Fetal Development and Placenta Function

Stages of Fetal Development

• Timeline: Nine weeks until birth.
• Placenta: Functions by the end of the third month.

Corpus Luteum and Corpus Albicans

• Corpus Luteum: Remains for a couple of months if pregnant, until placenta produces hormones.
• Corpus Albicans: Scar tissue formed as corpus luteum shrivels.
• Corpus Hemorrhagicum: Preceding stage.

Fertilization Process

• Occurs in the uterine tube.
• Cleavage results in the formation of a morula.
• Morula transforms into a blastocyst with a trophoblast and inner cell mass (embryoblast).

Implantation

• Timing: About 6 days after fertilization.
• Trophoblast: Releases enzymes to digest into the uterine lining.
• Nutrient Absorption: Utilizes nutrients from digested tissues.

Sperm Capacitation

• Takes 4-6 hours; necessary for fertilization.
• Assisted by uterine contractions induced by prostaglandins.

Prevention of Polyspermy

• Fast Block: Oocyte membrane depolarizes 1-3 seconds after contact.
• Slow Block: Hardening of zona pellucida and destruction of ZP3 receptors.

Early Embryonic Development

• Formation of morula and blastocyst.
• Implantation: Development of syncytiotrophoblast and cytotrophoblast.
• Creates lacunae filled with maternal blood for nutrient supply.

Layers of the Uterus Post-Implantation

• Decidua: Three regions - basalis, capsularis, parietalis.
• Decidua Basalis: Maternal part of the placenta.

Complications

• Ectopic Pregnancy: Occurs outside uterine tubes.
• Placenta Previa: Placenta covers cervix, causing risky bleeding.

Embryonic Development

• Neurulation: Formation of neural tube.
• Heart and Limb Development: Early heart formation and limb bud appearance.
• Amniotic Cavity: Formation of amniotic fluid and cavity.

Umbilical Cord Components

• Yolk Sac and Allantois: Part of umbilical cord development.
• Chorionic Villi: Sampled during early tests for genetic abnormalities.

Fetal Circulation

• Lungs Bypassed: Foramen ovale and ductus arteriosus enable bypass.
• Umbilical Arteries and Veins: Arteries take deoxygenated blood to placenta, veins bring oxygenated blood.

Placenta and Fetal Development

• Placenta Formation: Complete by the 10th week, secretes estrogen and progesterone.
• Immunological Transfer: IgG antibodies can cross placenta, transmitted via breast milk.

Diagnostic Techniques

• Ultrasound: Measures growth, determines sex, checks positioning.
• Amniocentesis/Chorionic Villi Sampling: Detects genetic abnormalities.