A&P 2: Pregnancy & Development

Fertilization

Usually occurs within 24 hours of ovulation, while the egg is in the fallopian tube; happens in the distal third of the fallopian tube

Zygote

Fertilized egg cell; diploid; containing 46 chromosomes

Cleavage

Rapid mitotic cell division of the zygote without growth, producing smaller cells called blastomeres

Morula

A solid ball of 16–32 cells, formed around 3–4 days after fertilization

Blastocyst

Hollow ball; implants in the edometrium about day 6 after fertilization; outer layer is the trophoblast; and becomes part of the placenta; inner part is the embryoblast and develops into the embryo

Embryo

Developing human from implantation until the end of week 8

Fetus

From week 9 until birth

Ectopic Pregnancy

Occurs when the fertilized egg implants outside the uterus (e.g., in the fallopian tube)

Tubal Pregnancy

A common type of ectopic pregnancy where implantation happens in the fallopian tube

Placenta Previa

When the placenta covers part or all of the cervix, posing a risk of bleeding

HCG

Human chorionic gonadtropin hormone; released by the embryo; helps maintain the corpus luteum in the ovary (which releases progesterone) and prevents the next menstrual cycle; detected in urine by pregnancy tests

Gastrulation

Process that reorganizes the embryoblast into a three-layered disc (gastrula) during week 3

Ectoderm

Develops into the outer components of the body: skin, hair, mammary glands, and the nervous system (neurulation)

Mesoderm

Develops into muscle, cartilage, bone, heart, blood vessels (circulatory system), gonads, and the urogenital system

Endoderm

Develops into the epithelial lining of the digestive tract, lungs, liver, pancreas, and thyroid

Placenta

Allows nutrient exchange, waste removal, and oxygen supply from mother to fetus without blood mixing directly

Ductus Arteriosus

Shunt connecting the pulmonary artery to the aorta; between pulmonary trunk and aortic arch; should close at birth to become ligamentum arteriosum

Foramen Ovale

A hole connecting the right and left atria, allowing blood to skip the lungs; hole in interatrial septum; should close at birth to become fossa ovalis

Umbilical Vein

Carries oxygenated, nutrient-rich blood from the placenta to the fetus

Umbilical Artery

Carry deoxygenated, waste-filled blood from the fetus to the placenta

Dieting for Pregnant Women

Generally not recommended; nutrition is critical; eating for two is a myth; only need a small increase in calories, especially in the third trimester

Activity and Sleeping

Walking and swimming are generally safe for most women; sleeping on the left side is recommended to improve blood flow to the placenta

First Trimester (Week 1–12)

Most critical, as this is when all major organ systems form (organogenesis); by end all systems are developed; most important

Second Trimester (Week 13–26)

Rapid growth and structural refinement.

Third Trimester (Week 27–40)

Significant weight gain and maturation of systems (especially lungs)

First System to Develop

Nervous system (neural plate/tube)

Iron

Needed to support increased maternal red blood cell mass and fetal development; increased hemoglobin; two extra liters are being produced

Folic Acid Deficiency

Linked to neural tube defects like spina bifida

Teratogens

Agents (like alcohol, certain drugs, viruses) that cause birth defects

Amniocentosis

A medical procedure taking a sample of amniotic fluid for genetic testing

Dizygotic Twins (Fraternal)

Formed when two separate eggs are fertilized by two separate sperm

Monozygotic Twins (Identical)

Formed when a single fertilized egg splits into two

Lochia

Vaginal discharge after childbirth (contains blood and uterine tissue)

Meconium

First, dark stool passed by a newborn; baby’s first bowel movement; normally quite sticky; ideally happens after baby is born; more likely to happen before baby is born if over the due date; composed of amniotic fluid, mucus, fetal hair, and bile

Pre-eclampsia

A pregnancy complication characterized by high blood pressure; also known as Toxemia; symptoms include severe hypertension, severe headaches, protein (albumin) in urine, rapid weight gain, and edema in face and body

Eclampsia

A severe form of pre-eclampsia that includes seizures

Gestational Diabetes

Diabetes developed during pregnancy due to hormonal changes