United States or Senegal ? Vote for the TOP Country of the Week !
The simple, spindle-shaped heart-tube, found in the same form in the embryo of all the Craniotes, is divided into two sections or chambers in the Cyclostomes, and these are separated by a pair of valves. The hind section, the auricle, receives the venous blood from the body and passes it on to the anterior section, the ventricle.
The short downward curve from the apex means relaxation of the auricle. The second lesser rise, called the carotid wave, is believed to be due to the impact of the sudden expansion of the carotid artery. The drop of the wave tracing after this cartoid rise is due to the auricular diastole.
All things, in short, permit us to believe that in the embryo the blood must constantly pass by this foramen from the vena cava into the pulmonary vein, and from thence into the left auricle of the heart; and having once entered there, it can never regurgitate.
From this it will be understood that in the human embryo, and in the embryos of animals in which the communications are not closed, the same thing happens, namely, that the heart by its motion propels the blood by obvious and open passages from the vena cava into the aorta through the cavities of both the ventricles, the right one receiving the blood from the auricle, and propelling it by the pulmonary artery and its continuation, named the ductus arteriosus, into the aorta; the left, in like manner, charged by the contraction of its auricle, which has received its supply through the foramen ovale from the vena cava, contracting, and projecting the blood through the root of the aorta into the trunk of that vessel.
These little irregular stimuli proceeding from the auricle reach the auriculoventricular node and are transmitted to the ventricle as rapidly as the ventricle is able to react. Such rapid stimuli may soon cause death; or, if for any reason, medicinal or otherwise, the ventricle becomes indifferent to these stimuli, it may not take note of more than a certain portion of the stimuli.
An autopsy showed that some of the pins had reached the lungs, some were in the mediastinum, on the back part of the right auricle; the descending vena cave was perforated, the anterior portion of the left ventricle was transfixed by a needle, and several of the articles were found in the liver. Andrews removed 300 needles from the body of an insane female.
Playfair showed the heart of a child which had lived nine months in which one ventricle was absent. In King's College Hospital in London there is a heart of a boy of thirteen in which the cavities consist of a single ventricle and a single auricle.
Mary's Church, to see the Beauchamp chapel. . . . On one side of it were some worn steps ascending to a confessional, where the priest used to sit, while the penitent, in the body of the church, poured his sins through a perforated auricle into this unseen receptacle. The sexton showed us, too, a very old chest which had been found in the burial vault, with some ancient armor stored away in it.
The valve between the right auricle and the right ventricle is called the tricuspid valve. It consists of three parts, as its name implies, which are thrown together in closing the opening. Joined to the free edges of this valve are many small, tendinous cords which connect at their lower ends with muscular pillars in the walls of the ventricle.
The pulmonary artery thus finds the pressure ahead unusually great, and the right ventricle reflexly learns that it requires a greater force to empty itself than before; in fact, it may not succeed in completely accomplishing this until its distention, by an incomplete evacuation of its contained blood plus the blood coming from the right auricle, has caused the right ventricle also to become hypertrophied.
Word Of The Day