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.
1. Perichondrium. 2. Ring of hyaline cartilage. 3. Adipose (fat) cells. Close-Up View. This slide shows a stained section of the trachea (windpipe). Note the rings of hyaline cartilage embedded in the walls of the trachea that provide support and help to maintain an open airway.ing of hyaline cartilage. 3. Adipose (fat) cells. Close-Up View. This slide shows a stained section of the trachea (windpipe). Note the rings of hyaline cartilage embedded in the walls of the trachea that provide support and help to maintain an open airway.