormones that work together to increase blood pressure

58
Q

What triggers the RAAS?

A

A systolic BP below 100mmHg

59
Q

What happens when the RAAS is triggered?

A
  1. The enzyme renin is released by the kidneys into the blood
  2. Angiotensinogen (inactive) gets converted to angiotensin I in the liver
  3. Angiotensin I is converted to angiotensin II by the angiotensin-converting enzyme (ACE) in the lungs
  4. Angiotensin II causes release of aldosterone from the adrenal cortex
60
Q

What does Angiotensin II do?

A
  1. Triggers vasoconstriction which increases blood pressure
  2. Triggers the pituitary gland to release ADH
  3. Stimulates the adrenal cortex to produce aldosterone
61
Q

What does Aldosterone do?

A

Increases renal sodium and water reabsorption which increases BP

62
Q

What does Antidiuretic Hormone (ADH) do?

A

Increases the permeability of the DCT, increasing water reabsorption in the kidneys

63
Q

What stimulates the secretion of ADH?

A

Osmoreceptor cells in the hypothalamus detect an increase in the osmolarity of the blood.

This triggers the release of ADH from the posterior pituitary gland.

osmolarity = concentration of a solution

64
Q

What does Atrial Natriuretic Peptide (ANP) do? How ?

A

Increases urine output and lowers BP

Inhibits the reabsorption of sodium and water in the renal tubules

65
Q

What stimulates the secretion of ANP?

From where?

A

A large increase in blood volume promotes the release of ANP from the heart

It’s released from the myocardium in response to atrial stretch

66
Q

Which hormones does ANP suppress?

A

ADH
Aldosterone

67
Q

What does Parathyroid Hormone (PTH) do? How ?

Where is it released from? In response to what?

A

Increases blood calcium levels by:
1. Stimulating renal reabsorption of calcium and magnesium
2. Increasing osteoclast activity
3. Stimulating release of calcitriol (which increases gut calcium absorption)

Released by the parathyroid gland in response to low blood calcium levels

68
Q

Pathway of urine flow

A

Nephrons - papillary ducts of renal pyramids - minor/major calyces - renal pelvis - ureters - bladder-urethra

69
Q

Urine composition

A
Water (96%)
Urea (2%), uric acid, creatinine
Ammonia
Sodium, Potassium, Phosphorus, Chloride, Sulphur
Hormones
Oxalates
70
Q

What stimulates the micturition process

A

When the volume in the bladder exceeds 200-400ml, stretch receptors in the bladder wall transmit nerve impulses to the spinal cord (S2 and S3)

71
Q

Micturition process: infants

A

Increase in bladder volume generates a micturition reflex leading to contraction of the detrusor muscle and relaxation of the internal AND external urethral sphincters

72
Q

Micturition process: adults

A

Nervous system matures and consciously inhibits the reflex contraction of the bladder and relaxation of the internal urethral sphincter

Adults can control the external urethral sphincter and pelvic floor muscles

73
Q

How much urine do we produce a day?

A

1-2 litres

74
Q

What colour should urine be?

A

Yellow/amber coloured

75
Q

What is the odour of urine?

A

Slightly aromatic

Sweeter in diabetics

76
Q

What is the pH of urine?

A

4.5-8 pH

Average 6

77
Q

Urninary system homeostatic links with other systems:

Skin

A

Kidneys convert vit D precursor made in the skin into its active form, calcitriol
Uraemia can occur if urea accumulates due to kidney disease

78
Q

Urninary system homeostatic links with other systems:

Skeletal

A

The kidneys help adjust blood levels of calcium and phosphate

79
Q

Urninary system homeostatic links with other systems:

Muscular

A

Kidneys help to adjust blood calcium levels, required for muscle contraction

80
Q

Urninary system homeostatic links with other systems:

Nervous System

A

Kidneys can perform gluconeogenesis to provide glucose for neurons, especially during fasting or starvation

Kidneys regulate sodium and potassium levels via tubular secretion and reabsorption.

81
Q

Urninary system homeostatic links with other systems:

Endocrine

A

Kidneys produce calcitriol and erythropoietin

82
Q

Urninary system homeostatic links with other systems:

Lymphatic

A

Adjustment of water reabsorption affects the volume of interstitial fluid and lymph
Urine flushes out microbes

83
Q

Urninary system homeostatic links with other systems:

Respiratory

A

Lungs and kidneys work together to regulate pH of blood and all body tissues

84
Q

Urninary system homeostatic links with other systems:

Digestive

A

Calcitriol increases absorption of dietary calcium

85
Q

Urninary system homeostatic links with other systems:

Reproductive

A

In males, the urethra is the passageway for urine and semen

86
Q

Urninary system homeostatic links with other systems:

Cardiovascular

A

Kidneys can alter blood volume and pressure by adjusting water reabsorption (renin)

87
Q

Signs/symptoms of urinary tract pathology

A
  1. Frequent, urgent and painful urination
  2. Red urine (blood or beetroot?)
  3. Pain in loin (lower back)
  4. High urine volume with great thirst
  5. Low or no urine volume
  6. Nausea and vomiting
  7. Oedema (loss of albumin)
  8. Exhaustion (anaemia, blood loss into urine)
88
Q

Signs/symptoms of renal disease

A
  1. Pallor (due to anaemia)
  2. Frothy urine (due to proteinuria)
  3. Oedema (due to plasma protein loss)
  4. Itchy skin (due to uraemia)
  5. Altered mental state (common with UTIs)
  6. Puffy face/bags under eyes
  7. Dehydration
  8. Flapping tremor
89
Q

Urinalysis: what can the dipstick test?

A
Leukocytes
Ketones
Nitrites
Urobilinogen
pH
Erythrocytes
Protein
Glucose
Specific gravity
90
Q

Urinalysis: what can urine microscopy test?

A
Volume
Colour
Odour
pH
Leukocytes
Erythrocytes
Casts (clumps formed in nephrons)
Bacteria
Specific gravity
Microalbuminuria
91
Q

What can leukocytes indicate in urinalysis?

A

UTI

92
Q

What can ketones indicate in urinalysis?

A

Ketoacidosis (complication of diabetes mellitus) or ketone diet

93
Q

What can nitrites indicate in urinalysis?

A

Bacteria

UTI

94
Q

What can urobilinogen indicate in urinalysis?

A

Liver pathology

95
Q

What can erythrocytes indicate in urinalysis?

A

UTI
Tumour
Kidney stones

96
Q

What can protein indicate in urinalysis?

A

Kidney disease

97
Q

What can glucose indicate in urinalysis?

A

Diabetes mellitus

98
Q

What can specific gravity indicate in urinalysis?

A

Dehydration
Glucosuria
Proteinuria

99
Q

What can casts indicate in urinalysis?

Casts - clumps of blood cells/bacteria that have formed in the nephron

A

Nephron disease

100
Q

What can microalbuminuria indicate in urine microscopy?

A

Kidney disease

(early indicator of Diabetic kidney)

101
Q

What blood test parameters exist for the urinary system

A
Glomerular filtration rate (GFR)
Urea
Creatinine
Electrolytes
Inflammatory markers (ESR/CRP)
Leukocytes
102
Q

Urinary system medical examinations

A
Ultrasound
Renal arteriography
X-rays
CT (ureteric obstruction)
MRI (malignancy)
Cystoscopy (bladder camera)
103
Q

Dysuria

A

Painful, burning urination

104
Q

Polyuria

A

Large quantity of urine

105
Q

Oliguria

A

Little urine (<400ml/day)

106
Q

Anuria

A

No urine

107
Q

Proteinuria

A

Protein in urine

108
Q

Bacteriuria

A

Bacteria in urine

109
Q

Nocturia

A

Night-time urination

110
Q

Haematuria

A

Blood in urine

111
Q

Which metabolic wastes are excreted by the urinary system?

A

Urea,
Uric acid
Creatinine

(All contain nitrogen)

112
Q

How are toxins excreted by the urinary system?

A

Medications and toxins are mostly detoxified in the liver and then excreted via the kidneys

113
Q

Which electrolytes are regulated by the kidneys?

A

Sodium (Na+)
Potassium (K+)
Hydrogen (H+)

114
Q

What can electrolytes form to regulate changes in pH?

A

Buffer substances
A buffer can bind with free H+ ions resisting increase in H+ avoiding increase in acidity

115
Q

How much urine does a person need to pass a day to clear body waste

A

500ml/day

116
Q

What can alter the water balance feedback mechanism?

A

Pathologies e.g. untreated diabetes mellitus

117
Q

How is vitamin D synthesised?

A

UV light activates a vitamin D precursor in the skin

The kidneys convert inactive vitamin D into its active form - Calcitriol

118
Q

What functions does calcitriol play?

A

Increases bone formation by :
1) Stimulating calcium and magnesium uptake from GIT.
2) Reducing calcium loss in kidneys

119
Q

How is calcium uptake increased by calcitriol?

A
  1. Stimulates calcium and magnesium uptake from GIT
  2. Reduces calcium loss in kidneys (along with PTH)
120
Q

What can a vitamin D deficiency cause?

A

Rickets
Osteomalacia

121
Q

How is EPO secreted and under what conditions?

A

Secreted by kidney interstitial cells into the blood

Released in response to hypoxia (negative feedback)

122
Q

What happens to EPO production in renal failure?

A

EPO production is inadequate and results in anaemia

123
Q

How is EPO measured?

A

On blood EPO test

124
Q

What is the renal threshold for glucose?

A

9 mmol/L

125
Q

What happens if blood levels of glucose go above the renal threshold?

A

Glucose can’t be reabsorbed from the nephrons into the blood when passing through the kidney tubules.
It is therefore present in the urine (glucosuria)

126
Q

What is hyperglycaemia an indication of?

A

A pathology e.g. diabetes mellitus

127
Q

How do kidneys elevate blood sugar levels when a person is hypoglycaemic?

A

Kidneys make glucose from glutamine (an amino acid)

Process is called gluconeogenesis

128
Q

How is blood volume/pressure/concentration regulated by the kidneys?

A
  1. Conserving or eliminating water in urine
  2. Regulating loss of solute in the urine which helps to maintain a constant blood concentration/osmolarity
  3. Regulating blood pressure by secreting the enzyme renin. This activates the Renin-Angiotensin-Aldosterone pathway (increased renin causes an increase in blood pressure)
129
Q

What percentage of the cardiac output (blood) does the kidney receive?

A

20-25% (1.2L blood per min)

130
Q

What role does the renal tubules play?

A

Involved in reabsorption and secretion of various solutes

131
Q

How much fluid is in the bladder when the desire to urinate occurs?

A

200ml

132
Q

What is the total capacity of the bladder?

A

600-700ml

133
Q

Which unwanted substances are excreted by the urinary system?

A

Metabolic Wastes
* Urea: a metabolite of protein metabolism
* Uric acid: product of purine metabolism
* Creatinine: an end product of muscle metabolism
All contain nitrogen; the kidneys specialise in removing nitrogenous wastes.
Ions
In particular hydrogen (H+).
Toxins
Medications and toxins are mostly detoxified in the liver and then excreted via the kidneys.

134
Q

How is blood pH balance maintained in the body ?

A

Blood pH must remain fairly constant between 7.35 - 7.45

There are 2 primary pH control systems:
* Lungs: Excrete CO2 (the more CO2 in blood = more acidic)
* Kidneys: excrete H+ into urine and produce the buffer HCO3- (bicarbonate)

135
Q

Which hormones are produced by the kidneys ?

A

Calcitrol
Erythropoietin

136
Q

What is erythropoietin (EPO) ?
What does it stimulate ?

A

A protein hormone that stimulates erythropoiesis (red blood cell synthesis) in the red bone marrow.

137
Q

Hilum

A

On the concave kidney border. The region where blood vessels, lymph vessels, nerves and ureters enter and exit the kidney.

138
Q

Describe the structure of the renal corpuscle ?

A

Consists of glomerulus and Bowman’s capsule:
* The glomerulus is a tangled capillary network that receives blood from an afferent arteriole
* The Bowman’s capsule is a double-walled epithelial cup that surrounds the glomerulus, receiving contents of filtered blood

139
Q

Describe the structure of the renal tubules

A

Consists of 3 sections:
1. Proximal convoluted tubule.
2. Loop of Henle.
3. Distal convoluted tubule.
* Filtered fluid is passed through the tubule.
* Important role in reabsorption and secretion of various solutes.
* Anti-Diuretic Hormone (ADH) acts on the distal convoluted tubule to reabsorb water.

140
Q

What percentage of glomerular filtrate is reabsorbed by the renal tubules

A

99%