Anatomy of kidney | What is kidney | Anatomy of kidney blood supply | Medical World

ANATOMY OF KIDNEY | They are two bean-shaped, reddish-brown organs within the abdomen situated on the posterior abdominal wall.

   They are the major excretory organ and remove the waste products of protein metabolism and excess of water and salts from the blood and are thus essential for maintaining the electrolyte and water balance in the tissue fluids of the body, necessary for survival

 LOCATION

The kidneys lie on the posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum, opposite 12th thoracic and upper  three lumber.

SHAPE AND MEASUREMENTS OF KIDNEY

Shape -  Bean shaped.

Measurements: 

Length -  11 cm 

Width  -  6 cm 

Thickness  -  3cm (anteroposterior)

Weight. -   150 g in males 

                    135 g in females.

      EXTERNAL FEATURES OF KIDNEY

Each kidneys presents the following external features:

1-). Two poles (Superior and inferior)

2-). Two surfaces (anterior and posterior)

3-).  Two borders (medial and lateral)

4-).   A hilum 

POLES  OF KIDNEY

1-). The superior (upper) pole is thick  and round and lies nearer to the median plane than the inferior pole. It is related to the suprarenal gland.

2.).   The inferior (lower) pole is thin and pointed and lies 2.5cm above the iliac crest.

SURFACES  OF KIDNEY

1.) Anterior Surface : it is convex and faces anterolaterally. 

2.) Posterior Surface : it is flat and posteromedially

BORDERS OF KIDNEY

1.) Medial border - it is convex above and below near the poles and concave in the middle. It slopes downward and laterally, and presents a vertical fissure in its middle part called  hilum which has anterior and posterior lips.

2.)  Lateral border - lateral border of each kidney is convex. 

HILUM  OF KIDNEY

The medial border of they kidney presents a deep vertical slit called hilum.

It consist of the following structure:

1-  Right suprarenal gland 

2-  Right lobe of the liver 

3-   Second part of the duodenum

MACROSCOPIC STRUCTURE OF KIDNEY

When the kidney is slit longitudinally, it presents the kidney proper and the renal sinus.

KIDNEY PROPER

The naked eye examination of the kidney proper presents an outer cortex and an inner medulla. The Cortex is located just below the renal capsule and extends between the renal pyramids as renal column.

The Medulla is composed of 5-11 dark conical masses called Renal pyramids

RENAL SINUS

It is a cavity of considerable size present within the kidney. It takes up a large part of the interior of the kidney and opens at the medial border of the kidney as hilum.

1-  Greater part of the renal pelvis, major and minor calyces

2-  Renal vessels , lymphatic and nerves.

3-   Fat

  MICROSCOPIC STRUCTURE OF KIDNEY

Each kidney consists of 1 to 3 million of tubules , it consists of two components: nephron and collecting tubule .

1-). The nephron is the structural and functional units of kidney. The number of nephron in each kidney is about 1-3 million . Each nephron consists of a glomerulus and a tubule system. The glomerulus is a tuft of capillaries surrounded by Bowman's  capsule. The tubular system consists of the proximal convoluted tubule, loop of henle and distal convoluted tubule. 

2-).  Each collecting tubule begins as a junctional tubule from the distal convoluted tubule. Many collecting tubule unite    together to form collecting duct which opens on the apex of renal papilla The collecting tubules radiate from the renal pyramid into the cortical region to form radial striation called Medullary rays.

ANATOMY OF KIDNEY BLOOD SUPPLY

ARTERIAL SUPPLY

The kidneys are supplied by the renal arteries. Usually there is one renal artery for each kidney, but in about 30% individuals accessary renal arteries are also found. They commonly arise from the aorta and enter the kidney at the hilum or at one of its poles, usually the lower pole . The  renal arteries have a good flow in excess of 1L/minute.

    VENOUS DRAINAGE     

The venous blood from the kidneys is drained by the renal veins. The left renal vein passes in front of the aorta immediately below the origin of the inferior mesenteric artery .

    LYMPHATIC DRAINAGE                                       

                                                       

The lymphatic from kidney drain into the para-aorta lymph nodes at the level of origin of the renal arteries.

NERVE SUPPLY     

Each kidney is supplied by the renal plexus of nerves which reach the kidney along the renal artery. The renal plexus consist  of both sympathetic  and parasympathetic fibres. 

The sympathetic fibres are drived  from T10-L1 spinal segments and parasympathetic fibres are drived from both vagus nerves.