Circulatory SystemYuorick A. JardinBSED-2C MAPEH

Do NowWhy is it important for your heart to continue beating even when youre sleeping?What does your body need? What are some wastes?

Circulation and RespirationEach breath brings oxygen rich air into your bodyYour cells need that oxygenYour heart delivers oxygen to your cells

Working together, your circulatory and respiratory systems supply cells throughout the body with the nutrients and oxygen that they need to stay alive!

Multicellular NeedsUnicellular organisms dont need a circulatory system, because the cell is in direct contact with the environment and oxygen, nutrients and wastes can easily diffuse across the cell membrane by diffusion. Multicellular organisms need a circulatory system to transport substances made in one part of the body to sites where they are needed in another part of the body.

FunctionThe circulatory system transports substances including oxygen, nutrients and wastes to and from cells responding to changing demands by diffusion (from high to low concentration along concentration gradient).

StructureHumans have a closed circulatory system.Blood is pumped through a system of vessels(In an open system, blood flows in vessels and sinuses/gills)Sometimes the circulatory system is also called the cardiovascular system because:Cardio = heartVascular = vesselsThe human circulatory system consists of: The heartA series of blood vesselsBlood that flows through them

The HeartLocated near the center of your chestA hollow organ about the size of your fist composed of cardiac muscle.Enclosed in a protective sac of tissue called the pericardiumInside there are two thin layers of epithelial and connective tissueContractions of the myocardium, a thick cardiac muscle, pump blood through the circulatory systemThe heart contracts about 72 times a minuteEach contraction pumps about 70 mL of blood

HeartSeptum, or wall, separates the right side form the left side preventing mixing of oxygen-rich blood and oxygen-poor bloodFlaps of connective tissue called valves divide each side into 2 chambers: totaling 4 chambersUpper chambers receive blood = atriumLower chambers pump blood out of heart = ventricle

Types of CirculationPulmonary circulation = from right side of the heart to lungs where carbon dioxide leaves the blood and oxygen is absorbedSystemic circulation = from left side of the heart to organsCoronary circulation = through heart tissue

Pulmonary CirculationThe right side of the heart pumps blood from the heart to the lungs In the lungs, carbon dioxide leaves the blood while oxygen is absorbed.The oxygen-rich blood goes into the left side of the heart

Systemic CirculationThe oxygen-rich blood from the left side of the heart is pumped to the rest of the bodyOxygen-poor blood returns to the right side of the heartThis blood is oxygen-poor because the cells absorbed the oxygen and released carbon dioxide into the bloodThe oxygen-poor blood is ready for another trip to the lungs to get oxygen again

Section 37-1Figure 37-2 The Circulatory System

Coronary CirculationRemember: the heart is an organ and needs nutrients, oxygen and creates wastes.Blood flows to the tissues of the heart too!

Blood Flow through the heartBlood leaves the heart in arteries, and blood returns to heart in veins.

Oxygenated blood returns from the lungs through the pulmonary veins to the left atrium.Oxygenated blood is pumped from the left atrium through the mitral valve to the left ventricle.Oxygenated blood leaves the left ventricle through the aortic valve to the aorta, which is the largest artery of your body.The aorta branches into various arteries pumping blood through your body.Deoxygenated blood returns from the top of your body through the superior vena cava and from the bottom of your body through the inferior vena cava to the right atrium. Deoxygenated blood is pumped from the right atrium through the tricuspid valve to the right ventricle.Deoxygenated blood leaves the right ventricle through the pulmonary valve to the pulmonary arteries.The pulmonary arteries pump blood to the lungs to absorb oxygen and release carbon dioxide.

Heart circulation animation: http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

The Path of Blood

ValvesBlood enters into the atria of the heart, separated from the ventricles by valves, preventing back-flow of blood keeping the blood flowing in one directionWhen the atria contract, the valves open and blood flows into the ventricles When the ventricles contract, the valves close preventing blood from flowing back into the atria and blood flows out of the heartAt the exits of the ventricles, there are valves that prevent blood from flowing back into the heart

The lub-dup sound of your heart is caused by the closing of the hearts valves. The lub is when the ventricles contract and blood being forced against the artioventricular or A-V (tricuspid or mitral) valves. The dup is the blood being forced against the semilunar (aortic or pulmonary) valves.

Section 37-1Figure 37-3 The Structures of the HeartRight VentricleRight AtriumLeft AtriumLeft VentricleSeptum

HeartbeatThere are two muscle contractions in the heart: The atriaThe ventriclesEach contraction begins in a small group of cardiac muscle cells in the right atrium that stimulate the rest of the muscle cells = sinoatrial node (SA node)Since the sinoatrial node sets the pace for the heart it is also called the pacemakerThe impulse spreads from the pacemaker through fibers in the atria to the atrioventricular node (AV node) and through fibers in the ventricles

When the atria contract, blood flows into the ventriclesWhen the ventricle contract, blood flows out of the heart

Sinoatrial (SA) nodeAtrioventricular (AV) nodeConducting fibersContraction of AtriaContraction of VentriclesSection 37-1The Sinoatrial Node

Changing HeartbeatYour heart can beat faster or slower, depending on your bodys need for oxygen-rich bloodWhen you exercise, your heart rate can increase to 200 beats per minuteThe autonomic nervous system influences heart rateNeurotransmitters released by neurons in the sympathetic nervous system can increase heart rate, and those released by the parasympathetic nervous system can decrease heart rate

Blood vesselsBlood circulates in one direction and it is moved by the pumping of the heartAs blood flows through the circulatory system, it moves through three types of blood vessels:ArteriesCapillariesVeins

ArteriesLarge vessels that carry blood away from the heart to tissues of the bodyExcept for the pulmonary arteries, all arteries carry oxygen-rich blood.Arteries have thick walls of elastic connective tissue, contractible smooth muscle, and epithelial cells that help them withstand the powerful pressure produced when the heart contracts and pushes blood into the arteries.

CapillariesThe smallest of the blood vessels connecting arteries and veinsWalls are one cell thick allowing for easier diffusion of nutrients and oxygen from capillaries to body cells and wastes and carbon dioxide from body cells to capillaries

VeinsReturn blood to the heartVeins have walls of connective tissue and smooth muscleLarge veins contain valves that keep blood flowing towards the heartMany veins are located near skeletal muscles, so when the muscles contract, they help force blood through the veins, even against gravityExercise helps prevent accumulation of blood in limbs and stretching veins out of shape

Section 37-1Figure 37-5 The Three Types of Blood VesselsCapillaryVeinArtery

Blood PressureThe heart produces pressure when it contracts.The force of blood on the arteries walls = blood pressureBlood pressure decreases when the heart relaxes, but there must always be some pressure to keep the blood flowingDoctors measure blood pressure with a sphygmomanometer recording two numbersSystolic pressure = force felt in arteries when ventricles contractDiastolic pressure = force of blood felt in arteries when ventricles relaxAverage adults blood pressure = 120/80

Regulating Blood PressureWith the nervous system:Sensory neurons at several places in the body detect blood pressure and send impulses to brain stem (medulla oblongata)When too high, the autonomic nervous system releases neurotransmitters that cause the smooth muscles around blood vessels to relax, lowering blood pressure. When too low, neurotransmitters are released that cause the smooth muscles to contract, elevating blood pressure.With the endocrine/excretory system: Hormones produced by the heart and other organs cause kidneys to remove more water from the blood when blood pressure is too high, reducing blood volume and lowering blood pressure

DisordersDisorders of the circulatory system are very common:High Blood PressureHeart AttackStrokeMost stem from atherosclerosis = fatty deposits (plaque) builds up on walls of arteries, obstructing blood flow, increasing blood pressure and risk of blood clots

High Blood PressureAlso known as HypertensionForces heart to work harder, which may weaken or damage the heart muscle and vesselsMore likely to develop heart disease and increased risk of heart attack and stroke

Heart AttackA medical emergencyCoronary arteries (supplying heart blood) bring oxygen and nutrients to the heart muscle itselfBlockage of coronary artery may damage or kill part of heart muscle (myocardium) due to lack of oxygen = heart attackSymptoms include: chest pain/pressure, feeling of heartburn/indigestion, sudden dizziness, or brief loss of consciousness

StrokeBlood clots may break free from vessels and get stuck in a blood vessel leading to a part of the brain = strokeBrain cells relying on that vessel may begin to die from lack of oxygen and brain function in that region may be lostStrokes can also occur when a weakened artery in the brain burst, flooding the area with blood

PreventionCardiovascular diseases are easy to prevent:Exercise increases respiratory systems efficiencyWeight control reduces body fat and stressSensible diet low in saturated fat reduces risk of heart diseaseNot smoking reduces risk of heart disease

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