The Circulatory System

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The Circulatory System

• Prepared by
• Eric Johannesen
• Iowa-Grant High School

2
The Basic Structure of the Heart

• Mammals have a four-chambered heart
• This provides two separate circulatory paths
• Pulmonary Side where blood pumps to the lungs to
  exchange oxygen and carbon dioxide
• Systemic Side where blood is delivered to the
  entire body and delivers oxygen and nutrient rich
  blood to the organs.

3
The Heart

• The heart is located in the chest between the two
  lungs and is contained within a fine membrane
  called the pericardium
• Protects the heart
• The space between the heart and pericardium is
  called the pericardial sac.
• Healthy animals have very little space.

4
The Heart

• The heart is divided into four chambers
• The wall of the heart is mainly composed of
  cardiac muscle called the myocardium

5
Blood Vessels and Blood Flow

• The blood returning from the systemic circulation
  to the heart has delivered oxygen and nutrients
  and picked up carbon dioxide in it travels
• Blood returns to the heart through large vessels
  called the vena cava
• The cranial vena cava brings blood from
  structures in front of the heart and the caudal
  vena cava returns blood from the area behind the
  heart.
• In humans they are called the superior vena cava
  and the inferior vena cava

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Blood Flow
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The Heart Beating
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Tracing Blood Flow Through the Heart

• The blood returning to the heart from the
  systemic circulation to the heart has delivered
  oxygen and nutrients and picked up carbon dioxide
  and other waste products
• Blood returns to the heart through large vessels
  called the vena cava
• The cranial vena cava brings blood from
  structures in front of the heart
• The caudal vena cava brings blood from structures
  behind the heart.

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Tracing Blood Flow Through the Heart

• Blood flows from the vena cava into the right
  atrium
• As the blood fills the right atrium, much of it
  passively leaks to the right ventricle.
• Once the atrium contracts, it forces the
  remainder of the blood to the right ventricle.
• The Right Ventricle has a thicker muscle than the
  right atrium and pumps the blood to the lungs.

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Tracing Blood Flow Through the Heart

• Separating the right ventricle from the right
  atrium is the right atrioventricular valve (AV).
• The valve opens easily as the blood flows to the
  ventricle
• Pressure in the ventricle from the blood
  automatically forces the valve to close.
• The Blood is now pumped out to the lungs

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Tracing Blood Flow Through the Heart

• The Right AV (Atrioventricular Valve) has three
  flaps and is often referred to as a tricuspid
  valve.
• As the right ventricle contracts, the blood flows
  into the pulmonary arteries.
• Arteries carry blood away from the heart.
• In adult animals, pulmonary arteries are the only
  ones that carry oxygen poor blood. Arterial
  blood is usually very dark

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Tracing Blood Flow Through the Heart

• The right ventricle separates from the pulmonary
  arteries by the pulmonary valve.
• The pulmonary valve keeps blood that has entered
  the pulmonary artery from flowing back into the
  heart.
• Arteries branch into smaller arterioles as they
  distribute through the lungs.
• Arterioles branch out into capillaries
• Capillaries are the smallest of vessels
• They are thin walled and have an opening so small
  that only one red blood cells can pass through at
  a time.
• Transfer of nutrients and gasses occur in the
  capillaries.

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Tracing Blood Flow Through the Heart

• The oxygen rich blood then gathers into slightly
  larger venules. These venules join into veins.
• Veins carry blood toward the heart
• The veins join into the main pulmonary veins
  veins that return the blood to the heart.
• The Pulmonary Vein, the only vein in the adult
  animal that carry blood to the heart, enters the
  heart and delivers blood to the left atrium.

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Tracing Blood Flow Through the Heart

• The Left Atrium is very similar to the right.
• As the atrium fills, some of the blood leaks into
  the left ventricle.
• When the atrium is full, it pumps the remainder
  of the blood to the left ventricle.
• The Left Ventricle is the most thick, muscled
  wall chamber of the heart because it has to force
  blood out for systemic circulation.
• The Left ventricle makes up the point of the
  heart called the apex.

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Tracing Blood Flow Through the Heart

• As the ventricles contracts, the left
  atrioventricular valve prevents the blood from
  flowing back into the atrium. This valve is
  sometimes referred to as the bicuspid valve
  because it has two flaps.
• Blood is forced through the large elastic aorta
  by the left ventricle.
• The aortic valve separates the left ventricle
  from the aorta. This prevents blood flow back
  into the heart.
• Coronary arteries deliver blood to the cardiac
  muscle

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Tracing Blood Flow Through the Heart

• Four Branches of the aorta
• Carotid Arteries-Brain and head
• Mesenteric Arteries-Gastrointestinal Tract
• Renal Arteries-Kidneys
• Iliac Arteries-Supplies the Hind Legs