28-09-21 - Heart and Circulation Flashcards
How is the heart positioned in the chest?
What is it covered by?
What size and weight is it?
- The heart is position centrally in the middle mediastinum, resting on the diaphragmatic surface
- 2/3 lies of the left of the midsternal line
- It is flanked and partially obscured by the lungs
- It is fist sized – about 250-350g
What is the pericardium?
What are 2 parts of the pericardium?
What are they for?
- The pericardium is the fibrous sac that surrounds the heart
- The fibrous pericardium is the outermost layer
- It is a tough, dense connective tissue responsible for:
- Protection
- Anchoring to surrounding structures
- Prevents build-up of fluid
- Prevents heart from overextending
- The inner serous pericardium is continuous with the epicardium (outermost) layer of the heart
- It has a layer of serous fluid, which allows for friction free movement of the heart
- Visceral layer of cavity touches organ
- Parietal layer of cavity is away from organ
What is the pulmonary and systemic circulations in the circulatory system?
What are differences between the 2?
What % of blood is found in each system?
- Pulmonary circuit involves moving deoxygenated blood from the right side of the heart to the lungs to become oxygenated and then back to the left side of the heart (low pressure)
- Systemic circulation involves moving oxygenated blood from the left side of the heart to the tissues of the entire body and then back to the right side of the heart (high pressure when leaving heart, pressure decreases as blood moves through system, low pressure in veins)
- The majority of blood is found in the systemic circulation (around 84%), with around 9% of blood in pulmonary circulation and 7% of blood in the heart.
What are the differences in pressure, type of blood and destination in each side of the heart?
What is the similarity?
How does the process occur in each side?
- The right side of the heart pumps deoxygenated blood to the lungs (low pressure)
- The left side of the heart pumps oxygenated blood to the body’s tissues (higher pressure)
- Equal amounts are pumped into each side. The body’s full volume of blood (5 litres) is pumped through the heart in a minute
- Right side:
- Deoxygenated blood is pumped into the right atria of the heart via the superior vena cava, inferior vena cava and the coronary sinus (where blood that feeds the heart enters into the right atrium)
- Blood passively drains into the right ventricle through the tricuspid valve (about 80%)
- When blood fills in the right ventricle, this increases the pressure in the ventricle.
- Electrical activity and contraction further increase the pressure, which forces the tricuspid valve closed and the pulmonary valve open, allowing blood to move through to the pulmonary artery towards the lungs.
- Left side:
- Oxygenated blood is pumped into the left atria of the heart via the pulmonary veins
- Blood passively drains into the left ventricle through the mitral (bicuspid) valve (about 80%)
- When blood fills in the left ventricle, this increases the pressure in the ventricle.
- Electrical activity and contraction further increase the pressure, which forces the mitral valve closed and the aortic valve open, allowing blood to move through to the aorta and towards the tissues of the body.
What is a quick summary of this system?
What are the functional principles of the circulatory system?
What does the system require to function?
What is a mini description of this system?
- The heart – pump of the circulatory system
- Elastic arteries – arteries that are nearest to the heart
- The muscular arteries and arterioles – medium sized arteries that draw blood from the elastic arteries
- Capillary beds – interwoven network of capillaries that supply nutrients and carry away waste products from tissues via diffusion. They also connect arteries and veins
- The venules and veins – a venule is a small blood vessel that allows deoxygenated blood to return from capillary beds to larger blood vessels called veins. Veins then carry the deoxygenated blood back to the heart
- The system requires the right volume of blood to work effectively
- The system requires the right pressure to push blood through
- Heart, arterial system, microcirculation, venous system
Why is the left side of the heart bigger than the right side?
- The left ventricle is thicker than the right ventricle as it has to pump blood further around the body and against higher pressure compared to the right ventricle
What is heart contraction and relaxation known as?
- Systole – contractions of the chambers
- Diastole - relaxation – chambers filling with blood.
How does the heart prevent backflow of blood?
- Valves prevent back flow of blood by shutting after blood has gone through
- There are papillary muscles that attached to the cusps of the mitral and tricuspid valves using the chordae tendinea to prevent inversion or prolapse during contraction
Describe the diagram linking the systemic and pulmonary circulation systems
Why are blood vessels in the circulatory system lined by endothelial cells?
What type of epithelium are endothelial cells?
- Endothelial cells release substances that control vascular relaxation and contraction, enzymes that control clotting, immune function and platelet adhesion
- Resting endothelial cells prevent coagulation and control blood flow, allowing it to happen smoothly.
- Simple squamous epithelium.
What are the blood vessels that go into and out of the right atrium?
How do foetuses obtain oxygenated blood and how does it get pumped in the heart?
How does this change after birth?
- In – Superior vena cava, inferior vena cava, coronary sinus (where blood that feeds the heart tissue drains into right atria)
- Out – Tricuspid valve to right ventricle
- The fossa ovalis is the site of the foramen ovale which is an interatrial septum opening in foetuses
- It allows oxygenated blood from the mother (obtained via placental absorption) to move between atria in order to bypass the lungs
- Postnatally, the pressure from breathing causes the fossa ovalis to close, meaning the baby’s heart starts to function as normal.
What does the left atrium receive?
What are the blood vessels it receives blood from?
What are the internal features of the left side of the heart?
What prevents valves from flipping back into the atria?
- The left ventricle receives oxygenated blood from the lungs.
- It receives this blood from the 4 pulmonary veins: left, right, superior and inferior veins
- The left side of the heart contains:
- the mitral valve between the left atrium and left ventricle
- the aortic valve between the left ventricle and aorta
- the papillary muscle, which attaches to the cusps of the mitral valve with the chordae tendineae and protects the mitral valve from inversion or prolapse, which would cause allow the back flow of blood
- Muscular ridges
What kind of cusps do the pulmonary and aortic valves have?
When does blood go through and when is it stopped from going through the valves?
How can you differentiate between the pulmonary artery and aorta?
- The pulmonary and aortic valves have semi-lunar “watch pocket” cusps
- During systole (when the vesicles contract) blood passes through the valve, forcing the cusps against the vessel wall
- During diastole (when the ventricles relax) elastic coil in the pulmonary trunk and aorta forces blood between the cusps and the vessel wall, keeping the valve closed.
- The pulmonary artery and aorta can be differentiated by the origin of the large left coronary artery on the aorta
What do coronary arteries and veins do?
Where do they arise?
- Coronary arteries – carry oxygenated blood to the heart muscle
- The left and right coronary arteries arise from the aortic sinuses, just above the valve cusps
- The vessels lie in the epicardium and branch inwards
- Coronary veins – carry deoxygenated blood and put it into the chambers of the heart.
- The veins of the heart converge on the coronary sinus, which enters into the right atrium
- This is apart from the anterior cardiac veins that drain directly into the right atrium
What are important parts of the electrical conduction pathways of the heart?
How does the pathway function?
What does this system ensure?
- Sinoatrial Node (SA Node) – the pacemaker – can be sped up or slowed down by autonomic nervous system
- Atrioventricular node (AV Node) and bundle of His
- From the SA Node, depolarisation is spread through the atria
- Depolarisation spreads to the AV Node
- Contraction of the atria takes place immediately following this
- The impulse is carried down the septum via the bundles of His to the Purkinje fibred in the ventricle walls.
- The ventricles then contract
- This system ensures synchronous contraction, where both the left and right side of the heart contract at the same time and in a balanced symmetry
What are some ways the circulatory system interacts with other organ systems?
- Blood oxygenated in lungs
- Blood volume regulated by kidneys
- Circulatory system responsible for bulk flow of nutrients tot issues (gases, nutrients, hormones, waste)
- Involved in temperature regulation (vasodilation/vasoconstriction)
- Host defence by transporting defence cells around the baby
- Homeostasis
What direction do veins/arteries carry blood?
What type of blood do they carry?
What are exceptions to this?
- Veins carry deoxygenated blood towards the heart
- Arteries carry oxygenated blood away from the heart
- The exceptions to this are the pulmonary artery, which carries deoxygenated blood to the lungs and the pulmonary veins, which carry oxygenated blood to the left atrium of the heart.
- They are both part of the pulmonary system.
What structure forms the apex of the heart?
What structure forms the posterior base of the heart?
- The apex of the heart is formed by the left ventricle
- The posterior base of the heart is formed by both atria, but mianly the left atria
