A dominant gene will always be expressed when present, such as in the homozygous dominant genotype (RR), or heterozygous genotype (Rr). A recessive allele is only expressed wh â¦ en the genotype is homozygous recessive (rr).
(Lung alveoli, in contrast, are lined by very thin simple squamous epithelium .). Pseudostratified respiratory epithelium consists primarily of columnar ciliated cells. Ciliary beating sweeps mucus and the dust it carries up the bronchi and trachea toward the pharynx, where it can be swallowed.
The cells found in this epithelium type are flat and thin, making simple squamous epithelium ideal for lining areas where passive diffusion of gases occur. Areas where it can be found include: skin, capillary walls, glomeruli, pericardial lining, pleural lining, peritoneal cavity lining, and alveolar lining.