Chapter 32 Renal anatomy/physiology/pathophys & A managment Flashcards
main function of kidneys
excreting end products of metabolism and controlling the concentration of constituents of body fluids
kidney facts
- extend from 12th thoracic vertebrae to the 3rd lumbar vertebrae
- weighs approx. 125-170 g in men & 115-155g in women
- 11.25 cm long
- 5 to 7.5 cm wide
- 2.5 cm thick
- d/t hepatic displacement the right kidney’s position is slightly lower than the left
what structures enter or exit the kidney at the hilus
renal artery & vein, nerves, lymphatics, and urters
pyramids have a striated appearance d/t
presence of the loop of Henle and collecting ducts of the nephron
medulla is divided into how many triangular wedges called __
8 to 18 pyramids
the base of the pyramids is directed toward the renal cortex, and the apexes converge toward the
renal pelivis
apex of each pyramid is called the
papilla
papillary ducts empty into
minor calyx –> several minor calyces empty into –> major calyces —> come together to form renal pelvis
functional unit of the kidney
nephron
how many nephrons reside in each kidney
1,250,000
filtered blood flows through the nephrons, which, in turn, retained filter fluid know as
filtrate
through this process, end-products of metabolism are excreted, and metabolically important substances like water and electrolytes are reabsorbed as needed
formation of urine begins with the
nephron
begins in the cortex at the glomerulus and ends where the tubule joins the collecting duct at the papilla
glomerulus
tuft of capillaries derived from afferent arteriole
blood is transported to the glomerulus via the afferent arteriole
blood that is not filtered in the nephron returns to
the systemic circulation via efferent arteriole
the filtrate from the glomeruli enters the __ __ or __ __
bowman capsule; capsula glomeruli
then flows through a torturous pathway in the proximal convoluted tubule, to the loop of Henle, the distal convoluted tubule, and finally to the collecting duct
cortex contains:
bowman capsule, glomerulus, & proximal and distal tubules
descending loop of Henle comes from
the proximal tubule and extends toward the pyramid
kidneys have 2 types of nephrons:
cortical nephrons:
- extend only partially into the medulla
juxtamedullary nephrons:
- lie deep in the cortex and extend deep into the medulla
- compromise 1/5 to 1/3 of total nephrons
- important role in the concentration of urine !!
how much blood per minute do the kidneys recieve?
1,100 - 1,200 mL of blood
or 20% to 25% of the cardiac output
renal artery divides into several __ arteries and then subdivides again into __ arteries, which run between the pyramids
lobar; interlobar
interlobar arteries reach the __ zone, they make well-defined arches over the bases of the __
corticomedullary; pyramids
arcuate arteries divide into a series of arteries known as
interlobular arteries
where do interlobular arteries terminate?
may terminate as an afferent arteriole or as a nutrient artery to the tubule
the afferent arterioles form the
high-pressure capillary bed within the bowman capsule that is called the glomerulus
little or no O2 is removed in the __, blood that is not filtered begins its passage to the __ __ via the __ __
glomerulus; venous system; efferent arteriole
T/F the efferent arteriole is smaller than the afferent arteriole
true
thereby affording some resistance to blood flow
efferent vessel becomes a plexus of capillaries AKA
peritubular capillary bed
low-pressure bed
the cardiac output portion that passes through the kidney is called the
renal fraction
normal renal fraction of CO is between 20% & 25%
T/F renal medulla has a larger distribution of renal blood flow compared to the renal cortex
FALSE
renal cortex receives larger distribution of renal blood flow
blood flow to any organ is determined by
the arteriovenous pressure difference across the vascular bed
RPF
renal plasma flow
how is renal blood flow regualed
- intrinsic autoregualtion
- neural regulation: the sympathetic nervous system innervates afferent & efferent arterioles, acute sympathetic stimulation will have associated vasoconstriction & can decrease renal blood flow
if mean systemic pressure falls below 50 mm Hg
filtration ceases
T/F direct relationship between RBF & glomeruli filtration
true
reduction of glomerular filtration leads to dilation of
afferent arteriole
an increase in blood flow to the glomerulus returns glomeruli filtrations to normal
myogenic mechanisms
arterial pressure rises, the arterial walls are stretched, the vessel constricts, & blood flow remains normal
- when arterial pressure decreases the opposite effect occurs
renal physiology:
filtration, reabsorption, and tubular secretion
filtration
results from pressures forcing fluids and solutes through the glomerulus, is the first step in the formation of urine
GFR
quantity of glomerular filtrate formed each minute in all nephrons
filtration fraction
quantity of renal plasma flow that becomes filtrate and is defined as GFR divided by the flow to one kidney
regulation of GFR
- the pressure inside the glomerular capillaries
- the pressure in the bowman capsule
- the colloid osmotic pressure of the plasma proteins
pressure of the glomerulus
60 mm Hg
is an outward force
colloid osmotic pressure
28 mm Hg
created by proteins and is an inward force that tends to hold fluid within the glomerulus
pressure in the bowman capsule
18 mm Hg
opposes filtration
filtration pressure is the pressure that forces __ through the __ __ and is equal to the glomeruli pressure minus the sum of the glomerular colloid osmotic pressure and the capsular pressure
fluid; glomerular membrane
normal filtration pressure is
10 mm Hg
factors that can alter GFR
- increased renal blood flow
- dilation of the afferent arteriole
- increased resistance in the efferent arteriole
all increase GFR
what structure regulates GFR
juxtaglomerular complex
*distal convoluted tubule lies between the afferent and efferent arterioles *
what decreased GFR
afferent arteriole constriction and efferent arteriole dilation
cells of the distal tubule encountering the arterioles are __, and therefore are referred to as the __ __
dense; macula densa
smooth muscle cells of both aff & eff arterioles consist of
juxtaglomerular cells, which contain renin
decreased glomeruli filtration causes
overabsorption of Na and Cl in the ascending limb of the loop of Henle resulting in a reduction in the delivery of these ions to the macula densa
macula densa function
detect small changes in osmolarity
the structure is arranged to allow fluid in the distal tubule to alter aff & eff arteriole
tone and thus regulate GFR
decreases in Na and Cl concentrations causes __ arterioles to dilate, thus increasing ___ & __
afferent; RBF; GFR
permeability at the glomerulus is __ to __ times greater than most capillaries
100 to 150
glomeruli capillary containes
negatively charged pores
freely permeable to water and small molecules
glomerulus is almost impermeable to all
plasma proteins but highly permeable to most other dissolved substances
conversion of glomeruli filtrate to urine is the result of
filtration at the glomerulus, tubular reabsorption, or transport from the tubular lumen to the renal cell, and secretion or transport from the renal cell to the filtrate
approx __% if plasma filtrate is reabsorbed in the nephron
99%
once blood has reacherd the peritubullary capillary
tubular reabsorption permits conservation of substances such as:
water, glucose, amino acids, and electrolytes
water and Na are reabsorbed throughout the nephron
proximal tubule
- active transport of NA is the primary function
- reabsorption of water leaves an increased concentration of urea within the tubular lumen
- hydrogen ions are actively secreted in exchange for Na
Loop of Henle
- function is to establish a hyperosmotic state within the medullary area –> vital to conserve salt and water
- the longer the loop, the greater the concentration gradient –> as the gradient increases, the movement of water is enhanced
late distal tubule
- Na under the influence of aldosterone is reabsorbed
- K is excreted into the lumen in exchange for Na
- secretes H ions against a concentration gradient –> role in acid/base balance and determines the final degree of urine acidification
- area is permeable to H2O only in the presence of ADH
