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Quaestio: What structures transport substances throughout the human body? Nunc Agenda: What are 3 parts of a circulatory system? What are they called in the human body? Function of the Circulatory System • To transport oxygen, nutrients, and other dissolved substances throughout the body • Remove wastes from cells • Maintain body temperature by distributing heat Vertebrate circulatory system overview • Heart pumps blood – Atrium – collects blood from veins – Ventricle – pumps blood out to the body • Blood Vessels – Arteries – carry blood away from the heart – Capillaries – tiny vessels where exchange of materials between blood and body cells occurs – Veins – carry blood toward the heart Other vertebrate hearts • Fish – 2 chamber heart – 1 atrium, 1 ventricle • Amphibians – 3 chamber heart – 2 atria, 1 ventricle • Birds / mammals – 4 chamber – 2 atria , 2 ventricles – Prevents oxygenated and deoxygenated blood from mixing, allows for more efficiency and ability to be warm-blooded The Developing Heart of a Zebrafish Embryo http://bioimaging.caltech.edu/index_content.ht ml Note: In Crocodilians, heart is actually completely separated. They can prevent blood from flowing through the pulmonary circuit while underwater by using a muscular valve. Overview of Vertebrate Circulatory Systems Interesting… • Average adult body contains about 5 L of blood • On average , your blood circulates from your heart, throughout your body and back about every 60 seconds. • Everyday your heart beats about 100,000 times • First heartbeat in human embryo occurs about 45 weeks after conception • The leading cause of death in the US is heart disease The heart is a muscular double-pump • Pulmonary circulation – right side of the heart pumps deoxygenated blood to the lungs – Heart lungs – Pulmo = “lung” (latin) – -ary = “belonging to or connected with” • Systemic circulation – left side of the heart pumps oxygen rich blood to the rest of the body – Heart brain and body Blue=Deoxygenated blood. Red = oxygenated blood Lungs replenish the blood with oxygen. How it works: RBCs pick up O2 through diffusion across the capillary membrane. Pericardium – a tough membrane that covers the heart and protects it The Heart • The heart consists of four chambers: – – – – 1. Left Atrium 2. Left Ventricle 3. Right Atrium 4. Right Ventricle • Atria: Upper, thin-walled chambers. • Ventricles: Lower, thick-walled chambers. • Septum: A wall that separates the left and right sides of the heart. • Valves: flaps of tissue that prevent blood from flowing backwards The heart • Composed almost entirely of cardiac muscle – Cells are connected together in an electrical network that stimulates contraction – When one cell is stimulated, all of the fibers contract at the same time – Can work continuously without getting tired Cardiac Muscle Cells Human Heart Beat • 2 contractions 1. Atria contract “lub” • • Begins at the SA node (sinoatrial) a.k.a. “the pacemaker” Electrical impulse spreads causing both atria to contract 2. Ventricles contract “dub” • • Impulse is picked up by the AV node (atrioventricular) Split-second delay then both ventricles contract, pumping blood out of the heart – (allows both atria to contract and ventricle to fill with blood) Circulation Pathways (1) • Steps: – 1. Deoxygenated blood enters the right atrium of the heart from the body tissues. • This blood reaches the heart through the superior and inferior vena cava veins. – 2. Deoxygenated blood is pumped from the right atrium to the right ventricle through a valve. – 3. Deoxygenated blood is pumped out of the heart to the lungs by the right ventricle. • This blood is pumped out through the pulmonary artery. – 4. The lungs replenish the blood with oxygen. It is now oxygenated blood. Circulation Pathways (2) • Steps: – 5. Oxygenated blood enters the left atrium of the heart from the lungs. • This blood reaches the heart through the pulmonary veins. – 6. Oxygenated blood is pumped from the left atrium to the left ventricle through a valve. – 7. Oxygenated blood is pumped out of the heart to the body tissues by the left ventricle. • This blood is pumped out through the aorta. – 8. The body tissues use the oxygen carried by the red blood cells. The blood then becomes deoxygenated and must be returned to the heart where the cycle repeats. Simplified Sequence • Blood flows from Right Atrium Right Ventricle Lungs Left Atrium Left Ventricle Rest of Body Right Atrium again. Pulmonary Circuit: Right Ventricle Lungs Left Atrium Systemic Circuit: Left Ventricle Body Right Atrium Questions • The left ventricle is the largest chamber of the heart. How is its size related to its function? • If the valves in the right ventricle do not close properly, where in the body might circulation be affected the most? • Why is it important to have two separate pathways for circulation? • Describe some of the adaptations of the mammalian heart that allow it to be efficient and coordinated.