Question

Questions: 1. Why would the pulmonary arteries be small at development? les be small at the fetal stage of 2. What is the advantage of the circu arteriosus? avantage of the circuit of fetal blood flow through the ductus 3. The trachea is composed of rings of cartilage; the nearby esophagus is composed of muscle and lacks cartilage. How are these structural differences related to the functions of each?

Answer 1

Question 1:

Answer: The main function of the pulmonary artery is to carry deoxygenated (low in oxygen) blood from the heart to the lungs.

The basic channel it follows is: Right ventricle --> pulmonary trunk --> right and left pulmonary arteries -- Lungs.

But before birth the path is: Right ventricle -> Pulmonary artery --> ductus arteriosus (blood vessel) --> descending aorta --> Umbilical arteries --> Placenta --> mother's blood.

Hence, immature pulmonary arteries which have low metabolic requirements are not needed yet considering how fetal circulation occurs through ductus arteriosus (connecting blood vessel between pulmonary artery and descending aorta) which directs most of the deoxygenated blood away from the lungs. At this time, the fetal lungs are non functional as the fetus is in the amniotic fuid before birth.

Due to this, the pulmonary arteries are small at the fetal stage of development.

Question 2:

Answer: During the fetal development, the lungs are not developed as the fetus is in the amniotic fluid. So in order to tackle this, the circulatory system has 3 shunts or paths. These shunts/paths are blood vessels that redirect blood  that needs to be oxygenated from lungs and liver. Out of the three ductus arteriosus is one. The main advantage of having ductus arteriosus is it bypasses the deoxygenated blood from the non functional lungs to the placenta and act as an connecting blood vessel between the pulmonary artery (the one carrying deoxygenated blood) and descending aorta.

Question 3:

Answer: Trachea which is also called wind pipe is a cartilaginous tube which connects the upper respiratory part (Nasal cavity, Pharynx, Larynx) to the lower respiratory tract (Lungs). The cartilaginous rings around the trachea prevents the windpipe from collapsing and obstructing the airway. On the other hand esophagus, which connects the throat to the stomach is made up of smooth and striated muscles. These muscles expand and help to push the food down to the stomach. Just imagine, if trachea would be made up of muscles, then there would be chances of collapsing hence it needed cartilages to create hollow passage, vice a versa esophagus made of cartilage would not allow the food to move through the whole channel.