Transcript CIRCULATORY AND RESPIRATORY SYSTEMS

CIRCULATORY AND RESPIRATORY
SYSTEMS
37-1 The Circulatory System
Functions of the Circulatory System
• Organisms which have a small number of cells do not need a
circulatory system. Larger organisms need one.
• Humans and other vertebrates have a closed circulatory system. This
means that the blood is contained inside of vessels.
• The human circulatory system consists of the heart, a series of blood
vessels, and the blood that flows through them.
The Heart
• Your heart is located near the center of your chest. The heart is made
up of mostly muscle. It is a hollow organ that is about the size of your
clenched fist.
• The heart is enclosed in a protective sac of tissue called the
pericardium.
• Myocardium – thick middle muscle layer of the heart that pumps
blood through the circulatory system.
• The heart muscle contracts about 73 times a minute and pumps
about 70 milliliters of blood with each contraction.
• The septum divides the right and left sides of the heart. The septum
prevents the blood with little oxygen from mixing with blood rich in
oxygen.
• Atrium – the upper chamber that receives the blood
• Ventricle – the lower chamber that pumps blood out of the heart.
• The right side of the heart pumps blood from the heart to the lungs.
This is called pulmonary circulation (the word pulmonary refers to
the lungs)
• In the lungs, carbon dioxide leaves the blood and oxygen is absorbed.
The oxygen-rich blood then flows into the left side of the heart and is
pumped to the rest of the body. This is called systemic circulation.
Oxygen that returns to the right side of the heart has little oxygen
because cells have absorbed a lot of the oxygen and loaded the blood
with carbon dioxide. It now needs another trip to the lungs.
• Valves – flaps of connective tissue between the atria and the
ventricles.
• Blood moving from the atria holds the valves open. When the
ventricles contract, the valves close, which prevents blood from
flowing back into the atria.
• There are also valves that stops blood that has left the heart from
flowing back in. These valves keep the blood moving through the
heart in one direction.
• There are two sets of muscle fibers in the heart, one in the atria and
one in the ventricles. When a single fiber is stimulated, all the fibers
are stimulated and all contract. Each contraction begins in a small
group of cardiac muscle cells These cells are called the sinoatrial
node, but also called the pacemaker, because it sets a pace for the
heart to beat.
• How fast your heart beats depends on how much oxygen-rich blood
your body needs.
• For example, when you are exercising, your heart beat faster because
your body needs more oxygen.
Blood Vessels
• Aorta – a large blood vessel that the blood leaves the heart through
• There are three types of blood vessels that blood flows through:
arteries, capillaries, and veins.
• Arteries – large vessels that carry blood away from the heart to the
tissues of the body
(Artery = Away)
• Capillaries – the smallest of the blood vessels. They bring nutrients
and oxygen to the tissues and absorb carbon dioxide and other waste
products from them.
• Veins – carry blood to the heart after it has passed through the
capillary system.
(think of a tv: To = Veins)
• Large veins contain valves that keep blood moving toward the heart.
Blood Pressure
Blood pressure is the force of the blood on the arteries’ walls. Blood
pressure decreases when the heart relaxes, but there is still pressure.
The pressure is needed to pump the blood throughout the body.
The body regulates blood pressure. When it is too high, the autonomic
nervous system releases neurotransmitters that cause the smooth
muscles in blood vessel walls to relax, which lowers the blood pressure.
When blood pressure is too low, neurotransmitters are released that
elevate blood pressure by causing these smooth muscles to contract.
Kidneys also help to regulate blood pressure. They remove more water
from the blood when blood pressure is high. This reduces blood
volume, which lowers the blood pressure.
Diseases of the Circulatory System
• Cardiovascular disease (ex – heart disease and stroke) are among the
leading causes of death and disability in the US. High blood pressure
and atherosclerosis are two main causes of cardiovascular disease.
• Atherosclerosis – fatty deposits, called plaque, build up on the inner
walls of the arteries.
• High blood pressure is also called hypertension. It forces the heart to
work harder, which can weaken or damage the heart and blood
vessels. It increases the risk of heart attack or stroke.
• Atherosclerosis is dangerous in the coronary arteries, which bring
oxygen and nutrients to the heart. If a coronary artery becomes
blocked, the heart muscle may begin to die from lack of oxygen. If
enough of the heart muscle is damaged, a heart attack can occur.
Symptoms of a heart attack are nausea, shortness of breath, and
severe crushing chest pain
Blood clots that can form from atherosclerosis can break free and get
stuck in one of the blood vessels leading to a part of the brain. This is
called a stroke.
• To avoid a cardiovascular disease, get regular exercise, eat a balance
diet, and DO NOT SMOKE!
37-2 Blood and the Lymphatic System
Blood Plasma
• The Human body contains 4 to 6 liters of blood, about 8% of the total
mass of the body. 45% of blood is made up of cells and the other
55% is plasma.
• Plasma – a straw-colored fluid which blood cells are suspended in
• Plasma is 90% water and 10% dissolved gases, salts, nutrients,
enzymes, hormones, waste products, and proteins called plasma
proteins.
Blood Cells
• Blood contains red blood cells, white blood cells, and platelets.
Red Blood Cells (erythrocytes)
• The most numerous cells in the blood
• Red blood cells transport oxygen.
They contain hemoglobin, which is the iron-containing protein that
binds to oxygen in the lungs and transports it to tissues throughout
the body where the oxygen is released.
• Red blood cells are produced from cells in red bone marrow.
White Blood Cells (leukocytes)
• There are much less white blood cells in the blood than there are red
blood cells (1000 to 1)
• White blood cells are the “army” of the circulatory system. They
guard against infection, fight parasites, and attack bacteria.
• Lymphocytes – a special class of white blood cells that produce
antibodies that are proteins that help destroy pathogens.
• Antibodies are essential to fighting infection and help to produce
immunity to many diseases.
Platelets and Blood Clotting
• Blood has the ability to form a clot. Blood clotting is made possible
by plasma proteins and cell fragments called platelets.
• Platelet – cell fragment released by bone marrow that helps in blood
clotting.
When a platelets come into contact with the edges of a broken blood
vessel, their surfaces become sticky, and a cluster of platelets develops
around the wound. These platelets release proteins called clotting
factors. A clot is formed and the bleeding is stopped.
• In small wounds, the wound is sealed and bleeding stops in a few
minutes.
• Hemophilia is a genetic disorder that results from a defective protein
in the clotting pathway. People with hemophilia can’t produce blood
clots that are firm enough to stop even minor bleeding. Without
clotting, they can bleed too much.
The Lymphatic System
• Blood can leak out into tissues. If nothing is done about this, the
body can swell with fluid. The lymphatic system is a network of
vessels, nodes, and organs that collects fluid that is lost by the blood
and returns it back to the circulatory system. The fluid is called
lymph.
Lymph nodes are small bean-shaped enlargements along the length of
the lymph vessels. Lymph nodes act as filters, trapping bacteria and
other microorganisms that cause disease. When a large number of
microorganisms are trapped, the nodes become enlarged. Swollen
glands are swollen lymph nodes.
The thymus and spleen also have important roles in the lymphatic
system. The thymus is located beneath the sternum. Certain
lymphocytes called T cells mature in the thymus before they can
function in the immune system. T cells recognize foreign “invaders” in
the body. The spleen helps to cleanse the blood and removes damaged
blood cells from the circulatory system.
37-3 The Respiratory System
What is Respiration?
• In cells, cellular respiration is the release of energy from the
breakdown of food molecules when oxygen is present.
• In the human body, respiration is the process of gas exchange – the
release of carbon dioxide and the uptake of oxygen between the
lungs and the environment
The Human Respiratory System
• The basic function of the human respiratory system is to bring about
the exchange of oxygen and carbon dioxide between the blood, the
air, and tissues.
• Pharynx – a passageway for air and food
• Trachea – windpipe – air moves from the pharynx to the trachea. A
flap of tissue called the epiglottis covers the entrance to the trachea
when you swallow.
To keep lung tissue healthy, air entering the respiratory system must be
warmed, moistened, and filtered. Large dust particles get trapped by
the hairs (cilia) lining the entrance to the nasal cavity. Some of the cells
that line the respiratory system produce a thin layer of mucus. Mucus
moistens the air and traps inhaled particles of dust or smoke. Cilia
sweep the trapped particles and mucus away from the lungs toward
the pharynx. The mucus and trapped particles are either swallowed or
spit out. This helps keep the lungs clean and open.
• Larynx – contains the vocal cords. Gives us the ability to makes
sounds (speak, shout, sing…)
• Bronchi – two large passageways in the chest cavity that air from the
trachea go into. Each bronchus leads into one of the lungs.
• Bronchi lead into smaller passageways called bronchioles.
Bronchioles subdivide until they reach a series of dead ends, millions
of tiny air sacs called alveoli. Alveoli looks like bunches of grapes.
Gas Exchange
• There are about 150 million alveoli in each healthy lung. Oxygen
dissolves in the alveoli and then diffuses across the thin-walled
capillaries in to the blood. Carbon dioxide in the bloodstream
diffuses in the opposite direction across the membrane of an alveolus
and into the air within it.
Breathing
• Breathing is the movement of air into and out of the lungs.
• Diaphragm – large flat muscle at the bottom of the chest cavity that
helps with breathing.
• When you inhale, the diaphragm contracts and the rib cage rises up.
When you exhale, the diaphragm is relaxing and the rib cage lowers.
A puncture wound to the chest, even if it is not in the lungs, may allow
air to leak into the chest cavity and make breathing impossible.
How Breathing is Controlled
• Breathing isn’t totally voluntarily. We can control our breathing to an
extent, but if we hold our breath, our bodies force us to breath after
some time. Also, breathing in our sleep in involuntary.
• The medulla oblongata controls breathing. When carbon dioxide
levels rise, nerve impulses cause the diaphragm to contract, bringing
air into the lungs. The higher the carbon dioxide level, the stronger
the impulses. If carbon dioxide levels reaches a critical point, the
impulses become so powerful that you cannot keep from breathing.
Tobacco and the Respiratory System
• The upper part of the respiratory system filters out dust and foreign
particles that could damage the lungs. Smoking tobacco damages
and eventually destroys this protective system.
• Tobacco smoke contains many substances. Three of the most
dangerous are nicotine, carbon monoxide, and tar.
• Nicotine – stimulant drug that increases the heart rate and blood
pressure.
• Carbon monoxide is a poisonous gas that blocks the transport of
oxygen by hemoglobin in the blood. It decreases the blood’s ability to
supply oxygen to its tissues, depriving the heart and other organs of
the oxygen they need to function.
• Tar has been shown to cause cancer.
Smoking paralyzes the cilia, causing the inhaled particles to stick to the
walls of the respiratory tract or enter the lungs. Without cilia, smokeladen mucus becomes trapped along the airways. This is why smokers
often cough. Smoking also causes the lining of the respiratory tract to
swell, reducing air flow to the alveoli.
Diseases Caused by Smoking
Smoking can cause chronic bronchitis, emphysema, and lung cancer.
In chronic bronchitis, the bronchi become swollen and clogged with
mucus
Emphysema – the loss of elasticity in the tissues of the lungs. People
with emphysema cannot get enough oxygen to the body tissues or rid
the body of excess carbon dioxide.
About 160,000 people are diagnosed with lung cancer each year. By
the time it’s detected, lung cancer usually spreads to other parts of the
body. Few will survive for five years after the diagnosis.
Smoking is a major cause of heart disease. Smoking narrows the blood
vessels, causing blood pressure to rise and makes the heart work
harder.
Evidence has shown that tobacco smoke is damaging to anyone who
inhales it, not just the smoker. This is called second-hand smoke.