Mock Exam Flashcards
What is the general anatomy of the urinary system?
10-14cm (male) and 9-13cm (female)
150-260g
3cm in antero-posterior thickness
Left kidney just below spleen
Right kidney just below liver (slightly lower than left kidney)
Situated to either side of the spine
What is the general physiology of the urinary system?
Controls plasma pH
Controls plasma volume
Excretion of drugs
Excretion of metabolic waste products
Regulates extracellular fluid (ECF) electrolytes
Secretion: erythropoietin and renin
Water balance
Describe and name the 3 distinct regions of the urinary system
Renal cortex; outer layer, dark in colour
Renal medulla; reddish brown, contains cone shaped masses called Malpighian pyramids
Renal pelvis; transitional epithelia, calyces extend towards papilla and collect urine draining into them from each pyramid
What are major calyces?
2 or 3 branching extensions of the pelvis; each 1 subdivides to form several minor calyces
Calyces collect urine; drains continuously from the papillae, and empties into the renal pelvis
Urine enters the major calyces of the kidney: collecting ducts >ducts of Bellini> ureters> bladder> urethra>outside world
What do the walls of the calyces, pelvis and ureter contain and what does it do?
Smooth muscle; contracts rhythmically to propel urine along
What is the name of the type of contraction that propels urine along?
Peristalsis
Where are major calyces found?
Kidneys
What is the functional anatomy of the urinary system?
Glomerulus
Bowman’s capsule
Proximal convoluted tubule (PCT)
Loop of Henle
Distal convoluted tubule (DCT)
Collecting ducts and ducts of Bellini (end part of collecting ducts)
What is the nephron?
Structural and functional units of the kidney
Over 1.5 million per kidney
They form urine
3 parts: glomerulus, Bowman’s capsule, loop of Henle
Describe the cortical nephron
Located in outer 2/3 of kidney
Very short loop of Henle
85% of all nephrons
Describe the juxtamedullary nephron
Located in inner 1/3 of kidney
Long loops of Henle
15% of all nephrons
What happens in the glomerulus?
Blood enters at high pressure for ultrafiltration, via afferent ateriole
Efferent arteriole narrower as it leaves
Pressure forces water and solutes through the barriers between capillary and capsule
What happens in the Bowman’s capsule?
Ultrafiltration of blood; separation of large and small molecules
H2O, glucose, amino acids, nitrogenous waste pass into the Bowman’s capsule
Contains specialised cells called podocytes; podocytes help in the filtration
What happens in the proximal convoluted tubule (PCT)?
Cuboidal/columnar epithelia with brush border; cells contain large number of mitochondria, active transport occurs in these cells
85% water in tubule is reabsorbed - ADH
45% of urea excreted in urine
Reabsorption of: glucose, vitamins, AA, K+, Mg2+, Ca2+, Cl-, HCO3-, Na3+
What happens in the Loop of Henle?
Squamous epithelium
Osmotic gradient created which allows water to be reabsorbed from urine; minimises water loss
Final salt concentration depend on length of loop; longer loop = increased final salt concentration depend
Reaborption if: Na+, Cl-, Ca2+, Mg2+
What happens in the distal convoluted tubule (DCT)?
Cuboidal/columnar epithelia
Osmoregulation occurs (only 25% of original water remains)
Reabsorption of: Na+, Cl-, Ca2+ ; most Reabsorption from this point depends on the body’s needs
Active transport absorption regulated by hormones: aldosterone - Na+
ADH - H2O
PTH - Ca2+
What happens in the collecting ducts?
Cuboidal epithelia
Receives filtrate from many nephrons
Reabsorption of: Na+, H+, HCO3-, H2O, urea
What is the countercurrent multiplier rule?
Water leaves the descending (but not the ascending) limb of Henle’s loop, and the opposite is true for solutes
What is diabetes insipidus?
A rare disorder
System used by the body to regulate its water level becomes disrupted
Where is ADH made and stored and what is its function?
Made in hypothalamus
Stored in pituitary gland
When a decrease in water is detected ADH is released
Describe the relationship between ADH and diabetes insipidus
Diabetes insipidus caused by problems with ADH
ADH role:
Regulates the amount of liquid in the body
In diabetes insipidus, ADH doesn’t stop the kidneys from producing urine; too much water is lost, PCT and loop of Henle do no reabsorb H2O effectively
Where is aldosterone produced and secreted?
Adrenal cortex
What is the function of aldosterone?
Stimulates Na+ reabsorption from: nephron, colon, gastric glands, ducts of sweat and salivary glands
Promotes H+ and K+ secretion
-Increase K+ concentration in plasma = increase aldosterone secretion
-decrease in Na+ concentration in plasma = increase aldosterone secretion
What is the Renin-angiotensin mechanism?
Triggered when blood pressure falls (mean arterial pressure below 80mm Hg)
Renin acts enzymatically on angiotensinogen
Angiotensinogen is converted to angiotensin I
What hormone is released when blood pressure falls and where from?
Release of hormone renin from kidney
What is angiotensinogen?
Plasma globular protein made by liver
How is angiotensin I converted to angiotensin II?
By angiotensin converting enzyme (ACE) which is secreted by capillary endothelium, particularly the lungs
What happens in angiotensin II?
Stabilisation of ECF and systemic blood pressure. Occurs in 5 ways
What is the first way the stabilisation of ECF and systemic blood pressure occurs?
Acts as a potent vasoconstrictor
Activates smooth muscle of arterioles throughout the body; rising MAP
What is the second way the stabilisation of ECF and systemic blood pressure occurs?
Stimulates the reabsorption of Na+ both directly by acting on PCT and DCT, and indirectly by triggering the release of aldosterone
Because H2O follows Na+ osmotically, blood volume and blood pressure increases
What is the third way the stabilisation of ECF and systemic blood pressure occurs?
Stimulates the hypothalamus to release ADH
Activates the hypothalamus thirst centre; increased blood volume, ECF volume and blood pressure
What is the fourth way the stabilisation of ECF and systemic blood pressure occurs?
Increased reabsorption of H2O in the loop of Henle
What is the fifth way the stabilisation of ECF and systemic blood pressure occurs?
Causes a decrease in SA available for filtration by the glomerular capillaries; results in less fluid lost
