Kidneys
The kidneys are organs which form part of our body’s excretory system. They’re
primarily responsible for waste removal (excretory) as well as the regulation of water
and electrolyte concentrations within the body (osmoregulation). The kidneys are
located on either side of the spine, beneath the ribs
Function of the Components
Renal artery
Blood vessels which carry oxygenated blood from the heart, to the
kidney for filtration
Renal vein
Blood vessel which carries filtrated blood from the kidneys, back to the
heart
Renal Capsule
A thin, fibrous membrane covering the outer surface of the kidneys
Renal cortex
The renal cortex is the outer layer of the kidneys. It is a functional tissue
containing the glomerulus, distal proximal tubules, and distal convoluted
tubules of the nephrons
Renal Medulla
The renal medulla is the smooth, inner layer of tissue in the kidneys. It
contains the Loop of Henle and the collecting ducts of the nephrons
Renal pyramids
The tissue of the medulla is constituted of cone-shaped sections of tissue
called the renal pyramids
Pelvis
As the nephrons in the renal cortex and medulla filter the blood entering
the kidney, they remove wastes and toxins which is removed from the
body in the form of urine
The pelvis is a cavity in the centre of the kidney into which urine is
directed as it is produced by the nephrons
Ureter
Tube consists of smooth muscle which carries urine from the kidney to
the bladder, where it is stored prior to excretion. The pelvis empties into
the ureter
Nephrons
Waste in the Human
Body
During the process of digestion (breaking down proteins) we form smaller
molecules such as carbon, hydrogen and oxygen and the nitrogen
component of these proteins are used for amino acids and proteins
However if we have too much of this it is called nitrogenous waste
Which has to be excreted from the body because it forms ammonia
(increased blood pH and disturb homeostasis)
In the human body we convert ammonia to a different form called urea
We excrete urea by urine which is formed by the nephrons
-​ Urine is also formed by chemical waste product such as drugs,
excess quantities of water and salt
Functional Units
Transport of molecules
Nephrons are the functional units (smallest elements) of the kidney
They are microscopic structures responsible for:
●​ Filtration: movement of water and solute molecules from the blood
into the nephrons
●​ Reabsorption: movement of water and essential solutes from the
nephron back into the blood of the capillaries adjacent to the
nephrons
●​ Secretion: active transport of nitrogenous wastes, toxins, drugs
and excess ions from blood of adjacent capillaries into nephron
tubules
Active transport: movement of substances against the concentration
gradient which requires the input of energy
Passive transport: movement of substances along the concentration
gradient which does not require the input energy
Structure