Chapter 24 - Pregnancy & Human Development

A set of vocabulary flashcards covering the biological processes of fertilization, prenatal stages, fetal circulation, physiological changes in pregnancy, and the stages of childbirth and lactation.

Acrosomes

Structures at the head of sperm that release enzymes to break down the zona pellucida during fertilization.

Zona pellucida

The protective outer layer of the ovum that sperm must penetrate for fertilization to occur.

Gestation

The period from conception until birth, typically lasting $266$ days.

First trimester

The initial phase of gestation, encompassing the first $12$ weeks.

Second trimester

The middle phase of gestation, from weeks $13$ through $24$.

Third trimester

The final phase of gestation, from week $25$ until birth.

Preembryonic stage

The first stage of prenatal development occurring during the first $16$ days.

Embryonic stage

The stage of prenatal development from after the $16\text{th}$ day until the eighth week.

Fetal stage

The final stage of prenatal development beginning at the eighth week and lasting until birth.

Zygote

The single cell with $46$ chromosomes formed at the time of fertilization.

Morula

The stage of the fertilized egg when it first enters the uterine cavity.

Blastocyst

The stage of the fertilized egg when it implants in the uterus.

Amniotic cavity

The space created when the inner cell mass separates from the trophoblast during implantation.

Embryonic disc

The flattened inner cell mass that gives rise to the three germ layers: endoderm, mesoderm, and ectoderm.

Placenta

The organ through which fetal waste moves to maternal veins and oxygen, nutrients, and antibodies pass to fetal blood.

Ductus venosus

A fetal circulatory shunt that diverts blood from the umbilical vein to the inferior vena cava to bypass the liver.

Foramen ovale

An opening in the fetal heart that diverts blood from the right to the left atrium to bypass the lungs.

Ductus arteriosus

A fetal circulatory shunt that diverts blood from the pulmonary artery to the descending aorta to bypass the lungs.

Lanugo

A fine, downy hair that covers the body of the fetus, appearing around $20$ weeks.

Vernix caseosa

A cheeselike substance that covers the fetal skin, appearing around $20$ weeks.

$28$ weeks gestation

The point at which the fetus's respiratory system is capable of gas exchange.

Linea nigra

A line of pigment extending from the umbilicus to the pubis that may appear on the mother's abdomen during pregnancy.

Chloasma

The darkening or discoloration of facial skin during pregnancy, often called the mask of pregnancy.

Lactobacillus

The type of bacteria that increases in the vaginal microbiota during pregnancy, causing the environment to become more acidic.

Prolactin

The hormone secreted by the anterior pituitary that initiates milk production.

Oxytocin

The hormone secreted by the posterior pituitary responsible for the let-down reflex and triggering uterine contractions during childbirth.

Let-down reflex

The process by which oxytocin forces milk into the ducts of the mammary glands.

Stage 1 (Dilation)

The first stage of childbirth involving the dilation and effacement of the cervix, lasting $6$ to $18$ hours in first-time mothers.

Stage 2 (Expulsion)

The stage of childbirth involving the expulsion of the baby, typically lasting $30$ to $60$ minutes in first-time mothers.

Stage 3 (Delivery)

The final stage of childbirth involving the delivery of the placenta, lasting between $5$ and $30$ minutes.