Topic 1.2/1.3, Risk factors for CVD Blood Pressure and tissue fluid formation

Introduction  Read pages  Summarise the risk factors for CVD and answer questions  Describing and interpreting data and trends:  Describe what can be observed from the data  Pay attention to quantifying data and the differences

Does one’s sex (male/female) affect risk?  Does gender affect risk of CVD?  Before 60 males are much more likely to have a heart attack.  Why?  Genetic factors  Oestrogen  Lifestyle

Does age affect risk?  Why does age affect risk of CVD?  Positive corellation between age and risk of CVD.  Arteries are less elastic and more easily damaged. Other risk factors can also increase.

What is blood pressure?  Hydrostatic force of blood pushing against the walls of the blood vessels.  Measured using a sphygmomanometer and stethoscope or a blood pressure monitor  The result is expressed as- systolic pressure/diastolic pressure  Normal range is mm Hg (systolic) mm Hg (diastolic)

Blood pressure measurements  2 measurements  Systolic, heart contraction  Diastolic, relaxation  What happens during the cardiac cycle during systole?  Cardiac muscle is contracting. Systolic pressure- maximum pressure in the arteries which occurs during ventricular systole  What happens during the cardiac cycle during diastole?  All cardiac muscle relaxed. Diastolic pressure- pressure minimum in the arteries which occurs during diastole when ventricles are filling with blood

Measuring blood pressure  Read Activity 1.12 Measuring BP and answer Q 1 & 2 Answer Q 3 – Q5

What’s your risk of heart disease? 

Blood Pressure  Hy pertension: elevated blood pressure.  Hypotension: abnormally low blood pressure.

What determines the blood pressure?  Peripheral resistance  Contact between the blood and blood vessel wall causes friction and slows the flow  Cardiac output  Pulse rate-  number of beats per minute  Stroke volume-  volume of blood pumped out of the left ventricle in one beat  Cardiac output = heart rate X stroke volume  If the cardiac output increases, the blood pressure will ______________.

What determines the blood pressure?  The force of blood hitting the vessel walls.  What happens to your aorta further away from your heart? Compare the structure of arteries, veins & capillaries.

 What is found in the tunica media?  Elastic fibers and muscle tissue  What is the function of the elastic fibers?  It allows the vessel to recoil and maintain blood pressure during diastole.  What is the function of the muscle tissue?  It can constrict and dilate, altering blood flow.  Structure of the capillaries and veins:  Veins have much less collagen, elastic fibres, and smooth muscle.  Capillaries are only made up of tunica intima (endothelium).

 Pressure is affected by the:  Size of the lumen and speed of the blood.  In which blood vessels is blood pressure the highest and why?  Arteries, narrow lumen and the blood has just left the heart.  Where is atheroma more likely to happen?

Why does the pressure decrease? Along the arterioles and capillaries there is a high surface area so more blood is in contact with the blood vessel walls Increased peripheral resistance (due to more friction) Blood slows down and blood pressure decreases What causes the pressure fluctuations in the arteries? Contraction and relaxation of the heart muscle. The pressure in the arteries does not drop too much even when the heart is relaxing. Why? Elastic recoil of the artery walls maintains the blood pressure

In summary, The greater the surface area of the blood vessels, the higher the peripheral resistance and… the further from the heart, the lower the blood pressure

 Arteries Constrict  Peripheral resistance increases  Blood pressure increases  Arteries Dilate  Peripheral resistance decreases  Blood pressure decreases What is the function of the smooth muscle tissue in the arteries and arterioles? It can constrict and dilate the blood vessel lumen altering blood flow.

 Natural loss of elasticity with age  High salt diet  Release of hormones e.g. adrenaline Factors causing arterioles and arteries to constrict and increasing blood pressure

 What is another way in which adrenaline increases the blood pressure?  It increases the cardiac output so also increases the B.P.  Stroke volume: amount of blood leaving the heart during 1 beat.  Cardiac output: amount of blood leaving the heart in 1 min  Stroke volume x heart rate  Adrenaline increases cardiac output = higher BP

Tissue Fluid  Interstitial fluid  Surrounds tissue and allows for diffusion between blood and cells.  Formed from plasma which leaks out of capillary walls.  Complete Tissue Fluid Formation in your handout, use your textbook

 Hydrostatic pressure:  Force exerted by the liquid on the capillary walls  Generated by the systolic force of the heart  Pushes water out of the capillaries.  Osmotic pressure  Water potential is created due to the ability of small solutes to pass through the capillary walls.  The buildup of solutes induces osmosis.  Water passes from an area of high concentration outside of the vessel to an area of low concentration inside of the vessels.  Osmotic pressure pushes water back into the capillaries.

 At the arterial end of the capillary the hydrostatic pressure is greater than the osmotic pressure, so fluid flows out of the capillary.  At the venule end of the capillary the osmotic pressure is greater than the hydrostatic pressure, so fluid flows into the capillary.

Lymph  Lymphatic system: excess tissue fluid drains into system, lymph nodes and macrophages.  Lymphatic system is part of the immune system,  Important for the production of lymphocytes, white blood cells.  Oedema: excess tissue fluid formed due to hypertension. This causes swelling.