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 wall of the trachea consists of, from inside to outside, respiratory epithelium, a lamina propria of fibroelastic connective tissue and, at the anterior end of the trachea, glands, the hyaline cartilages covered by perichondrium and connected by smooth muscle, and a connective tissue adventitia.