Cardiovas His Dent 2023 PDF

ELEMENTS HEART ARTERIES CAPILLARIES. VEINS.  THE HEART v Four chambers. v Contracts rhythmically. v The right and left ventricles propel blood to the pulmonary and systemic circulation, respectively. v Consist of three major layers: The internal endocardium. The midd...

ELEMENTS HEART ARTERIES CAPILLARIES. VEINS.  THE HEART v Four chambers. v Contracts rhythmically. v The right and left ventricles propel blood to the pulmonary and systemic circulation, respectively. v Consist of three major layers: The internal endocardium. The middle myocardium. The external epicardium.  En=endothelium. SEn= subendocardial. P= purkinjie. M=muscle THE HEART 1. The endocardium consists of a: Thin inner layer of endothelium and supporting CT. Middle myoelastic layer of smooth muscle fibers and CT. Deep layer of CT called the subendocardial layer that merges with the myocardium (conducting system) 2. The myocardium, consists mainly of cardiac muscle, fibers arranged spirally around chamber. Much thicker in ventricles especially the left. 3. The epicardium is a simple squamous mesothelium supported by a layer of LCT. Is reflected back as the parietal layer lining the pericardium.  Cardiac skeleton Dense irregular CT. Forms part of the interventricular and interatrial septa, Surrounds all valves of the heart, and extends into the valve cusps and the chordae tendineae to which they are attached (support). Providing firm points of insertion for cardiac muscle Insulation between atria and ventricles (coordinate the heartbeat)  Conducting system: Modifies cardiac muscles: smaller size, fewer myofibrils, and fewer typical intercalated disks SA and AV nodes, AV bundle, Subendocardial conducting network (Purkinjie fibers) SA: loacted in rt atrium near superior vena cava---impulses---contraction of atria. AV node: located in base of rt atrium near av valve---conducting cells---- AV bundle. AV bundle: pass through an opening in the cardiac skeleton into the interventricular septum-- bifurcate into left and right bundle branches. Purkinjie fibers: pale-staining fibers, larger than the adjacent muscle fibers, with sparse myofibrils and much glycogen  Structure Of The Vessels Endothelium+ct+smooth muscles! Smooth muscle fibers occur in the walls of all vessels >capillaries and are arranged helically in layers. In arterioles and small arteries-- smooth muscle cells--gap junctions--- permit vasoconstriction/vasodilation---regulating blood pressure.  Structure Of The Vessels Connective tissue components are present variable amounts. Collagen fibers are found in the subendothelial layer, between the smooth muscle layers, and outer layer Elastic fibers provide resiliency. Forms parallel lamellae in major vessels. Variable amount of of ground substance components (proteoglycans and hyaluronate). Tunica intima---endothelium and a thin subendothelial layer (smooth muscle+). Larger arteries— —fenestrated.  Structure Of The Vessels Tunica media-- concentric layers of helically arranged smooth muscle ---interposed among the muscle are variable amounts of elastic fibers/elastic lamellae, reticular fibers, and proteoglycans (smooth muscle). Larger arteries--- EEL Tunica adventitia-- is CT consisting of type I collagen and elastic fibers. Is continuous with and bound to the stroma of the organ. The adventitia of larger vessels also contains a network of unmyelinated autonomic nerve fibers Vasa vasorum: vessels of the vessels; arterioles, capillaries, and venules in the adventitia of larger vessels. More in veins due to the deoxygenated blood.  ARTERIAL SENSORY STRUCTURES Carotid sinuses–- baroreceptors: slight dilations of the bilateral internal carotid arteries (the aortic arch). Chemoreceptors: Monitor blood CO2 and O2 levels, and pH, carotid bodies and aortic bodies located in the walls carotid sinus and aortic arch.  ELASTIC ARTERIES Carry blood to smaller arteries----conducting As. The aorta, the pulmonary artery, and their largest branches. Thick tunica media --elastic lamellae alternate with layers of smooth muscles. The tunica intima is well developed--many smooth muscle cells in the subendothelial connective tissue. Presence of internal elastic lamina (between int. And med.) The adventitia is much thinner than the media. Presence of external elastic lamina (between med. And adv.) but less well-defined than the IEL.  MUSCULAR ARTERIES Also called distributing arteries----to the organs. Regulate blood pressure---smooth muscle in the media. The intima has a thin subendothelial layer and a prominent internal elastic lamina The media may contain up to 40 layers of large smooth muscle cells interspersed with a variable number of elastic lamellae. An external elastic lamina is present only in the larger muscular arteries. The adventitial contains lymphatic capillaries, vasa vasorum, and nerves  ARTERIOLES Have only one or two smooth muscle layers--beginning of an organ’s microvasculature Arterioles are less than 0.1 mm in diameter, with lumens approximately as wide as the wall is thick. Elastic laminae are absent The media consists of the circularly arranged smooth muscle cells. The adventitia is very thin and inconspicuous. At the ends of arterioles the smooth muscle fibers act as sphincters and produce periodic blood flow into capillaries. The major determinants of systemic blood pressure.  CAPILLARIES Composed of the simple layer of endothelial cells surrounded by basement membrane The average diameter is 4 to 10 μm. Make up over 90% of the body’s vasculature. Permit and regulate metabolic exchange between blood and surrounding tissues. Function in networks called capillary beds----size and shape conforms to the structure supplied. Supplied by one or more terminal arteriole branches called metarterioles--- continuous with thoroughfare channels connected with the postcapillary venules. Precapillary sphincters (metarteriole muscle cells ): control blood flow in capillaries.  CAPILLARIES Arteriovenous shunts: arterioles that can bypass capillary networks and connect directly to venules. Portal system: blood flows through two successive capillary beds separated by a portal vein.  VARIATIONS IN CAPILLARIES Grouped into three types, depending on the continuity of the endothelial cells and their basement membrane. 1. Continuous capillaries: have many tight, well-developed occluding junctions between endothelial cells--- in muscle, connective tissue, lungs, exocrine glands, and nervous tissue. 2. Fenestrated capillaries: have a sievelike structure; more extensive molecular exchange the basement membrane is continuous ---kidneys, intestine, choroid plexus, and endocrine glands.  VARIATIONS IN CAPILLARIES 3. Discontinuous capillaries (sinusoids): permit maximal exchange of macromolecules and easier movement of cells. Large perforations and have highly discontinuous basement membranes-- liver, spleen, some endocrine organs, and bone marrow.  VENULES Are similar to capillaries larger. Diameter is 15 -20 μm. The primary site at which white blood cells leave the circulation at sites of infection or tissue damage. Converge into larger collecting venules (have smooth muscle cells). Muscular venules: larger venules with 2-3 smooth muscle layers. Large diameter of the lumen compared to the overall thinness of the wall.  VEINS Blood entering veins is under very low pressure---moves toward the heart by contraction of the smooth muscles and by external compressions from surrounding skeletal muscles and other organs. Most veins are small or medium veins: diameters of 10 mm or less. Located close and parallel to corresponding muscular arteries. The tunica intima is usually thin. The media has small bundles of smooth muscle cells mixed with reticular /elastic fibers. The adventitial is thick and well developed.  VEINS large veins: venous trunks, paired with elastic arteries--well- developed intima, thin media and a thicker adventitia. Internal elastic lamina may be present. Large and medium veins have valves: thin, paired folds of tunica intima projecting across the lumen, rich in elastic fibers. The valves in veins of the legs, help keep the flow of venous blood directed toward the heart.