Answer:
Surfactant is a liquid produced by the alveoli in the lungs to keep the lungs from collapsing.
Explanation:
Surfactant is a fluid composed of lipids and proteins produced in the lungs that keeps the airways open and prevent the lung from collapsing. It is secreted by the alveolar epithelial type-II (AT-II) cells of the tiny air sacs found in the lungs called alveoli. It prevents the collapse of alveoli under the surface tension by reducing the surface tension at the interface between air and the aqueous fluid lining the alveolar surfaces. If enough surfactant is not present, the surface tension causes the tissue surrounding the alveoli to stick together after each exhalation and results in the collapse of alveoli.
Usually, in unborn babies, the production of surfactant starts at about 6 months of pregnancy and the surfactant helps the babies to breathe in the air immediately after delivery. But a premature baby can not produce enough surfactant and it results in the collapse of alveoli with each breath. The damaged alveolar cells collected in the airways affect breathing and the baby takes in less oxygen. This disorder is known as respiratory distress syndrome (RDS).
The level of carbon dioxide in the blood increases and results in acidosis which affects other organs in the body. Since the premature babies having RDS need extra oxygen and help with breathing, the treatment methods include providing extra oxygen through CPAP, placing a breathing tube into your baby's trachea, providing artificial surfactant and ventilator support.
You should draw these simple Punnett Squares as it's easy to see the answers:
1. Crossing RR x Rr results in all (100%) red cow offspring. 50% will be RR (homozygous dominant), 50% will be Rr (heterozygous).
2. Crossing Rr x Rr results in 3 red offspring (75%) and 1 white (25%). Genotypes though will be 25% RR, 50% Rr, and 25% rr.
3. Crossing rr x rr will result in 100% white offspring. All offspring will be rr.
C........................................................................
