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 helps to keep the lungs free of particles and bacteria. 1  show labels. This is a cross section through the trachea, showing the major layers. 2  show labels. This is a higher power image of the trachea showing the glands and epithelium in more detail. Can you classify the epithelium? There are lots of sero-mucous glands in the submucosa layer. The layer of cartilage is not seen here, but instead there is a layer of fibro-elastic connective tissue which runs between the rings of cartilage. Bronchii