Pregnancy and development falsh cards

Flashcards covering key concepts of the reproductive system.

What is the conceptus?

The conceptus includes the developing baby (embryo or fetus), plus all its extra structures like the placenta.

What is an embryo?

The embryo is what the conceptus is called from week 3 through week 8 of development.

What is a fetus?

After week 8, the embryo becomes a fetus, which lasts until birth (week 9–38).

What is the difference between an embryo and a fetus?

An embryo is the developing human in the early stages (weeks 3–8), while a fetus is the later stage (week 9 to birth) when it looks more like a baby and keeps growing.

When is the secondary oocyte referred to as an “egg”?

Once it is fertilized by a sperm, the secondary oocyte is considered the “egg” and becomes a zygote.

How long is the secondary oocyte viable after ovulation?

The secondary oocyte is viable for 12 to 24 hours after ovulation.

How long is sperm viable in the female reproductive tract?

Sperm can survive up to 5 days, but fertilization usually happens within 24 hours after ovulation.

Why is sperm viability important?

Fertilization is most likely when intercourse happens during the window of 1–2 days before ovulation, since the sperm needs to meet the egg before it dies.

What barriers must sperm overcome to reach the oocyte?

Sperm must travel through the vagina, cervix, uterus, and uterine tubes, and then pass through the corona radiata, zona pellucida, and finally reach the oocyte membrane.

What is capacitation?

Capacitation is a process in the uterus/tubes where sperm become motile and their membranes become fragile enough to release acrosomal enzymes.

Why is capacitation important?

Without capacitation, sperm can’t undergo the acrosomal reaction or fertilize the egg.

What is the acrosomal reaction?

The acrosomal reaction is when enzymes are released from the sperm’s acrosome to digest a path through the zona pellucida.

Why is the acrosomal reaction important?

It allows the sperm to reach and bind to the egg’s membrane, which is required for fertilization to happen.

What are the layers sperm must pass through to reach the oocyte membrane?

The sperm passes through: 1. Corona radiata 2. Zona pellucida 3. Plasma membrane of the oocyte

What is polyspermy?

Polyspermy is when more than one sperm enters the egg — this is prevented by fast and slow blocks.

What is the fast block to polyspermy?

The fast block is a quick change in the egg’s membrane (depolarization) that prevents more sperm from entering right away.

What is the slow block to polyspermy (cortical reaction)?

The cortical reaction (slow block) hardens the zona pellucida and removes sperm receptors so no more sperm can get in.

What triggers the slow block to polyspermy?

The cortical reaction happens when cortical granules release enzymes that modify the zona pellucida.

Do we inherit mitochondria from our mother or father?

From our mother.

Why do we inherit mitochondria only from our mother?

Because only the egg contributes cytoplasm and organelles; the sperm’s mitochondria are destroyed after fertilization.

What is the fast block to polyspermy?

An immediate electrical change (membrane depolarization) in the oocyte after one sperm enters.

What is the slow block to polyspermy?

A longer-lasting reaction where enzymes from cortical granules destroy sperm receptors and harden the zona pellucida.

What reaction is responsible for the slow block?

The cortical reaction.

How are the acrosomal and cortical reactions connected to blocking polyspermy?

The acrosomal reaction helps the first sperm enter; the cortical reaction prevents others from entering by starting the slow block.

Why does the zygote have to move down to the uterus?

The uterus is where the zygote can implant into the thick, nutrient-rich endometrial lining. This environment is necessary to support its development into an embryo.

When does the zygote reach the uterus?

The zygote reaches the uterus about 3–4 days after ovulation while it’s dividing and becoming a blastocyst.

What structural change must happen before implantation?

The blastocyst must “hatch” out of the zona pellucida, a protective layer, so it can attach to the uterine wall.

What contributes to the movement of the zygote from the oviduct (fallopian tube) to the uterus?

Movement is helped by cilia lining the uterine tube and smooth muscle contractions that gently push the zygote along.

What is the connection between this process and ectopic pregnancy?

If the zygote fails to reach the uterus and implants in the fallopian tube instead, this results in an ectopic pregnancy.

What is a blastocyst?

a fluid-filled hollow ball of cells that forms about 4–5 days after fertilization. It is the structure that implants into the uterus.

What cells make up a blastocyst?

Trophoblast: outer layer that helps form the placenta. Inner cell mass (embryoblast): group of cells inside the blastocyst that will become the embryo.

Why are these cells important?

The trophoblast invades the uterus and starts forming the placenta. The inner cell mass gives rise to the developing baby.

When is implantation completed?

Implantation usually begins around day 6 after ovulation and is complete by day 12.

What is hCG and which cells produce it?

hCG (human chorionic gonadotropin) is a hormone made by the syncytiotrophoblast cells of the embryo.

What is the importance of hCG in pregnancy?

hCG keeps the corpus luteum alive so it continues to make progesterone and estrogen, which maintain the uterine lining and prevent menstruation.

How is hCG used clinically?

hCG is what pregnancy tests detect in urine or blood to confirm pregnancy.

What is placentation?

Placentation is the formation of the placenta, the organ that supports the growing fetus.

When does placentation occur and when is it complete?

It starts with implantation and is complete by the end of the third month of pregnancy.

Why is placentation important?

The placenta allows for nutrient and gas exchange, removes waste, and makes hormones to support the pregnancy.

Which tissues form the placenta?

It forms from both embryonic tissue (chorionic villi) and maternal tissue (decidua basalis).

What is the connection between placental hormones and the corpus luteum?

At first, the corpus luteum makes progesterone and estrogen. Later, the placenta takes over hormone production by the end of the third month.

What is the placental barrier?

is the thin membrane that separates the mother’s blood from the baby’s blood. It allows nutrients, gases, and waste to exchange without mixing the blood.

What kind of capillaries are in the placenta?

The placenta contains chorionic villi with fetal capillaries inside. These are thin-walled and allow for efficient exchange between maternal and fetal blood.

What are the four extraembryonic membranes?

Amnion.

Yolk sac

Allantois

Chorion

Chorion

outermost membrane; helps form the placenta.

Allantois

helps form the umbilical cord and contributes to the urinary bladder.

Yolk sac

forms part of the gut and makes the first blood cells and vessels.

Amnion

surrounds the embryo with amniotic fluid, protecting it from shock and temperature changes.

Why are these membranes important?

They support the developing embryo by providing protection, nourishment, waste removal, and hormone production.

What is gastrulation?

Gastrulation is a key step in embryonic development when the inner cell mass becomes a three-layered embryo.

When does gastrulation occur?

It happens during the third week of development.

What is formed during gastrulation?

The three primary germ layers: • Ectoderm • Mesoderm • Endoderm These layers will form all the tissues and organs in the body.

What does the ectoderm form?

The ectoderm forms structures like the nervous system, epidermis of the skin, and parts of the eyes and ears.

What does the mesoderm form?

The mesoderm forms muscles, bones, the heart, blood vessels, and most of the urinary and reproductive systems.

What does the endoderm form?

The endoderm forms the linings of the digestive and respiratory tracts, as well as glands like the liver and pancreas.

What is neurulation?

Neurulation is the process during the third to fourth week of development where the neural tube forms, which will become the brain and spinal cord.

What structure does the neural tube arise from?

It forms from the ectoderm layer through a series of folds and closures.

Why is neurulation important?

Without proper formation of the neural tube, birth defects like spina bifida or anencephaly can occur.

When does the fetal period begin?

The fetal period starts at week 9 and lasts until birth.

What happens during the fetal period?

• The body grows rapidly. • Organs continue to develop and mature. • Sex can usually be determined around week 12. • By the end of the fetal period, most organs are fully functional. • The fetus gains weight and stores fat for insulation after birth.

What is lordosis and why does it happen in pregnancy?

Lordosis is the exaggerated inward curve of the lower back. It happens during pregnancy as the woman’s center of gravity shifts forward, helping to balance the growing uterus.

What is the Chadwick sign?

The Chadwick sign is a purplish-blue coloration of the cervix, vagina, and labia, caused by increased blood flow. It’s one of the earliest signs of pregnancy.

What happens to digestion during pregnancy?

Morning sickness may occur (especially in early pregnancy). Heartburn and constipation are common due to hormonal effects and pressure from the growing uterus.

What happens to the urinary system during pregnancy?

The kidneys process more blood, increasing urine production. Urinary frequency increases due to pressure on the bladder.

How does pregnancy affect the respiratory system?

Breathing rate may increase slightly. The diaphragm is pushed up by the uterus, but lung capacity is mostly maintained.

How does the cardiovascular system change in pregnancy?

Blood volume increases up to 30–50% to supply the growing fetus. Heart rate rises slightly. Blood pressure may drop slightly early in pregnancy due to hormone effects.

What is parturition?

Parturition is the act of giving birth — it includes labor and delivery of the baby.

What are the three stages of labor?

1. Dilation stage – longest stage; cervix dilates to 10 cm, contractions start, and the amniotic sac may rupture (“water breaks”). 2. Expulsion stage – full dilation to birth; baby is delivered. 3. Placental stage – delivery of the placenta (afterbirth), usually within 30 minutes after the baby.

What is true labor?

True labor includes regular, stronger uterine contractions that get closer together and cause cervical dilation.

What is false labor (Braxton Hicks contractions)?

False labor has irregular, less intense contractions that don’t cause cervical changes — often a “practice run” for real labor.

What does oxytocin do during labor?

Oxytocin is a hormone that triggers strong uterine contractions during labor. It works with prostaglandins in a positive feedback loop to make contractions stronger and closer together until the baby is born.

How is oxytocin released?

It’s released by the posterior pituitary in response to uterine stretching and pressure on the cervix.

What triggers the newborn’s first breath?

The accumulation of carbon dioxide in the baby’s blood causes the respiratory centers in the brain to trigger the first breath — this is usually within 10 seconds after birth.

What hormone is responsible for milk production?

Prolactin, from the anterior pituitary, stimulates the production of milk in the mammary glands.

What hormone is responsible for milk let-down (release)?

Oxytocin, from the posterior pituitary, causes the ejection of milk when the baby suckles.

What is colostrum and why is it important?

Colostrum is the first milk produced for 2–3 days after birth. It’s yellowish and thick, rich in antibodies and proteins, helping the baby’s immune system and digestion.