Pulmonary alveolus thin fluid coating within all alveoli. The fluid coating is produced by the body in order to facilitate the transfer of gases between blood and alveolar air. The surfactant is produced by the type II cells which are the most numerous cells in the alveoli, yet do not cover as much surface area as the squamous alveolar cells (a squamous epithelium). Type II cells also repair the endothelium of the alveolus when it becomes damaged. Insufficient surfactant in the alveoli can contribute to atelectasis (collapse of part or all of the lung). Without pulmonary surfactant, atelectasis is a certainty; however,
Muscular evolution in humans Muscular evolution in humans Muscular evolution in humans is an overview of the muscular adaptations made by humans from their early ancestors to the modern man. Humans are believed to be predisposed to develop muscle density as early humans depended on muscle structures to hunt and survive. Modern man's need for muscle is not as dire, but muscle development is still just as rapid if not faster due to new muscle building techniques and knowledge of the human body. Humans are widely thought to be one of the fastest muscle growing organisms due to surplus of calories, specialized amino acids,