In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart.
Best Answer: Well they always calculate due date based on your period. Even the doctor will. If you know your exact date of conception you either add 2 weeks to that date or just count 38 weeks from that date.40 weeks gestation is based on your last period. So technically speaking a women is never actually pregnant for her first 2 weeks.est Answer: Well they always calculate due date based on your period. Even the doctor will. If you know your exact date of conception you either add 2 weeks to that date or just count 38 weeks from that date.
To calculate the number of weeks you are, you simply start with the first day of your last menstrual period, also called LMP. So if the first day of your last period was January 1st, your first week of pregnancy is January 1-7th, though you are one week pregnant on January 7th as you complete the week. 1  January 8-14th would be the second week, two weeks pregnant on January 14th. Your doctor or midwife may even count days.