Gastrulation is the process by which a single-layered embryo becomes a three-layered embryo, consisting of the ectoderm, mesoderm, and endoderm.

Neuroectoderm is not a germ layer formed during gastrulation. It is a specialized region of the ectoderm that gives rise to the nervous system.

Organogenesis is the process by which organs are formed from the germ layers. It occurs after gastrulation and involves the differentiation and specialization of cells.

The brain is derived from the ectoderm. It is the control center of the nervous system and is responsible for coordinating actions, thoughts, and emotions.

The heart is derived from the mesoderm. It is a muscular organ that pumps blood throughout the body.

The liver is derived from the endoderm. It is a large organ that performs many functions, including filtering toxins from the blood, producing bile, and storing glucose.

Differentiation is the process by which cells become specialized and take on specific functions. It occurs during organogenesis and involves the expression of specific genes that control cell fate.

Morphogenesis is the process by which an organism's shape and form are determined. Elongation of the body is an example of morphogenesis.

Cavitation is the process by which a hollow structure is formed from a solid mass of cells. It occurs during organogenesis and is essential for the formation of many organs, such as the lungs and heart.

A congenital anomaly is a birth defect that occurs during embryonic development. Cleft lip is an example of a congenital anomaly.

Implantation is the process by which an embryo implants into the uterine wall. It occurs about 6-10 days after fertilization.

The allantois is not a type of extraembryonic membrane. It is a sac that extends from the hindgut of the embryo and is involved in respiration, excretion, and storage of waste products.

Amnion formation is the process by which the embryo is surrounded by a fluid-filled sac. It occurs during the second week of embryonic development.

The placenta does not produce hormones. It is responsible for gas exchange, nutrient transport, and waste removal.

Placentation is the process by which the umbilical cord is formed. It occurs during the third week of embryonic development.