Question

outline the structure of the kidney, limited to the cortex, medulla and ureter

Answer 1

Location and External Anatomy of the Kidneys

The kidneys are located at the rear wall of the abdominal cavity and they are protected by the ribcage

Key Points

 The kidneys lie in the lower abdominal cavity, on its rear wall.Adhering to the surface of each kidney are two layers of fat to help cushion them.The kidneys are located at the rear wall of the abdominal cavity just above the waistline and are protected by the ribcage. They are considered retroperitoneal, which means that they lie behind the peritoneum.The renal artery connects the kidneys to the aorta, while the renal vein connects the kidneys to the inferior vena cava.The adrenal glands lie superior to the kidneys.

Key Terms

adrenal gland: Two glands that are responsible for releasing hormones in response to stress, such as catecholamines, and that also produce aldosterone, a renal system hormone.

The Kidneys

The kidneys are the primary functional organ of the renal system. They are essential in homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and the regulation of blood pressure (by maintaining salt and water balance). They serve the body as a natural filter of the blood and remove wastes that are excreted through the urine. 

They are also responsible for the reabsorption of water, glucose, and amino acids, and will maintain the balance of these molecules in the body. In addition, the kidneys produce hormones including calcitriol, erythropoietin, and the enzyme renin, which are involved in renal and hemotological physiological processes.

Anatomical Location

The kidneys are a pair of bean-shaped, brown organs about the size of your fist. They are covered by the renal capsule, which is a tough capsule of fibrous connective tissue. Adhering to the surface of each kidney are two layers of fat to help cushion them. 

The asymmetry within the abdominal cavity caused by the liver typically results in the right kidney being slightly lower than the left, and left kidney being located slightly more medial than the right. The right kidney sits just below the diaphragm and posterior to the liver, the left below the diaphragm and posterior to the spleen.



The kidneys: Human kidneys viewed from behind with the spine removed.

Resting on top of each kidney is an adrenal gland (adrenal meaning on top of renal), which are involved in some renal system processes despite being a primarily endocrine organ. The upper parts of the kidneys are partially protected by lower ribs, and each whole kidney and adrenal gland are surrounded by two layers of fat (the perirenal and pararenal fat) and the renal fascia. 

The kidneys are located at the rear wall of the abdominal cavity just above the waistline and are protected by the ribcage. They are considered retroperitoneal, which means that they lie behind the peritoneum, the membrane lining of the abdominal cavity. 

There are a number of important external structures connecting the kidneys to the rest of the body. The renal artery branches off from the lower part of the aorta and provides the blood supply to the kidneys. Renal veins take blood away from the kidneys into the inferior vena cava. The ureters are structures that come out of the kidneys, bringing urine downward into the bladder.

Internal Anatomy of the Kidneys

The cortex and medulla make up two of the internal layers of a kidney and are composed of individual filtering units known as nephron.



Key Terms

renal medulla: The inner-most region of the kidney, arranged into pyramid-like structures, that consists of the bulk of nephron structure.renal cortex: The outer region of the kidney, between the renal capsule and the renal medulla, that consists of a space that contains blood vessels that connect to the nephrons.nephron: The basic structural and functional unit of the kidney that filters the blood in order to regulate chemical concentrations and produce urine.

Kidney structure: The kidney is made up of three main areas: the outer cortex, a medulla in the middle, and the renal pelvis.

Renal Medulla

The medulla is the inner region of the parenchyma of the kidney.
The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are triangle structures that contain a dense network of nephrons.

At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman’s capsule. It surrounds a tuft of capillaries called the glomerulus that carries blood from the renal arteries into the nephron, where plasma is filtered through the capsule. 

After entering the capsule, the filtered fluid flows along the proximal convoluted tubule to the loop of Henle and then to the distal convoluted tubule and the collecting ducts, which flow into the ureter. Each of the different components of the nephrons are selectively permeable to different molecules, and enable the complex regulation of water and ion concentrations in the body.