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.
This protective epithelium is partially keratinized on the hard palate and gums and on the tips of filiform papillae of the tongue. Elsewhere in the oral cavity, esophagus, and anal canal the epithelium is non-keratinized. Along the lining of the stomach, small intestine, and colon, the epithelium is simple columnar.