Embryology

1. The Basics of Embryology

• Understand the stages of development of the human embryo
• Understand the progression through weeks and how each of the germ layers (the three layers of cells in the early embryo, called ectoderm, mesoderm and endoderm, that go on to form the organs) develops during this time
• Be aware of the germ layers and how these correspond to full-term organs and their development

2. Development of the Limbs and Body Wall

• Follow limb-bud (the small outgrowth from the body wall of the embryo that becomes a limb) signalling, finger and toe separation, rotation and body-wall folding to predict adult anatomy and developmental defects.

3. Teratology and Congenital Malformations

• Teratology is the study of congenital abnormalities (those present from birth) and their causes. Use timing, mechanism and critical periods (the stages when an organ is most vulnerable to harm) to distinguish malformation (a structure that formed abnormally), deformation (abnormal forces acting on a structure that formed normally) and disruption (damage to a structure that formed normally), and to interpret prenatal detection (finding abnormalities before birth, for example on an ultrasound scan).

4. Development of the Gastrointestinal Tract

• Be aware of the structure of the gastrointestinal tract
• Understand the foregut, midgut and hindgut classifications (the three embryonic parts of the gut tube) and their boundaries
• Understand the basic anatomy of the gut, including the mesenteries and omenta (folds of peritoneum, the lining of the abdominal cavity, that suspend the gut and connect it to other organs)
• Understand which organs are peritoneal (inside the abdominal cavity and wrapped by the peritoneum, its lining) and which are retroperitoneal (not suspended by a mesentery, lying behind the peritoneum)
• Understand the embryological development of the gut and how it relates to its function

5. Development of the Reproductive System

• Understand the progression of development of the reproductive tracts and gonads (the testes and ovaries)
• Understand the hormonal control of these developmental mechanisms
• Be aware of the gubernaculum (a band of tissue attached to the lower end of the developing testis or ovary that guides its descent), its function and descent, and the potential complications if descent goes wrong, for example an undescended testis
• Be aware of potential issues with the development of the genitalia (the sex organs) and how these present in the newborn or adult

• Understand the three stages of kidney development: pronephros, mesonephros and metanephros
• Pronephros (a rudimentary first stage, not a working kidney in humans)
• Mesonephros (the second, temporary stage)
• Metanephros (the third stage, which forms the permanent kidney)

7. Development of the Respiratory System

• Be aware of a basic outline of the embryological development of the respiratory system and how errors in this development can cause birth defects
• Understand the basic neonatal (newborn) complications of embryological development

8. Development of the Head and Neck

• Understand the individual components of the head and neck and how they evolve embryologically and chronologically
• Understand the nervous, muscular, cartilaginous (cartilage) and arterial developments of the pharyngeal arches (the bulges on the side of the embryonic head that develop into structures of the face, mouth and throat)
• Understand why certain birth defects, for example cleft lip and palate (a gap or split in the upper lip, the roof of the mouth, or both), may develop from an embryological point of view
• Understand the development of the thyroid gland, tongue and pituitary gland and how knowing this information can aid in clinically distinguishing neck lumps

• Neural tube formation (the tube that becomes the brain and spinal cord)
• Neural tube defects (the neural tube fails to close): anencephaly (absence of most of the brain and the roof of the skull), spina bifida (incomplete closure of the spine around the spinal cord) and rachischisis (a severe open split of the spine with exposed nervous tissue)
• Anencephaly
• Spina Bifida

10. Embryology of the Cardiovascular System (CVS)

• Understand how the cardiovascular system develops in the womb (in utero)