L23: Renal System I Flashcards
kidneys process blood by
removing substances from it and in a few cases adding substances to it
major renal functions
regulation of the volume, osmolarity, mineral composition, acidity of the body by excreting water and inorganic electrolytes in amounts adequate to achieve homeostasis
second renal function
excretion of waste products (urea, uric acid, creatinine, hemoglobin waste products)
urea is a waste product of
proteins
uric acid is a waste product of
nucleic acids
creatinine is a waste product of
muscle creatinine
third renal function
removal of foreign chemicals
fourth renal function
gluconeogenesis (synthesis of glucose from amino acids and other precursors)
fifth renal function
production of hormones and enzymes
what enzymes/hormones do kidney produce?
erythropoietin (erythrocyte production)
renin (blood pressure, sodium balance)
1,25-dihydroxyvitamin D (calcium balance)
kidneys location
abdominal (peritoneal) cavity in the posterior abdominal wall
ureters
transport urine from kidneys to the bladder
the bladder
stores urine until voided from body
urethra
carries urine from bladder to the outside of the body
two major regions of kidneys
inner renal medulla and outer renal cortex
the site of ultrafiltration
outer renal cortex
kidneys receive ___% of the cardiac output
20-25%
kidneys constitute __% of the total body weight
0.4%
___ is critical to renal function
high rate of blood flow
renal arteries
branch off the abdominal aorta, supply blood to the kidneys
renal veins
carry blood from the kidneys to the inferior vena cava
each kidney has over __ million nephrons
1 million
the basic structural & functional unit of the kidney
nephron
two types of nephrons
cortical and juxtamedullary
cortical nephrons
most nephrons (80-85%), have short loop of Henle
juxtamedullary nephrons
15% of nephrons, have long loop of Henle, maintain osmotic gradient to produce concentrated urine
renal corpuscle
filtering unit responsible for the initial step in urine formation, large and charged proteins and formed elements stay in plasma, while some nutrients, electrolytes, water, and waste products go to renal tubules
renal corpuscle consists of
tuft of interconnected capillary loops called glomerulus and ballon-like fluid-filled capsule called Bowman’s capsule into which the glomerulus protrudes
Bowman’s capsule
receives the filtrate, inflow to renal tubules
glomerulus
capillary network for filtration
filtration barrier in the renal corpuscle consists of
three layers
first inner layer of filtration barrier
capillary endothelium that is perforated by many large fenestrae
second layer of filtration barrier
basement membrane, a gel-like acellular meshwork of glycoproteins and proteoglycans, does not allow negatively charged species to pass through
third layer of the filtration barrier
podocytes, capsular epithelial cells, extend foot processes into the basement membrane, have nephrin protein that does not allow big substances to pass
filtration slits
between adjacent foot processes constitute the path through which the filtrate, once through the capillary endothelial cells and basement membrane, travels to enter Bowman’s space
from Bowman’s capsule, filtered fluid flows into
the proximal tubule, which leads into the loop of Henle
the tubule is made up of
a single layer of epithelial cells resting on a basement membrane
one common feature of epithelial cells in tubules
tight junctions between adjacent cells
From Bowman’s capsule to the collecting ducts,
each nephron is ___
separated from one another
the separation of nephrons ends when
ducts merge into the renal pelvis
renal arteries
branch off the abdominal aorta, supply blood to the kidneys
renal veins
carry blood from the kidneys to the inferior vena cava
each nephron has
two arterioles and two sets of capillaries
blood enters the glomerular capillaries via
afferent arterioles
glomerular capillaries form
efferent arterioles
efferent arteriole of a cortical nephron subdivides into
a second set of capillaries called the peritubular capillaries which are profusely distributed to the tubule
peritibular capillaries
rejoin to form the veins by which blood leaves the kidney
efferent arterioles of juxtamedullary nephrons give rise to
long, looping vasa recta
vasa recta
peritibular capillaries that dip into the medulla and then go back up to the cortex, forming hairpin loops
vasa recta has significance for
the formation of concentrated urine
juxtaglomerular apparatus
in all nephrons, this is the final part of the ascending limb of the loop of Henle, when it passes between the afferent and efferent arterioles
the proximity of the ascending limb and the arterioles allows
paracrine communication between the two structures, a key feature of kidney autoregulation
nephrons consists of
renal corpuscle and tubule
renal corpuscle consists of
capillary tuft, called glomerulus, and Bowman capsule that the tuft protrudes into
tubule consists of
proximal tubule, loop of Henle, distal convoluted tubule, and collecting duct-system
at the end,
in the collecting ducts, multiple tubes join and empty into the renal pelvis, from which urine flows through the ureters into the bladder
each glomerulus is supplied by
afferent arteriole
___ leaves the glomerulus
efferent arteriole
tubules are supplied by
peritubular capillaries
