The Urinary Systemdocx

=== The urinary system ===

The urinary system

The urinary system includes the kidneys and urinary tract. The urinary tract is composed of the superior and the inferior tract. The superior urinary tract is formed by the minor and major calyces, renal pelvis and the ureter. The inferior urinary tract is represented by the bladder and urethra.

The main function of the urinary system is excretion.

The kidney

The kidney is a parenchymal, primary retroperitoneal organ, located deep in the lumbo-diaphragmatic region of the abdominal cavity, between T12 and L3 on each side of the vertebral column. The right kidney presents a lower position due to the liver.

The kideney presents an important role in maintaining the body homeostasys and has multiple functions, like:

Excretion, by removing the terminal metabolic products and the foreign products which entered the organism

Keeps the normal oncotic and osmotic pressure, and also the normal acido-basic balance;

Maintaines the normal plasmatic volume by removing the water excess;

Regulates glycemia through gluconeogenesis;

Regulates blood pressure through the production of renin;

Regulates the phospho-calcic metabolism by the secretion of the D3 vitamin.

External configuration of the kidney

The kidney is a bean-shape, paired organ. In normal conditions the surface of the adult kidney is smooth, but sometimes the fetal lobation may persist, this situation being of no clinical significance.

The kidney is brown-reddish in color and its consistency is described as firmly elastic.

Dimensions kidneys vary by age, in adult are:

-height: 10-12 cm

-width: 5-6 cm

-thickness: 2.5-3 cm

The kideney presents for describtion:

2 surfaces: anterior and posterior

2 borders: medial and lateral

2 extremities named poles: superior and inferior.

The surfaces

The anterior surface is convex and antero-laterally orientated.

The posterior surface is flat and postero-medially orientated.

The borders

The medial border is concave and presents the renal hilum. The hilum is vertical slit and presents two lips: anterior and posterior. The hilum is passed by all anatomical elements of the renal pedicle (renal artery, vein and pelvis).

The lateral border is convex and presents a vertical groove which corresponds to an internal region characterized by the absence of large vessels (paucivascular region of Boyce).

The vertical groove on the lateral border is the region to surgical approach the kidney.

The extremities (poles)

Superior pole is round and thick.

Inferior pole is slender.

Relations of the kidney

The left kidney presents a higher position, while the righ is 2-3 cm bellow it due to its relation with the liver.

Anterior relations

The anterior relations are different between the right and the left kidney. The perirenal fat and the anterior sheath of the renal fascia interposes anterior to the kidneys.

In the right kidney, the anterior relations are:

Medial: descending part of the duodenum (DII), through the coalescing fascia of Treitz;

Lateral: from superior to inferior with:

Right suprarenal gland;

Right lobe of the liver;

Right colic flexure, through the coalescing fascia of Toldt I;

Root of the transverse mesocolon;

Ileal loops.

In the left kidney, the anterior relations are:

Superior, from medial to lateral with:

Left suprarenal gland;

Posterior surface of the stomach, through the omental bursa;

Spleen (visceral surface).

In the middle, with:

Posterior surface of the body of the pancreas;

Splenic artery, vein and lymph nodes;

The root of the transverse mesocolon.

Inferior, with:

Medial: jejunal loops

Lateral: left colic flexure and descending colon, through the coalescing fascia of Toldt II.

Figure . The anterior relations of the kidneys. (sarasotakidney.com)

Posterior relations

The posterior relations are similar in both kidneys, eventhough the right kidney is located 2-3 cm bellow the left kidney. The posterior sheath of the renal fascia and the pararenal fat of Gerota interposes betwee the posterior surface of the kidney and the posterior abdominal wall.

The posterior surface is related with the medial and lateral arcuate ligaments of the diaphragm, which divides the posterior surface in 2 regions:

Superior (thoracic) part, related to the diaphragm.

Inferior (abdominal) part, related to the posterior abdominal wall.

Relations of the superior (thoracic) part:

Lumbar part of the diaphragm;

11 and 12 rib (11 rib only in the left kidney);

Costodiaphragmatic pleural recess.

Relations of the inferior (abdominal) part:

Pararenal fat of Gerota;

Subcostal vessels and nerves;

Iliohypogastric nerve;

Ilioinguinal nerve;

Lumbar vessels;

Deep layer of the posterior abdominal wall:

Medial: psoas major m.

Middle: quadratus lumborum m.

Lateral: transversal abdominal m.

The kidney relation with these nerves explains how the renal pain is reffered to the cutaneous regions innervated by the nerves: hypogastric region and external genital organs.

Figure . The posterior relations of the kidney. (sarasotakidney.com)