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Art connection

The kidney is shaped like a kidney bean standing on end. Two layers, the outer renal fascia and an inner capsule, cover the outside of the kidney. The inside of the kidney consists of three layers: the outer cortex, the middle medulla and the inner renal pelvis. The renal pelvis is flush with the concave side of the kidney, and empties into the ureter, a tube that runs down outside the concave side of the kidney. Nine renal pyramids are embedded in the medulla, which is the thickest kidney layer. Each renal pyramid is teardrop-shaped, with the narrow end facing the renal pelvis. The renal artery and renal vein enter the concave part of the kidney, just above the ureter. The renal artery and renal vein branch into arterioles and venuoles, respectively, which extend into the kidney and branch into capillaries in the cortex.
The internal structure of the kidney is shown. (credit: modification of work by NCI)

Because the kidney filters blood, its network of blood vessels is an important component of its structure and function. The arteries, veins, and nerves that supply the kidney enter and exit at the renal hilum. Renal blood supply starts with the branching of the aorta into the renal arteries and ends with the exiting of the renal veins to join the inferior vena cava    , which transports blood back to the right atrium of the heart. The renal arteries split multiple times to form other blood vessels before branching into numerous afferent arterioles, and then enter the capillaries supplying the nephrons.

As mentioned previously, the functional unit of the kidney is the nephron, illustrated in [link] . Each kidney is made up of over one million nephrons that dot the renal cortex. A nephron consists of three parts—a renal corpuscle    , a renal tubule    , and the associated capillary network.

Art connection

Illustration shows the nephron, a tube-like structure that begins in the kidney cortex. Here, arterioles converge in a bulb-like structure called the glomerulus, which is partly surrounded by a Bowman’s capsule. Afferent arterioles enter the glomerulus, and efferent arterioles leave. The glomerulus empties into the proximal convoluted tubule. A long loop, called the loop of Henle, extends from the proximal convoluted tubule to the inner medulla of the kidney, and then back out to the cortex. There, the loop of Henle joins a distal convoluted tubule. The distal convoluted tubule joins a collecting duct, which travels from the medulla back into the cortex, toward the center of the kidney. Eventually, the contents of the renal pyramid empty into the renal pelvis, and then the ureter.
The nephron is the functional unit of the kidney. The glomerulus and convoluted tubules are located in the kidney cortex, while collecting ducts are located in the pyramids of the medulla. (credit: modification of work by NIDDK)

Renal corpuscle

The renal corpuscle, located in the renal cortex, is made up of a network of capillaries known as the glomerulus and the capsule, a cup-shaped chamber that surrounds it, called the glomerular or Bowman's capsule    .

Renal tubule

The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT)    due to its proximity to the glomerulus. The second part is called the loop of Henle    , because it forms a loop (with descending and ascending limbs ). The third part of the renal tubule is called the distal convoluted tubule (DCT)    . The DCT, which is the last part of the nephron, connects and empties its contents into collecting ducts. The urine will ultimately move into the renal pelvis and then into the ureters.

Capillary network within the nephron

The capillary network that originates from the renal arteries supplies the nephron with blood that needs to be filtered. The branch that enters the glomerulus is called the afferent arteriole    . The branch that exits the glomerulus is called the efferent arteriole    . Within the glomerulus, the network of capillaries is called the glomerular capillary bed. Once the efferent arteriole exits the glomerulus, it forms the peritubular capillary network    , which surrounds and interacts with parts of the renal tubule.

Go to this website to see another section of the kidney and to explore an animation of the workings of nephrons.

Kidney function and physiology

Kidneys filter blood in a three-step process. First, the nephrons filter blood that runs through the capillary network in the glomerulus. Almost all solutes, except for proteins, are filtered out into the glomerulus by a process called glomerular filtration    . Second, the filtrate is collected in the renal tubules. Most of the solutes get reabsorbed in the PCT by a process called tubular reabsorption    . In the loop of Henle, the filtrate continues to exchange solutes and water with the peritubular capillary network. Water is also reabsorbed during this step. Then, additional solutes and wastes are secreted into the kidney tubules during tubular secretion    , which is, in essence, the opposite process to tubular reabsorption. The collecting ducts collect filtrate coming from the nephrons and this filtrate, called urine, will be transported into the renal pelvis and then to the ureters. This entire process is illustrated in [link] .

Questions & Answers

1-chemical level 2-cellular level 3-organ system level 4-tissue level 5-organism level 6-molecules
Dennis Reply
when cell are dead in any part of the body what happen to that place
Dennis Reply
describe the Krebs cycle
Lian Reply
the sequence of reactions by which most living cells generate energy during the process of aerobic respiration. It takes place in the mitochondria, consuming oxygen, producing carbon dioxide and water as waste products, and converting ADP to energy
shea
thanks
Lian
Andy is 1.0 m tall and weighs 45kg Bmi= weight / Height (squared) what's his bmi? Is it high or low?
zafirah Reply
where did our atmosphere came from
Thomas Reply
Our atmospher came from outer space.
R0se
Do mitotic and mitosis mean same?
Abhishek Reply
yes
momo
what are some mechanisms for regulating electrolytes and fluid in the body?
Anita
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Jaheim Reply
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Twayne Reply
what is life?
Suliman Reply
define unit membran model?
Suliman
define unit membran model?
Suliman
different between human being and animals
Habeeb Reply
what is fat soluble drugs
Acho Reply
drugs that dissolve mostly in fatty tissues
shea
what is cell
Sesay Reply
cell is the basic unit of life.
ibtisam
how many double bond present in arachidonic acid?
Rekha
what is the source of the homologous chromosomes and the importance of its event?
Tani Reply
what is biology
Habeeb
bio mean life. logy mean study. so study of life. life is the diffrent between living and non living such as digestion ,respiration, reproduction,movment etc
Suliman
chemical, cellular, tissue, organ, organ system, organisms
Saleema Reply
chemical, tissue, cellular, organ, organism, organ system
Saleema
yes, both parts are apart of the reproductive and endocrine system because they function in both
Saleema
du antigen
gambo
what is antigenic
gambo
how many bones are there in a human
Tih Reply
206
Shivani
206 when they fused together
gambo
206 bones
Kate
206bones
R0se
206
Mahmmad
define ornithology
Aniowo
ornithology is the study of birds in every aspect.
Hemamalene

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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