Safety  You’ll be using a scalpel to cut the heart, which can just as easily cut you!  Handling raw meat can be dangerous – wear gloves, and wash hands thoroughly afterwards

Hearts  The hearts have come from the butcher shop – the animals have not been especially killed for this dissection  If you wish to try this at home, most butchers can accommodate getting hearts.  Try to get hearts which are intact, and if possible pick the hearts the day of the dissection – they are easier to cut when fresh  Remember to think about all safety aspects…

Circulatory SystemCirculatory System  The circulation system’s main function is to get food and O 2 to every cell in the body - as well as being a delivery service, it is also a waste collection service (CO 2 and urea)  Heart – right side pumps deoxygenated blood to the lungs to collect O 2 and remove CO 2 ; left side pumps the oxygenated blood around the body  Arteries carry blood away from the heart (high pressure)  Arteries eventually split off into thousands of tiny capillaries which take blood to every cell  Veins collect the ‘used’ blood and carry it back to the heart (at a low pressure)…

The HeartThe Heart  The heart is a muscular organ – it keeps beating at about 70 times per minute  The muscle cells in the heart need a constant supply of oxygen and nutrients, and their waste products removing – the heart requires its own blood supply to keep beating  Blood vessels called the coronary arteries supply blood to the heart muscles – if they become blocked, a heart attack can happen

Heart AttackHeart Attack  The muscle cells in the heart need a constant supply of oxygen and nutrients, and their waste products removing. So the heart requires its own blood supply to keep beating  Blood vessels called the coronary arteries supply blood to the heart muscles – if they become blocked, a heart attack can happen: -  Fatty deposits build up in the coronary arteries  A blood clot can form on a fatty deposit  The blood clot can block a coronary artery  Some heart muscle cells do not get the oxygen and nutrients they need  These cells start to die  In the UK, every year about 300,000 people have a heart attack

Heart Attack - SpecificsHeart Attack - Specifics  A heart attack is the death of cardiac muscle tissue resulting from prolonged blockages of one or more coronary arteries (the vessels which supply oxygen-rich blood to the heart)  Arteries gradually become impaired by chronic cardiovascular disease known as atherosclerosis (growths called plaques develop on the inner walls of the arteries, narrowing them) which can trap an embolous (clot)  Hypertension (high blood pressure) can lead to an increased risk of a heart attack, as well as smoking, lack of exercise, diets rich in animal fats and high cholesterol within the blood (low-density lipoproteins are associated with depositing cholesterol)

Circulatory System

Blood Flow

 The pulmonary circuit carries blood to the lungs to be oxygenated and then back to the heart – in the lungs, CO 2 is removed from the blood, and oxygen taken up by the haemoglobin in the red blood cells  The systemic circuit carries blood around the body to deliver the O 2 and returns de-oxygenated blood to the heart – blood also carries nutrients and waste

The HeartThe Heart

 Vena cava (superior and inferior) – drains blood from the body into the right atrium  Right atrium – collects deoxygenated blood from body and pumps into right ventricle (through the tricuspid valve)  Right ventricle – pumps deoxygenated blood to the lungs via the pulmonary artery (through the pulmonary valve)  Left atrium – collects oxygenated blood from lungs via the pulmonary vein and pumps into left ventricle (through the mitral valve)  Left ventricle – pumps oxygenated blood around the body via the aorta (through the aortic (semi lunar) valve) Vena cava

Examination  Firstly examine the outside of the heart  This shows the heart from the front, with the portion on the right of the picture being the left side of the heart and vice versa  The aorta is clearly visible at the top, with an atrium on either side, while the ventricles are on the bottom left

Incision  Cut along the right ventricle (the right ventricle can be identified by squeezing the heart, since the myocardium on the right side is much less rigid than that of the left ventricle)  This allows us to see the tricuspid valve and the right ventricular outflow tract which includes the pulmonary valve

Incision  With a longitudinal cut, the right ventricle has been cut open from the bottom towards the top  The myocardium is being held back, with my finger stuck underneath one leaflet of the tricuspid valve, leading to the pulmonary valve

Tricuspid ValveTricuspid Valve  The tricuspid valve allows blood to flow from the right atrium into the right ventricle

Pulmonary ValvePulmonary Valve  When the heart is contracting, the pulmonary valve is open because the blood pushes the cusps out of the way  After contracting, the ventricles begin to relax and the pulmonary valve closes and prevents back-flow (called regurgitation ) of blood into the ventricle

Left Ventricle  This longitudinal incision extends from the bottom to the top of the left ventricle, then continues up into the atrium to allow us to view the entire left heart

The Mitral (Bicuspid) ValveThe Mitral (Bicuspid) Valve  The mitral valve prevents blood from flowing back into the left atrium  The mitral valve is positioned between the atrium (top) and ventricle (bottom)

Left Ventricular OutflowLeft Ventricular Outflow  Blood flows into the ventricles by passing through the mitral valve

Dissection

Clean Up  Place all material in the plastic bag, as well as gloves and tissues  Wash the desk thoroughly, followed by your hands (make sure you use the disinfectant)