Embryology

1. Embryo: the initial stage of development for a multicellular organism that begins just after fertilization of the female egg cells by the male sperm cell

2. Fetus: unborn mammalian offspring that develops from an embryo; is characterized by the presence of all major body organs

3. Blastocyst: a mammalian embryo at the early stage of development when it is a hollow ball of cells  

4. Embryoblast: mass of cells inside the blastocyst that will eventually give rise to the structures of the fetus

5. Epiblast: columnar cells that form a layer of the embryoblast

6. Hypoblast: simple cuboidal cells that form a layer of the embryoblast

7. Extraembryonic mesoderm: layer of tissue that forms between the embryoblast and the cytotrophoblast and syncytiotrophoblast layers

8. Gastrula: early multicellular embryo that contains three layers of cells from which organs later derive

9. Gastrulation: process during embryonic development when the embryonic disc containing 2 layers changes into a structure that has 3 layers

10. Mesoderm: layer of the embryo (gastrula phase) that is situated between the ectoderm and the endoderm.  

11. Endoderm: innermost of the three layers of the embryo when it is a gastrula

12. Ectoderm: outermost layer of the three layers of the embryo when it is a gastrula

13. Chorionic cavity: fluid-filled cavity that surrounds the embryo, yolk sac and amniotic sac (also called the extraembryonic coelom)

14. Coelom: fluid-filled cavity

15. Cephalic: relates to the head

16. Caudal: relates to the bottom end of the spinal cord

17. Cloaca: common cavity at the caudal end that serves as the only opening for the digestive, reproductive and urinary tracts

18. Somatic mesoderm: the outer layer of the lateral plate of the mesoderm after it is divided into two parts by the intraembryonic coelom

19. Splanchnic mesoderm: the inner layer of the lateral plate of the mesoderm after it is divided into two parts by the intraembryonic coelom

20. Somatopleure: layer of tissue in the embryo that is comprised of the ectoderm and the outer layer of the mesoderm (somatic mesoderm)

21. Splanchnopleure: layer of tissue in the embryo that is comprised of the endoderm and the inner layer of the mesoderm (splanchnic mesoderm); gives rise to the gut and lungs

22. Intraembryonic coelom: cavity that forms in the lateral plate mesoderm; divides the lateral plate mesoderm into the somatic and splanchnic mesoderm layers

23. Somites: blocks of mesoderm that are located on either side of the neural tube in the developing embryo

24. Dermatome: the lateral wall of the somite, gives rise to the skin

25. Myotome: the dorsal portion of each somite; gives rise to muscle

26. Sclerotome: the portion of the somite that gives risk to skeletal tissue

27. Diencephalon: region of the neural tube that gives rise to the thalamus, hypothalamus, and posterior pituitary

28. Telencephalon: anterior portion of the forebrain; gives rise to the cerebral hemispheres

29. Bulbus cordis: structure in the developing heart that contributes to the right ventricle, part of the outflow tracts and some portions of the left ventricle

30. Truncus arteriosus: structure in the developing heart that later divides into the aorta and the pulmonary trunk

31. Atrioventricular canal: junction between the primitive atrium and primitive ventricle in the embryo

32. Endocardial cushions: cells in the developing heart that contribute to the separation of the chambers of the heart