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THE HEART

CIRCULATION

THE MAIN COMPONENT OF THE CIRCULATORY SYSTEM IS THE HEART, A MUSCULAR PUMPING ORGAN SITUATED IN THE THORAX(CHEST CAVITY).IT IS CONNECTED BY BLOOD VESSELS TO EVERY TISSUE IN THE BODY, AND CARRIES OUT THE FOLLOWING FUNCTIONS:

PUMPING OXYGENATED BLOOD FROM THE LUNGS TO THE BODY TISSUES SO THAT THEY CAN WORK

COLLECTING DEOXYGENATED BLOOD FROM THE BODY AND TRANSPORTING IT TO THE LUNGS WHERE THE WASTE PRODUCTS ARE EXCRETED, BY BEING BREATHED OUT.

THE HEART HAS FOUR CHAMBERS WITHIN, THE UPPER TWO CALLED THE ATRIA AND THE LOWER TWO THE VENTRICLES. THE ATRIA AND THE VENTRICLES ARE SEPARATED BY ONE-WAY VALVES THAT ALLOW BLOOD FLOW IN THE DIRECTION OF ATRIA TO VENTRICLES ONLY, AND THE LEFT AND RIGHT SIDE OF THE HEART HAVE NO COMMUNICATION BETWEEN THEM.THE RIGHT SIDE OF THE HEART TRANSPORTS ONLY DEOXYGENATED BLOOD, FROM THE BODY TO THE LUNGS, WHILE THE LEFT SIDE OF THE HEART TRANSPORTS ONLY OXYGENATED BLOOD, FROM THE LUNGS TO THE RESTOF THE BODY AGAIN.

ACTION OF THE HEART

DEOXYGENATED BLOOD IS COLLECTED FROM THE WHOLE BODY THROUGH THE VEINS AND TRANSPORTED TO THE RIGHT ATRIUM VIA THE INFERIOR AND SUPERIOR VENAE CAVAE.

AS THE HEART BEATS, IT PUMPS THIS BLOOD THROUGH THE ONE-WAY VALVE BETWEEN THE TWO RIGHT HEART CHAMBERS( TRICUSPID VALVE) AND INTO THE RIGHT VENTRICLE. THE NEXT BEAT PUMPS IT OUT OF THE RIGHT VENTRICLE AND INTO PULMONARY ARTERY WHERE IT PASSES TO THE LUNGS FOR REOXYGENATION.

ONCE OXYGENATED, THE BLOOD RETURNS TO THE LEFT ATRIUM THROUGH THE PULMONARY VEIN,THEN IT IS PUMPED THROUGH THE ONE- WAY VALVE ( mitral valve) into the left ventricle. THE next heart beat

THE HEART FIGURE 4.1

PULMONARY ARTERY

SUPERIOR VENA CAVA

RIGHT ATRIUM

INFERIOR VENA CAVA

RIGHT VENTRICLE

AORTA

BRANCH FOR CORONARY ARTERIES

PULMONARY VEIN

HEART VALVES

ENDOCARDIUM(INNER SURFACE OF HEART)

THERE ARE FOUR BASIC TYPES OF CELL IN THE HUMAN BODY:

MUSCLE CELLS- these generate forces and produce motion; they may be attached to bones to allow limb movement, or enclose hollow cavities so that their forces cause expulsion of the cavity contents( such as movement of food through the digestive tract.

NERVE CELLS- these can initiate and carry electrical impulses to distnat areas of the body along their lenght to produce many actions, such as to cause muscle cells to contact, or to cause glands to release chemicals or fluids in the body (such as the salivary glands.)

EPITHELIAL CELLS- these cover the body surface as skin, or surround organs or line hollow structures within the body; they act to separate areas of the body form each other and from the external environment, to prevent the uncontrolled movement of harmful micro-organisms.

CONNECTIVE TISSUE CELLS- THESE CONNECT VARIOUS PARTS OF THE BODY TOGETHER BY ANCHORAGE AND SUPPORT, SUCH AS IN THE WHOLE BONY SKELETON AND TENDONS AND LIGAMENTS.

ALL OF THESE CELLS REQUIRE A SOURCE OF FUEL TO PRODUCE THE ENERGY THEY NEED TO BE ABLE TO WORK AND CARRY OUT THEIR INDIVIDUAL FUNCTIONS, AND THE FUEL IS PROVIDED BE THE FOOD THAT WE EAT. THE ENERGY IN THE FOOD IS RELEASED FOR USE BY THE CELLS BY THEACTION OF FOOD DIGESTION IN THE DIGESTIVE SYSTEM, AND IS USED FOR ANY OF THE FOLLOWING:

MAINTENANCE OF BODY TEMPERATURE ABOVE OR BELLOW THAT OF THE SURROUNDINGS- THIS CALLED HOMEOSTASIS

PRODUCTION OF MOVEMENT TO ALLOW FOOD GATHERING, AND THEREFORE THE PRODUCTION OF MORE ENERGY

REPRODUCTION FOR THE SURVIVAL OF THE SPECIES.

THE HUMAN BODY HAS 10 ORGAN SYSTEMS, EACH WITH VARIOUS COMPONENTS AND SPECIFIC FUNCTIONS TO ALLOW THE CONTINUATION OF LIFE. THE ORGAN SYSTEMS ARELISTED BELOW:

CIRCULATORY SYSTEM- composed of heart, blood vesels, blood; functions to allow therapid bulk flow of blood around the body tissues.

RESPIRATORY SYSTEM- composed of nose throat, larynx, trachea, lungs; functions to allow the axchange of oxygen and carbon dioxide between the body and the external environment.

DIGESTIVE SYSTEM- composed of mouth, pharynx, oesophangus, stomach, intestines,pancrease, salivary glads, liver, gall bladder, functions to digest, process and absorb nutrients, and to excrete waste products.

URINARY SYSTEM- composed of kidneys, ureter, bladder, urethra; functions to regulate blood plasma and excrete waste products.

MUSCULO-SKELETAL SYSTEM-composed of cartilage, bone, ligaments,tendons, joints, skeletal muscle; functions to support and protect the internal organs, and allow movement.

IMMUNE SYSTEM- composed of white blood cells, lymph,, spleen, bone marrow, thymus gland; functions to defend against infection, and produce red and white blood cells.

NERVOUS SYSTEM- composed of brain, spinal cord, nerves, sensory organs (eye, ear. etc.), functionsto give consciousness, and regulate and coordinate body activities.

ENDOCRINE SYSTEM- composed of all the glands that secrete hormons; functions to regulate and coordinate the workings of the whole body.

REPRODUCTIVE SYSTEM- composed of the male and femaile sex organs; functions to allow reproduction and the the continuation of human species.

INTEGUMENTARY SYSTEM- composed of the skin; functions to rpotect against injury and dehydration, and maintain the body temperature.

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