Urinary System 1 Flashcards
Name the 4 main components that make up the Urinary System
kidneys (2)
ureters (2)
Urinary bladder
urethra
Give the main function of the urinary system
maintaining homeostasis by controlling composition and volume of blood
Describe the 3 main roles of the kidneys
remove waste, control blood pH, regulate blood pressure
Describe the external structure of the kidneys
bean-shaped, reddish in colour, retro-peritoneal between levels T12-L3, protected by 11th & 12th ribs, right kidney is slightly lower, 10cm x 5cm x 3cm, upper pole of each kidney = closer to spine, convex lateral border, concave medial border where the hilus is found - where the ureter, blood vessels, lymph and nerve supply enter and leave the kidney
Describe the internal structure of the kidneys
surrounded by a fibrous capsule and made up of outer cortex and inner medulla, medulla house renal pyramid which form collecting ducts, renal cortex and renal pyramids make up the parenchyma - ‘functioning’ portion of kidney - houses the nephrons - regulate blood composition and produce filtrate
Describe what happens to the filtrate
drains through large papillary ducts from the nephrons, through the renal papillae of the renal pyramids into cup like extensions called calyces, filtrate drains firstly into the minor calyces (8-18) and then onto the major calcyes (3)
this route allows for reabsorption of water for the body’s needs, once filtrate enters the calyces it becomes urine as no further reabsorption will take place
Describe where the calyces open into
open into the renal pelvis where the ureter leaves the kidney
Describe nephrons
the ‘functional’ unit of the kidney, consist of a renal corpuscle where blood plasma is filtered and the renal tubule in which the filtered fluid passes
Describe the renal corpuscle of the nephrons
made up of a glomerulus (capillary network) and Bowman’s capsule or glomerular - double walled epithelial cup which surrounds the glomerular capillaries, blood passes through the capillary network and is filtered into the tubule
Give the tubule route taken by the filtrate
through the proximal convoluted tubule (PCT) > into loop of Henle > returns to distal convoluted tubule (DCT) > collecting ducts > papillary ducts > minor calcyes > major calyces > renal pelvis > ureter > leaves kidney
The glomerulus and the PCT & DCT all lie in the …
cortex of the kidney
The loop of Henle (descending and ascending limbs) lie in the …
medulla
Describe where glomerular filtration occurs
in the glomerular capillaries within the Bowman’s space
Which parts of the renal tubule does the filtrate pass through
passes through the PCT, loop of Henle and DCT of renal tubule
close contact between the capillary network and the tubule allows …
for reabsorption and secretion to take place effectively
Describe the role of microvilli
the tubule wall is made up of microvilli to increase the surface area for the reabsorption and secretion
Describe what the reabsorption is
99% water and useful solutes, which are returned to the bloodstream
What does the tubule secrete
waste, drugs and excess ions for excretion
Describe the reabsorption of glomerular filtrate
within the renal tubule it is very effective
glomerular filtration can be altered depending on …
the needs of the body
Describe glomerular blood pressure in the renal tubule
its greater than elsewhere in the body thereby increasing the potential for filtration across the membranes
Describe how the surface area can be changed in the renal tubule
cell walls can contract or relax altering the surface area available for filtration/reabsorption
when the cell walls are constricted there is less of a s.a. = rate of filtration is decreased
Describe the Glomerular Filtration Rate (GFR)
this is the amount of filtrate formed in the renal corpuscles, 125ml/min = males
105ml/min = females
Describe what happens if the GFR is too low/too high
GFR too high = substances needed by the body may pass through too quickly for reabsorption to take place
GFR too low = nearly all the filtrate will be reabsorbed, so waste products will not be excreted into the urine
Describe how GFR can be affected
severe blood less causes arterial BP reduction, which causes lowering of the GFR - if pressure falls below 45mmHg = filtrations ceases
GFR can be affected by altering blood flow in and out of the glomerulus and altering capillary surface available for filtration
Describe GFR regulation in muscular contraction
BP rises > GFR rises > causes afferent renal arteriole wall to stretch > stretch receptors in these walls activate the smooth muscles > they contract > lowering renal blood flow > reduces GFR
Describe GFR regulation in association with Nitric oxide dilation
greater BP causes rise in renal blood flow = absorption of Na and Cl ions is reduced as less time for reabsorption, less Na and Cl ions inhibits release of Nitric Oxide (NO), NO causes vasodilation so therefore due to a reduction in NO levels > reduced vasodilation, more vasoconstriction > less blood flow > allowing time for reabsorption
Describe GFR regulation in association with hormones
Angiotensin II causes vasoconstriction of arterioles = reduces GFR
Atrial Natriuretic Peptide (ANP) relaxes capillary surface causing vasodilation with a greater surface area for filtration = increases GFR
Describe the tubular reabsorption within the PCT
majority of the reabsorption is of glucose, amino acids, urea, sodium, potassium and calcium ions
Describe the role of reabsorption further on in the tubule
maintains homeostasis by fine tuning the balance of ions etc.
pH is maintained by controlling reabsorption of H ions
Describe water reabsorption
takes place through osmosis although anti-diuretic (ADH) affects the final 10% reabsorption dependent on the needs of the body
Describe what materials are removed from the blood and excreted
potassium, hydrogen, ammonium, urea creatine and drugs
what % of water is reabsorbed through osmosis
90%
what % of reabsorption/secretion is ADH regulated depending on bodily needs
10%
Describe what happens when there is no ADH
dilute urine as renal tubules absorb more solutes than water
Describe what happens when there is ADH
concentrated urine means more water reabsorbed than solutes
Describe the main role of ADH in filtration/secretion/reabsorption
to make sure optimum concentration of urine is produced
Name 6 things which could be potentially present in urineand why
Albumin Glucose RBCs Ketones Urobilinogen Microbes
Describe if albumin was in urine
not normally present as its too large for normal filtration, traces would indicate damage to the renal membranes allowing increased permeability - could be raised BP or toxic influence
Describe if glucose was in urine
diabetes mellitus or stress causes release of Epinephrine which stimulates breakdown of glycogen in liver to make glucose
Describe if RBCs was in urine
inflammation of kidney cells, presence of kidney stones or trauma
Describe if Ketones was in urine
diabetes mellitus, anorexia, starvation, reduced carbohydrate intake
Describe if Urobilinogen was in urine
this is the breakdown of Hb, result of liver disease, CCF and bilary obstruction
Describe if microbes was in urine
infections affecting urinary tract
