renal Flashcards
What four systems are involved in excretion?
urinary, respiratory, digestive and integumentary
microscopic filtering units of the kidneys composed of renal corpuscle, renal tubules and a rich blood supply?
The nephron
What is the functional unit of the kidney?
The nephron
Where are the nephrons located?
mostly in the renal cortex with some tubules extending into renal pyramids of the medulla
What four processes are required for urine formation?
glomerular filtration
tubular reabsorption
tubular secretion
excretion
Define glomerular filtration.
glomerular filtration of water and solutes from the glomerular capillaries blood into Bowman’s capsular space
non-selective filter
Define tubular reabsorption.
tubular reabsorption of useful substances from renal tubules filtrate into the peritubular capillaries blood
Define tubular secretion and then excretion.
tubular secretion of waste products from the peritubular capillaries blood into the renal tubules filterate. Excretion then occurs as urine.
What is the ‘filtration membrane’ fromed from? What is the glomerular capillary hydrostatic pressure?
formed by the glomerular capillary wall and the visceral layer of Bowman capsule
60 mmHg
What does GFR stand for and what is the average L/day?
glomerular filtration rate
180 L/day
What is the equation for filtration fraction?
GFR/Renal Plasma Flow
In comparison to the glomerular capillary pressure; what is the blood capillary pressure in other parts of the body?
Ranges form 7-17 mmHg; opposed to the 60 mmHg in the glomerular capillary
What is used to calculate the net filtration pressure (NFP)?
Blood hydrostatic pressure (BHP), Colloid osmotic pressure (COP), and the capsular pressure (CP) BHP 60 mmHg OUT COP -32 mmHg IN CP -18 mmHg IN = 10 mm Hg OUT
What is fluid in the capsular space called and what does it NOT consist of?
glomerular filtrate- no blood cells, plasma proteins or fatty acids
What does glomerular filtrate contain?
metabolic wastes such as urea & uric acid
useful substances such as water, organic nutrients & electrolytes
Regulation is done by controlling the amount of glomerular blood flow. what effect does dilation of the afferent arteriole and constriction of efferent arteriole have on the GFR?
increase in GFR
Regulation is done by controlling the amount of glomerular blood flow. what effect does constriction of the afferent arteriole and dilation of efferent arteriole have on the GFR?
decrease in GFR
What 3 hormones DECREASE GFR?
NE, Epi, and endothelin
What 3 hormones INCREASE GFR?
PG, bradykinin, and enothelial-derived NO
What is autoregulation of GFR?
regulation of GFR by the juxtaglomerular/ macula densa apparatus that is found in every nephron
What is neural regulation of GFR?
sympathetic nervous system stimulation during exercise or in circulatory shock that DECREASES GFR
In tubular reabsorption, what is ultrafiltration?
Bulk flow- from the interstitial fluid through the peritubular capillary wall into the blood
In tubular reabsorption, what is transport maximum?
the amount of substance that can be transported before the transport proteins for that substance becomes fully saturated
How many liters of urine are excreted a day? How manyliters of water are reabsorbed per day?
1-2 liters of urine excreted/ day
148-178 liters of water are reabsorbed /day
Where does most of the water reabsorption take place?
- 65% in the proximal convoluted tubules (PCT)
- 15% in descending limb of loop of Henle (LOH)
- 10% in distal convoluted tubules (DCT)
- 10% in collecting ducts (CD)
How much water is reabsorped in the ascending loop of Henle?
NONE
What is passive water reabsorption coupled to?
passive water reabsorption by osmosis is coupled to sodium reabsorption