Cardio-Respiratory System

• The circulatory system is also known as the

  cardiovascular system.

  It consists of the heart, blood vessels, and blood.

  It transports oxygen and nutrients to the body cells, and

  carbon dioxide and wastes away from the body cells.
• The heart is a hollow, muscular organ that weighs

  about 1 pound and is about the size of your closed

  fist.

  It contracts about 100,000 times each day to pump

  the equivalent of 7,500 liters of blood through the

  body.

  How does it keep going?

  Cardiac muscle tissue can work continuously without

  becoming tired.
• The heart is divided into a right side and a left side,

  and these are kept separated by the septum.

  The septum is a muscular wall that prevents blood

  from moving between the right and left sides
• The heart is divided into four parts, or chambers.

  The two upper chambers are called atria, and the two

  lower chambers are called ventricles.

  One-way valves in the chambers of the heart keep

  the blood flowing in the right direction.
• The right atrium receives blood as it returns from

  the body cells.

  The right ventricle receives blood from the right

  atrium and pumps the blood to the lungs for

  oxygen.

  The left atrium receives oxygenated blood from the

  lungs.

  The left ventricle receives blood from the left

  atrium and pumps the blood back to the body cells.
• The heartbeat consists of two contractions: the first

  takes place in the atria and the second in the

  ventricles.

  The first contraction of the heart begins in the right

  atrium at a signal from the sinoatrial (SA) node.

  This node is known as the heart’s pacemaker because it

  generates an electrical signal that starts the

  contractions.
• Once the atria have contracted, the electrical signal

  spreads to the atrioventricular (AV) node, located

  in the right ventricle.

  This stimulates both ventricles to contract at the same

  time.
• Blood always enters the heart through an

  atrium and leaves the heart through a ventricle.
• Oxygen-poor blood from the body enters the right

  atrium. The SA node signals the atria to contract,

  and blood flows into the right ventricle.
• When the AV node signals the ventricles to

  contract, blood is pumped from the right ventricle

  into the pulmonary artery.

  This artery goes to the lungs

  The blood enters the lungs, where CO2 diffuse into

  the lungs and O2 diffuses into the blood.
• Oxygen-rich blood returns to the heart through

  the pulmonary vein and enters the left atrium.

  As the atria contract, blood is pumped into the left

  ventricle, the largest chamber in the heart.
• When the ventricles contract, blood is pumped

  from the left ventricle into a large artery called

  the aorta, and is circulated to the rest of the body.

  After oxygen is delivered to the cells, oxygen-poor

  blood returns to the heart and the cycle begins

  again.
• The heart pumps blood

  through two main pathways

  that meet at the heart.

  These pathways are called

  the pulmonary and systemic

  circulation. All of your

  blood travels through both of

  these pathways.
• Pulmonary Circulation occurs only between the

  heart and the lungs.

  The main function is to expel carbon dioxide, pick

  up oxygen, and carry it back to the heart.
• Systemic circulation occurs between the heart and

  the rest of the body, except for the lungs.

  The main function of this circulation is to carry

  oxygen-rich blood to all cells and transport

  oxygen-poor blood back to the heart.
• As the body’s need for oxygen changes, sensors in

  the walls of major arteries in both pathways send

  information to the brain stem.

  Homeostasis is maintained by matching heart rate and

  respiration rate with the oxygen needs of the body.
• Almost every winter, people are killed by carbon

  monoxide (CO) gas in their homes.

  This odorless gas escapes from leaks in furnaces

  Your body readily absorbs it into the blood, which

  means less oxygen is absorbed

  In a short time, your cells become oxygen starved
• The cells in your body carry out cellular

  respiration, which requires O2 and produces CO2 as

  a waste product.

  Every cell in the body needs O2 and must get rid of

  CO2.

  Therefore, the lungs bring in a steady supply of O2 and

  expel excess CO2.
• Gas exchange in the lungs is based on three

  principles:

  O2 and CO2 are carried by the blood.

  Gases move by diffusion – that is, they move from an

  area of higher concentration to an area of lower

  concentration.

  The lining of the alveoli must be moist to help gases

  diffuse.
• The nose and mouth are the entry points.

  At the back of the throat, a small piece of tissue

  called the epiglottis regulates airflow into the

  trachea.

  The trachea is a long structure that looks like the

  hose of a vacuum cleaner. It divides into two

  bronchi, with one branch going into each lung.
• The lungs are the organs that absorb O2 from the air

  you inhale.

  Inside the lungs, the bronchi divide into smaller and

  smaller branches that resemble the limbs and twigs of a

  tree.

  The smallest branches end in clusters of tiny air sacs

  called alveoli. There are 300 to 600 million alveoli in

  your lungs!
• In the alveoli, the respiratory and circulatory

  systems come together in the process of gas

  exchange.

  When you inhale, air flows from the bronchi to the

  alveoli.

  Each alveoli is about the size of a grain of sand

  Without this huge area for gas exchange, the lungs

  would be unable to extract enough O2 from the air to

  keep you alive.
• A complex network of capillaries surrounds and

  penetrates the alveoli.

  Recall: Capillaries are the tiny blood vessels that

  transport blood to and from the cells of the body.

  Blood entering the capillaries is oxygen-poor. As a

  result, O2 diffuses from the alveoli to the

  capillaries. Blood leaving the capillaries is

  oxygen-rich.

  In contrast, CO2 diffuses from the capillaries to the

  alveoli.

  The CO2 is exhaled from our bodies
• Your brain stem monitors O2 and CO2

  concentrations in your blood.

  As you become more active, CO2 levels increase and

  your blood becomes more acidic.

  Your brain sends messages to stimulate your

  diaphragm and rib cage muscles to work harder.
• Damage to the respiratory system makes gas

  exchange more difficult, which in turn affects every

  cell in the body.

  Smoking is the leading cause of respiratory

  diseases such as lung cancer and emphysema.

  Cigarette smoke contains more than 4800 chemicals

  that can damage alveoli and cause genetic mutations

  leading to cancer.
• Emphysema is a lung disorder caused mainly by

  smoking. Over time, many alveoli are destroyed.

  This gradually reduces the surface area for gas

  exchange, and not enough oxygen can enter the blood.

  Eventually the lungs fail
• Asthma causes the bronchi to constrict due to

  muscle spasms.

  This makes it hard to move air in and out of the

  lungs.

  A person having a severe asthma attack can die from

  lack of oxygen.

  Attacks can be triggered by allergies, stress, exposure

  to smoke and chemicals, or exercise.