Xxx webchat rus, erotic sex story and webcams, sex tv online. Frame 1 illustrates that the embryo’s main vein and artery pass close to each other in the chest cavity.These problems are known as congenital heart defects.
When the septum forms down the center (Frame 5), the heart contains four separate chambers.
In embryological development, the heart and its major blood vessels are formed and functioning long before any other organ.
The nervous system is one of the major influences on the heart that allows it to respond rapidly to the changing requirements of the body’s tissues.
The autonomic nervous system is the part of the central nervous system that controls involuntary activities such as digestion, respiration, and cardiac function.
Three weeks after conception these two tubes link together, fusing to form a single chamber (Frame 2) before the upper atria and lower ventricles begin to take shape (shown in Frame 3).
Beginning in the 5th week (Frame 4), the atrioventricular canal is gradually split by growing ridges of tissue to provide two separate pathways for blood, one through each side of the heart.In the absence of extrinsic neural or hormonal influences, the SA node would discharge at a rate of about 100 impulses per minute.Heart rate and cardiac output, however, must vary in response to the needs of the body’s cells for oxygen and nutrients.VSD, ventricular septal defect- an abnormal opening between the ventricles- blood passes from left to right ventricle 2. ASD, atrial septal defect- an opening in the atrial septum permits mixing of oxygenated and unoxygenated blood 3. coarctation of the aorta– the aortic lumen is narrowed b. Many such heart defects are congenital, although they may not be obvious at birth.