introduction to circulatory system.pptx by DR SHAZIA SUKHEIRA

BDS 1st year slides of physiology by physiology professor DR. Sharia Sukheira teaching in Rashid Latif Medical & Dental College, Lahore, Pakistan.

1. Overview of Circulation and classification of blood vessels Dr Shazia Sukhera Assistant Professor Physiology

2. Circulation A transportation system The function of the circulation is to: serve the needs of the body tissues transport nutrients to the body tissues transport waste products away to transport hormones from one part of the body to another

3. COMPONENTS OF CIRCULATION Three main components Heart – a double pump Blood – a fluid acts as transport media Vessels – one way path for the blood flow through out the body

4. TYPES OF CIRCULATION Circulatory system can be divided into two parts: Pulmonary circulation Systemic circulation

5. PULMONARY CIRCULATION Pulmonary circulation – carries deoxygenated blood to the lungs then oxygenated blood back to the heart - includes the pulmonary trunk, the left and right pulmonary arteries, and the pulmonary veins

6. SYSTEMIC CIRCULATION Systemic circulation – carries oxygenated blood to the body tissues and bring deoxygenated blood from body back to heart - includes the coronary circuit, which supplies the myocardium

7. Volumes of Blood in the Different Parts of the Circulation: 84% of the entire blood volume of the body is in the systemic circulation and 16%is in the heart and lungs. Of the 84 % in the systemic circulation 64% veins 13 % arteries 7% capillaries The heart contains 7’ percent of the blood, and the pulmonary vessels-------- 9 percent.

8. BLOOD VESSELS Three main Types: Arteries Capillaries Veins Others: Arterioles Venules Sinosides

9. Blood Vessels

10. FUNCTION OF BLOOD VESSELS Arteries – transport blood under high pressure to tissues. Have strong muscular valves Arterioles - small arteries that deliver blood to capillaries Capillaries – thin walled vessels allow for exchange between blood and tissue cells ( nutrients,electrolytes,hormones etc )

11. Venules - collect and drain blood into veins Veins –thin walled vessels, return blood to heart under low pressure Sinosides – special types present in few organs like liver FUNCTION OF BLOOD VESSELS

12. Cross-Sectional Areas and Velocities of Blood Flow Much larger cross-sectional areas of the veins than of the arteries, averaging about four times those of the corresponding arteries. This explains the large blood storage capacity of the venous system in comparison with the arterial system.

13. Velocities: Because the same volume of blood flow (F) must pass through each segment of the circulation each minute, the velocity of blood flow (v) is inversely proportional to vascular cross-sectional area (A) V = F/A

14. PRESSURES IN THE VARIOUS PORTIONS OF THE CIRCULATION Because the heart pumps blood continually into the aorta, the mean pressure in the aorta is high, averaging about 100 mmHg . As the blood flows through the systemic circulation, its mean pressure falls progressively to about 0 mmHg by the time it reaches the termination of the venae cavae where they empty into the right atrium of the heart.

15. The pressure in the systemic capillaries varies from as high as 35mm Hg near the arteriolar ends to as low as 10 mmHg near the venous ends, but their average "functional" pressure in most vascular beds is about 17 mmHg

16. FUNCTIONAL CLASSIFICATION OF BLOOD VESSELS Windkessel (Elastic reservoir) Vessels Characteristics: Large arteries elastic tissue up to 40% high dispensability Functions: Work as buffer to damp the large pressure fluctuation generated by the heart e.g.…aortic & pulmonary arteries

17. Resistance Vessels Characteristics: Thick walled Abundant amount of smooth muscles in walls Highly tonus(tone can be increased or decreased by chemical mediators) Functions: Provide total peripheral resistance(arterioles) Marked changes in blood pressure(by undergoing constriction & dialation ) E.g arterioles, metarterioles

18. Sphincter Vessels Comprise of: Pre/ capilary sphincters, metarterioles, part of pre capillary resistance vessels Have discrete muscular coat near arteriolar origin Functions: Provide finer regulation of capillary flow Exchange vessels Consists of Capillaries Single layer of endothelium with basement membrane and presence of pores Functions: Acts as exchange vessels(exchange of substances b/w blood & tissue spaces)

19. Capacitance vessels (veins) Characteristics: Have small amount of smooth muscle & elastic tissues Larger in caliber Lower pressure Functions: Almost 2/3 of total blood is present in veins which act as storage house Shunt vessels Present in skin subcutaneous tissue Concerned with body temperature regulation Controlled by sympathetic nervous system

20. BASIC PRINCIPLES OF CIRCULATION The rate of blood flow to each tissue of body is almost always precisely controlled in relation to the tissue need. When tissues are active ,they need greatly increased supply of nutrients & blood flow than at rest. This is controlled locally by availability of oxygen and other nutrients, which act directly on local blood vessels,to control local blood flow, and by nervous and hormonal system

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