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Overview of the Human Circulatory System: Structure, Functions, and Key Components

The human circulatory system is a complex network crucial for transporting vital materials like oxygen and nutrients to cells, removing waste products, regulating body temperature, and transporting hormones and antibodies. It comprises two primary types: the open circulatory system found in invertebrates, and the closed circulatory system in vertebrates, including humans. The latter features a muscular heart and a system of blood vessels: arteries, veins, and capillaries. This system ensures effective blood flow, as characterized by the cardiac cycle, blood pressure measurements, and heartbeat regulation through intrinsic and extrinsic stimuli.

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Overview of the Human Circulatory System: Structure, Functions, and Key Components

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  1. Internal Transport System SBI 3UO

  2. Function • To circulate necessary materials to all of the cells in the body e.g. Oxygen • To remove the waste products of cell metabolism • To regulate body temperature • To carry materials e.g. Hormones and antibodies to various organs • Clotting at the site of a wound to minimize blood loss

  3. Two Types of Circulatory Systems • Open (invertebrates) – hemolymph is pumped into the body cavity • Closed (vertebrates) – blood is physically contained within vessels and separated from other body tissues See fig. 12.1 pg. 479

  4. Structure • A closed system of blood vessels pumped by a muscular heart • It consists of: • heart: a muscular organ which pumps blood throughout the body • Artery: a vessel that carries blood AWAY from the heart – arterioles (small arteries) • Vein: carries blood TO the heart – thinner layer of muscle – venules: smaller veins • Capillaries: link arterioles and venules

  5. Heart • http://www.youtube.com/watch?v=H04d3rJCLCE

  6. Three subdivisions of the circulatory system (the double circulatory system) • Systemic system: blood travels through the body cells (at any time 80-90% of the blood) • Pulmonary system: blood travels through the lungs (rest of blood) • Cardiac system: Blood travels through the tissues of the heart Complete worksheet – Double circulatory system (pg. 483, fig. 12.7)

  7. Blood Pressure • When the heart contracts blood is forced out at a high pressure (blood makes a swishing noise)  this is called the “systole” • As the heart relaxes the blood is no longer being forced (noise stops)  “diastole” • Pressure is measured in mm Hg • Blood pressure is measured using an instrument called a sphygmomanometer (pronounced: sfig-mow-mah-nah-meh-ter).

  8. Blood Pressure – Contn’ • Average systolic is approx. 120 mmHg • Average diastolic is approx. 80 mmHg • Together the systole and diastole are called the “cardiac cycle” or a heartbeat

  9. Heartbeats • Average male = 75/80 b/m • Average female = 85/90 b/m • Resting = 60 b/m • Active = 160 b/m Live Beating Heart surgery http://www.youtube.com/watch?v=Pes9O5z8efk&feature=related

  10. Sounds of the Heart • “ LUBDUB LUBDUBLUBDUB” • LUB – ventricles contract causing the AV to slap shut • WHY? • DUB – semi-lunar valves slap shut • WHY? SinoatrialSVnode – right atrium – rhythmic signals that causes atria to contract Atrioventricular AV node – between atria and ventricles (signal reaches AV node through the specialized bundles – bundles of His  Purkinje fibres initiate contraction of right and left ventricles

  11. Components of blood

  12. Heart • Large strong muscle • 4 chambers • Septum divides the oxygenated and deoxygenated blood • Beats in rhythmic contractions • Valves control the flow/back flow of blood • Pumped to 3 main areas: • Lungs = pulmonary system • Heart = cardiac system • Body = systemic system - Label the parts of the heart (pg. 480 fig. 12.2) - Draw the cross-section of the human heart (pg. 481 fig. 12.3)

  13. Arteries • Carry blood away from the heart • Thick elastic muscle walls, small in diameter • Can withstand the great pressure that is created when the blood is forced out of the heart • When the blood is pumped into the arteries they stretch, as the blood flows away they recoil • This creates the pulse you fell in your wrist and neck • Main artery is the AORTA • Branch off into smaller arterioles • Draw fig. 12.4 pg. 482 – Arteries and Veins

  14. Veins • Bring blood back to the heart • Thin walls, larger diameter • Not heavily muscled, elastic • Cannot handle high pressure • Very elastic and will stretch with pooled blood • Smaller veins - venules branch into veins • Muscles contract around the veins and force the blood through the veins • Veins have a one-way flap called the venous valve that stops the blood from flowing backwards • Two main veins lead to the heart: • Superior Vena Cava • Inferior Vena Cava

  15. Capillaries • Smallest of the vessels • Join the arterioles to the venules • Form dense capillary beds, have valve that control blood flow

  16. Heartbeat • Cardiac muscles contract by “inherent rhythm”, no other stimulus required • Can beat even if nerves are severed • In order to beat faster or slower it does receive messages from the brain • 3 types of stimuli: • Nervous stimuli – fear, excitement, tension • Physical stimuli – exercise • Chemical stimuli – drugs, alcohol, adrenalin

  17. Pathway of the Stimulus Medulla Oblongata 2 Nerve cords 1. through spinal cord (carries stimulus to beat faster) 2. vagus nerve (inhibitor, causes to beat slower) Pacemaker right atrium

  18. Lymphatic System • Function – drains excess fluid from the tissues and adds this fluid to the veins • EFC extracellular fluid comes from the blood and must be returned • Small capillaries called lacteals drain the excess fluid from the tissue • This fluid is now called lymph (pale yellow) • Lymph is forced through the vessels like blood in the veins (by muscle contractions) • Lymph nodes located in the lymphatic system produce white blood cells = phagocytes, leucocytes (destroy foreign substances and organisms)

  19. DID you know? • Your heart beats 100,000 times a day. • Your heart beats 2 billion times in your lifetime! • Blood cells are formed in your bone marrow. Videos: http://www.learn360.com/ShowVideo.aspx?ID=129270&SearchText=circulatory+system&lid=13216000 Blood components: http://www.youtube.com/watch?v=R-sKZWqsUpw http://www.sciencekids.co.nz/videos/humanbody/circulatorysystem.html Once upon a time... Life - The tiny platelets (1 of 3) http://www.youtube.com/watch?v=JvOH5skxqoA&feature=fvwrel

  20. Homework • Read pages 478-488 and answer questions #1-15 • Read pages 489-492 and answer questions #1, 2, 5, 6, 8.

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