The Interlobular Veins Are Parallel and Travel Alongside the Renal Lobules
The interlobular veins are parallel and travel alongside the renal lobules, the blood vessels that separate the kidney cortex from the medulla. This arrangement helps to keep the nephrons in proper alignment, so they can properly filter & produce urine.
Blood reaches each nephron through an afferent arteriole and leaves in an efferent arteriole. The capillaries of each nephron are arranged in groups that form a glomerulus, a network of spherical capillary loops that contains the renal glomerular capsule (Bowman’s capsule).
After reaching each nephron, the afferent arterioles branch to the PERITUBULAR CAPILLARIES surrounding the proximal & distal convoluted tubules. In juxtamedullary nephrons, the peritubular capillaries also are connected to vasa recta, which extend deep into the renal medulla.
Once in the peritubular capillaries, the blood enters a network of venules and small veins that converge on INTERLOBULAR VEINS. These veins drain into the renal vein, which then transports blood to the inferior vena cava at a right angle.
As the blood carries filtered substances through each nephron, it is delivered to the cortical radiate veins that extend at right angles to the interlobular veins. These veins carry blood from the nephron to its corticomedullary junction, which is a region of cortex adjacent to the base of the medullary pyramid.
Each cortical nephron receives about 1200 ml of blood each minute, or some 20 to 25 percent of the cardiac output. This is about a fifth of the total volume of the nephron.
A portion of this flow is diverted to the ureter and renal pelvis by an arch that connects the kidney to the ureter and the descending aorta. The ureter is the portal of entry for blood from other organs such as the intestine, spleen, pancreas, and gallbladder.
Another portion of the blood, or filtrate, containing unfiltered substances, is returned to the afferent arteriole by the efferent arterioles. This filtrate consists of water, salts, and minerals that have been removed from the blood as it flows through the renal glomerulus.
The glomerulus consists of a spherical bag of capillary loops arranged in a number of lobules. The glomerular capillaries merge to form an efferent arteriole that exits the glomerulus to form the glomerular capsule (Bowman’s).
In most nephrons, the afferent arterioles leave the glomerulus as peritubular capillaries. These capillaries surround the proximal and distal convoluted tubules as well as the loops of Henle. The peritubular capillaries of the nephrons are important because they serve as the route for the pickup and delivery of substances that are reabsorbed or secreted by the tubules.
Once the peritubular capillaries have reabsorbed the substances that have been filtered, the venous blood drains into the interlobular veins of the kidney. The interlobular veins are long and thin, running along the sides of the renal lobules to the bases of the medullary pyramids.
The interlobular arteries then pass through the renal columns and the ureter & renal pelvis as segmental arteries. They then branch to the interlobar veins, which supply the nephrons with blood as they filter & produce urine.