A&P 2 - Module 13, Development

Development

The process of anatomical and physiological change over time that any organism goes through during it's lifetime.

Prenatal Development

The period of development from fertilization to birth.

Postnatal Development

The period of development after birth.

Embryo

The developing human from fertilization through the end of the eighth week.

Fetus

The developing human from the ninth week after fertilization until birth.

Gestation

The length of time of prenatal development.

Pregnancy

The physiological condition in which a female carries a developing embryo or fetus within the uterus.

Fertilization

The fusion of a sperm and secondary oocyte to form a zygote.

Zygote

The diploid cell formed by fertilization.

Cleavage

A series of rapid mitotic cell divisions of the zygote that increase cell number without increasing overall size.

Blastomere

Any of the smaller cells produced during cleavage of the zygote.

Morula

A solid ball of blastomeres formed after several rounds of cleavage.

Blastocyst

A hollow, fluid-filled structure consisting of an inner cell mass and outer trophoblasts, capable of implantation.

Trophoblast

The outer cell layer of the blastocyst that contributes to formation of the placenta.

Blastocoel

The fluid-filled cavity within the blastocyst.

Inner Cell Mass

A cluster of cells within the blastocyst that will develop into the embryo.

Implantation

The process by which the blastocyst attaches to and embeds within the endometrium of the uterus.

Amniotic Cavity

The fluid-filled space surrounding the developing embryo, enclosed by the amnion.

Amniotic Fluid

The fluid within the amniotic cavity that cushions the embryo/fetus and allows movement.

Amnion

The membrane that forms the amniotic sac and encloses the amniotic fluid.

Yolk Sac

An extraembryonic membrane involved in early nutrient transfer.

Embryonic Disc

A bilayered flattened group of cells sandwiched between the amniotic cavity and the yolk sac that gives rise to the three primary germ layers.

Ectoderm

The outer germ layer that develops into the nervous system, epidermis, and related structures.

Mesoderm

The middle germ layer that forms muscles, bones, connective tissues, and the cardiovascular system.

Endoderm

The inner germ layer that develops into the lining of the digestive and respiratory systems and associated organs.

Monozygotic Twin

Identical twins formed when a single fertilized egg splits into two embryos.

Dizygotic Twin

Fraternal twins formed from the fertilization of two separate oocytes by two different sperm.

Placenta

A temporary organ that facilitates exchange of nutrients, gases, and wastes between maternal and fetal blood.

Umbilical Cord

A flexible structure connecting the fetus to the placenta, containing blood vessels that support fetal circulation.

Umbilical Artery

Blood vessels that carry deoxygenated blood and waste products from the fetus to the placenta (typically two).

Umbilical Vein

A blood vessel that carries oxygenated, nutrient-rich blood from the placenta to the fetus (typically one).

Labor

The physiological process of childbirth involving uterine contractions leading to delivery of the fetus.

Braxton Hicks Contractions

Irregular, nonproductive uterine contractions that occur during pregnancy and do not lead to cervical dilation; false labor.

True Labor

Regular, intensifying uterine contractions that result in progressive cervical dilation and eventual delivery.

Parturition

The act of giving birth; the complete process of labor and delivery.

Dilation Stage

The first stage of labor, during which the cervix dilates.

Expulsion Stage

The second stage of labor, during which the fetus is delivered.

Placental Stage

The third stage of labor, during which the placenta is expelled from the uterus.

Pre-Term Delivery

Birth occurring before 37 weeks of gestation.

Early Term Delivery

Birth occurring between 37 weeks and 38 weeks + 6 days of gestation.

Full Term Delivery

Birth occurring between 39 weeks and 40 weeks + 6 days of gestation.

Late Term Delivery

Birth occurring between 41 weeks and 41 weeks + 6 days of gestation.

Post-Term Delivery

Birth occurring at or after 42 weeks of gestation.

Cesarean (C) Section

A surgical procedure in which the fetus is delivered through incisions in the abdominal wall and uterus.

Lactation

The production and secretion of milk by the mammary glands.

Prolactin

A hormone from the anterior pituitary that stimulates milk production.

Oxytocin

A hormone from the hypothalamus that stimulates uterine contractions during labor and milk ejection during breastfeeding.

Neonatal (Neonate)

The developmental stage from birth to 1 month of age.

Infancy (Infant)

The developmental stage from 1 month to 1 year of age.

Childhood (Child)

The developmental stage from 1 year of age to puberty.

Adolescence (Adolescent)

The developmental stage during puberty, transitioning an individual to adulthood.

Maturity / Adulthood (Adult)

The developmental stage the begins after puberty.