Circulatory System. Chapter 32

Transcription

1 Circulatory System Chapter 32

2 Invertebrates w/o a Circulatory System If an organism has a sac body plan, circulatory systems are not necessary. Sac body plans mean cells are capable of gas and nutrient exchange individually Simple diffusion and osmosis principles are all that is necessary Single-celled organisms or members of the cnidarian phyla (sea anemones, jellyfish, etc) For other organisms, cells do not always have direct access to nutrients and gasses. These organisms need a circulatory system, or a system of transporting water, gasses, and nutrients throughout an organism from specified entry and exit points.

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4 Open Circulatory System Open circulatory systems are those which the circulatory fluid itself makes contact with the environment. Most mollusks and arthropods have open circulatory systems with hemolymph (a mixture of blood and interstitial fluid) instead of pure blood The hearts of these organisms pump hemolymph into body cavities called hemocoels. The hemolymph contains nutrients, but no oxygen. Eventually, the hemolymph releases its nutrients then makes it s way back to the heart for circulation. For oxygen, organisms have special air tubes called trachea. Trachea flow all throughout the body, providing gas exchange for individual cells that is independent from the blood and heart.

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6 Closed Circulatory System A few members of the mollusk and arthropod classes have a closed circulatory system. Blood (a mixture of cells and plasma) is pumped by the heart into a system of branching blood vessels. Some organisms, like earthworms, even contain multiple hearts Red blood cells contains a pigment called hemoglobin, which turns the blood of closed circulatory systems red. Blood is capable of carrying both nutrients and oxygen to the cells of the organism. Some gas exchange always occurs through the body wall or epidermis in organisms. For humans, hardly any. For earthworms, it s a much higher percentage.

7 Cardiovascular System All vertebrates have a closed circulatory system called a cardiovascular system. The cardiovascular system uses an organ called a heart for pumping substances, and contains 3 types of vascular tissue called blood vessels (vascular=transport) Arteries: carry blood away from the heart Capillaries: exchange materials with tissue fluid Veins: return blood to the heart Arteries have thick walls that are able to expand and aid in pumping blood. Arterioles are smaller arteries that branch into capillaries Capillary beds allow for exchange of nutrients and waste for the cells Veinules carry deoxygenated blood and waste materials into veins Heart artery arteriole capillaries capillary beds cells capillary beds capillaries veinules veins heart

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10 Circulatory System Pathways Vertebrates show three separate circulatory pathways 1) One-circuit (single-loop) system (Fishes) The heart has a single atrium and a single ventricle. Blood is oxygenated at gills then carried throughout the body. 2) Two-circuit (double-loop), single ventricle system (Amphibians and most reptiles) The heart pumps blood to the tissues (the systemic circuit) and also to the lungs (the pulmonary circuit) This is an evolutionary trait of air-breathing organisms 3) Two-circuit, double ventricle system (Crocodiles, birds and mammals) A separate atrium and ventricle for each circuit. Helps to ensure the blood pressure is adjustable for both the systemic and pulmonary circuit)

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12 The Human Heart The human heart is located between the two lungs and is tilted toward the left side of the organism (all directions are from the perspective of the organism) The major portion of the heart is the myocardium, where the majority of cardiac muscle resides The heart lies within the pericardium, a membranous sac that secretes lubricating fluid (like engine oil). The heart itself is separated by a septum, a wall dividing the heart into the right and left sides. The two upper chambers of the heart are the atria, while the lower chambers are the ventricles

13 The Human Heart The heart has four valves which direct the flow of blood and prevent its backward movement. Between the atria and ventricles the valves are called the atrioventricular valves. Between the ventricles and their attached vessels, the valves are called the semilunar valves They look like half-moons. The vein carrying blood from the body to the heart is the Vena Cava (Inferior/Superior) The vein carrying blood from to lungs to heart is the Pulmonary Vein The artery carrying blood from heart to lungs is the Pulmonary Artery The artery carrying blood from the heart to the rest of the body is the Aorta

14 The Human Heart The two Vena Cava veins carry O 2 -poor and CO 2 -rich blood from the body where it enters the right atrium. The tricuspid valve opens and allows a specific amount of blood to enter the right ventricle The right ventricle pushes the blood through the pulmonary valve into the pulmonary artery, where it will travel to the lungs for oxygenation

15 The Human Heart Four pulmonary veins bring O 2 - rich blood back from the lungs to the left atrium The bicuspid valve opens and lets blood flow into the left ventricle The left ventricle pushes blood through the aortic valve into the aorta, where it takes blood throughout the body

16 Heartbeat Each heartbeat lasts around.85 seconds, for 70 beats per minute Systole refers to when the heart chambers contract, while diastole refers to when the chambers relax. The heartbeat s familiar lub dub sound is the valves opening and closing lub the atrioventricular valves closing dub the semilunar valves closing pause while the atria fill with blood The rhythmic contraction of the heart is due to the cardiac conduction system, run by nodal tissue SA node (sinoatrial): pacemaker AV node (atrioventricular): opens the ventricle valves

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18 Blood Pressure As blood is pushed out of the ventricles, blood pressure rises. As blood flows from the aorta into the arteries and arterioles, blood pressure falls. Veins, however, have too low of blood pressure to push blood back toward the heart. Instead, skeletal muscles aid the veins Veins also have tiny valves which prevent blood from flowing backwards Blood pressure is measured with a sphygmomanometer and recorded in mm HG (millimeters of mercury)

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20 Cardiovascular Disorders Hypertension Hypertension is high blood pressure Hypertension is usually not detected until a stroke or heart attack occurs Atherosclerosis Accumulation of soft masses of fatty materials such as cholesterol The plaque causes clots to form, which can either remain stationary (thrombus) or move with the blood (embolus) Stroke An embolus blocks the cranial artery, preventing oxygen from getting to the brain Heart attack When a portion of heart muscle dies due to blockage

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22 Blood Blood consists of 1) transport substances for the capillaries, 2) immune agents for fighting off foreign invaders and transporting combative agents, 3) body temperature regulators 4) clotting factors Formed Elements The red and white blood cells (discussed in ch 33) Plasma Water, proteins, salts, gases, nutrients, wastes and hormones

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24 Red Blood Cells There are 6 million blood cells for every cubic mm of blood. Each blood cell contains 250 million hemoglobin molecules Hemoglobin, a combination of protein and iron, is able to electrically hold 4 oxygen molecules/molecule of hemoglobin. RBC s are manufactured in the marrow of the skull, ribs, vertebrae and long bones. RBC s contain no nucleus. They live for 120 days and then are swallowed by the liver or spleen for recycling The iron is returned to marrow for reuse; the heme of the blood is released as waste Hence, the reddish-brown hue of feces

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26 Platelets Platelets are small factors that are involved in the 12 steps of blood clotting. When a blood vessel is damaged, platelets clump at the site and partially seal the leak. Cell tissues release prothrombin, which activates the production of thrombin. Thrombin then activates fibrins, which will thread around a platelet until the injury is sealed. The process is complicated because formation of clots (scabs) can be deadly if it happens at the wrong time. The complicated process virtually ensures clotting only occurs when necessary, never by accident.

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28 Extra Credit Question This question is worth an extra 5% on your essay exam You may check your answers with me ahead of time for a yes or no response as many times as you like. The most common types of cancers are lung, skin, and colon cancer. Explain why.