Figure 5: A Embryo at gestational days 14.5 and 15. It is possible to see the forming heart, ventricle (V), atrium (A), the pericardium (P), and the diaphragm (D) outlining the cavities. Note also the liver (L). B The heart of a full-term fetus at gestational days 20 and 20.5, note structures such as the right atrium (RA), left atrium (LA), right ventricle (RV), left ventricle (LV), endocardium (E), myocardium (M), and epicardium (Ep). C Detail of the heart from the same animal; note the endocardium (E), myocardium (M), and epicardium (Ep) and the arrangement of the muscle fibers. D Fetuses at gestational days 20 and 20.5; note the thymus dividing in the cortical region (C) and medullary region (M); lobes (L) can be observed along with the capsule (Cp) covering the thymus. E Alveolar sacs (S) and bronchioles (B), components of the lung (Lu). F, alveolus (A) and bronchioles (B). G Note the fetal liver at gestational days 20 and 20.5. H, Note the centrilobular vein (Vc), sinusoids (S), and hepatocytes (H). I Note the layers constituting the fetal eye at gestational days 16.5 to 17.5: lens (L), retina (R), cornea (C), and retinal pigmented layer (Pl)