BIO307- Bioengineering principles FALL 2016 Lecture 6 Circulation and Removal of Molecules from the Body Lecturer: Jasmin Sutkovic 24.11.2016

Content Chapter 8: Circulation – An Introduction The circulating fluid The human heart Chapter 9: Examples of elimination of molecules from the body Biotransformation and biliary excretions Kidneys role in eliminations of molecules Book chapter 8 and 9 (page 229-353)

Introduction Blood moves at high velocity throughout the body within an interconnected and highly branched network of vessels. The human circulatory system is responsible for the movement of fluid (and therefore vital nutrients contained in the fluid) throughout the body.

Mixing machine The purpose of the circulatory system is a familiar one to engineers and bakers; it provides mixing, and good mixing is an essential element of many successful enterprises. But why must humans be mixed? Mixing exposes cells throughout the body to oxygen and other nutrients, while simultaneously providing a pathway for removal of waste products.

The human cardiovascular system is composed of three separate organs: The heart serves as a pump The vasculature serves as the plumbing (the supply of vessels to a specific region) The blood is the circulated fluid

Microcirculation The circulatory system carries oxygenated blood to every section of the body. Most cells in the body are less than 100 μm from the nearest small blood vessel. https://drsvenkatesan.com/2011/10/25/coronary-microcirculation-what-you-see-includes-what-you-dont-see-as-well/

The circulating fluid Blood is a suspension of cells, primarily red blood cells (RBCs), within a protein-rich fluid called plasma. The presence of RBCs and proteins in blood both contribute to its higher viscosity. Viscosity is related to the resistance to “flow” or deformation of a fluid.

Blood.. Blood contains a number of other cell types in addition to RBCs, which do not contribute substantially to its properties as a viscous fluid, but are of biological importance. RBCs are the greatest in number and are the only cells that contain hemoglobin. Together with certain blood proteins, such as fibrinogen, platelets are important in clot formation. A variety of white blood cells also circulate within the blood.

The blood vessels The Circulatory system in connected by vessels Flow of oxygenated blood emerges from the heart into the aorta. The aorta branches into large arteries, which further branch into main arterial branches, which further branch into terminal arteries, then arterioles, and finally into capillaries.

The circulatory system is also remarkably efficient at mixing. When drug molecules are injected into a vein, the concentration of that agent at the injection site is suddenly increased. When a vessel wall becomes weakened because of disease, it can no longer distend in its usual fashion and an aneurysm, or local bulging in the vessel wall, may occur.

Capillary function In the capillaries that the exchange of molecules such as oxygen, carbon dioxide, glucose, and other nutrients occurs Unlike arteries and veins, capillaries have no smooth muscle, no elastic fibers, and very thin walls

Heart and cappilaries The heart continually circulates about 5 L/min of fluid throughout the day. Because of the pressure inside the blood vessels, fluid can leak out of the capillaries. This loss is about 20 L/day. Much of this fluid (16–18 L/day) is recovered in the capillaries because of the effects of osmotic forces

How Heart works.. https://www.medicalvideos.us/video/5289/how-the-heart-works-3d-video

Cardiac cycle of the heart Electrical activity generates high efficient squeezing of heart muscle (of the four chambers) One beat of the heart, or one round of electrical activation and contraction, is called a cardiac cycle The contraction phase of the cardiac cycle is called systole and the relaxation phase, or the period in between excitation/contraction events, is called diastole

Ejection of this volume of blood is accompanied by an increase in aortic pressure from ∼80 mmHg (diastolic pressure prior to ejection) to ∼120 mmHg (systolic pressure during ejection). The aortic pressure is sufficient to drive flow throughout the circulatory system, with the energy stored in the pressure drop being converted into flow throughout the body

Chapter 9 next time..