Human Biology

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Chapter 7

• Human Biology
• Seventh Edition
• Mader
• (c) The McGraw-Hill Companies, Inc.

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The Blood Vessels

• The Arteries
• Arteries and arterioles take blood away from the
  heart. The middle layer of arteries consists of
  smooth muscle that can constrict to regulate
  blood flow and blood pressure.
• The Capillaries
• The capillaries with walls that are only one cell
  thick allow the exchange of substances with
  tissue fluid.
• The Veins
• Venules drain into veins that take blood to the
  heart.

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The Heart

• The cone-shaped, muscular heart is made up of
  myocardium lying inside a fibrous pericardium.
  Coronary arteries supply the myocardium with
  oxygen and nutrients. The right and left atria
  empty into the right and left ventricles
  respectively. Atrioventricular valves occur
  between the atria and ventricles and semilunar
  valves occur between the ventricles and the
  attached arteries.

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Passage of Blood Through the Heart

• This sequence traces the path of blood through
  the heart superior and inferior vena cava, right
  atrium, right ventricle, pulmonary arteries to
  the lungs. Pulmonary veins, left atrium, left
  ventricle, aorta.

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The Heartbeat

• Each heartbeat is called a cardiac cycle.
  Systole refers to the contraction of the heart
  chamber and diastole refers to the relaxation.
  The heart sounds, lub-dup, are due to the closing
  of the atrioventricular valves, followed by the
  closing of the semilunar valves. The surge of
  blood entering the arteries results in your pulse.

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The Electrocardiogram

• An electrocardiogram (ECG) is a recording of the
  electrical changes that occur in myocardium
  during a cardiac cycle.

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Pulse

• The surge of blood entering the arteries
  following a heart beat causes their elastic walls
  to stretch and then recoil. This is felt as a
  pulse. The pulse rate of the radial and carotid
  artery are most often used to tell the heartbeat
  rate.

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