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THE CIRCULATORY SYSTEM
All organisms must be able to transport nutrients and wastes. Smaller organisms rely on _diffusion_____ for
this movement; humans require an organized circulatory system for the movement of substances through the
body. We have a _closed________ circulatory system, which means our blood is _enclosed in vessels__.
The human circulatory system includes the heart, the blood vessels, and the blood.
I. THE HEART
(pp. 943-946)
The function of the heart is to _pump the blood to the body cells_______. The heart itself is
mostly composed of _cardiac_______ muscle which forms a thick layer of tissue known as the
_myocardium_______. Humans have a __4____-chambered heart, divided by a _septum_____
into right and left sides to prevent _mixing of blood_______________.
A. Structure
1. Chambers
 Atria (atrium = singular) _Upper_ chambers of the heart that _receive_______ blood.
 Ventricles - _Lower________ chambers of the heart that _pump________ blood to the
_lungs___ and _body_____. Have thicker _myocardium___________ than atria.
2. Valves – Flaps of tissue that keep blood flowing _in one direction_______________ to
increase pumping efficiency of the heart; prevent _backwash__________________.
 Tricuspid valve – Valve between __R atrium________ and __R ventricle___________
 Mitral valve – Valve between _L atrium________ and _L ventricle_________
 Pulmonary valve – Valve between _R ventricle______ and _pulmonary artery_______
 Aortic valve – Valve between _L ventricle____ and _aorta__________
B. Pathway of Blood Through the Heart
__________________________________________________________________________________
__________________________________________________________________________________
C. Circulatory Pathways
1. Pulmonary Circulation – The blood entering the right atrium from the body is _low_____ in
oxygen and _high___ in carbon dioxide. The flow of blood from the right side of the heart to the
__lungs__________ and back to the heart is referred to as __pulmonary______ circulation.
2. Systemic Circulation – The blood entering the left atrium from the lungs is _high_____ in O2 and
_low_ in CO2. The flow of blood from the left side of the heart to the _body____ and back to the
heart is referred to as _systemic______ circulation.
D. The Heartbeat
1. Stimulus for Contraction
Although the brain can change the rate & force of contraction, the heart generates and
maintains its own beat. There is a small cluster of cardiac muscle cells in the
_R atrium______ referred to as the _pacemaker________. They trigger an
_electrical ___ impulse that stimulates the contraction of cardiac muscle cells.
2. The Pulse
The powerful contraction of the _L ventricle_________ causes a surge of blood to leave
through the _aorta_______. This surging action of the blood continues into the _arteries______
that branch off from the aorta. Each contraction of the left ventricle results in another surge of
blood in the arteries leading away from the heart. This surge can be felt and is known as the
_pulse_____.
II. BLOOD VESSELS
(pp. 946-949)
A. Types – There are three types of blood vessels, _arteries____, _veins___, and
_capillaries_____. Arteries and veins are composed of three tissue layers:
 The outer layer is composed of _connective______ tissue for protection. One of the
proteins found in the _matrix_____ is _elastin_______, which allows for the vessels to be
_“stretchable”______.
 The middle layer is composed of _smooth_______ muscle tissue to regulate blood flow.
 The lining of arteries and veins is composed of _epithelial_____ tissue.
1. Arteries
 Carry blood __away from___ the heart
 Have _thicker____ walls to withstand the pressure of spurts of blood from contraction of the
heart
 Are deeply buried in skin for _protection___
 Carry blood that is _high__ in oxygen and _low__ in carbon dioxide, except for the
_pulmonary____ artery
2. Veins
 Carry blood _to____ the heart
 Have _thinner_____ walls
 Also contain _valves___ to keep blood flowing in one direction; especially important in the
_legs_____ because _blood flow is working against gravity_______________________.
 Veins carry blood _low___ in O2 and _high___ in CO2, except for the _pulmonary vein_____.
3. Capillaries
 Network in which _O2___, _glucose______, and other nutrients are exchanged with __ CO2___
and other wastes
 _One___- cell thick to allow for _diffusion_____
 Red blood cells flow through _one-by-one_________
B. Blood Pressure – Measurement of pressure exerted on walls of _arteries__________.
1. Systolic pressure is the pressure on the artery walls when the ventricles _contract_____
2. Diastolic pressure is the pressure when the ventricles _relax__________.
3. Written as a fraction → systolic pressure / diastolic pressure.
4. Average = _100 – 140 / 60 – 90 mm Hg_____
III. THE BLOOD
(pp. 951-953)
Blood is _connective_______ tissue with a _matrix____ known as _plasma_______. Plasma
makes up approximately _55__% of blood and contains dissolved _nutrients, wastes, and other
important molecules______. All blood cells are produced in the _red marrow_______ of
_spongy________ bone.
A. Red blood cells
 Function is to deliver _oxygen____ to _body cells___.
 Most numerous cells in blood
 Doughnut-shaped cells that lose their _nucleus_____ as they mature in the red marrow.
o Allows them to _squeeze through tiny capillaries
o Provides more area for _oxygen transport______
 Contain _hemoglobin___, an _iron___- containing protein that binds oxygen.
B. White Blood Cells
 Larger and fewer in number than RBCs
 Function is to _fight infection______
C. Platelets
 Cell __fragments______ that break off from large cells produced in the _bone__ marrow.
 Lack a _nucleus___ like _red___ blood cells
 Begin the _clotting__ process by sticking together to form a __plug____ when they come in
contact with a _rough____ surface.
IV. Diseases of the Circulatory System
anemia
atherosclerosis




heart attack
hypertension
__Atherosclerosis______________ – Plaques of cholesterol build up on the wall of arteries.
Restricts blood flow and creates a rough surface that may trigger clot formation.
__Heart attack_______________ – Caused by blockage of coronary artery which cuts off blood
flow to the myocardium of the heart. Cells die due to lack of oxygen, glucose.
__Anemia_______ – Caused by either a deficiency of red blood cells or hemoglobin in RBCs.
Less O2 available for cells results in a lack of energy due to decreased ATP production.
_Hypertension_____ – High blood pressure. Called the “silent killer” because it may be fatal
before noticeable symptoms appear. Risk of hypertension is increased by smoking, obesity,
high salt intake, lack of exercise.
THE RESPIRATORY SYSTEM
The function of the respiratory system is to bring about the exchange of _O2__ and _CO2___.
I. THE RESPIRATORY PASSAGEWAY
(pp. 956-958)
A. Airway to the Lungs
 _Nasal Cavity______ - Begin the process of warming, filtering, moisturizing the air
 _Pharynx_____ - Upper throat
 _Larynx____ - Also known as the voicebox. Bands of tissue that tighten and vibrate to
create sound when air passes through.
o Attached to the larynx is a flap of tissue called the _epiglottis_____. The
epiglottis closes when food is swallowed to prevent food from entering the
_respiratory___ tract.
 _Trachea___ - Airway supported by bands of _cartilage_______ to prevent it from
_collapsing_____ when air passes in and out
 _Bronchi_________ - Trachea divides into two tubes leading to each _lung_____
o Trachea and bronchi are lined with _cilia____ and cells that secrete
_mucus_____. The mucus traps _pathogens____ and other contaminants. The
cilia beat _upwards__ to sweep contaminants toward the _pharynx_____.
B. Inside the Lungs
 _Bronchioles_____ - Smaller branches leading from bronchi. Contain _smooth____ muscle
tissue to facilitate air flow.
 _Alveoli__________ - The bronchioles end in millions of tiny sacs called alveoli. Site for the
exchange of _O2___ and _CO2____. Each alveolus is surrounded by a _capillary_______ to
allow _ O2____ to _diffuse____ from the lung to the blood to be delivered to cells for
_cellular respiration___ and _ CO2____ to diffuse from the blood to the lung to be exhaled.
C. Pathway of Air
__________________________________________________________________________________
__________________________________________________________________________________
II. BREATHING
(p. 959-961)
A. Inhalation & Exhalation - Breathing is a _passive___ response to a change in _pressure_______
in the chest cavity. Although there are no _muscles____ attached to the lungs, the change in
pressure is caused by the contraction of muscles involved in breathing.
 Diaphragm – Dome-shaped muscle located below (but not attached to!) the _lung_____.
When the diaphragm _contracts_______, it flattens which _increases_____ the volume of the
chest cavity and _decreases____ the pressure. Air rushes into the lungs.
 Intercostal Muscles – Also contract to further _increase_____ volume of chest cavity
 As the diaphragm and intercostal muscles relax, volume of the chest cavity _decreases___, and
the _elasticity_______ of the lungs help force the air back out.
B. Control of Breathing
Breathing is controlled by the _medulla oblongata__, which is monitoring the concentration of
_CO2____ in the blood.
III. DISEASES OF THE RESPIRATORY SYSTEM
(pp.949-950, 961-963)
 Emphysema – Progressive disease in which _alveoli_______ lose their elasticity.
Affected individuals cannot fully exhale which reduces ability to inhale. O2 and CO2 do not
diffuse properly. All _smokers________ eventually develop emphysema.
 Asthma – Allergic reaction that affects _smooth______ muscles of _bronchioles_______.
They _constrict______ which prevents airflow into the _alveoli_____. Gas exchange is
reduced.
 Smoking – Three dangerous substances found in cigarette smoke are nicotine, carbon
monoxide, and tar.
 Nicotine – stimulant that increases heart rate, constricts blood vessels; _increases______
blood pressure.
 Carbon monoxide – binds to _hemoglobin____; reduces oxygen-carrying capacity of
_hemoglobin_____ blood cells. Also, combination of nicotine & CO paralyzes _cilia____
lining respiratory tract resulting in frequent respiratory _infections__________.
 Tar – carcinogen; smokers have a much higher incidence of lung cancer.