The Heart Noadswood Science, 2016

The Heart To label the heart and explain its function

Precise Learning The heart is an organ that pumps blood around the body in a double circulatory system. The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body. Knowledge of the blood vessels associated with the heart is limited to the aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries. Knowledge of the names of the heart valves is not required. The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.

Circulatory System The circulation system’s main function is to get food and O2 to every cell in the body - as well as being a delivery service, it is also a waste collection service (CO2 and urea) Heart – right side pumps deoxygenated blood to the lungs to collect O2 and remove CO2; 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 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 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 - 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

Blood Flow The pulmonary circuit carries blood to the lungs to be oxygenated and then back to the heart – in the lungs, CO2 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 O2 and returns de-oxygenated blood to the heart – blood also carries nutrients and waste

The Heart

Heart Key Areas

Blood Flow Blood flows into the two atria from the vena cava and the pulmonary vein

Blood Flow The atria contract, pushing the blood into the ventricles

Blood Flow The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart

Blood Flow The blood then flows to the organs through the arteries and return via the veins where the atria fill again the cycle repeats The resting heart rate is controlled by a group of cells in the right atrium wall that act as a pacemaker – these cells produce a small electric impulse which spreads to the surrounding cells, causing them to contract

The 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

Dissection 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…

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

Pulmonary 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) 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 Outflow Blood flows into the ventricles by passing through the mitral valve

Heart Replacement Heart dissection video: http://www.bbc.co.uk/education/clips/zjqb9j6

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)

Practice Questions In the circulatory system of a fish, blood is pumped from the heart, across the gills to pick up oxygen, to the body tissues and then back to the heart in a single circuit. Give one similarity and one difference between the circulatory system of a fish and a human

Answers In the circulatory system of a fish, blood is pumped from the heart, across the gills to pick up oxygen, to the body tissues and then back to the heart in a single circuit. Give one similarity and one difference between the circulatory system of a fish and a human – both circulatory systems involve the blood going to an organ to pick up oxygen. Both systems involve a heart pumping blood around the body. However the circulatory system of a fish is just one circuit where a human is a double circuit (and humans pick up oxygen at lungs not gills)!