Kidney Flashcards
renal capsule
connective tissue surrounding the kidney
renal cortex
area immediately beneath the capsule, which contains the glomeruli and portions of tubules- receives most of the blood flow- mostly concerned with reabsorbing filtered material
Renal Medulla
the innermost part of the kidney
Renal artery
supplies each kidney with blood
Renal sinus
cavity within the kidney which is occupied by the renal pelvis
Calyces
tubes through which urine drains into the renal pelvis
Glomerulus
clusters of capillaries-plasma is filtered from capillaries into the Bowman’s capsule
Bowman’s capsule
double membrane that surrounds the glomerulus
PCT
reabsorbs most of the filtered load
Loop of Henle
Urine concentration
DCT
reabsorbs Na and H2O
Collecting Duct
collects urine from excretion
Ureters
transports urine from the calyces to the bladder
Urethra
transports urine from bladder to urinary meatus
How many nephrons are in each kidney?
Approximately 1 million nephrons i
How much blood flow does the kidney receive?
~22% of cardiac output
What are the functions of the kidney?
- Excretion of metabolic waste products
- Excretion of foreign chemicals
- Hormone synthesis, metabolism, and excretion
- Regulation of acid base balance
- Regulation of arterial pressure
- Regulation of water and electrolyte balance
- Gluconeogenesis
What is involved in urine formation?
Glomerular Filtration
Tubular Reabsorption
Tubular Secretion
What is involved in filtration?
Non selective; averages 20% of renal plasma flow
what is involved in reabsorption?
highly variable and selective; most electrolytes and nutritional substances are almost completely reabsorbed
what is involved in secretion?
highly variable; important for rapidly excreting some waste products, foreign substances, and toxins
Glomerular Filtration
- Urine formation begins with filtration of large amounts of fluid through the glomerular capillaries into Bowman’s capsule
- the glomerular capillaries are relatively impermeable to proteins
Constituents of glomerular filtrate
most salts, organic molecules (similar to the concentrations in the plasma)
The 3 layers of glomerular filtration barrier
- The endothelium of the capillary
- A basement membrane
- A layer of epithelial cells
Constant GFR
80-180 mmHg
The Net Filtration Pressure
The sum of the hydrostatic and colloid osmotic forces that either favor or oppose filtration across the glomerular capillaries
How much water is excreted each day?
1 liter
How much sodium is excreted each day?
150 mmol
How much glucose is excreted each day?
0
How much creatinine is excreted each day?
1.8 gm
Autoregulation
feedback mechanism intrinsic to the kidneys normally to keep renal blood flow and GFR relatively constant, despite marked changes in arterial blood pressure (80-180 mmHg)
What is the Juxtaglomerular Complex equation
Juxtaglomerular Complex = Macula Densa + Juxtaglomerular Cells
Clearance of insulin (Cin)
if CxCin: indicates secretion of X
Formation of a Dilute Urine
- Continue electrolyte reabsorption
- Decrease water reabsorption
- Mechanism: decreased ADH release and reduced water permeability in distal and collecting tubules
Formation of a Concentrated Urine
- Continued electrolyte reabsorption
- Increase water reabsorption
- Mechanism:
- increased ADH release which increases water permeability in distal and collecting tubule
- high osmolarity of renal medulla
- countercurrent flow of tubular fluid
Characteristics of normal urine
No protein No RBC No Heme No cellular casts No fat No sugar
