Prenatal Development and Pregnancy - CHP 3

Vocabulary practice flashcards covering the stages of prenatal development, fundamental principles of growth, key embryonic structures, and milestones.

Gestation

The prenatal period of development between conception and birth, which normally ranges from $37$ to $41$ weeks.

Cephalocaudal principle

The principle that development proceeds in a head-to-tail direction, meaning upper parts of the body develop before lower parts of the trunk.

Proximodistal principle

The principle that development proceeds from within to without, meaning parts of the body near the center develop before the extremities.

Germinal stage

The first $2$ weeks of prenatal development, characterized by rapid cell division, increasing complexity and differentiation, and implantation in the wall of the uterus.

Human chorionic gonadotropin

A hormone typically produced only by fetuses that is detected by pregnancy tests to confirm that a conception has occurred.

Blastocyst

A fluid-filled sphere formed by the dividing ovum that floats freely in the uterus until it begins implanting in the uterine wall on the $6\text{th}$ day after fertilization.

Embryonic disk

A thickened cell mass formed from a cluster of cells on one side of the blastocyst, from which the embryo begins to develop.

Ectoderm

The upper layer of the embryonic disk that develops into the outer layer of skin, nails, hair, teeth, sensory organs, and the nervous system.

Endoderm

The lower layer of the embryonic disk that develops into the digestive system, liver, pancreas, salivary glands, and respiratory system.

Mesoderm

The middle layer of the embryonic disk that differentiates into the inner layer of skin, muscles, skeleton, and excretory and circulatory systems.

Amniotic sac

A fluid-filled membrane that encases the developing embryo, giving it room to move.

Placenta

An organ containing maternal and embryonic tissue that permits oxygen, nutrients, and wastes to pass between mother and embryo via diffusion.

Embryonic stage

The second stage of prenatal development ($2$ to $8$ weeks), characterized by rapid growth and development of major body systems and organs.

Organogenesis

The formation of major organ systems and overall body structure during the embryonic stage, making the embryo highly vulnerable to teratogens.

Spontaneous abortion

The natural expulsion from the uterus of an embryo or fetus that cannot survive outside the womb, commonly called a miscarriage.

Stillbirth

The expulsion of a dead fetus occurring at or after $20$ weeks of gestation.

Fetal stage

The final stage of prenatal development (from $8$ weeks to birth), signaled by the appearance of the first bone cells and characterized by increased body differentiation and enlarged size.

Ultrasound

A prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements.

Neurons

Nerve cells that are produced at an estimated rate of $250,000$ per minute starting in the $8\text{th}$ week of gestation.

Lanugo

A fine downy hair covering the baby that appears by $20$ weeks of gestation.

Quickening

Fetal movements felt by the expectant mother, typically detected between $16$ and $25$ weeks of gestation.