The Human Circulatory System

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The Human Circulatory System
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Introduction

• Humans and other vertebrates have a closed
  circulatory system
• This means that circulating blood is pumped
  through a system of vessels
• This system consists of the heart (pump), series
  of blood vessels and the blood that flows through
  them.

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The Truth About Your Heart
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The Heart

• Located near the center of your chest
• Hollow structure
• Composed almost entirely of muscle
• About the size of your clenched fist

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The Heart

• Enclosed in a protective sac called the
  pericardium

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The Heart

• In the walls of the heart, two layers of tissue
  form a sandwich around a thick layer of muscle
  called the myocardium.
• Contractions of the myocardium pump blood through
  the circulatory system.

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The Heart

• The heart contracts about 72 times per minute
• Pumps about 70mL of blood with each contraction.

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The Heart

• The right and left sides of the heart are
  separated by a septum, or wall.
• The septum prevents the mixing of oxygen rich and
  oxygen poor blood.

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The Heart

• On each side of the septum are two chambers.
• The upper chamber (receives blood) is the atrium.
• The lower chamber (pumps blood out of heart) is
  the ventricle.

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The Heart

• The heart has a total of 4 chambers
• 2 atriums
• 2 ventricles

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Pathway of Blood

• Deoxygenated blood passes from the right atrium
  into the right ventricle and then goes to the
  lungs.
• From the lungs, blood moves back toward the heart
  into the left atrium to the left ventricle and
  then passes into the aorta to go to the rest of
  the body

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Valves

• As the heart contracts, blood flows into the
  ventricles and then out through the ventricles.
• Flaps of connective tissue, called valves, are
  located between the atria and ventricles.
• Blood moving keeps the valves open.
• When the ventricles contract, the valves close
  which prevent blood from flowing back into the
  atria.

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Valves

• There are also valves that stop blood from
  re-entering the ventricles after the blood has
  left.
• This system of valves keeps blood moving in one
  direction which increases the pumping efficiency
  of the heart.

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Heart Beat

• Heart muscles are composed of individual fibers
• Each atrium and ventricle contracts as a unit.
• Each contraction begins with a group of cardiac
  muscle cells in the right atrium known as the
  sinoatrial node (SA node)

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Heart Beat

• Because the SA node paces the heart it is known
  as the pacemaker.
• The impulse spreads from the pacemaker to the
  rest of the atria.
• From the atria, a signal is sent to the
  atrioventricular node and then to a bundle of
  fibers in the ventricle.
• When the ventricle contracts, blood flows out.

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Blood Vessels

• As blood moves through the circulatory system it
  moves through 3 types of blood vessels
• Arteries
• Capillaries
• Veins

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Arteries

• Large vessels
• Carry blood from heart to tissues of body
• Carry oxygen rich blood, with the exception of
  pulmonary arteries.
• Thick walls-need to withstand pressure produced
  when heart pushes blood into them.

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Capillaries

• Smallest blood vessels
• Walls are only one cell thick and very narrow.
• Important for bringing nutrients and oxygen to
  tissues and absorbing CO2 and other waste
  products.

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Veins

• Once blood has passed through the capillary
  systems it must be returned to the heart.
• Done by veins
• Walls contains connective tissue and smooth
  muscle.
• Largest veins contain one way valves that keep
  blood flowing toward heart.
• Many found near skeletal muscles. When muscles
  contract, blood is forced through veins.

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Blood Pressure

• The heart produces pressure
• The force of blood on the wall of the arteries is
  known as blood pressure.
• Blood pressure decreases as the heart relaxes,
  but the rest of the circulatory system is still
  under pressure.

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Blood Pressure

• When blood pressure is taken, the cuff is wrapped
  around the upper portion of the arm and pumped
  with air until blood flow in the artery is
  blocked.
• As the pressure in the cuff is relaxed, 2 numbers
  are recorded.
• Systolic pressure- the first number taken, is the
  force felt in the arteries when the ventricles
  contract.
• Diastolic pressure- the second number taken, is
  the force of the blood on the arteries when the
  ventricles relax.

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Disorders of Circulatory System

• Atherosclerosis
• Fatty deposits (plaque) in walls of arteries
• Deposits can obstruct flow of blood which can
  raise blood pressure
• Increases risk of blood clots
• If clot breaks free it can obstruct blood flow to
  tissues.

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Disorders of Circulatory System

• Heart Attack
• Due to atherosclerosis, coronary arteries may
  become blocked (blood cant get to heart muscle)
• Heart muscle begins to die due to lack of O2

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Disorders of Circulatory System

• Stroke
• Blood clot may break free and block a vessel
  leading to the brain.
• Brain cells are starved of oxygen and nutrients
• Loss of function may occur
• Can cause paralysis, loss of ability to speak or
  death.

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Blood

• Composed of plasma and blood cells
• Types of Cells are
• Red Blood Cells
• White Blood Cells
• Platelets

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Blood

• Plasma
• Straw colored
• 90 water
• 10 dissolved gases, salts, nutrients, enzymes,
  hormones, wastes, and proteins.

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Blood

• Plasma proteins
• 3 Types Albumins, globulins and fibrinogen.
• Albumins and Globulins- transport substances such
  as fatty acids, hormones and vitamins.
• Fibrinogen- Responsible for bloods ability to
  clot

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Blood

• Red Blood Cells
• Most numerous type
• Transport oxygen
• Get color from hemoglobin
• Disk shaped
• Made in red bone marrow
• Circulate for 120 days

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Blood

• White Blood Cells
• Guard against infection, fight parasites, and
  attack bacteria
• Number of WBCs increases when body is fighting
• Lymphocytes produce antibodies which fight
  pathogens and remember them

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Blood

• Platelets
• Aid the body in clotting
• Small fragments
• Stick to edges of broken blood cell and secrete
  clotting factor to help form clot.

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Blood Clotting Problems

• Hemophelia
• Genetic disorder that disrupts clotting
• People must be very careful to avoid injury
• Can be treated by injecting extracts that contain
  the missing clotting factor.