1. The Circulatory System

2. Human circulatory system
Closed system-blood moves through a series of vessels
Consists of the heart, a series of blood vessels, and the blood

3. Heart
Hollow organ, composed mostly of muscle, the size of your clenched fist
Enclosed in protective covering called pericardium
Heart walls have two layers of epithelial and connective tissues that form around the muscle called myocardium
Contractions of myocardium pump blood through the system

4. Heart
Contracts 72 times per minute and pumps 70 ml of blood with each contraction
Septum divides the right side from the left side and prevents mixing of oxygen-rich and oxygen-poor blood
Upper chambers, atria (atrium), receive blood
Lower chambers, ventricles, pump blood away from the heart

5. Circulation through the body
Right side of heart pumps blood from heart to lungs in pulmonary circulation to exchange carbon dioxide and oxygen
Oxygen-rich blood returns to the left side of the heart to be pumped to the body in systemic circulation
Systemic circulation carries oxygen to all cells and picks up carbon dioxide before returning to the right side of the heart

6. Circulation through the heart
Blood enters heart through right and left atria
When heart contracts blood moves from atria to ventricles (and out of ventricles to body or lungs)
Valves between atria and ventricles prevent blood from flowing backwards
Valves also prevent blood from flowing back into the ventricles when it leaves the heart
Valves keep blood moving in one direction and increases pumping efficiency

7. Blood vessels Blood moves through 3 types of vessels Arteries
Capillaries
Veins

8. Arteries Large vessels that carry blood from heart to tissues
All carry oxygen-rich blood (except for the pulmonary artery that carries oxygen-poor blood from heart to lungs)
Blood leaving heart to go to body tissues must first pass through the aorta (large artery)

9. Capillaries Smallest blood vessels Walls only 1 cell thick
Bring oxygen and nutrients to tissues and absorb carbon dioxide and other wastes

10. Veins Return blood to heart after passing through capillaries
Walls contain connective tissue and smooth muscle
Large veins also contain valves to prevent back flow
Many located between or within skeletal muscles whose contractions help force blood toward the heart

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Arteries & Capillaries
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12. Blood pressure
Produced when heart contracts and forces a wave of fluid through the arteries
Force of blood on arterial walls is blood pressure
Without pressure, blood would stop flow

13. Regulation of blood pressure
Sensory receptors in body detect level of blood pressure and sends impulses to medulla oblongata
If pressure is too high, neurotransmitters are released by autonomic nervous sys. Causing vessel walls to relax and lower pressure
If pressure is too low, neurotransmitters can elevate pressure by causing vessel walls to contract

14. Regulation of blood pressure
Kidneys also help control blood pressure
Hormones from heart and other organs cause kidneys to remove water from blood when pressure is too high
This reduces blood volume and lowers blood pressure

15. Blood plasma 55% of blood is fluid called plasma
Plasma is 90% water and 10% dissolved gases, salts, nutrients, enzymes, hormones, wastes, and plasma proteins (albumins, globulins, fibrinogen)
Albumins and globulins transport fatty acids, hormones, and vitamins
Albumins regulate osmotic pressure and blood volume
Globulins fight viral and bacterial infections
Fibrinogens are proteins that help blood to clot

16. Red blood cells
Most numerous cells in blood (also called erythrocytes)
Used to transport oxygen
Color comes from hemoglobin (iron-containing protein that binds oxygen for transport)
Produced from red marrow
Do NOT have nuclei
Circulate for 120 days and are then destroyed by the spleen

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Blood Type Chart
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18. White blood cells Also called leukocytes Do NOT have hemoglobin
Produced in bone marrow and have nuclei
Live for days, months, or years
Guard against infection, fight parasites, and attack bacteria

19. Types of white blood cells
Phagocytes-engulf and digest bacteria and other disease-causing microorganisms; some release histamines that produce redness and swelling (allergies)
Lymphocytes-produce antibodies (proteins) that destroy pathogens; essential to fighting infection and produce immunity to diseases

20. Importance of white blood cells
First lines of defense in fighting infection
Part of immune system

21. Platelets Made of plasma proteins and cell fragments
Produced in bone marrow
Platelets come in contact with broken blood vessel, they become “sticky” and gather at the wound
Platelets release clotting factor (thromboplastin) that converts prothrombin to thrombin (changes fibrinogen to mesh of fibrin filaments) to stop bleeding

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Blood Components
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