-
Kidney
- produces hormones for regulation of circulatory system, formation of RBC, and bone metabolism
- Maintenance:
- regulates composition and volume of body fluids
- adjust to continuously varying conditions by inc/dec/adjusting urine volume, concentration and composition to actual requirments
- only need 1/3 to be functional
-
water - intake and output
- all intake through intestines
- (small amount from metabolic water (camels have a lot)
- somes leaves through lungs as vapor, evaporated off skin, most excreted by kidney
-
water balance
- intake = output
- 2.5 L in = 2.5 L out
-
kidneys fail
- transplantaion
- peritoneal dialysis (inject lots of fluid into abdomen so that high wasteconcentration leaves the blood, fluid can then be drawn out of body)
- dialysis machine
- functions of kidneys becoem apperent when then fail
-
when kidneys fail
- accumulation of metabolites - urea, creatinine, uric acid, NH4+,
- disorder of water and electrolyte metabolism - hyperkalaemia (potassium, heart electrial system), hypernatraemia (Na, more in blood volume), hyermagnesaemia, hyerphosphataemia
- hypertension of arterial blood pressure - renin, angiotensin, aldosterone system(increase Na in blood)
- hormonal deficiency - anemia, erythropoietin(produced by kidneys
-
Kidney anatomy
- retroperitoneal
- protected by layer of fat
-
Equine kidney
triangle in shape
-
-
Functional unit - Nephron
- basic unit for formation of urine
- each kidney contains ~ 1 million nephrons
-
vasculature
renal artery - arcuate ateries (form boundary between cortex and medulla - interlobular arteries
-
Macula Densa
- measures NaCl concentration to regulate tubular flow
- causes constriction
- part of DCT next to afferent arteriole
- "control center" - for urine flow and concentration
-
filtration
- 99% fluid filtered into bowmans capsule is reabsorbed by peritubular capillaries
- 1% remains and excreted as urine carrying waste
-
nephron pressure in arterioles
- 60 mmHg - glomerulus
- 13 mmHg - peritubular capillaries
- 15-25% - cardiac output flow through kidneys
- 1-2% - total renal blood flow through vasa recta
-
nephron pressure in collecting ducts
- 18 mmHg - Bowmans capsule
- 0 mmHg - at end of collecting duct
-
glomerular filtration
- humna - 180 L per day
- excret only 1 L
-
Glomerular wall
- visceral epi (podocytes)
- basement membrane
- capilary endothelium
- fenestrated channels - water passage and noncellular components
- 100 - 500 more permeable than other capillaries
-
Selective permeability
- molecular weight of 5200 - filter like water, inulin
- proteins - almost impermeable
- pores are negatively charged (proteoglycans) reject negative proteins even if smaller diameter than pore
- positive > neutral > negative
-
Nephritis
- negative charge on membrane is neutralized
- increased protien found in urine
- clinically significant - use test strip to test for protein
-
Glomerular filtrate = no significant amount of protein
-
Urine
- fluid is filtered from blood, processed in tubular system
- Flow speed - highly critical, saturable, directly depends on glomerular filtration rate
- increase speed, decrease amount of time for reabsorption (lost to urine)
- decrease speed, waste backup in blood
-
glomerular filtration - regulated by afferent and efferent arteriole
rate - fluid volume filtered per min from capillary blood into Bowman's capsule
-
Normal conditions of GLomerular filtration
- filtration rate - blood pressure, oncotic pressure, hydrostatic pressure, and oncotic pressure of ultrafiltrate(normally 0)
- net filtrate = (60-32)-(18-0) = 10 mmHg
- 60 = mean glomerular blood pressureof afferent and efferent arterioles
-
Filtration increases = glomerular blood pressure or ultrafiltrate oncotic pressure increases
-
Filtration decreases = oncotic pressure or the ultrafiltrate hydrostatic pressure icreases
-
Afferent constriction
- increases resistance to blood = decreases blood pressure in glomerulus
- net = 5 mmHg
- decrease in net filtration pressure
- decrease consequently the filtration
- decrease hydrosatic pressure in capsule
-
Moderate Efferent vasoconstriction
- increase glomerular blood pressure
- increase in filtration
- net = 15 mmHg
-
Sever Efferent Vasoconstriction
- increases glomerular blood pressure
- decrease in blood flow
- decrease in filtration (less blood passes through per min)
- increase in blood oncotic pressure
- net = 5 mmHg
-
Low GFR
- decrease in tubular flow
- extends time for resorption
- increase reabsorption of wastes
- more NaCl causes vasodilation by Macula Densa to increase speed of blood flow
-
High GFR
- increase speed of tubular fluid
- decrease time for reabsorption
- valuable nutrients are lost in urine
- Macula Densa senses NaCL and causes constriction to decrease speed by secretion of Renin
-
5% deviation from normal GFR
excess loss of solutes and water
of
increases retention of waste products
-
autoregulation of GFR
- myogenic reflex
- tubuloglomerular feedback
-
myogenic reflex
- increase in arterial pressure streches wall of arteriole b/c of to high of blood flow
- vessels constrict
- increased blood flow returns to normal
-
tubulorglomerular feedback
- afferent arteriolar vasodilation
- efferent arteriolar vasoconstriction
- juxtaglomerular complex
-
Affernt Arteriolar Vasodilation
- when - decrease in tubular flow, NaCl - increase in absorption
- decease in concentration at Macula Densa -
- decrease in concentration
- dilation of afferent arteriole
- increase glomerular filtration pressure
- increase in fluid filtered
- increase in tubular fluid flow
-
Efferent Arteriolar Vasoconstriction
- NaCl - increase in absorption, decease in concentration at Macula Densa
- release of Renin from Macula Densa
- Renin - angiotensin II - constrition of effernt arterioles
- increase in GFR
-
Renin - Angiotensin - Aldosterone System
- short system - angiotensin increases systemic blood pressure (vasoconstrition)
- long system - aldosterone increases blood volume
-
Renal vasodilators prostaglandins
- E2 and I2
- help maintain renal vascular resistance at normal levels by conteracting angiotensin II
-
renal vascular tone hormones - Vasoconstrictors
- endothelin
- thromboxane A2
- Angiotensin II
-
renal vascular tone hormones - Vasodilation
- Nitric oxide
- prostaglandin E2 and I2
|
|