Urinary System Flashcards
Describe the location of the kidneys
Retroperitoneal, one on each side on posterior abdominal wall high up under diaphragm
What protects the kidneys?
Encapsulation and protective layers of fascia and firm renal fat
What is the renal cortex?
Outer region of the kidney
What do renal pyramids do?
House nephrons with their function of filtration and reabsorption
What forms the renal pelvis and where is this found?
Minor calyces that converge on major calyces form the renal pelvis found at the hilum of the kidney
What does the renal pelvis do?
Transports urine to the bladder
What are the different components of the nephron?
renal corpsucle/glomerulus proximal convoluted tubule loop of henle distal convoluted tubule collecting duct
What are the 2 types of nephron?
Juxtamedullary
Superficial
Properties of juxtamedullary nephron
Recieves 10% of renal supply Concentrates urine Has glomeruli in inner cortical regions Has long nephron loops Associated with vasa recta
Properties of superficial nephron
Receives 90% of renal supply
Resorbs large amount of fluid that filters from vasculature
Has glomeruli in outer cortical regions
Has short nephron loops
Describe the process of urine entering the bladder from the ureter
Urine is channeled by renal calyces and the renal sinus into the ureter. Peristaltic waves propel urine down ureter which fills the bladder by relaxation of the detrusor muscular wall
How is the bladder emptied?
By detrusor muscular contraction which is aided by raised intra-abdominal pressure
Are the components of the bladder striated/non-striated and voluntary/involuntary?
Muscle is smooth and involuntary
External sphincter found around urethra is striated and voluntary
Explain the process of filtering urine
Beginning of urine production:
blood supply enters through renal artery through a
dense network of capillaries in the glomerulus where filtration can take place
high hydrostatic pressure forces plasma through capillaries and forces out ultrafiltrate
fenestrations allow filtration of unwanted substances such as water out and keeps desired substances in such as plasma proteins
circulation leaves again filtered into Bowman’s capsule through podocytes ready for entry into tubule of nephron
What are podocytes?
Make up epithelial lining in Bowman’s capsule
What is the kidney’s function as an excretory organ?
Cleanses the blood of metabolic end products/toxins/water that may be surplus to body’s needs
What is the kidney’s function as a homeostatic and endocrine organ?
controls blood pressure levels, tissue osmolality and electrolyte levels
What is reabsorption?
Transferring water and solutes from the lumen of nephron tubules to the interstitium to come back into circulation
Describe the 2 different paths of reabsorption
Paracellular: substances reabsorbed can enter through tight junctions, passive process
Transcellular: through cells of the nephron through channels and transporters, active process requiring energy from Na/K-ATPase
Explain how transcellular reabsorption occurs
Na/K-ATPase creates a Na gradient between outside and inside of cell
Ion transport results in voltage gradient between tubule lumen and interstitium
Water follows Na by osmosis entering the basolateral domain carrying solutes
What are the components of what is excreted out in urine?
what is filtered out - what is reabsorbed + what is secreted later on
hormonal regulation plays a major role
What are the surface modifications of proximal tube of the kidney nephron epithelial cells?
Have apical microvilli that increase the surface area
Have junctions between cells which are leaky and maximise free flow of water and dissolved solutes
How is Na reabsorbed by the proximal tube of the kidney nephron?
Driven by basolateral Na/K-ATPase through cotransport with organic solutes in exchange for H+
How is Cl- absorbed by the PT of the kidney nephron?
Occurs in the late proximal tube by paracellular route or by a Cl- base exchanger
How is water reabsorbed by the PT in the kidney nephron?
Occurs by osmosis, driven by influx Na, Cl and solutes
What is the role of the peritubular network?
Returning reabsorbed fluid to the vasculature
What occurs during a spinal micturition reflex?
Parasympathetic motor efferents stimulate bladder contraction. Emptying of the bladder is prevented by the CNS until the outer sphincter is relaxed voluntarily
What is micturition?
Urinating
What triggers a spinal micturition reflex?
The bladder filling stretching its muscular wall
