CP Chp. Fetal Development and Genetics

Preembryonic Stage: Fertilization through the second week
- Fertilization occurs in the fallopian tubes within 12 hours of ovulation. The zygote is transported to the uterine cavity where it undergoes cleavage to form a morula.
- The morula develops into a blastocyst, consisting of an inner cell mass (which forms the embryo) and trophoblast (which develops into chorion and placenta).
Embryonic Stage: End of the second week through the eighth week
- Major body organs and external features begin to form; amniotic fluid surrounds the embryo, providing protection and environment for growth.
Fetal Stage: End of the eighth week until birth
- This is the longest stage where significant growth and refinement of all organ systems occur.
- Average pregnancy lasts about 280 days.

Ectoderm: Forms central nervous system, skin, and glands.
Mesoderm: Forms skeletal system, muscles, urinary, circulatory, and reproductive organs.
Endoderm: Forms respiratory system, liver, pancreas, and digestive system.

Week 3: Development of brain, spinal cord; neural tube forms; limb buds appear.
Week 4: Differentiation of the brain; limb buds develop more.
Week 5 to 8: Heart beats; development of sensory organs; limbs and facial features begin forming; by Week 8, resembles a human being.

Week 12: Fetus 6-9 cm, kidneys forming urine.
Week 16: Active movements show; skin transparent.
Week 20: Lanugo covers body; significant muscle development.
Week 24: Fetus can hear; reflex hand grasp functioning.
Weeks 28-40: Further growth, skin changes, and development of reproductive features.

Forms a protective sac and permits fetal movements, enhancing musculoskeletal development.
Maintains constant body temperature and cushions the fetus.
Associated with fetal well-being; abnormalities such as oligohydramnios (<500 mL) or hydramnios (>2,000 mL) can indicate fetal problems.

Exchange of nutrients and waste between mother and fetus without direct blood contact, influencing maternal physiology and fetal development.
Produces important hormones (hCG, hPL, estrogen, progesterone, relaxin).

Forms from amnion; contains one vein and two arteries, serving as a lifeline between mother and fetus.
Encased in Wharton's jelly to prevent compression.

Unique circulation with shunts directing blood away from lungs (foramen ovale, ductus arteriosus, ductus venosus).
Major changes at birth with closure of shunts as lungs fill with air.

Study of individual genes and their inheritance; includes genetic testing for diseases.
Advances in genetic knowledge influence pharmacogenomics and gene therapy.

An international project aimed at sequencing all human genes, identifying their functions and variations.
Important for understanding genotypes and phenotypes.

Mendelian Disorders: Involve autosomal dominant, autosomal recessive, and X-linked inheritance patterns.
- Examples include Huntington Disease (dominant) and Cystic Fibrosis (recessive).
Multifactorial Disorders: Involve genetic and environmental interactions (e.g., heart disease).
Nontraditional Inheritance: Patterns like Prader-Willi and Angelman Syndromes.

Monosomies: Missing a chromosome; Trisomies: Extra chromosome (e.g., Down syndrome).
Sex Chromosome Abnormalities: Turner syndrome (missing X chromosome) and Klinefelter syndrome (extra X chromosome in males).

Process of advising at-risk individuals about inheritance disorders and management options.
Potential misuse of genetic information can lead to privacy violations and discrimination.

Involve preconception counseling, genetic testing scheduling, risk assessment, and emotional support for families.