The Excretory System
~Notes~
Introduction:
The excretory system, sometimes referred to as the urinary system, is in charge of eliminating excess
substances and waste items from the blood in order to preserve the internal balance of the body. It is
essential for maintaining electrolyte and fluid balance as well as for getting rid of metabolic waste.
Main Components of the Excretory System:
1. Kidneys
○ Structure:
■ Location: Situated on either side of the spine retroperitoneally, or behind the
peritoneum.
■ Shape: Bean-shaped organs, about 10-12 cm long.
■ Parts:
■ Cortex: Outer region of the kidney.
■ Medulla: Inner region, consisting of renal pyramids.
■ Renal Pelvis: Funnel-shaped structure that collects urine from the
renal pyramids.
○ Function:
■ Filtration: Excess and waste materials are taken out of the blood.
■ Reabsorption: The body absorbs water and vital nutrients back into the
bloodstream.
■ Secretion: Additional waste products are secreted into the urine.
2. Nephrons
○ Structure: The kidneys' functioning units, each containing roughly a million nephrons.
○ Renal Corpuscle: Includes the glomerulus (a network of capillaries) and Bowman's
capsule (a cup-like structure that collects filtrate).
■ Renal Tubule: Consists of the proximal convoluted tubule (PCT), loop of Henle,
distal convoluted tubule (DCT), and connecting tubule.
○ Function:
■ Glomerular Filtration: Blood pressure forces water and solutes from the blood
into the Bowman's capsule.
■ Tubular Reabsorption: Selective reabsorption of water, ions, and nutrients
from the filtrate back into the blood.
■ Tubular Secretion: Additional substances are secreted from the blood into the
tubules for excretion.
~Notes~
Introduction:
The excretory system, sometimes referred to as the urinary system, is in charge of eliminating excess
substances and waste items from the blood in order to preserve the internal balance of the body. It is
essential for maintaining electrolyte and fluid balance as well as for getting rid of metabolic waste.
Main Components of the Excretory System:
1. Kidneys
○ Structure:
■ Location: Situated on either side of the spine retroperitoneally, or behind the
peritoneum.
■ Shape: Bean-shaped organs, about 10-12 cm long.
■ Parts:
■ Cortex: Outer region of the kidney.
■ Medulla: Inner region, consisting of renal pyramids.
■ Renal Pelvis: Funnel-shaped structure that collects urine from the
renal pyramids.
○ Function:
■ Filtration: Excess and waste materials are taken out of the blood.
■ Reabsorption: The body absorbs water and vital nutrients back into the
bloodstream.
■ Secretion: Additional waste products are secreted into the urine.
2. Nephrons
○ Structure: The kidneys' functioning units, each containing roughly a million nephrons.
○ Renal Corpuscle: Includes the glomerulus (a network of capillaries) and Bowman's
capsule (a cup-like structure that collects filtrate).
■ Renal Tubule: Consists of the proximal convoluted tubule (PCT), loop of Henle,
distal convoluted tubule (DCT), and connecting tubule.
○ Function:
■ Glomerular Filtration: Blood pressure forces water and solutes from the blood
into the Bowman's capsule.
■ Tubular Reabsorption: Selective reabsorption of water, ions, and nutrients
from the filtrate back into the blood.
■ Tubular Secretion: Additional substances are secreted from the blood into the
tubules for excretion.
