Glossary of developmental biology

This glossary of developmental biology is a list of definitions of terms and concepts commonly used in the study of developmental biology and related disciplines in biology, including embryology and reproductive biology, primarily as they pertain to vertebrate animals and particularly to humans and other mammals. The developmental biology of invertebrates, plants, fungi, and other organisms is treated in other articles; e.g terms relating to the reproduction and development of insects are listed in Glossary of entomology, and those relating to plants are listed in Glossary of botany.

This glossary is intended as introductory material for novices; for more specific and technical detail, see the article corresponding to each term. Additional terms relevant to vertebrate reproduction and development may also be found in Glossary of biology, Glossary of cell biology, Glossary of genetics, and Glossary of evolutionary biology.

A
acrosomal vesicle:

acrosome:

allantois: One of four extraembryonic membranes formed during the development of amniotes, arising as a sac-like extension of the and having the dual function of excretion and respiration. In mammals, the allantois arises as a made of  almost as soon as the hindgut is established, and quickly builds a dense network of circulatory vessels which eventually assumes responsibility for all metabolic interchange between the  and mother.

amniocentesis:

amnion: One of four extraembryonic membranes formed during the development of animals belonging to the clade Amniota, all of which are terrestrial vertebrates. Arising from very early in development, the amnion grows to surround and define the, which contains that cushions and protects the developing embryo from injury.

amniotic fluid:

amniotic sac:

archenteron:

The central internal cavity of the in most animal embryos, fated to develop into the lumen of the digestive tube; the primitive gut. The archenteron initially has only one open end, known as the.

B
birth:

blastocoel:

The fluid-filled or -filled cavity that forms in the developing or in virtually all animal species. The blastocoel appears to serve two functions: it permits cell migration during, and it prevents cells beneath it from interacting prematurely with cells above it by physically separating them.

blastocyst:

blastodisc:

blastomere:

blastopore:

blastula: An early form of the animal generally consisting of a hollow sphere of cells in a single layer (the ) surrounding a fluid-filled cavity (the ). Mammalian embryos develop into a specialized blastula known as a, containing a differentiated and.

blastulation: A stage in the embryonic development of all animals defined by the formation of the, following and preceding. During blastulation, the early embryo develops from a solid ball of cells called a into a hollow sphere consisting of an  surrounded by a single layer of ; a significant amount of embryonic activity is also dedicated to establishing cell polarity and the basic axes of the, determining the fates of specific cells, , and ultimately  full control of gene expression from the mother to the embryo. In mammals, blastulation results in a, a specialized blastula marked by very early of cell populations.

C
cavitation: The hollowing out of a fluid-filled space within a solid mass of cells, e.g. during or.

chorion:

One of four extraembryonic membranes formed during the development of amniotes, arising from and as a corollary of the  and enclosing both the amnion and the. The chorion provides the fetal contribution to the formation of the. A tough coat surrounding the eggs of some insects and fish.

cleavage:

concealed ovulation:

conception:

D
delamination:

deuterostome:

developmental biology:

diakinesis:

dioestrus:

In the mammalian, the long period of quiescence following, during which the prepares to receive a.

differentiation:

diplonema:

diplont: An organism having somatic cells and.

diverticulum:

E
ectoderm:

embryo:

embryo transfer:

embryoblast: Another name for the, i.e. that portion of the that actually gives rise to tissues, as opposed to extraembryonic tissues.

embryogenesis:

The growth and formation of the ; the course of development that occurs during the time period beginning with the of the and ending when the developing animal can no longer be considered an embryo, the criteria for which may vary widely and arbitrarily depending on species. In humans, the embryonic period ends nine weeks after conception, after which time the term is used instead of embryo. In many other animals, embryogenesis is considered complete only after hatching or birth.

embryology:

embryonate: Containing a developing ; e.g. an embryonated hen's egg, as opposed to an unfertilized egg.

endoderm:

endometrium:

epiblast:

epiboly:

estrous cycle:

F
Fallopian tubes:

false amnion: See.

fate map: A diagram that shows what will become of each region of the during the course of normal development. Fate maps are created by selectively marking populations of cells in distinct regions of the early embryo with distinct visual reporters (by any of a variety of methods designed to permit easy visualization of the marked cells, e.g. vital stains, fluorescent compounds, or retroviral transfection) and then allowing the embryo to proceed normally through the subsequent stages of development, after which each specific reporter can again be visualized, thereby revealing the new positions and morphologies of the marked cells and/or their daughter cells. Visualizing the reporters at two or more different developmental stages shows how the different parts of the embryo have moved and changed over time.

fertilization:

follicle-stimulating hormone (FSH):

G
gastrocoel: See.

gastrula:

gastrulation: A stage in the embryonic development of most animals defined by the formation of the, following and preceding. During gastrulation, the or  undergoes a major reorganization from a single, continuous layer of cells surrounding a single cavity into the complex, multilayered, multicavity gastrula, in which all of the primordial  are present. Though the precise pattern of morphogenetic changes constituting gastrulation varies considerably between species, all types of gastrulation are unified by five basic classes of cell movements: the of one side of the blastula into the ; the  of the inner layer of cells over the basal surface of the outer layer; the  of individual cells into the embryo; the  of one layer into two layers via splitting or migration; and the  or expansion of one layer over other cells or layers. By the end of gastrulation, the cells of the embryo have begun into distinct lineages, the basic axes of the  have been established (e.g. dorsal-ventral, anterior-posterior, etc.), and one or more layers of cells have been internalized, including the.

germ cell:

germ layer:

gonad:

H
histogenesis: The process by which the definite cells and tissues that make up the body of an organism arise from embryonic cells; or, more generally, the generation of new tissues at any stage of life.

hypoblast:

I
in vitro fertilization (IVF):

ingression:

inner cell mass:

invagination:

involution:

L
leptonema:

Leydig cell:

M
meiosis:

meiotic arrest:

mesoderm:

mid-blastula transition (MBT):

morula: A very early form of the animal consisting of a solid ball of 16 to 32. By the morula stage, these cells have become flattened and have begun to develop stronger cell-to-cell adhesion, as well as to pump fluid into an internal cavity that will eventually become the.

N
neonatal:

neurula:

neurulation:

notochord:

O
oestrous cycle: See.

oocyte:

oogenesis:

organogenesis:

ovary:

oviduct:

ovulation:

ovum:

P
pachynema:

parthenogenesis:

parturition:

placenta:

polar body:

postimplantation:

postnatal:

postpartum:

preimplantation:

prenatal:

primary spermatocyte:

primitive streak:

primordium:

pronucleus: Either of the haploid nuclei, i.e. that of the or, as they exist prior to. The female pronucleus is formed during at the time of the, which occurs before ; in contrast, the nucleus of a spermatozoon is generally only considered a pronucleus after fertilization, once it is inside the cytoplasm of the egg and has begun to decondense.

protoblast:

protostome:

R
reproductive biology:

S
secondary spermatocyte:

semen:

serosa: See.

Sertoli cell:

somatic cell nuclear transfer (SCNT):

somatopleure:

somite:

sperm:

spermatid:

spermatocyte:

spermatogonium:

spermiogenesis:

splanchnopleure:

superovulation:

T
teratogen:

testis:

trophectoderm:

trophoblast:

U
uterus:

V
vas deferens:

W
undefined:

X
undefined:

Y
undefined:

Z
zona pellucida:

zygonema:

zygote:

zygotic genome activation (ZGA):