Anatomy Lecture 1 PDF

# What are heart valves? - A fold of endocardium with the connective tissue in between. - One-way valves that prevent backflow of blood. - Located at the entrance and the exit of each ventricle. The heart has 4 valves: - 2 Atrioventricular (AV) valves (entrance) - 2 Semilunar (SL) valves (exit) ##...

# What are heart valves? - A fold of endocardium with the connective tissue in between. - One-way valves that prevent backflow of blood. - Located at the entrance and the exit of each ventricle. The heart has 4 valves: - 2 Atrioventricular (AV) valves (entrance) - 2 Semilunar (SL) valves (exit) ## Atrioventricular (AV) valves 2 AV valves located between the atria and ventricles: - **Tricuspid (right AV valve):** 3 cusps - **Bicuspid/mitral (left AV valve):** 2 cusps - Opened by the blood flowing from atria to the ventricles. - Closed when the ventricles contract. - Held by chordae tendinae, which attached to papillary muscles. - Contraction of papillary muscles prevents eversion of the valves and therefore backflow of blood into the atria. The closing of the AV valves (tricuspid and mitral) produces S1 ("Lub"): - **Mitral valve:** Heard at the apex (5th intercostal space, midclavicular line). - **Tricuspid valve:** Heard at the left lower sternal border (4th intercostal space ## Semilunar Valves: - 2 AV valves located between the ventricles and major vessels to guard the exit: - **Pulmonary valve:** 3 cusps - **Aortic valve:** 3 cusps - Opened by the force of blood as the ventricles contract. - Blood flows backwards in the aorta and pulmonary trunk during ventricular relaxation, this pools in the cusps and pushes them shut. - Prevent backflow of blood into the ventricles. The closing of the semilunar valves produces S2 ("Dub"): - **Aortic valve:** Right 2nd intercostal space, near sternum. - **Pulmonary valve:** Left 2nd intercostal space, near sternum ## Fibrous Skeleton of the Heart: - Dense connective tissue structure that lies between the atria and ventricles, corresponding to the atrioventricular groove and orifices. - Components: circular fibrous rings (surround the 4 heart valves) that interconnected by fibrous tissue. - **Functions:** - **Central support:** provides a stable framework for the heart's structure. - **Prevents overdilation:** limits the excessive dilation of valve openings. - **Maintains valve competency:** ensures the proper functioning of the valves. - **Attachment Points:** - Heart valves - Cardiac muscle fibbers of the atria and ventricles - Membranous part of the interventricular septum - **Electrical Insulator:** blocks the direct passage of electrical impulses from the atria to the ventricles, maintaining synchronized heart contractions. ## Heart wall Made up of three layers: - **Endocardium:** inner layer – endothelium - **Myocardium:** middle layer - cardiac muscle - **Pericardium:** outer layer – visceral pericardium ## Pericardium A fibro-serous sac that surrounds the heart and the roots of the great vessels, consisting of two main layers: 1. **Fibrous Pericardium:** - Inelastic, composed of dense connective tissue. - Fuses inferiorly with the diaphragm and superiorly with the great vessels. - Functions: prevents overfilling of the heart and holds it in position. 2. **Serous Pericardium:** - A double-layered structure with pericardial fluid in between. - **Parietal Layer:** Lines the inner surface of the fibrous pericardium. - **Visceral Layer (Epicardium):** Adheres closely to the surface of the heart. - Function: Prevents friction during heart movement. ## Circulatory System 1. **Pulmonary Circulation:** - Involves the right side of the heart and the lungs. - Deoxygenated blood is pumped from the right heart to the lungs where it is oxygenated. 2. **Systemic Circulation:** - Involves the left side of the heart and the body. - Oxygenated blood is pumped from the left heart to the organs and tissues of the body to deliver oxygen and nutrients. ## Coronary Circulation Flow of blood through the coronary arteries, which supply the heart muscle with oxygen and nutrients, and through the cardiac veins, which remove waste products by draining into the heart. ### Coronary Arteries: - Coronary arteries arise from the cusps of the aortic valves at the root of the aorta. - The heart receives approximately 250 ml/min of blood, delivered to the myocardium during ventricular relaxation (diastole). - **Main Branches:** 1. **Right Coronary Artery (RCA):** - Marginal artery or acute Marginal artery - Posterior interventricular artery or Posterior Descending Artery (PDA) 2. **Left Coronary Artery (LCA):** - Anterior interventricular artery or Left anterior descending artery (LAD) - Circumflex artery (CX) or Left Circumflex artery ### Cardiac Veins: - The great, middle and small cardiac veins drain into the coronary sinus which empties into the right atrium. - The anterior cardiac veins drain directly into the right atrium ### Coronary Angiography (Angiogram) The patency of the coronary vessels can be examined by angiography ## Regulation of cardiac activity 1. **Conduction system of the heart** 2. **Autonomic nervous system (ANS)** - Sympathetic fibres - Parasympathetic fibres - Visceral afferent fibres ## Conduction system of the heart: Consists of non-contractile cells that initiate electrical impulses: - Sinoatrial (SA) node - Atrioventricular (AV) node - AV bundle (bundle of His) - Right & left bundle branches - Purkinje fibres ## Fibrous Skeleton of the Heart: **Electrical Insulator:** blocks the direct passage of electrical impulses from the atria to the ventricles, maintaining synchronized heart contractions. ## Autonomic nervous system (ANS): - Sympathetic fibres - Parasympathetic fibres ### Sympathetic Nervous System (SNS): - Increase heart rate - Increase force of contraction - Dilate coronary vessels ### Parasympathetic Nervous System (PNS): - Decrease heart rate - Decrease force of contraction ### Visceral sensory: - Afferent fibres parallel to the vagus nerve sense changes in blood oxygen, carbon dioxide, and pH levels, and regulate cardiac reflexes - Afferent fibres parallel to the sympathetic fibres sense ischemia and tissue damage ## Regulation of cardiac activity: 1. **Conduction system of the heart** - Sinoatrial (SA) node - Atrioventricular (AV) node - AV bundle (bundle of His) - Right & left bundle branches - Purkinje fibres 2. **Autonomic nervous system (ANS)** - **Sympathetic fibres** - Arise from lower 3 cervical and upper 4 sympathetic chain ganglia - Increase heart rate & force of contraction, dilate coronary vessels - **Parasympathetic fibres** - Arise from vagus nerve - Decrease heart rate - **Visceral afferent fibres** - Travel with sympathetic fibres to spinal cord at levels C6-8 &T1-4 - Referred pain is perceived in neck, upper limb and chest ## Cardiac plexus - located between the aortic arch (anteriorly) and bifurcation of the trachea (posteriorly). ## Foetal Circulation: - Different from usual circulation because Oxygen and nutrients are received from the placenta via the umbilical vein - Need to bypass non-functional lungs, intestine and liver. ### Three circulatory shortcuts 1. **Foramen ovale** connects the right to the left atria - bypassing right ventricle and pulmonary system. 2. **Ductus arteriosus** connects the pulmonary trunk to arch of aorta - bypassing pulmonary system and left side of heart. 3. **Ductus venosus** connects the umbilical vein to inferior vena cava - bypasses the liver.