Topic 1A

what is th function of water in the body

water tansports substances. substances can be transported more easily if they are dissolved in a solvent so the fact that water is a liquid and a solvent means it can easily transport all sorts of materials like glucose and oxygen

describe the structure of water

* it is one molecule of O and two moleules of H (H2O)
* because the shared negative hyrogen electrons are pulled towards the oxygen, the otherside of each hydrogen atom has a slight positive charge
* the unshared negative electrons on the oxygen atom give it a slight negative charge
* this makes water a dipolar molecule( partial negative chage on ones side and partial positive charge on the other side)
* the slightly negativly charged oxygen atoms attrat the slightly positivly charged hydrogen atoms on the other water molecules
* this attraction is called hydrogen bonding and it gives water many useful properties

how do things dissolve in water

because water is dipolar the slightly positive end of the water molecule will be attracted to the slightly negative end of an ion and the slightly negative end of the molecule will be attracted to a positive ion. this means they will be totally surrouned in water molecules causing them to dissolve

why do multicellular orgaisms need a mass transport system? and why do single cellular organisms not need one?

cells need enery they mostly get this through aerobic resperation. the raw materials for this is glucose and oxygen so the bodu has to make sur it dan deliver enoguh of these to all of the cells.

* in single celled organisms these materials can diffuse directl into the cells across a cell membrane and the diffusion rate is quicker due to a short diffusion distance
* in multicellular organisms, diffusion across the outer membrane would be too slow because of the large distance substances would have to travel to reach all cells therefore they need a mass transport system

what is a mass transport system

they are usedd to carry raw materials from specalised exchange organs to body cells and remove metaolic waste

* in mammles the mass flow system is the circularatory sysem where the heart is used to pump blood around the body
* individual cells in tissues and organs get nutriets and oxygen from the blood and dispose of metabolic waste into the blood

describe an external examination of a heart

you will see 4 main vessles attached to it. the feel of the vessles helps identidy each one. arteries feel thick and rubery and veins feel much thinner. you will be able to see the left atria, right and left ventricles and coronary artery

describe an internal examination of a heart

the ventricles can be cut open using a scalpal do you can see inside each one. you should see that the wall of the left ventricle is thicker then the wall of the right ventricle. the atria can be cut open if you look in the atria walls tou will notice they are thinner then the ventricle walls. you can also look at the structures of the atrioventricular valves and the semi-lunar valves

what does the left ventricle do?

it needs to contract powerfully to pump blood all the way around the body this means it is a lot thicker then the right ventricle

what does the right ventricle do?

pumps blood to the lungs

do the ventricles have thicker or thinner walls then the atria, why?

thicker walls because they have to push blood out of the heart where as atria just needs to pump blood a short distance into the ventricles

what do the atrioventricular valves do

they link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract. cords attach the atroventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract

what do the semilunar valves do

they link the ventricles to the pulmonery artery and aorta and stop blood flowing back into the heart after the ventricles contract

what is the purpose of valves

they only open one way. weather they are open or closed depends on the relative preassure in the heart chambers . if there is higher preassure behind a valve its foced open but if the preassure is higher infront its foced shut. this means blood can only flow in one direction through the heart. valves prevent the backflow of blood.

describe the structure and function of arteries

they carry blood away from the heart to the rest of the body. they have a thick wall, are muscular and have elastic tissue in their walls to help withstand high blood preassure caused by heart beat. the endothelium is folded which allows the artery to expand which also helps with high bloos preassure. they have a small lumen to help maintain a high blood preassure

describe the structure and function of a vein

they take blood back to the heart. they are wider with little elastic or muscle tissue as the blood is under a low preassure. veins contain valves to prevent backflow . blood flow through the veins is helped by the contraction of body muscles surrounding them.

describe the structure and function of capillaries

they are the smallest blood vessles they are were metabolic exchange occurs. substances are exchanged between cells and capillaries. the walls are only one cell thick which speeds up diffusion of substances

what are the 3 stages of the cardiac cycle

ventricular diastole, atrial diastole and cardiac diastole

what happenes in ventricular diastole/ atrial systole

ventricles are relaxed, atria contract decreasing the volum of the chambres and increasing the preassure in the chambres. this pushes blood into the ventricles. there is a slight increase in ventricular preassure and the chambre volume as the ventricles recieve the ejected blood from the atria

what happenes in ventricular systole/ areial diastole

the atria relax. ventricles contract decreasing the volume and increasing their preassure. the preassure becomes higher in the ventricles then the atria which forces the AV valves closed to prevent backflow. (this creates a lub) preassure in the ventricles is also higher then the aorta and pulmonery artery which forces open the semilunar valves and foces blood out into these arteries

what happenes in cardiac diastole

ventricles and atria relax. higher preassure in pulmonery artery and aorta closes the SL valves to prevent backflow back into the ventricles. blood returns to the heart and the atria fills again due to high preassure in the vena cava and pulmonery vein. this starts to increase the preassure of the atria and so AV valves open. this allows blood to flow passivly into the ventricles from atria. the atria contract and the process begins again