Bioengineering【Physiological fluid dynamics Part2】

– Cardiac diastole
• Heart muscle relaxation
Pathway of Blood Through the Heart and Lungs
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Close up of the circulatory system
The Distribution of Blood in the Cardiovascular System
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nerve fibers.
Differences between arteries and veins
• Compared to veins, arteries
– Have thicker walls – Have more smooth muscle and elastic fibers – Are more resilient
• Veins to venules
– Some veins to have smooth muscle in them (the very largest). – Have same layers as arteries, but tunica media is much thinner. – Have relatively less elastic tissue. – Operate at low pressure. – Have periodic bicuspid-shaped valves to prevent backflow. – Smallest (venules) receive capillary blood – have no tunica media
Capillary Beds
• An interconnected network of vessels • Smallest and thinnest of blood vessels – usually constructed of only a single layer of tunica intima. • Often as narrow as a single blood cell. • Greatest loss of blood pressure at the capillary level. Location of nutrient and gas exchange with other tissues. This slow movement of blood through capillaries allows time for exchange of substances between the blood and surrounding tissues.
Veins – From the periphery towards the heart – Cylindrical shape, thin wall and large lumen – Less thickness, less elastin in the media – Thick adventitia – Dvein>Dartery and Pvein<Partery (in the same body location) – Blood reservoir of the body (65% of total blood) – Compliance > structure collapse – Valves that prevent backflow
Direction of blood flow in vein
Valve (closed)
Skeletal muscle
Valve (open)
Summary
• Arteries to Arterioles
• • Smallest definable arteries are arterioles. They have relatively more smooth muscular tissue, less elastic tissue. Thus, they are more easily regulated by (autonomic) nervous control. Very smallest arterioles (terminal arterioles): • Have no internal elastic layer. • Tunica media densely supplied with sympathetic
Physiological fluid dynamics
The human circulatory system Flow in the circulatory system
Elements of the human circulatory system
• Pump
Blood is pumped by the heart. Heart embeds two synchronous cardiac pumps. The right heart receives blood from the systemic system, and the left one from the pulmonary system. Each pump consists of a low pressure chamber (called the atrium) and a high pressure chamber (ventricle). The atrium is filled from veins, and empties via a valve (tricuspid for the right heart and mitral for the left) into the ventricle. The ventricle pushes blood through another valve (pulmonary or aortic) to the arteries. High pressure flow system – Arterial circulation Low pressure flow system – Venous circulation –
Artery and Vein
The veins
• Veins are compliant
• Veins have thinner walls, thus higher compliance.
– Capacitance vessels. • 2/3 blood volume is in veins. • Veins possess valves
• CO = SV x Heart rate ( HR)
Pressure produced generates flow
Some terms
• Cardiac Output (CO) is volume of blood pumped/min by each ventricle • Stroke volume (SV) = blood pumped/beat by each ventricle
Blood vessels: Physical characteristics
Blood vessels: – part of circulatory system – Function: to transport the blood throughout the body Blood vessel wall: – Complex structure specific function for specific body location – General anatomical description: three concentric layers • Tunica intima (thinnest layer): – Single layer of endothelial cells – Direct contact with blood – Elastin and internal elastic lamina (membrane) • Tunica media (thickest layer) – Different structures for different body locations (aorta vs veins) – External elastic lamina • Tunica adventitia – Collagen fibers (longitudinal direction) – Function: anchorage and protection – Nerves – Vasa vasorum
How does blood flow in the circulation?
• Looking at the way blood flows from a physiological view point • Looking at the way blood flows from a fluid dynamic view point
– Counteract gravity in postural adjustments
Venous return
– Three factors keep blood moving back to the heart
• muscle contractions • breathing • one-way valves
Make Up of Blood Vessels
• Endothelium – Surface in contact with blood • Elastic tissues – Rebounds – Evens flow • Smooth muscles • Fibrous tissue – Resists stretch