Pregnancy and Childbirth 2

The reproductive system plays a critical role in human development, focusing on pregnancy and childbirth processes.

Definition: The process where the embryo adheres to the endometrium of the uterus.
Nutritional Support: Endometrial cells provide essential nutrients, serving as the only nutritional source for the first week post-implantation.
Placenta Formation: The endometrium grows over the embryo, and the placenta begins to form.
Hormonal Activity: The embryo secretes human chorionic gonadotropin (HCG), which stimulates the corpus luteum to secrete estrogen and progesterone for maintaining the pregnancy.

Definition: Occurs when the embryo implants outside the uterus, commonly in the fallopian tubes.
Signs and Symptoms: This includes vaginal bleeding, pelvic pain, and low HCG levels.
Risks: Possible risk of tubal rupture leading to severe abdominal pain, fainting, and shock.
Treatment Options: Can involve medication or surgical intervention.

Structure: A temporary organ formed from both maternal (endometrium) and fetal (outer layer of embryo) tissues.
Function: Provides fetal nutrition from week 9 until birth.
Connection: The placenta is connected to the fetus through the umbilical cord, containing two umbilical arteries carrying deoxygenated blood and one umbilical vein carrying oxygenated blood.

Chorionic Villi: Contain fetal capillaries and are surrounded by maternal blood for nutrient exchange.
Placental Barrier: A semipermeable membrane separating maternal and fetal blood, facilitating diffusion of oxygen, nutrients, and waste products.
Delivery Impact: Rupture of chorionic villi during delivery can allow fetal blood to cross into maternal circulation.

Monozygotic: Single fertilized egg divides, usually sharing one placenta and being genetically identical.
Multizygotic: Two or more eggs fertilized separately, each developing its own placenta, resulting in non-identical siblings.

Major Developments: All body systems and major brain regions are present, and the heart is fully functional.
Hemopoiesis Starts: Blood cell formation begins, with the development of limbs, fingers, and toes.

Pathway: The umbilical vein passes through the liver as the ductus venosus and drains into the inferior vena cava (IVC).
Blood Bypass: Cardiac blood bypasses the lungs via the foramen ovale and ductus arteriosus.
Artery Function: Umbilical arteries branch from the internal iliac arteries returning to the placenta.

Brain Development: The brain enlarges; retina forms; nervous control develops.

Sensory Reception: General sensory systems begin establishing; digestive glands develop.

Physical Developments: The fetus assumes a position due to spatial constraints; lanugo covers the body.

CNS Changes: Myelination of the central nervous system begins; lungs prepare producing surfactant.

Final Developments: The skin thickens and subcutaneous fat accumulates; most babies born at 35-40 weeks.

Closure of Bypass Structures: Foramen ovale becomes fossa ovalis; ductus arteriosus becomes ligamentum arteriosum.
Arteries & Veins: Umbilical arteries/vein undergo fibrosis, becoming ligaments and aiding in postnatal adaptations.

Adaptive Immunity: Development of the adaptive immune system; newborns receive IgG from the mother, which declines as their own levels rise.
IgA: Present in breast milk, providing critical immune support until weaning.

Hormonal Control: Estrogen and progesterone levels stimulate mammary gland growth; prolactin promotes milk production.
Neuroendocrine Reflex: Suckling triggers oxytocin release for milk ejection, simultaneously contracting the uterus.

Colostrum: Initial milk high in protein and antibodies, produced in small amounts for the first few days.
Breast Milk: Transition to mature milk occurs postpartum; it is primarily water, higher in fat and lactose than colostrum, providing critical immunity.

Milk Ejection Mechanism: Involves positive feedback from mechanoreceptors in the nipples, stimulating both prolactin for production and oxytocin for ejection during nursing.

Understanding the anatomy and physiology of the reproductive system provides insights into the stages of pregnancy, childbirth, and early infant development.