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Biomedicine II > 11. Urinary System > Flashcards

11. Urinary System Flashcards

1
Q

Urinary System Components

A

Two kidneys
Two ureters
One bladder
One urethra

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2
Q

Urinary System Functions

A
  1. Excretion of unwanted substances.
  2. Maintenance of water & electrolyte balance.
  3. pH regulation of body fluids (especially the blood).
  4. Production of hormones (erythropoietin & calcitriol).
  5. Regulation of red blood cell (erythrocyte) production.
  6. Regulation of blood glucose levels.
  7. Regulation of blood pressure, volume & osmolarity.
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3
Q

Excretion

A

Metabolic Wastes
1.Urea: a metabolite of protein metabolism.
2.Uric acid: product of purine metabolism.
3.Creatinine: an end product of muscle metabolism.
• All containnitrogen;the kidneys specialisein removing nitrogenous wastes.
Ions
• In particular hydrogen(H+).
Toxins
• Medications andtoxins are mostly detoxified in the liver and then excreted via the kidneys.

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4
Q

Water Balance

A
  • The body’s water balance is mainly controlled by the kidneys.
  • Minimum urine content required to clear body waste is 500ml/day.
  • The feedback mechanism may be altered in pathologies e.g. untreated diabetes mellitus.
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5
Q

Electrolyte Balance

A

• Electrolytes are charged atoms in solution
(they can conduct electricity).
• The most important electrolytes regulated by the kidneys are: Sodium (Na+), Potassium (K+) and Hydrogen (H+).
• Electrolytes can form buffer substances. These are molecules that can buffer/regulate changes in pH.
• An excess of H+ions is an acidic solution. If a buffer is present it can bind with the free H+ions thus resisting a change in pH (resisting an increase in H+ions).

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6
Q

pH Balance

A

• Blood pH mustremain fairly constant between 7.35-7.45
• There are 2 primary pH control systems:
1. Lungs: Excrete CO2(the more CO2in blood = more acidic).
2. Kidneys: excrete H+into urine and produce the buffer HCO3-(bicarbonate).

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7
Q

Hormones produced by the kidneys

A

Calcitrol

Erythropoietin

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8
Q

Calcitrol

A

• Calcitriol is the active form of vitamin D.
• UV light activates a vitamin D precursor in the skin. The kidneys convert inactive Vitamin D into its active form.
• Increases bone formation (increases calcium):
1) Stimulates calcium & magnesium uptake from GIT.
2) Reduces calcium loss in kidneys (along with PTH).
• A deficiency can cause‘rickets’ and ‘osteomalacia’.

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9
Q

Erythropoietin

A
  • A protein hormone that stimulates erythropoiesis (red blood cell synthesis) in the red bone marrow.
  • Secreted by kidney interstitial cells into blood (10% produced in liver).
  • Released in response to hypoxia(negative feedback).
  • In renal failure, erythropoietin production is inadequate and hence results in anaemia.
  • Can be measured on blood test (EPO test).
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10
Q

Blood Sugar Regulation

A
  • The renal threshold for glucose is 9mmol/L.
  • Above this level (in the blood), glucose cannot be reabsorbed from the nephron into the blood when passing through the kidney tubules.
  • The normal blood glucose level is 4-7 mmol/L.
  • Hyperglycaemia indicates pathology e.g. diabetes mellitus.
  • The kidneys are able to make glucose from the amino acid glutamineto help elevate blood sugar levels when hypoglycaemic -gluconeogenesis.
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11
Q

Blood Volume, Pressure and Concentration

A
  1. Conserving or eliminating water in urine.
  2. Regulating the loss of solutein the urine which helps to maintain a constant blood concentration/osmolality.
  3. The kidneys help to regulate blood pressure by secreting the enzyme renin, which activates the Renin-Angiotensin-Aldosterone pathway.Increased renin causes an increase in blood pressure.
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12
Q

Kidney Anatomy

A
  1. Renal Capsule
  2. Adipose capsule
  3. Renal fascia
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13
Q

Renal capsule

A

Deep layer

•Smooth, transparent sheet of connective tissue. Maintains the kidney shape.

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14
Q

Adipose capsule

A

Middle layer

• Mass of fatty tissue, providing protection and support.

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15
Q

Renal fascia

A

Superficial layer

• Thin layer of connective tissue that anchors kidneys to surrounding structures.

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16
Q

Renal Cortex

A

Superficial, light red area.

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17
Q

Renal medulla

A

Darker area composed of several cone-shaped structures called the renal pyramids.
• The apex of each renal pyramid is called a renal papilla.
• Together, the renal pyramids and renal cortex make up the ‘functional’ portion of the kidney. Within this area are the functional units of the kidney –‘nephrons’.
• Urine formed by the nephron drains into the minor and major calyces.

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18
Q

Hilum

A

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

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19
Q

Blood supply

A

Renal artery and vein. The kidney receives 20-25% of the cardiac output (1.2L blood per minute), despite its mass accounting for 0.5% of body weight.

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20
Q

Nephron

A

The ‘nephron’ is the functional unit of the kidney.
• More than 1 million per kidney.
• Single epithelial layer throughout.

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21
Q

Nephron Parts

A
  1. Renal corpuscle

2. Renal Tubule

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22
Q

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.

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23
Q

Renal tubule

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.

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24
Q

Nephron structure

A
  • The renal corpuscle & both convoluted tubules (proximal and distal) lie in the renal cortex.
  • This means that filtration of blood (takes place in the renal corpuscle) occurs in the renal cortex.
  • The Loop of Henle often extends into the renal medulla, where it makes a hair pin turn & returns to the cortex.
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25
Q

Ureters

A
  • The 2 ureters transport urine from the renal pelvis to the urinary bladder.
  • Each ureter is about 25-30cm long and is retroperitoneal.
  • Peristaltic contractions of the ureters muscular walls propels urine towards the bladder aided by the pressure of urine & gravity (1-5 waves per minute).
  • The ureters enter the bladder through the posterior wall.
  • A physiological valve exists which prevents the backflow of urine.
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26
Q

Ureter structure

A
  1. Inner mucous membrane:
    •Contains transitional epithelium, which is able to stretch. Also contains goblet cells, which secrete mucous, providing protection from urine.
  2. Muscularis:
    • Consists of smooth muscle fibres which produces peristaltic contractions.
  3. Adventitia:
    • An outer coat of connective tissue that contains blood and lymph vessels, as well as nerves.
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27
Q

Urinary Bladder

A
  • The bladder is a hollow, muscular organ that acts as a reservoir for urine.
  • The bladder becomes spherical as it accumulates urine. When empty, it collapses. Folds of the peritoneum hold the bladder in its position.
  • The desire to urinate occurs when the bladder exceeds about 200 ml of urine within the organ. The total capacity is 600-700 ml.
  • On the posterior floor of the bladder is a small triangular area called thetrigone, which is bordered by the two ureteral openings and the urethral opening.
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28
Q

Bladder Structure

A

Inner mucosa layer:
• Transitional epithelium supported by connective tissue. The mucosa folds to permit expansion of the bladder.
Muscularis:
•Also known as the “detrusor” muscle (smooth).
•At the urethral opening, smooth muscle fibres accumulate and form the internal urethral sphincter(involuntary).
Adventitia:
•Outer layer of connective tissue.

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29
Q

Urethra

A
  • The urethra is the tube leading from the bladder to the exterior of the body –passageway for discharging urine.
  • Between the internal urethral sphincter (involuntary) & external urethral sphincter (voluntary).
  • The female urethra is 4 cmin length, whilst the male urethra is about 20 cm.
  • The male urethra is divided into three portions: Prostatic, membranous, spongy. The male urethra passes through the prostate, where it receives semen during ejaculation.
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30
Q

Urine Formation

A

To produce urine, the nephrons & collecting ducts perform 3 basic processes:

  1. Glomerular filtration: Occurs in the renal corpuscle.
  2. Tubular reabsorption: Occurs in the renal tubules.
  3. Tubular secretion: Occurs in the renal tubules.
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31
Q

Glomerular filtration

A

• Glomerular capillaries present a large surface area for filtration.
• Water & small molecules pass through pores in the glomerular capillaries into the Bowman’s capsule.
• Blood cells, plasma proteins and other large molecules are unableto filter through because of the size of the pores (they reside in the blood).
Glomerular filtration is adapted for filtration by:
1. The diameter of the efferent arteriole is less than that of the afferent arteriole.
2. Glomerular capillaries are ~50x more leaky than normal capillaries.

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32
Q

Glomerular filtration pressures

A
  1. Blood pressure in the glomerular capillaries promotes filtration by forcing substances through the membrane.
  2. Blood colloid osmotic pressure: proteins present in blood plasma (i.e. albumin, globulins, fibrinogen) within the glomerular capillaries opposefiltration.
  3. Capsular hydrostatic pressure: back pressure of the fluid that has already filtered through opposes filtration.
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33
Q

Blood constituents that pass into Glomerular Filtrate

A 
•Water
•Mineral salts (electrolytes)
•Amino acids & glucose
•Ketoacids
•Hormones
•Creatinine
Wastes
•Urea
•Uric acid
•Toxins
34
Q

Blood constituents remaining in Glomerular Capillaries

A
  • Leukocytes
  • Erythrocytes
  • Platelets
  • Plasma Proteins
35
Q

Glomerular Filtration Rate (GFR)

A
  • The amount of filtrate formed in the renal corpuscles of both kidneys each minute.
  • In adults, the GFR averages 125ml/min in males and 105 ml/min in females. A normal GFR should be over 90ml/min.
  • The rate needs to be constant for body homeostasis.
  • GFR is calculated through a blood test and the result is important in determining severity of kidney disease.
  • Anything affecting the 3 filtration pressures will affect the GFR e.g. severe blood loss.
36
Q

Colloid Osmotic Pressure

A
  • Damage to the glomerular capillaries can lead to plasma protein loss into urine.
  • Albumin leaks into the filtrate leading to albuminuria.
  • Less albumin in the blood makes it hypotonic& fluid moves via osmosis from the blood into tissues.
  • Blood volume decreases & interstitial fluid volume increases causing oedema.
  • Remember there are other causes of oedema such as heart failure, venous pathologies, lymphatic system pathologies etc
37
Q

Tubular Reabsorption

A
  • About 99% of glomerular filtrate is reabsorbed into the bloodstream along the renal tubules and collecting ducts. Including:
  • Water (65% in PCT)
  • Amino acids and glucose.
  • Electrolytes
  • Substances are reabsorbed by active and passive processes. They pass into nearby blood vessels and are returned to general circulation.
  • Most reabsorption occurs in the PCT.
38
Q

Tubular Secretion

A
  • As well as reabsorbing key substances, the blood and tubule cells also secrete certain materials into tubular fluid:
  • Waste products -creatinine, ammonium ions, urea.
  • Certain drugs e.g. penicillin.
  • Excess ions such as H+ (pH regulation).
  • This allows these substances to be removed from the blood & excreted in the urine.
39
Q

Urine formation: Hormones

A

Five hormones affect kidney reabsorption of sodium, chloride, calcium & water as well as the secretion of potassium:

  1. Angiotensin II
  2. Aldosterone
  3. Antidiuretic hormone
  4. Atrial natriuretic peptide
  5. Parathyroid hormone
40
Q

Renin-Angiotensin-Aldosterone System (RAAS)

A

• The ‘RAAS’ increases blood pressure.
• If systolic BP is below 100mmHg, the afferent arteriole walls are stretched less, causing:
1. The enzyme Renin released by the kidney into the blood.
2. Coverts angiotensinogen to angiotensin I (in Liver).
3. Angiotensin I is converted to angiotensin II by Angiotensin Converting Enzyme (ACE) in the lungs.
4. Angiotensin II causes release of Aldosterone from the adrenal cortex.

41
Q

Angiotensin II

A
  • AngtiotensinII triggers vasoconstriction, which subsequently increases blood pressure.
  • Angiotensin II also triggers the pituitary gland to release Anti-Diuretic Hormone (ADH).
  • Stimulates adrenal cortex to produce aldosterone.
  • Aldosterone increases renal sodium and water reabsorption.
42
Q

Antidiuretic Hormone (ADH)

A
  • Reduced water concentration in the blood & lowered blood volume causes increases blood osmotic pressure.
  • Osmoreceptors in the hypothalamus stimulates the posterior pituitary to secrete ADH.
  • ADH increases the permeability of the distal convoluted tubules, thus increasing water reabsorption in the kidneys, thereby aiding in rebalancing the osmotic pressure.
43
Q

Atrial Natriuretic Peptide (ANP)

A
  • ANP inhibits reabsorption of Na+& water in the renal tubules.
  • A large increase in blood volume promotes release of ANP from the heart.
  • ANP is released from the myocardium in response to atrial stretch.
  • ANP also suppresses the release of ADH & aldosterone.
  • These effects increase urine output and reduce blood volume (and hence lower blood pressure).
44
Q

Parathyroid Hormone (PTH)

A

• PTH is released by the parathyroid gland in response to low blood calcium levels.
• PTH increases blood calcium levels by:
1. Stimulating renal reabsorption of calcium & magnesium.
2. Increasing osteoclastic activity.
3. Stimulating calcitriol release. (increases gut calcium absorption)

45
Q

Kidneys: Urine flow

A
  • Urine formed in the nephrons drains into papillary ducts in the renal papillae of the renal pyramids.
  • The papillary ducts drain into cup-like structures called minor and major calyces.
  • From the major calyces, urine drains into a single large cavity called the renal pelvis & then out to the bladder through the ureters.
46
Q

Micturition

A
  • Micturition is the discharge of urine from the bladder.
  • When the volume in the bladder exceeds 200-400ml, stretch receptors in the bladder wall transmit nerve impulses to the spinal cord at levels S2 and S3.
  • In infants this generates a micturition reflex leading to contraction of the detrusor muscle, & relaxation of the internal andexternal urethral sphincter.
  • In adults, the nervous system has matured adequately to consciously inhibit reflex contraction of the bladder & relaxation of the internal sphincter. Adults can also control the external urethral sphincter & pelvic floor muscles.
  • Although urination occurs via a reflex, we learn to initiate and stop micturitionvoluntarily in early childhood.
47
Q

Urine Composition

A 
• We typically produce 1–2L of urine in 24 hrs.
• Urine should be yellow/amber coloured.
• Odour: slightly aromatic, sweeter in diabetics.
• pH: varies from 4.5 -8 (average 6).
Composition:
• Water (96%).
• Urea (2%) Uric acid & Creatinine.
• Ammonia.
• Na, K, Cl, P, S.
• Hormones.
• Oxalates.
48
Q

Body Homeostasis: Integumentary

A

Kidneys convert vitamin D precursor made in the skin into its active form calcitriol.

49
Q

Body Homeostasis: Skeletal

A

Skeletal system: The kidneys help adjust blood levels of calcium and phosphate.

50
Q

Body Homeostasis: Muscular

A

Muscular system: Kidneys help adjust blood calcium levels, required for contraction.

51
Q

Body Homeostasis: Nervous system

A

Nervous system: Kidneys can perform gluconeogenesis to provide glucose for neurons, especially during fasting or starvation.

52
Q

Body Homeostasis: Endocrine system

A

Endocrine system: Kidneys produce calcitriol and erythropoietin.

53
Q

Body Homeostasis: Lymphatic system

A

Lymphatic system: Adjustment of water reabsorption affects the volume of interstitial fluid & lymph. Urine flushes out microbes.

54
Q

Body Homeostasis: Respiratory system

A

Respiratory system: The lungs & kidneys help adjust pH of body fluids.

55
Q

Body Homeostasis: Digestive system

A

Digestive system: Calcitriol increases absorption of dietary calcium.

56
Q

Body Homeostasis: Reproductive system

A

Reproductive system: In males the urethra is a passageway for semen and urine.

57
Q

Body Homeostasis: Cardiovascular system

A

Cardiovascular system: Kidneys can alter blood volume and pressure by adjusting water reabsorption (renin).

58
Q

Urinary System Examination

A 
Medical History:
Signs & symptoms which indicate urinary tract pathology:
1. Frequent & painful urination with urgency.
2. Red urine (blood or beetroot?)
3. Pain in the loin.
4. High urine volume with great thirst.
5. Low or no urine volume.
6. Nausea and vomiting.
7. Oedema.
8.Exhaustion.
59
Q

Signs of Renal disease

A
  • Pallor (due to anaemia).
  • Frothy urine (due to proteinuria).
  • Oedema (due to protein loss).
  • Signs of itching of skin (due to uraemia).
  • Altered mental state(common with UTI’s).
  • Puffy face and bags under the eyes.
  • Dehydration and flapping tremor.
60
Q

Dipstick

A
  • Leukocytes
  • Ketones
  • Nitrates (bacteria)
  • Urobilinogen
  • pH
  • Erythrocytes
  • Protein
  • Glucose
  • Specific gravity
61
Q

Urine microscopy

A
  • Volume/Colour/Odour
  • pH
  • Leukocytes
  • Erythrocytes
  • Casts
  • Bacteria
  • Specific gravity
  • Microalbuminuria
62
Q

Urinanalysis - Leukocytes

A

Urinary tract infection (UTI)

63
Q

Urinanalysis- Ketones

A

Keto-acidosis(complication of diabetes mellitus) or ketone diet

64
Q

Urinanalysis- Nitrates (bacteria)

A

UTI

65
Q

Urinanalysis- Urobilinogen

A

Liver pathology

66
Q

Urinanalysis- Erythrocytes

A

UTI
Tumour
Kidney Stone

67
Q

Urinanalysis- Protein

A

Kidney disease

68
Q

Urinanalysis- Glucose

A

Diabetes mellitus

69
Q

Urinanalysis- specific gravity

A

Dehydration, glucosuria, proteinuria

70
Q

Urinanalysis- Casts

A

Nephron disesase

71
Q

Urinanalysis- Microalbuminuria

A

Kidney disease (i.e. diabetic kidney)

72
Q

Urinary System Examination

A 
Blood test:
• Glomerular filtration rate (GFR)
• Urea
• Creatinine
• Electrolytes
• Inflammatory markers: ESR (Erythrocyte Sedimentation Rate) & C-Reactive Protein (CRP)
• Leukocytes
Medical examinations:
•Ultrasound
•Renal arteriography
•X-rays
•CT (uretericobstruction)
•MRI (malignancy)
•Cystoscopy (bladdercamera)
73
Q

Dysuria

A

Painful, burning urination

74
Q

Polyuria

A

Large quantity of urine

75
Q

Oliguria

A

Little urine (<400ml/day)

76
Q

Anuria

A

No urine

77
Q

Proteinuria

A

Protein in the urine

78
Q

Bacteriuria

A

Bacteria in the urine

79
Q

Nocturia

A

Night urination

80
Q

Haematuria

A

Blood in the urine

Biomedicine II (16 decks)

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