CITA(Baryonix @ May 23 2008, 01:00 PM)
Muy buen aporte Ge.Pe, en tu linea
A propósito de esto, recomiendo 100% la visita a la exposición "Bodies" en Santiago, que creo que está desde el 24 de Marzo en Chile.
Tuve la oportunidad de estar allí, y sirve para profundizar todos estos temas, y verlos en vivo, con cuerpos donados que han sido especialmente "sellados" para la exposición. Pueden encontrar desde los músculos del cuerpo, pasando por tocar cerebros, etc., hasta el sistema circulatorio de un ser humano
Gracias por tus palabras Baryonix y gracias por tu sugerencia, creo que muchos seguirán tu consejo.
____________________________________________________________Completando, ampliando, resumiendo y repitiendo conceptos...
___________________________________________________________Henry Gray (1821–1865). Anatomy of the Human Body. 1918.
VII. The Veins
THE VEINS convey the blood from the capillaries of the different parts of the body to the heart. They consist of two distinct sets of vessels, the pulmonary and systemic.
The Pulmonary Veins, unlike other veins, contain arterial blood, which they return from the lungs to the left atrium of the heart.
The Systemic Veins return the venous blood from the body generally to the right atrium of the heart.
The Portal Vein, an appendage to the systemic venous system, is confined to the abdominal cavity, and returns the venous blood from the spleen and the viscera of digestion to the liver. This vessel ramifies in the substance of the liver and there breaks up into a minute network of capillary-like vessels, from which the blood is conveyed by the hepatic veins to the inferior vena cava.
The veins commence by minute plexuses which receive the blood from the capillaries. The branches arising from these plexuses unite together into trunks, and these, in their passage toward the heart, constantly increase in size as they receive tributaries, or join other veins. The veins are larger and altogether more numerous than the arteries; hence, the entire capacity of the venous system is much greater than that of the arterial; the capacity of the pulmonary veins, however, only slightly exceeds that of the pulmonary arteries. The veins are cylindrical like the arteries; their walls, however, are thin and they collapse when the vessels are empty, and the uniformity of their surfaces is interrupted at intervals by slight constrictions, which indicate the existence of valves in their interior. They communicate very freely with one another, especially in certain regions of the body; and these communications exist between the larger trunks as well as between the smaller branches. Thus, between the venous sinuses of the cranium, and between the veins of the neck, where obstruction would be attended with imminent danger to the cerebral venous system, large and frequent anastomoses are found. The same free communication exists between the veins throughout the whole extent of the vertebral canal, and between the veins composing the various venous plexuses in the abdomen and pelvis, e. g., the spermatic, uterine, vesical, and pudendal.
The systemic venous channels are subdivided into three sets, viz., superficial and deep veins, and venous sinuses.
The Superficial Veins (cutaneous veins) are found between the layers of the superficial fascia immediately beneath the skin; they return the blood from these structures, and communicate with the deep veins by perforating the deep fascia.
The Deep Veins accompany the arteries, and are usually enclosed in the same sheaths with those vessels. With the smaller arteries—as the radial, unlar, brachial, tibial, peroneal—they exist generally in pairs, one lying on each side of the vessel, and are called venæ comitantes. The larger arteries—such as the axillary, subclavian, popliteal, and femoral—have usually only one accompanying vein. In certain organs of the body, however, the deep veins do not accompany the arteries; for instance, the veins in the skull and vertebral canal, the hepatic veins in the liver, and the larger veins returning blood from the bones.
Venous Sinuses are found only in the interior of the skull, and consist of canals formed by a separation of the two layers of the dura mater; their outer coat consists of fibrous tissue, their inner of an endothelial layer continuous with the lining membrane of the veins.
2. The Pulmonary Veins
The pulmonary veins return the arterialized blood from the lungs to the left atrium of the heart. They are four in number, two from each lung, and are destitute of valves. The commence in a capillary net-work upon the walls of the air sacs, where they are continuous with the capillary ramifications of the pulmonary artery, and, joining together, form one vessel for each lobule.
Pulmonary vessels, seen in a dorsal view of the heart and lungs. The lungs have been pulled away from the median line, and a part of the right lung has been cut away to display the air-ducts and bloodvessels. (Testut.)
3. The Systemic Veins
The systemic veins may be arranged into three groups: (1) The veins of the heart. (2) The veins of the upper extremities, head, neck, and thorax, which end in the superior vena cava. (3) The veins of the lower extremities, abdomen, and pelvis, which end in the inferior vena cava.
a. The Veins of the Heart
Coronary Sinus (sinus coronarius).—
—Most of the veins of the heart (Fig. 556) open into the coronary sinus. This is a wide venous channel about 2.25 cm. in length situated in the posterior part of the coronary sulcus, and covered by muscular fibers from the left atrium. It ends in the right atrium between the opening of the inferior vena cava and the atrioventricular aperture, its orifice being guarded by a semilunar valve, the valve of the coronary sinus (valve of Thebesius).
Base and diaphragmatic surface of heart.
3b. The Veins of the Head and Neck
The veins of the head and neck may be subdivided into three groups: (1) The veins of the exterior of the head and face. (2) The veins of the neck. (3) The diploic veins, the veins of the brain, and the venous sinuses of the dura mater.
1. The Veins of the Exterior of the Head and Face—The veins of the exterior of the head and face (Fig. 557) are:
Veins of the head and neck.
3b. 2. The Veins of the Neck
The veins of the neck (Fig. 558), which return the blood from the head and face, are:
Posterior External Jugular.
The veins of the neck, viewed from in front. (Spalteholz.)
Veins of the tongue. The hypoglossal nerve has been displaced downward in this preparation. (Testut after Hirschfeld.)
The veins of the thyroid gland.
Diagram showing common arrangement of thyroid veins. (Kocher.)
The fascia and middle thyroid veins. The veins here designated the inferior thyroid are called by Kocher the thyroidea ima. (Poirier and Charpy.)
The vertebral vein. (Poirier and Charpy.)
3b. 3. The Diploic Veins
The diploic veins (Fig. 564) occupy channels in the diploë of the cranial bones. They are large and exhibit at irregular intervals pouch-like dilatations; their walls are thin, and formed of endothelium resting upon a layer of elastic tissue.
They consist of
(1) the frontal, which opens into the supraorbital vein and the superior sagittal sinus;
(2) the anterior temporal, which is confined chiefly to the frontal bone, and opens into the sphenoparietal sinus and into one of the deep temporal veins, through an aperture in the great wing of the sphenoid;
(3) the posterior temporal, which is situated in the parietal bone, and ends in the transverse sinus, through an aperture at the mastoid angle of the parietal bone or through the mastoid foramen; and
(4) the occipital, the largest of the four, which is confined to the occipital bone, and opens either externally into the occipital vein, or internally into the transverse sinus or into the confluence of the sinuses (torcular Herophili).
Veins of the diploë as displayed by the removal of the outer table of the skull.