Renal System Flashcards
What is the position of the kidneys?
-posterior abdominal wall
-12th rib
-T12-L3
List some internal structures of the kidneys
-renal cortex
-renal medulla
-major calyx
-papilla of pyramid
-renal pelvis
-minor calyx
-ureter
-renal pyramid in renal medulla
-renal column
-fiborous capsule
What are the functions of the kidneys?
-maintenance of homeostasis formation of urine
-excretion of toxins and waste products
-regulation of electrolyte balance
-regulation of fluid balance
-regulation of acid-base balance
-produce renin
-produce erythropoietin
-metabolism of vit D inactive-active
Desxcribe the structure of the nephron
-functional unit of kidney
-consists of: Glomerulus, bowmans capsule,PCT, loop of henle,DCT,collecting duct
-glomerulus-cappilary network inside the glomerular capsule
What are the three main steps in the formation of urine?
1-glomerular filtration
2-tubular reabsorption
3-tubular secretion
What are some main structure and functions in the glomerulus?
-granular cells in afferent arteriole (release renin)
-Macula densa cells in ascending limb of loop of henle
-efferent artery-monitor Na+ conc in filtrate
Describe what happnes during glomerular filtration
1-Movement of H2O and solute from blood into filtrate under pressure
2-glomerular filtration rate
3-filtrate passing into PCT contains everything in blood but not RBC and WBC, platelets and large proteins-albumin
4-filtrate has glucose, AA, waster, vitamins,electrolytes,nutrients,H2O- plasma without proteins
What is GFT?
the rate at which the kidney/nephron filters the blood
Explain GFT quantitavily
-approx 125ml/min
-measured using
eGFR (MDRD formula) >90/min/1.73m2
-albumin>30mg/mmol
-GFR maintained in part by auto-regulation
What are the three main structure in the filtration membrane?
-fenestration pores and capillaries
-membrane-negative charge
-podocytes
Describe the promotion of filtration
-BP
-Net filtration pressure:
out:
-hydrostatic pressure in glomerular cappilaries 55mgHg
-efferent arteriole narrower than afferent
In:
pressure in capsular space (15mmHg)
-colloid osmotic pressure in cappilaries (30mmHg)
net outward force= 10mmHg
Whats the formula for NFP?
outward pressures- inward pressures
What is autoregulation?
high pressure= afferent arteriole constricts to reduce pressure entering glomerulus
low pressure= efferent arteriole contsricts to increase pressure in glomerulus
low pressure in afferent arteriole stimulates renin release
Describe the process of tubular reabsorption
1-return of useful subs to H2O from filtrate into blood
2-selective reabsorption in PCT
3-Na+ actively reabsorbed from filtrate into blood
4-H2O some ions and nutrients passively follow
5-Transport maximum
What is transport maximum?
-maximum amount of a substance that can be reabsorbed
-if glucose exceeds the TM its lost in the urine
Describe the reabsorption process in more detail
-PCT
-Reabsorption continues through tubules by active and passive means -influence hormones
-aldosterone influences reabsorption in DCT-movement of H20 and Na+ follows passively
ADH-affects permeability of collecting ducts to H20-reabsorb water or increase water loss
Describe what happens in tubular secretion
1-active removal of unwanted subs from the blood into filtrate
2-occurs all along tubule
k+ mainly in PCT but also in DCT in exchange for Na+
3-H+,K+,NH4, creatine,drugs
4-important for regulating k+ (3.5-5mmol) and PH (7.35-7.45)
Describe the urine chemical composition
95%-water
5%-solute
water, urea, sodium, potassium,phosphate, sulphate,creatine, uric acid
creatine-metabolism in muscle tissue
Uric acid-metabolism in nucleic acids
describe the regulation of urine conc and volume
-kidneys make adjustments to maintain body fluid osmotic conc at around 300mOsm
osmolality-number of solute particles in 1kg of H2O
body fluids-expressed in milliosmols
Describe the role of ADH within the kidney
-permeability of CD and latter part of DT under ADH influence
-aquaporin channels allow H2O movement
-plasma osmolality is detected by osmos receptors in hypothalamus
-ADH secretion from posterior pituatary is increased or decreased in response to osmotality
high>300mosmol low<300mosmol
What happens if there is an increase or decrease in ADH ?
increase=greater reabsorption-less urine
decrease=less reabsorption-more urine
describe the renin-angiotensin aldosterone mechanism
1-renin released form juxta-glomerular apparatus in respone to low pressure
2-renin converts circulating angiotensinogen (inactive protein) into angiotensin I
3-Angiotensin I is converted into angiotensin II by angiotensin converting enzyme from lungs (ACE)
What does angiotensin II cause?
-vasoconstriction of systemic blood vessels
-release of aldosterone from adrenal cortex
-reabsorption of Na+ and H2O in renal tubules (DCT)
-influences ADH release
How does the renal system regulate the acid-base balance?
-normal range 7.35-7.45
-H+ constantly produced as a result of metabolism-needs to be eliminated
gluocse->ATP+CO2+ H2O
-more H+ in blood the more acidic the blood PH
-more OH- in blood the more alkaline the blood PH
Whats the acid base balance?
CO2+H20->H2CO3->H+ + HCO3-
Goes both ways
How does the respiratory system maintain acid base balance?
-detects change in H+ conc
-if H+ increase-respiratory rate increases, excess H+ breathed out as CO2
How do buffers e.g bicarb in blood, proteins and phosphates in cells maintain acid base balance?
-acts as a sponge, soaks up excess H+ or OH- ions
Describe erythropoietin production
-EPO stimulates bone marrow to produce RBC (eryhtropiesis)
-HB is a principle carrier of O2 to body cells
-EPO production is stimulated by hypoxaemia
describe the role of the kidneys in Ca2+ and Phosphate regulation in vitamin D metabolism
-Main homeostatic control of Ca2+ is through PTH release
-kidneys role in Ca2+ = reabsorption of Ca2+ and the metabolism of Vitamin D into an active form
-Ca2+ is reabsorbed as phosphate is excreted
Describe the process of PO43- and Ca2+ of
Vitamin D regulation
1-low Ca2+-PTH released
increases the absorption of Ca2+ from kidney to GI tract
-releases Ca2+ from bones to maintain plasma Ca2+
2-kidneys convert vitamin D to active form-stimulates Ca2+ absorption from GI tract, maintains normal Ca2+ levels
What is Ca2+ needed for?
-strong bones and teeth
-normal transmission of nerve impulse
-normal muscle contraction
-blood clotting
