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 epithelium is a layer of cells-epithelial cells. They are highly specialised for selective secretion and absorption of ions and molecules. Epithelial cells line any surface that comes into contact with the external environment. So-the airways, the gut, the urinary tract, the cornea etc.tratified squamous epithelium is found in areas where layers of epithelial cells are likely to be sloughed off. Examples of simple squamous epithelium: 1  Endothelium-lines the circulatory system. 2  Mesothelium-lines the peritoneal (abdominal), pleural (lung) and pericardial (heart) cavites.