Diagrammatic cross section of an artery with a plaque. If the fibrous cap ruptures, a clot will form that can completely obstruct the artery, or the clot can break loose and clog a narrower artery “downstream.”
Arteries and arterioles are more muscular than are veins and venules. Capillaries have walls only one cell thick. Oxygenated blood moves from arteries to arterioles to capillaries. Capillaries empty deoxygenated blood into venules, which empty into veins. The movement of blood from arterioles into capillaries is regulated by muscular rings called precapillary sphincters.
Veins and venules have one-way valves that maintain blood flow in the proper direction. When the vein is compressed by nearby muscles, the valves allow blood to flow toward the heart but clamp shut to prevent backflow.
(a) In the open circulatory system of insects and other arthropods, a series of hearts pumps blood through vessels into the hemocoel, where blood directly bathes the other organs. When the hearts relax, blood is sucked back into them through openings guarded by one-way valves. When the hearts contract, the valves are pressed shut, forcing the blood to travel out through the vessels and back to the hemocoel. (b) In a closed circulatory system, blood remains confined to the heart and the blood vessels. In the earthworm, five contractile vessels serve as hearts and pump blood through major ventral and dorsal vessels from which smaller vessels branch.
(a) The earliest vertebrate heart is represented by the two-chambered heart of fishes. (b) Amphibians and most reptiles have a heart with two atria, from which blood empties into a single ventricle. Many reptiles have a partial wall down the middle of the ventricle. (c) The hearts of birds and mammals are actually two separate pumps that prevent mixing of oxygenated and deoxygenated blood. Note that in this and in subsequent illustrations, oxygenated blood is depicted as bright red, while deoxygenated blood is colored blue.
The heart is drawn as if it were in a body facing you, so that right and left appear reversed. Note the thickened walls of the left ventricle, which must pump blood much farther through the body than does the right ventricle, which propels blood to the lungs. One-way valves, called semilunar valves, are located between the aorta and the left ventricle, and between the pulmonary artery and the right ventricle. Atrioventricular valves separate the atria and ventricles.
Most veins (right) carry deoxygenated blood to the heart, and most arteries (left) conduct oxygenated blood away from the heart. The pulmonary veins (carrying oxygenated blood) and arteries (carrying deoxygenated blood) are exceptions. All organs receive blood from arteries, send it back via veins, and are nourished by capillaries (only lung capillaries are illustrated and these are greatly enlarged, since capillaries are microscopic).
Cardiac muscle cells are branched. Adjacent plasma membranes meet in folded areas that are densely packed with gap junctions (pores), which connect the interiors of adjacent cells. This arrangement allows direct transmission of electrical signals between the cells, coordinating their contractions.
The sinoatrial (SA) node, a spontaneously active mass of modified muscle fibers in the right atrium, serves as the heart’s pacemaker. The signal to contract spreads from the SA node through the muscle fibers of both atria, finally exciting the atrioventricular (AV) node in the lower right atrium. The AV node then transmits the signal to contract through bundles of excitable fibers that stimulate the ventricular muscle.
(a) Lymph vessels, lymph nodes, and two auxiliary lymph organs, the thymus and spleen. Lymph is returned to the circulatory system by way of the thoracic duct, which empties into the vena cava, a large vein. (b) A cross section of a lymph node. The node is filled with channels lined with white blood cells (lymphocytes) that attack foreign matter in the lymph.
Lymph capillaries end blindly in the body tissues, where pressure from the accumulation of interstitial fluid forces the fluid into the lymph capillaries.
Sistema circulatorio PROFESOR HUGO A. SALVO FELIÚ [email_address]
Las placas obstruyen las arterias endotelio colesterol en la sangre centro graso tapa fibrosa
OXÍGENO DIÓXIDO DE CARBONO OXÍGENO Ojo no todas las venas llevan sangre rica en CO2 Como es el caso de las venas pulmonares que llegan a la auricula izquierda arteria vena corazón Capilares sistémicos Capilares pulmonares
El recorrido de la sangre se inicia en el ventrículo derecho pasando por las arterias pulmonares hacia los lechos capilares, de ahí retorna a través de las venas pulmonares a la aurícula izquierda.
Marcapaso cardíaco y sus conexiones en el automatismo cardiaco el cual genera sus propios estimulos para generar los latidos Nodo senoauricular S A O SINUSAL Nodo aurículoventricular A V Fibras excitables Haz de hiss
Sangre Desoxigenada desde el cuerpo Sangre Oxígenada desde los pulmones (b) Contracción ventricular Sangre desoxígenada hacia los pulmones Sangre desoxigenada hacia el cuerpo (c) Corazón Relajado; aurículas pasivas
CICLO CARDIACO Total del ciclo 0,8 segundos Diástole Diástole 0,4 seg. Sístole Diástole 0,3 seg. Diástole Sístole 0,1 seg. ventrículo aurícula tiempo