THE CIRCULATORY AND RESPIRATORY

SYSTEMS

The Circulatory System The circulatory system contains the network of

blood vessels that connects the organs and muscles of the body, the muscular heart that pumps the blood and the lymphatic vessels that collect excess fluid.

The circulatory system:– transports food, oxygen, wastes– transports hormones– helps defend the body– helps distribute body heat

Components of Circulatory System

There are four major components of the human circulatory system:– blood vessels - network of tubes that carry blood– lymphatic vessels - recover fluid that leaks out of

blood vessels– blood - connective tissue of cells and fluid– heart - pumps blood throughout body

Blood clotting

Blood VesselsThere are three main vessels:– arteries - thick, muscular walls

» carry blood away from heart» blood pulses

– veins -less muscular walls » valves prevent back flow» carry blood toward heart

– capillaries - link arteries and veins» walls only one cell thick » narrow diameter - RBC line up single

file to pass » where actual exchange of materials

takes place

Patterns of Circulation

General circulation path of blood:– heartarteries arterioles capillaries venules veins

heart

Patterns of Circulation Pulmonary circulation -

pumping blood from heart to the lungs & back to heart.

Systemic circulation - blood is pumped from heart to the body’s tissues & back to heart.

Coronary circulation - supplies blood to the heart muscle itself.

The HeartThe Heart The central organ of the

cardiovascular system A double pump

– upper chambers = atria– lower chambers = ventricles

Within the thoracic cavity

Control of the Heartbeat

Contraction of the heart is initiated by a small cluster of cardiac muscle cells embedded in the right atrium.

This “pacemaker” of the heart is called the sinoatrial node (SA node).

These cells initiate their own electrical impulse and cause the atria to contract.

After this initiation the impulse then travels to the AV node to contract the ventricles.

Cardiovascular Functions Cardiovascular functions can be monitored:

– pulse = heart rate– blood pressure is measured with a

sphygmomanometer; relaxation of heart = diastolic; contraction of heart = systolic pressure (Normal = 120/80)

– electrical impulses produced by the heart muscle is measured with an EKG

Blood The blood has two main components:

– plasma - liquid portion (60% by volume)»90% water; 10% solutes such as proteins,

glucose, salts– cells & cell fragments (40% by volume); three types:

»red blood cells (RBC) - erythrocytes5M/mlcontain hemoglobin; carry oxygen

»white blood cells (WBC) - leukocytes8,000/ml ( during infection)defend body against disease, invasion

»platelets - thrombocytesrelease fibrin to help blood clot

RBCWBC

Platelet

Cardiovascular Diseases

Cardiovascular diseases– high blood pressure (hypertension)– heart attack– atherosclerosis (build-up of plaque )– arteriosclerosis ( loss of elasticity)– stroke

The Respiratory System It is the function of the respiratory system

exchange gases with the atmosphere and to transport these gases to and from the circulatory system.

Remember that the body requires O2 and creates CO2 in the process of cellular respiration.

There are two places where gas exchange takes place– Between the lungs and blood vessels– Between the blood vessels and the tissues.

The Respiratory System Air is carried to the lungs by way of a branched

system of tubes and air sacs. Path of air through respiratory system:

– nostrils - air is warmed, moistened and filtered

– pharynx - upper throat– larynx - voice box– trachea - covered by epiglottis

» tube reinforced with cartilage; divides into bronchi

– bronchi - divide into bronchioles – bronchioles - enter lungs– lungs with alveoli (air sacs)

Alveoli

The end of the air passageway are air sacs surrounded by capillaries.

This is where gas exchange in the lungs takes place.

The alveoli are designed to increase surface area for gas exchange.

Gas Exchange- O2 Oxygen molecules diffuse from the alveoli into the

blood plasma where it is picked up by RBC, containing hemoglobin (Hb).

Oxygen is transported to tissues where the O2 levels are lower O2 is released from Hb.

Regulation of Breathing The amount of O2 needed (and CO2 produced) by the body

depends upon the activity of the cells. It is involuntary. Breathing rate is controlled by amount of CO2 in blood (not the

amount of O2) The respiratory control center of brain regulates breathing rate.

Mechanism of Breathing Breathing is the result of pressure changes inside the thoracic

cavity. During inhalation/inspiration, the diaphragm contracts, moves

downward, the ribs move up and out causing an increase in the size of the cavity a decrease in pressure inside the lungs.– The higher air pressure outside body allows air to enter the lungs.

During exhalation/expiration, the diaphragm and ribs return to original position, causing a decrease in size of cavity causing an increase in air pressure inside lungs.– This forces air from the lungs.