KIDNEYS

KIDNEYS(disambiguation)

-principal excretory organ of the body

- functions such as the regulation of electrolytes, maintenance of acid–base balance, and regulation

of blood pressure

LOCATION OF KIDNEYS

• The kidneys lie on either side of the vertebral column in a depression high on the posterior wall

of the abdominal cavity.

• The upper and lower borders of the kidneys are generally at the levels of the twelfth thoracic

and third lumbar vertebrae, respectively.

STRUCTURE OF KIDNEYS

The superior end of the ureter is expanded to

form a funnel-shaped sac called the renal pelvis, which

is located inside the renal sinus. The pelvis is subdivided

into two or three tubes, called major

calyces (sing., calyx), and they, in turn, are subdivided

into several minor calyces.

A series of small elevations project into the

renal sinus from its wall. These projections are

called renal papillae, and each is pierced by tiny

openings that lead into a minor calyx.

The substance of the kidney includes two

distinct regions - an inner medulla and an outer cortex.

The renal medulla is composed of conical masses of

tissue called renal pyramids.

The renal cortex, which appears somewhat

granular in a sectioned kidney, forms a shell around the

medulla. Its tissue dips into the medulla between

adjacent renal pyramids, forming renal columns. The

granular appearance of the cortex is due to the random

arrangement of tiny tubules associated with

the nephrons, the functional units of the kidney.

FUNCTIONS OF KIDNEYS

• The kidney remove metabolic wastes from the blood and excrete them to the outside. They also

carry on a variety of equally important regulatory activities, including helping control the rate of

red blood cell formation by secreting the hormone erythropoietin and helping regulate the

blood pressure by secreting the enzyme renin.

• The kidneys also help regulate the volume, composition, and pH of the body fluids. These

function involve complex mechanisms that lead to the formation of urine.

Renal Blood Vessels

• A renal artery enters a kidney through the hilum and gives off several branches, called

the interlobar arteries, which pass between the renal pyramids. At the junction between the

medulla and cortex, the interlobar arteries branch to form a series of incomplete arches, the

arcuate arteries which, in turn, give rise to interlobular arteries. The lateral branches of the

interlobular arteries, called afferent arterioles, lead to the nephrons, which are functional units

of the kidneys.

• Venous blood is returned through a series of vessels that correspond generally to the arterial

pathways. The renal vein then joins the inferior vena cava as it courses through the abdominal

cavity.

Nephrons

-basic structural and functional unit of the kidney.

- chief function is to regulate the concentration of water and soluble

substances like sodium salts by filtering the blood, reabsorbing what is

needed and excreting the rest as urine

Blood Supply of a Nephron