Heart Anatomy PDF

Heart Anatomy Created & Presented by: Ieman Al Tallal Senior Specialist Cardiovascular Nursing Learning objectives: By the end of this lecture, you will be able to understand: Structure of heart wall. Types of cardiomyocytes and Purkinji fibers. Histological structure of...

Heart Anatomy Created & Presented by: Ieman Al Tallal Senior Specialist Cardiovascular Nursing Learning objectives: By the end of this lecture, you will be able to understand: Structure of heart wall. Types of cardiomyocytes and Purkinji fibers. Histological structure of the wall of blood vessels. Heart: The heart is a hollow, muscular, four-chambered organ, it is composed of 3 layers: Endocardium. Myocardium. Epicardium. Pericardium Endocardium: The endocardium is a serous membrane consisting of connective tissues, elastic fibers, and a thin layer of epithelial cells that form a smooth surface for the movement of blood and prevention of clot formation. The subendocardium is found between the endocardium and myocardium and contains the impulse-conducting system. Myocardium: It is the thick middle layer of the and the largest layer of the heart. The myocardium contains cardiac muscle fibers that have the ability to contract and to conduct electrical stimuli. Epicardium: The smooth outer layer of the heart that contains the network of coronary arteries and veins, the autonomic nerves, the lymphatic system, and fat tissue. The epicardium is also called the visceral (inner) layer of the pericardium. Pericardium: The thin sac surrounding the heart is called the pericardium. It has 2 walls: visceral (inner) and parietal (outer). In between the two wall, there is a small amount of fluid (around 10-30ml). It is a fibrous sac which protects the heart from infection and traumatic injury. The pericardium has little elastic tissue and cannot expand easily. Types of cardiomyocytes: 1- Contractile cardiomyocytes. 2- Endocrine cardiomyocytes: Found in the right atrium. it has natriuretic and vasodilator effects that play a fundamental role in water and sodium regulation which aid in modulating blood volume thus controlling blood pressure. Types of cardiomyocytes: 3- Cardiomyocytes of the conduction system: These are modified cardiomyocytes that are specialized in initiation and conduction of the electrical impulses. They are found in: Sinoatrial node (SA node): present in the right atrium. It is the pacemaker of the heart. Atrioventricular node (AV node): cardiac impulse generated in the S-A node spread out through the atrial myocardium to the A-V node. Atrioventricular bundle of His (AV bundle): the A-V bundle enters the interventricular septum where it divides giving Purkinje fibers. Purkinji fibers: Site: present in the interventricular septum and the lateral wall of both ventricles Structure: they differ from contractile cardiomyocytes in the following 1. They are larger than cardiac muscle cells with fewer myofibrils. 2. Contains lots of glycogen and mitochondria and has no T-tubules. 3. Connected together by gap junctions, not by intercalated discs. Function: they are specialized to conduct the cardiac impulse faster than the ordinary cardiac muscle. BREAK Blood vessels: Three types of blood vessels: Arteries: carry blood away from the heart to the body. Veins: carry blood back to the heart. Capillaries: very small blood vessels that allow for exchange of gases (oxygen and carbon dioxide), water, nutrients, and waste products to and from the blood. Structure of Vessel Walls: Blood vessels walls have three layers: Tunica intima (interna) :Inner layer. Tunica media :Middle layer. Tunica adventitia ( externa ): Outer layer. Tunica Intima (Inner Layer): Includes: A. The endothelial lining: simple squamous epithelium. B. Subendothelial layer: loose connective tissue present in most medium to large vessels and contain scattered smooth muscle in larger vessels. C. Internal elastic lamella: marks the boundary between the tunica intima and the tunica media and most clearly seen in muscular artery. Tunica Media (Middle Layer) Contains layers of A. Elastic laminae/lamellae (fenestrated sheets) or of smooth muscle. B. External elastic lamina: Separates tunica media from tunica externa. Tunica Adventitia (Outer Layer) Contains loose to moderately dense connective tissue scattered smooth muscle cells and Vasa vasorum. -This layer: In arteries: contains collagen and elastic fibers. In veins : Contains elastic fibers and smooth muscle cells. Vasa vasorum (“vessels of vessels”) Found in the tunica adventitia of large arteries and veins. Supply cells of tunica media and tunica externa Basically, it's blood vessel from an artery supplying another blood vessel. Arteries: Arteries are classified accordance to their sizeinto three types: 1. Elastic arteries 2. Muscular arteries 3. Arterioles From heart to capillaries, arteries change from elastic arteries. To muscular arteries To arterioles Arterioles Smallest arteries; lead to capillary beds. Have very thin tunica interna. Control flow into capillary beds via vasodilation and constriction Arterioles contribute to maintaining mean arterial pressure and tissue perfusion as they are the essential site of total peripheral resistance. They reduces the pressure and velocity of blood flow to enable gas and nutrient exchange to occur within the capillaries. Arterioles are innervated also respond to various circulating hormones and other factors such as pH in order to regulate thus modulating the amount of blood flow into the capillary network and tissues. Major determinant of systemic blood pressure. Veins: Collect blood from capillaries in tissues and organs. Return blood to heart. Are larger in diameter than arteries. Have thinner walls with large flat lumen than arteries. Have lower blood pressure. Unlike arteries, veins have valves; to prevent reflux of blood and to maintain unidirectional blood flow. Veins’ structure differs from arteries: I. The wall of a vein is distinctly thinner than an artery II. Tunica adventia is thicker than media while in artery is the opposite. III. Tunica media contains less amount of elastic tissue or of muscle but contains larger quantity of collagen fibers. IV. Because of the difference mentioned above, the wall of vein is easy compressed or collapsed. V. Veins have valves which are folds of tunica intima, prevent blood from flowing backward and their compression pushes blood toward heart. Venules: Smallest veins. Important site to exchange metabolites. Blood pressure in venules is minimal (0-20mmHg) thus venules walls are very thin. Venules takes from the capillary beds to the heart. Capillaries: Are smallest vessels with thin walls. Microscopic capillary networks infuse all active tissues. Capillary function: Location of all exchange functions of cardiovascular system. Materials diffuse between blood and interstitial fluid. Capillary Structure: Endothelial tube, inside thin basement membrane. Consist only of endothelium but may be partially surrounded by cells called Pericytes. No tunica media. No tunica externa. Diameter is similar to red blood cell. TYPES OF CAPILLARIES: Continuous blood Fenestrated blood Sinusoidal blood capillaries capillaries capillaries Found in all tissues except Found in intestine, pancreas Red bone marrow, liver, epithelia and cartilage. and endocrine glands. spleen and certain The walls No pores or The walls of their endocrine glands. fenestrae in their walls. endothelial cells have pores Their endothelial cells have (fenestrae). large fenestrae without diaphragms. Functions: Functions: Functions: Permit diffusion of water, Permit rapid exchange of water Permit free small solutes, and lipid- and larger solutes between exchange of water soluble materials. plasma and interstitial fluid and large plasma Block blood cells and proteins between plasma proteins. blood and interstitial fluid. Example, the blood–brain barrier Phagocytic cells monitor blood at sinusoids KNOWLEDGE TEST ☺ Q1: What is the thickest layer of blood vessel? A. Tunica M. B. Tunica I. C. Tunica A. Q2: Which Blood Vessels is Thiker ? A. Veins B. Small arterioles C. Artery Q3: How Many Layers in the Hear Muscles? A. Two B. Four C. Six Q4: in veins, valves are absent in: A. Subclavian vein B. Femoral vein C. Inferior vena cavea Feel free to ask questions ☺ Thank you