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197
Lesson 1: Physical and Chemical Changes in Digestion
The Excretory System
The daily activities of cells include chemical reactions that require energy from food.
Chemical waste products are formed as a result of these activities and are moved
out of the cells and into the blood. In order to maintain a balance in the body, the
blood must be cleaned of these waste products. The kidneys are the main organs of
the excretory system.
Figure 5.2. The Excretory System
kidney
ureter
urinary bladder
urethra
The kidneys are bean-shaped organs that act as the main blood filters of the body.
More than a quart of blood is cleaned every minute as blood passes through the
filtering structures of the kidneys. Tiny tubelike structures called nephrons filter out
waste materials and extra fluid from the blood. This liquid is sent to the bladder to be
stored until it is released as urine.
Figure 5.3. The Kidney
renal vein
renal artery
nephrons
197
Lesson 1: Physical and Chemical Changes in Digestion
The Excretory System
The daily activities of cells include chemical reactions that require energy from food.
Chemical waste products are formed as a result of these activities and are moved
out of the cells and into the blood. In order to maintain a balance in the body, the
blood must be cleaned of these waste products. The kidneys are the main organs of
the excretory system.
Figure 5.2. The Excretory System
kidney
ureter
urinary bladder
urethra
The kidneys are bean-shaped organs that act as the main blood filters of the body.
More than a quart of blood is cleaned every minute as blood passes through the
filtering structures of the kidneys. Tiny tubelike structures called nephrons filter out
waste materials and extra fluid from the blood. This liquid is sent to the bladder to be
stored until it is released as urine.
Figure 5.3. The Kidney
renal vein
renal artery
nephrons
