Chapter A1.2 Human Body Systems

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Chapter A1.2 Human Body Systems
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The Circulatory System

• The circulatory system transports oxygen,
  nutrients, and wastes through the body in the
  blood.
• The liquid part of the blood, called plasma, is
  mostly water.
• Plasma also contains dissolved nutrients and
  waste products.
• The waste product in blood is what we call carbon
  dioxide.

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• The solid part of blood contains red blood cells
  and white blood cells.
• Red blood cells absorb oxygen and deliver it to
  the organs.
• White blood cells help the body fight infection.
  They attack and destroy the germs and viruses and
  bacteria that enter the body.

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• Blood also contains platelets tiny pieces of
  blood cells inside membranes.
• Platelets cause blood cells to clot when a cut or
  open wound occurs.
• They also repair damage to your blood vessels.
• The heart pumps blood through blood vessels. The
  oxygen rich blood flows through the body through
  arteries, and returns to the heart and lungs
  through veins.

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• Capillaries- are blood vessels so small that the
  red blood cells have to travel through single
  file.
• There are capillaries throughout the body so that
  oxygen can reach every part of your body.

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The Respiratory System

• When you breathe, you draw air into your lungs.
• The air is filtered by tiny hairs inside your
  nose and warmed by capillaries.
• The warmed air then travels down your trachea, or
  windpipe.
• The trachea branches into smaller tubes called
  bronchi.

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• Each bronchi tube leads to one of the lungs.
• In the lungs, the tubes divide smaller and
  smaller.
• At the end of the smallest tubes, there are tiny
  air sacs called alveoli.
• The walls of the alveoli are only one cell thick.
• The blood coming from the heart contains much
  carbon dioxide.

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• Carbon dioxide diffuses through the walls of the
  alveoli and then into the air you will breathe
  out.
• When you breathe in, the air diffuses through the
  alveoli and into the red blood cells. The oxygen
  rich blood then flows back to the heart. The
  heart then pumps the oxygenated blood
  throughout your body.

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The Digestive System

• Digestion starts as soon as you chew your food.
  Your chewing breaks the food into smaller pieces
  and mixes with your saliva.
• Saliva moistens the food and begins to break down
  the starchy foods into sugars.
• When you swallow, food goes through your
  esophagus, a long tube from your mouth to your
  stomach.

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• Juices in your stomach containing acid and other
  chemicals break down the proteins.
• After several hours in your stomach, the digested
  food moves into your small intestine.
• In the small intestine, more chemicals break down
  the food. Nutrients from the food are now able
  to diffuse through the villi, tiny finger like
  structures, into the blood.

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• Undigested food then travels to the large
  intestine, where water and minerals pass into the
  blood, and non-needed material are removed from
  the body.
• Two other organs aid in digestion. The liver
  produces bile, which is stored in the gallbladder
  until you need it. The pancreas produces a fluid
  that calms stomach acid and other chemicals that
  help complete digestion.

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The Excretory System

• The waste left over from the circulatory system
  must be removed from the blood. The food
  material not used by the body must be removed
  from the intestine. This is the job of the
  excretory system.
• Cell wastes include carbon dioxide and ammonia.
• Ammonia travels to the liver where it is
  converted into urea.

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• The urea then travels by way of the blood to the
  kidneys.
• The urea, water and other wastes then form urine
  and it flows from the kidney to the bladder
  through tubes called ureters.
• You empty the bladder when it is full through a
  tube called the urethra.

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• The body gets rid of wastes in other ways too.
  When you exercise you get warm and sweat. Sweat
  is a salty liquid that cools your body when it
  evaporates.