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.
Note the ciliated, pseudostratified columnar epithelium lining the tracheal lumen. This epithelium is commonly referred to as respiratory epithelium. Compare cilia with the microvilli on Slide 52. Note that the cilia are much longer. Study the ultrastructure of cilia and microvilli in electron micrographs.