Heart and Circulation Workbook PDF

**Heart and circulation** The heart and blood vessels carry out a transport function. They carry food molecules, water and oxygen to cells and remove waste products such as carbon dioxide. They form the circulatory system. ============================================================================...

**Heart and circulation** The heart and blood vessels carry out a transport function. They carry food molecules, water and oxygen to cells and remove waste products such as carbon dioxide. They form the circulatory system. ==================================================================================================================================================================================================== The circulatory system is made up of the following parts: - =========================================================== 1\. Heart 2\. Arteries 3\. Veins 4\. Capillaries 5\. Blood 6\. Lymphatic System The functions of the cardiovascular system include: - 1. **Transport of oxygen** to tissues and removal of carbon dioxide 2. **Transport of nutrients** to cells 3. **Removal of metabolic waste** products 4. Regulation of body temperature 5. **Hormone distribution** throughout the body 6. **Immune function**, transporting white blood cells and antibodies 7. **Clotting mechanism**, preventing excessive blood loss 8. **Maintaining blood pressure** to ensure efficient circulation 9. **Ensuring tissue perfusion**, delivering oxygenated blood where needed **The Structure of the Heart** A muscular organ made up from four chambers and its function is to circulate blood around the body. It is positioned within the thorax in a cavity known as the \_\_\_\_ **mediastinum**.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. The heart is conical in shape, lies in a slightly angled position, with the base lying cranio-dorsally above the apex. It lies slightly to the left of midline, the apex near the sternum The heart is enclosed within a double layered membranous sac known as the \_\_\_ **pericardium** The inner layer of the pericardium is the \_\_\_\_\_ **visceral pericardium** (also called the **epicardium**),\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ which is a serous membrane which is actually in contact with the surface of the heart wall. Between the two layers of the pericardium (the pericardial cavity) is a serous fluid which lubricates the heart as it beats.  The heart itself is made up of three layers: - - \_\_\_epicardium\_\_\_\_\_\_\_\_\_\_\_\_\_ - Outer layer (also inner layer of pericardium) - \_myocardium\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Middle layer (made of muscle) - \_\_\_endocardium\_\_\_\_\_\_\_\_\_\_\_\_\_ - Inner layer The middle layer of the heart is made up of muscle cells (cardiac muscle) that are unique in that it is the only muscle that does not fatigue following repeated contractions (unlike skeletal muscle that tires quickly). The cells are capable of rhythmic contractions without nerve supply due to the cells being joined by intercalated discs that lie between the branching muscle cells allowing contraction of one cell to stimulate the contraction of adjacent cells. The heart has \_\_\_\_four\_\_\_\_\_\_\_ chambers. The right side of the heart has no contact with the left side and is separated by a wall of cardiac\ \ muscle known as the \_\_\_\_\_\_\_\_\_\_septum\_\_\_\_\_\_\_\_\_\_\_\_\_\_**.** Each side is further divided into two chambers **Atrium** -- \_\_\_\_ The upper chamber that receives blood.\_\_\_\_ **Ventricle** -- \_\_\_ The lower chamber that pumps blood out of the heart. Although the heart is one large pump, the two sides are structured slightly differently for their specific functions. **[Left side of the heart]** The left side pumps blood into the **systemic circulation** -- from the heart around the body and back to the heart. Due to the fact that the left side has to supply the whole body, it requires a [thicker muscle wall] (than the right side) to enable this to happen.  The left side receives blood from the lungs which has been oxygenated. It receives this from a vein known as the \_\_\_\_\_ **pulmonary vein**.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. All veins carry deoxygenated blood apart from the [\_\_\_] **p[ulmonary vein, which carries oxygenated blood from the lungs to the heart]**[.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.] The blood moves from the pulmonary vein and into the holding chamber known as the left atrium (plural = atria). There are two sets of valves within the [left side] of the heart. 1. \_\_\_\_\_\_\_\_\_mitral valve\_\_\_\_\_\_\_\_\_\_\_\_\_\_ (also known as the **Bicuspid valve** or **left atrio-ventricular valve)** Once the oxygenated blood has moved from the left side of the heart, it travels to the rest of body to supply the tissues with oxygen. This exchange of gases takes place in the [capillaries] (to be discussed later) where waste products including deoxygenated blood are then returned to the circulation. This blood travels back to the heart and enters on the right side. The right side of the heart pumps blood into the **pulmonary circulation** -- from the heart to the lungs. Deoxygenated blood enters the right side of the heart via large veins known as the \_\_\_ **cranial and caudal vena cava**.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. The blood enters the heart and moves into the holding chamber called the \_\_\_right atrium \_ There are two sets of valves within the **[right side]** of the heart. They are:  Once the blood has moved from the atrium into the ventricle, the contraction of the heart muscle forces blood to leave the ventricle via the pulmonary artery to the lungs. [Rule] All arteries carry oxygenated blood apart from the [ **pulmonary artery**. ] All veins carry deoxygenated blood apart from the [ **pulmonary vein**. ] Arteries move blood \_\_\_ away\_\_\_\_\_\_\_ from the heart. Veins move blood \_\_towards\_\_\_\_\_\_\_\_ the heart. Diagrammatical Representation of the Heart Heart to label 1. [Aorta  ] 2. [Superior/cranial vena cava  ] 3. [Right pulmonary artery  ] 4. [Pulmonary veins  ] 5. [Right atrium  ] 6. [Tricuspid valve / atrioventricular valve ] 7. [Right ventrical  ] 8. [inferior vena cava ] 9. [pulmonary artery ] 10. [Pulmonary veins  ] 11. [Left atrium  ] 12. [Mitral valve/ bicuspid valve/ bicuspid valve ] 13. [Aortic valve/ semi luna valve  ] 14. [Left ventricle  ] 15. [Aorta  ] [**R**ight] [**A**trioventricular ] [**T**ricuspid valve] [**L**eft] [**A**trioventricular] [**M**itral] [**B**icuspid valve] [Heart Contraction.] The heart contracts when stimulated by an electrical wave. The initial stimulus for this wave arises\ \ spontaneously by depolarisation (discharging) of specialised\ \ muscles cells in the area of the heart known as the (1)\ \ \_\_\_\_**Sinoatrial (SA) node** \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ (often referred to as the\ \ pacemaker).This is located in the wall of the right atrium. The wave spreads across the left and right atria. When it reaches\ \ the (2) \_\_\_**Atrioventricular (AV) node** \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ (located in the wall of the\ \ septum) the wave then travels along structures known as\ \ (3) \_\_\_**Bundle of His** \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ within the septum, then spreading out along the\ \ (5) \_\_\_\_\_Purkinje fibres\_\_\_\_\_\_\_\_\_\_\_\_\_\_ that radiate upwards from the bottom of both ventricles; the ventricles\ \ then contract. The heart rate is stimulated by the **autonomic nervous system.** The **Vagus nerve** (10^th^ cranial nerve)\ \ slows the heart rate & decreases the power of contraction (through its effect on the SA node) The sympathetic & parasympathetic nervous system can modify the heartbeat in terms of its\ \ frequency and force of contraction. Areas of the brain can detect the chemical composition of blood\ \ and blood pressure and stimulate the heart to increase or decrease its output. [Electrical activity] An electrocardiogram (ECG) is the representation of the electrical activity of the heart (cardiac)\ \ muscle as it is recorded from the body surface. It can be taken by placing electrodes at certain points\ \ and recorded either digitally, but usually with paper and an electrical ink pen. **[What is measured or can be detected on the ECG?]** 1. [**P wave** -- Represents atrial depolarisation (contraction of the atria).] 2. [**QRS complex** -- Represents ventricular depolarisation (contraction of the ventricles).] 3. [**T wave** -- Represents ventricular repolarisation (relaxation of the ventricles).] 4. [**PR interval** -- The time it takes for electrical impulses to travel from the atria to the ventricles.] [5. **QT interval** -- The time taken for the ventricles to contract and then relax, from the beginning of the QRS complex to the end of the T wave.] [A normal ECG trace]  An ECG trace is made up of many 'complexes' that represent the electrical activity with each heartbeat. Each of the 'peaks and troughs' are allocated a letter to correspond with each activity. These are termed PQRST. The trace represents the contraction of the atria and ventricles and the 'rest' period between beats. When listening to the sound of the heart using a stethoscope, a\ \ practice known as \_\_\_\_\_ **auscultation**\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, the untrained ear hears two sounds in each\ \ heartbeat. These are known as the **first and second heart sounds.**The distinctive sound of\ \ 'lub-dub' is the sound of the valves closing. The first sound "lub" is the sound of the atrio-ventricular\ \ valves closing and the 'dub' is the sound of the semi-lunar valves closing as the ventricles start to fill\ \ following contraction. The heartbeat or cardiac cycle is described in two phases, a contraction phase\ \ known as \_\_\_ **systole** \_\_\_\_\_\_\_\_\_\_\_\_ and a relaxation phase known as \_\_\_ diastole\_\_\_\_\_\_\_\_\_\_\_\_. All muscle requires\ \ a blood supply to ensure a good oxygen supply and to remove waste products produced when\ \ contracting. The \_\_\_ coronary arteries\_\_\_\_\_\_\_\_\_\_\_\_\_\_ provide the heart with this critical blood supply. If a blood\ \ clot blocks the artery or a spasm occurs in the vessel, the heart muscle becomes \"starved\" for oxygen.\ \ Within a short time, death of heart muscle cells occurs, causing permanent damage. This is called a\ \ [myocardial infarction] (MI), or [heart attack.] ***Blood flow through the heart and around the body.*** 1. **Deoxygenated blood** enters the heart through the **superior and inferior vena cava**. 2. It moves into the **right atrium**. 3. The right atrium contracts, pushing the blood through the **right atrio-ventricular valve (tricuspid valve)** into the **right ventricle**. 4. The right ventricle contracts and pumps the blood through the **pulmonary semi-lunar valve** into the **pulmonary artery**. 5. The pulmonary artery carries the blood to the **lungs** where it is oxygenated. 6. Oxygenated blood returns from the lungs through the **pulmonary veins**. 7. It enters the **left atrium**. 8. The left atrium contracts and pushes the blood through the **left atrio-ventricular valve (bicuspid or mitral valve)** into the **left ventricle**. 9. The left ventricle contracts and pumps the oxygenated blood through the **aortic semi-lunar valve** into the **aorta**, which distributes the blood to the rest of the body.  **[The Circulation]** **[Systemic Circulation]** Carries oxygenated blood around the body, and returns deoxygenated blood to the heart **[Pulmonary Circulation]** Carries deoxygenated blood from the heart to the lungs, and returns oxygenated blood to the heart. This is known as a **double circulation**, as blood passes through the heart twice during one complete circuit. **RECAP** **[SYSTEMIC CIRCULATION]** **[\ ]** **[ARTERIAL SUPPLY]** Oxygenated blood leaves the left ventricle of the heart in the major artery - the \_\_\_aorta\_\_\_\_\_\_\_\_\_ The aorta leaves the heart and immediately branches taking blood to various parts of the body.  Main branches: [Upper body:] **Coronary arteries** -- supply the heart muscle **Common carotid arteries** -- supply the head **Right subclavian artery** -- supplies the right forelimb **Left subclavian artery** -- supplies the left forelimb **Brachial artery** -- follows on from subclavian artery in each forelimb **[PULMONARY CIRCULATION]** The pulmonary circulation involves the heart and lungs only. Deoxygenated blood is pumped from the right ventricle to the lings in the pulmonary artery. Within the lung tissue, the artery divides into many fine capillaries which wrap around the alveoli (small endings in the lungs where oxygen and carbon dioxide exchange). Oxygen in the inspired air diffuses into the blood, CO**~2~** in the blood diffuses into the air within the alveoli. Newly oxygenated blood is carried to the left atrium by the pulmonary veins, and around the body via the systemic circulation.