Download Chapter 47 – The Circulatory and Respiratory Systems

Chapter 47 – The Circulatory and Respiratory Systems
THE CIRCULATORY SYSTEM
Most of the cells in the human body are not in direct contact
with the external environment. The circulatory system acts as
a transport service for these cells. Two fluids move through
the circulatory system: blood and lymph. The blood, heart,
and blood vessels form the cardiovascular system. The
lymph, lymph nodes, and lymph vessels form the lymphatic
system. The cardiovascular system and lymphatic system
collectively make up the circulatory system.
The Heart
- Is the central organ of the cardiovascular system
- It beats more than 2.5 billion times in one lifespan.
- It is surrounded by a tough membrane called the pericardium
o Used to reduce friction
- it is divided vertically in half by the septum.
o The right side of the heart pumps blood to the lungs; the left side
pumps blood to the rest of the body.
- there are upper and lower parts to the heart. The upper parts are the
atria, the lower parts are the ventricles.
o The atrioventricular valves (AV) separate the atria from the
ventricles.
 The mitral valve (bicuspid) separates the left side.
 The tricuspid valve separates the right side.
 These both prevent blood from flowing back into the
atria when blood is being pumped.
- The semilunar (SL) valves prevent backflow of blood back into the
ventricles.
o The SL valve on the right side is called the pulmonary valve.
o The SL valve on the left side is called the aortic valve.
The Flow of Blood
The right atrium  the right ventricle  the pulmonary arteries  lungs  the
left atrium  the left ventricle  the aorta  the body  the vena cava.
Control of the Heartbeat
- done by the sinoatrial (SA) node (aka the pacemaker).
o The electrical impulses of the SA node reach the AV node, which in
turn causes the ventricles to contract, slightly after the atria.
- the heartbeat has 2 phases: systole and diastole.
o Phase one, systole, occurs when the ventricles contract , which
closes the AV valves and opens the SL valves.
o Phase two, diastole, occurs when the ventricles relax, closing the
SL valves and opening the AV valves.
 If one valve fails to close properly, you develop what is
known as a heart murmur.
Blood Vessels
- the circulatory system is a closed system because blood is contained
within the heart or blood vessels all of the time.
- The largest blood vessels are the arteries.
o They have 3 layers: an inner endothelial layer, a middle smooth
muscle layer, and an outer connective tissue layer. These give
arteries their strength.
 The stretching of your arteries is known as your pulse.
 The force with which the blood moves through blood vessels
is known as your blood pressure.
 Systolic pressure is caused by blood overcoming the
pressure exerted by the cuff, which means that some
blood has flowed through the artery.
 Diastolic pressure is caused by blood continuously
flowing through the artery.
o High blood pressure is known as hypertension.
- Arteries turn into smaller blood vessels called arterioles.
- Arterioles branch into capillaries.
o Capillaries are the site of gas and nutrient exchange.
- capillaries merge into thicker blood vessels called venules.
- Venules form veins.
o The inferior vena cava returns deoxygenated blood to the heart
from the bottom of the body.
o The superior vena cava returns deoxygenated blood to the heart
from the upper part of the body.
Patterns of Circulation
- there are 2 types of blood circulation: pulmonary and systemic.
o Pulmonary circulation is when blood travels between the heart and
the lungs.
 Note: the pulmonary vein carries oxygenated blood into the
left atrium of the heart.
o Systemic circulation is when blood travels between the heart and
the rest of the body (not the lungs).
 Coronary circulation is blood flow through the heart only and
is a subdivision of systemic circulation.
 Artherosclerosis is a condition in which a blood vessel
is blocked, thus impeding blood flow through the
heart, and usually leads to a heart attack.
 Renal circulation is a type of systemic circulation that is
characterized by blood flow to the kidneys.

Hepatic portal circulation is a type of systemic circulation in
which nutrients are absorbed in the small intestine and are
transported to the liver for storage
Lymphatic Circulation
Lymph -a clear yellowish, slightly alkaline, coagulable fluid, containing white
blood cells in a liquid resembling blood plasma, that is derived from the tissues of
the body and conveyed to the bloodstream by the lymphatic vessels.
- lymph vessels form a one-way system which transports excess lymphatic
fluid back into the bloodstream and moves when skeletal muscles
contract.
- As lymph moves through the body, it passes through lymph nodes, which
filter out impurities in the lymph before they reach the heart.
o Lymphocytes are WBCs which are stored in the lymph nodes and
will fight off bacteria and viruses.
Composition of Blood
- A healthy adult has about 4-5L of blood in their body.
- Plasma is the liquid medium. It contains dissolved minerals and protein
that nourish cells. It also carries waste products to the kidney for removal.
o Proteins – albumin, blood clotting factors, antibodies.
- RBCs (aka erythrocytes). Contains hemoglobin, which carries oxygen to
the body (and sometimes CO2).
o Mature RBCs don’t have a nucleus.
o They are replaced every 120-130 days.
- WBCs (aka leukocytes). Help defend the body against diseases. They
are capable of changing shape in order to reach the site of infection.
o Phagocytes
o Antibodies
- Platelets. Form blood clots using fibrin, which is a sticky substance that
forms a net to capture RBCs so that a clot (scab) will form.
Blood Types
- A, B, O, AB and the Rh factor.
o Erythroblastosis fetalis.
The Lungs
- are the site of gas exchange.
- The left lung has 2 lobes, the right lung has 3.
The Flow of Air
Mouth/nose  pharynx (protected by the epiglottis)  trachea (the upper part is
the larynx)  two bronchi  bronchioles  alveoli
Mechanisms for Breathing
- Inspiration: the process of taking in air.
o Flattens the diaphragm which allows the lungs to expand.
- Expiration: the process of letting out air.
o Diaphragm expands which causes the lungs to deflate.
- the rate of breathing is controlled by the brain and the brain stem, which
monitors the amount of CO2 present in the body and is all done
subconsciously.
o This subconscious control can be overridden for short periods of
time, like for swimming underwater.