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Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled ...
Embryo. An embryo is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes ...
Carnegie stages. In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo . The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain ...
Gestational age: 7 weeks and 0 days until 7 weeks and 6 days old. 50–56 days from last menstruation. Embryonic age: Week nr 6. 5 weeks old. 36–42 days from fertilization. The embryo measures 13 mm ( 1⁄2 in) in length. Lungs begin to form. The brain continues to develop.
The embryo, meanwhile, proliferates and develops both into embryonic and extra-embryonic tissue, the latter forming the fetal membranes and the placenta. In humans, the embryo is referred to as a fetus in the later stages of prenatal development. The transition from embryo to fetus is arbitrarily defined as occurring 8 weeks after fertilization.
Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo "; and -λογία, -logia) is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth ...
Implantation (embryology) Implantation, also known as nidation, [1] is the stage in the mammalian embryonic development in which the blastocyst hatches, attaches, adheres, and invades into the endometrium of the female's uterus. [2] Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. [3]
Animal embryonic development. Diagram of stages of embryo development to a larval and adult stage. In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell, ( spermatozoon ...