As noted previously, the structure of the kidney is divided into two principle regions—the peripheral rim of cortex and the central medulla. The two kidneys receive about 25 percent of cardiac output. They are protected in the retroperitoneal space by the renal fat pad and overlying ribs and muscle. Ureters, blood vessels, lymph vessels, and nerves enter and leave at the renal hilum. The renal arteries arise directly from the aorta, and the renal veins drain directly into the inferior vena cava. Kidney function is derived from the actions of about 1.3 million nephrons per kidney; these are the “functional units.” A capillary bed, the glomerulus, filters blood and the filtrate is captured by Bowman’s capsule. A portal system is formed when the blood flows through a second capillary bed surrounding the proximal and distal convoluted tubules and the loop of Henle. Most water and solutes are recovered by this second capillary bed. This filtrate is processed and finally gathered by collecting ducts that drain into the minor calyces, which merge to form major calyces; the filtrate then proceeds to the renal pelvis and finally the ureters.
Bowman’s capsule
cup-shaped sack lined by a simple squamous epithelium (parietal surface) and specialized cells called podocytes (visceral surface) that participate in the filtration process; receives the filtrate which then passes on to the PCTs
calyces
cup-like structures receiving urine from the collecting ducts where it passes on to the renal pelvis and ureter
cortical nephrons
nephrons with loops of Henle that do not extend into the renal medulla
distal convoluted tubules
portions of the nephron distal to the loop of Henle that receive hyposmotic filtrate from the loop of Henle and empty into collecting ducts
efferent arteriole
arteriole carrying blood from the glomerulus to the capillary beds around the convoluted tubules and loop of Henle; portion of the portal system
glomerulus
tuft of capillaries surrounded by Bowman’s capsule; filters the blood based on size
juxtamedullary nephrons
nephrons adjacent to the border of the cortex and medulla with loops of Henle that extend into the renal medulla
loop of Henle
descending and ascending portions between the proximal and distal convoluted tubules; those of cortical nephrons do not extend into the medulla, whereas those of juxtamedullary nephrons do extend into the medulla
nephrons
functional units of the kidney that carry out all filtration and modification to produce urine; consist of renal corpuscles, proximal and distal convoluted tubules, and descending and ascending loops of Henle; drain into collecting ducts
medulla
inner region of kidney containing the renal pyramids
peritubular capillaries
second capillary bed of the renal portal system; surround the proximal and distal convoluted tubules; associated with the vasa recta
proximal convoluted tubules (PCTs)
tortuous tubules receiving filtrate from Bowman’s capsule; most active part of the nephron in reabsorption and secretion
renal columns
extensions of the renal cortex into the renal medulla; separates the renal pyramids; contains blood vessels and connective tissues
renal corpuscle
consists of the glomerulus and Bowman’s capsule
renal cortex
outer part of kidney containing all of the nephrons; some nephrons have loops of Henle extending into the medulla
renal fat pad
adipose tissue between the renal fascia and the renal capsule that provides protective cushioning to the kidney
renal hilum
recessed medial area of the kidney through which the renal artery, renal vein, ureters, lymphatics, and nerves pass
renal papillae
medullary area of the renal pyramids where collecting ducts empty urine into the minor calyces
renal pyramids
six to eight cone-shaped tissues in the medulla of the kidney containing collecting ducts and the loops of Henle of juxtamedullary nephrons
vasa recta
branches of the efferent arterioles that parallel the course of the loops of Henle and are continuous with the peritubular capillaries; with the glomerulus, form a portal system
1. The renal pyramids are separated from each other by extensions of the renal cortex called ________.
A) renal medulla
B) minor calyces
C) medullary cortices
D) renal columns
D
2. The primary structure found within the medulla is the ________.
A) loop of Henle
B) minor calyces
C) portal system
D) ureter
A
3. The right kidney is slightly lower because ________.
A) it is displaced by the liver
B) it is displace by the heart
C) it is slightly smaller
D) it needs protection of the lower ribs
A
1. What anatomical structures provide protection to the kidney?
Retroperitoneal anchoring, renal fat pads, and ribs provide protection to the kidney.
2. How does the renal portal system differ from the hypothalamo–hypophyseal and digestive portal systems?
The renal portal system has an artery between the first and second capillary bed. The others have a vein.
3. Name the structures found in the renal hilum.
The structures found in the renal hilum are arteries, veins, ureters, lymphatics, and nerves.