The Circulatory System Rachael Barber, Annie Stupik, Stephanie Swanson

Circulatory system: an organ system that transports oxygen and nutrients to cells and takes away carbon dioxide and other wastes. All animals have some form of circulatory systems, ranging from simplest to most complex (diffusion, gastrovascular cavity, open circulatory system, closed circulatory system) A true circulatory system consists of a heart, blood, and a set of tubes or vessels

Open Circulatory System In most invertebrates, including mollusks and arthropods Inefficient when compared to a closed system Bathes organs in blood No true heart or capillaries It is “open” because fluid is pumped through open-ended vessels and flows out among the cells

Closed Circulatory System Present in earthworms, squids, octopuses, and vertebrates Also known as the cardiovascular system The blood is enclosed within veins, compared to the open blood of the open system

Vessels 3 kinds: –Arteries carry blood from the heart –Veins return blood to the heart –Capillaries convey blood b/w arteries and veins

Evolution of the Cardiovascular System (see page 469)

The Mechanism of the Heart Mammalian hearts have four chambers: –Left side: left ventricle, left atrium –Right side: right ventricle, right atrium –Ventricles distribute blood, while atriums receive blood FDdk0

Human Cardiovascular System Deoxygenated blood flows through the right ventricle to either lung, via pulmonary arteries Blood becomes oxygenated as it flows through the lungs, using oxygen that you breathe The blood goes to the left atrium, then to the left ventricle, where it pumps blood through the aorta to the systematic circuit The aorta is our largest blood vessel, about the width of a quarter

continued The blood goes to the coronary arteries, which supplies oxygen to the heart muscle Next, it branches to the vessels leading to the head, chest, and arms The next stop on the journey is the abdominal region and legs Arteries lead to arterioles  arterioles  capillaries  venules  veins. The superior or inferior vena cava transport the blood, lacking oxygen, to the right atrium, then the right ventricle, to restart the cycle

The Cardiac Cycle The heart contracts and relaxes rhythmically Heart in relaxation= Diastole -heart fills with blood Contraction= Systole -heart pumps blood when it contracts Cardiac output is the volume of blood each ventricle pumps per minute Heart rate is the number of beats per minute (average is 72) Heart murmur is when a stream of blood squirts backward from a valve. It can be developed or inherited.

Pacemakers sets the tempo of the heart Specialized region of cardiac muscle in right atrium that generates electrical signals. Pacemaker sets the rate at which the rate of the muscle cells contract Doctors have invented artificial pacemakers that emit electrical signals that trigger normal heartbeats.

Cardiovascular Disease Heart Attack- The damage or death of cardiac muscle tissue as a result of the blockage of blood vessels Stroke- The death of brain tissue, resulting from blockage of arteries in the head. Both strokes and heart attacks are the results of a chronic cardiovascular disease known as atherosclerosis. During this disease growths called plaques develop in the inner walls of arteries.

continued The artery wall thickens and is infiltrated by cholesterol and tissue. This can cause blood clots, which cause heart attacks There are different ways of treating cardiovascular disease including – clot dissolving drugs –Monitoring cholesterol and blood pressure –Angioplasty, stents and bypass surgery

Function of Blood Structure Structure fits function Capillaries –function: exchange of materials –structure: thin single celled wall of epithelial cells, inner smooth surface to keep blood flowing. Arteries and Veins –Structure: thicker wall, more sturdy –Pressure is highest in the arteries and lowest in the veins –Blood velocity is slowest in the capillaries

Blood pressure Blood pressure: the force that blood exerts against the walls of our blood vessels –Created by the pumping of the heart Depends on the volume of blood pumped into the aorta and the resistance to blood flow imposed by the narrow openings of the arterioles When your muscles relax, arterioles dilate, and blood flows more easily, lowering your blood pressure

continued By the time blood is ready to return to the heart, there is no pressure to drive it along To make up for this, when your body moves, your muscles pinches the blood towards your heart Veins have valves that allow the blood flow to flow only toward the heart, so blood doesn’t flow backwards (if these valves do not work, the blood will flow backwards, which creates heart murmur

Problems with Blood Pressure Blood pressure is an important indicator of cardiovascular health Hypertension: the condition of having high blood pressure Blood pressure is measured in mm Hg Elevated pressure makes the heart work harder, and over time the left ventricle enlarges. When the blood supply cannot keep up with this new muscle mass, the heart muscle weakens Blood pressure generally increases with age Lifestyle changes can prevent hypertension

Distribution of Blood Controlled by smooth muscle The brain, heart, kidney, and liver need a full supply of blood, but other organs have capillaries only 5-10% full. These muscles and tissues require a lot of blood only if they are working The muscle that controls the passage of blood through capillaries is a precapillary sphincter See picture on page 477

VERY IMPORTANT SLIDE Capillaries have walls that are thin enough for substances to cross between the blood and the interstitial fluid (fluid surrounding tissues, in multicellular animals). This transfer of materials is the most important function of the circulatory system Ways that substances are exchanged –Diffusion, ex. oxygen and carbon dioxide –Vesicles transport larger molecules through exocytosis and endocytosis –The capillary wall is leaky, allowing water and small solutes to slip through

How does this happen? Various forces drive fluid exchange –Blood pressure: pushes fluid outward –Osmotic pressure: draws fluid in, because the blood has a higher concentration of solutes than the interstitial fluid The direction of fluid movement depends on the difference between blood and osmotic pressure –Arterial end: blood pressure is higher –Venous end: osmotic pressure is higher

Blood consists of red and white blood cells suspended in plasma Blood consists of several types of cells suspended in a liquid called plasma Plasma is 90% water, but it includes proteins as well –Red blood cells (erythrocytes) –White blood cells (leukocytes) –Platelets

More about Red Blood Cells Anemia: a condition with an abnormally low amount of red blood cells (cells do not get enough oxygen) A hormone produced by the kidney, EPO, stimulates bone marrow to produce more red blood cells Humans living in high altitudes have adapted to produce more red blood cells to make up for the lower oxygen levels