L1 Intro To Renal Function Flashcards
Functions of the Kidneys
Regulation of water and inorganic ion balance
Regulation of body fluid osmolality and volume
Excretion of metabolic waste (ie urea, uric acid, creatinine)
Excretion of foreign chemicals (ie drugs, pesticides, food additives)
Secretion of hormones (Renin, Erythropoietin, 1,25-dihydroxycholecalciferol)
Regulate blood bicarbonate levels
Normal daily water input
Food and water = 1900 ml
Oxidative water = 400 ml
Total = 2300 ml
Normal daily water output
Fecal = 150 ml Sweat = 250 ml Insensible = 800 ml
Total output = 1200 ml
If total water input = 2300ml and total water output = 1200ml, what happens to the remaining 1100ml/day?
Urine flow
If urine output = 1100ml/day, then the subject is in steady state
If urine output > 1100ml/day, then the subject is in negative water balance
If urine output < 1100ml/day, then the subject is in positive water balance
Examples of physiologic conditions leading to negative sodium and water balance
Diarrhea
Diuretic medications
Insufficient aldosterone (ie adrenal dysfunction)
Basically, more water/sodium lost than brought in to the body
Examples of physiological conditions resulting in a positive sodium and water balance
Excess steroids (anabolic substances) Congestive heart failure Salt-retaining disease (ie hyperaldosteronism)
Gross structures of the kidney
Cortex (granular in appearance)
Medulla (striated)
- Renal pyramids
- Urine excreted from papillae into calyces
Pelvis - calyces drain into the renal pelvis
Ureter
Basic functional unit of the kidney:
The Nephron
Millions in each kidney
Consists of tubular component and a vascular component, as well as a combined component (JGA)
Different components of the nephron
Renal corpuscle (incl glomerulus and Bowman’s capsule)
Proximal tubule
Loop of Henle
Juxtaglomerular apparatus (JGA)
Distal convoluted tubule
Collecting duct
_______ drains the Bowman’s capsule, and site of 60-80% of filtered solute and water reabsorption (isosmotic)
Proximal Tubule
________ generates osmotic gradients in the medulla that allow kidney to concentrate the urine
Loop of Henle
Includes descending and ascending loops
Where the thick ascending limb passes between the afferent and efferent arteriole
Juxtaglomerular apparatus (JGA)
Site where final concentration of urine is adjusted (to make urine iso-, hypo-, or hyperosmotic)
Collecting duct
Water permeability controlled by vasopressin
Nephrons with glomeruli in outer cortex and short loop of Henle that does not extend into the inner medulla
Cortical nephrons
Nephrons with glomeruli near the corticomedullary border and long loop of Henle extending deep into the inner medulla
Juxtamedullary nephrons
Ability to produce concentrated urine is thought to be proportional to…
The number of juxtamedullary nephrons
All nephrons function in ______.
Parallel
Collecting ducts shared by many nephrons
The three layers of the filtration barrier within the renal corpuscle
Capillary endothelium
Glomerular basement membrane (=basal lamina)
Visceral epithelial cells (=podocytes)
Peddles are extensions of the podocytes
Slits between podocytes constitute the path of filtrate flow into Bowman’s capsule
Components of the juxtaglomerular apparatus (JGA)
Macula dense (MD) Extraglomerular mesangial cells (EGM) Granular cells (G, aka juxtaglomerular cells)
Function of the juxtaglomerular apparatus (JGA)
Helps control GFR
Controls renin secretion (which in turn controls blood pressure and volume)
_________ Cells between capillary loops contract in response to hormone angiotensin II
Mesangial cells
The two capillary beds that comprise the renal vasculature
Glomerular
Peritubular
• Corticol
• Vasa Recta (follow LOH of juxtamedullary nephrons in the medulla)
Corticol arteries give off ____________
Afferent arterioles
One afferent arteriole per glomerulus
Fluid not filtered goes to __________.
Efferent arteriole, then to peritubular capillaries
The two arterioles (afferent and efferent) and two capillary beds (glomerular and peritubular) are in ________.
Series
Specialized peritubular capillaries of juxtamedullary nephrons
Vasa Recta
Long, hairpin shaped capillaries that follow the LOH
__________ supply nutrients to medullary tissue and are important for recovery of water
Vasa Recta
Renal nerves are _________
Sympathetic (release norepinephrine and dopamine
Alpha-1 receptors present on afferent and efferent arterioles, but primarily afferent arterioles
NO parasympathetic innervation
Stimulation by the SNS tends to ….
Reduce RBF and GFR, but the simulaneous release of prostaglandins PGE2 and PGI1 oppose the effect so reductions in RBF and GFR are minimized
Granular cells are innervated by ______ and _______ is released upon stimulation of ______ receptors
SNS; renin; beta receptors
Production of a protein-free filtrate is called
Glomerular filtration
GFR is usually 120-125 ml/min
Other components of renal function besides glomerular filtration
Tubular reabsorption (from tubular lumen to PTC) Tubular secretion (from PTD to tubular lumen) Excretion (substance appears in urine)
