Fetal Development Flashcards
Stages of fetal development
-Preembryonic stage
-Embryonic stage
-Fetal stage
Preembryonic stage
-Fertilization AKA conception (union of ovum and sperm); cleavage –> morula
-Blastocyst (inner cell mass) and trophoblast (outer cell mass)
-Implantation (7-10 days after conception)
Gametogenesis
-Gametes (ovum or sperm) are produced
-Come together to form zygote
Embryonic stage
-End of 2nd week (day 15) thru 8th week
-Basic structures of major body organs and main external features
-Most susceptible to teratogens, infections, radiation, nutritional deficiencies
Major bodily structure development (table 10.1)
-Week 3: brain, spinal cord, heart, GI tract, neural tube, leg and arm buds
-Week 4: brain differentiates, limb buds
-Week 5: heart rhythm, eyes and ears, cranial nerves, muscles innervated
-Week 6: lungs, fetal circulation, liver produces RBC, brain, primitive skeleton, CNS, brain waves
-Week 7: trunk straightens, nipples, hair follicles, elbows, toes, legs move, diaphragm, mouth w/ lips, tooth buds
-Week 8: intestines, facial features, heart, resembles human, placenta works, eyelids form but sealed shut
-Weeks 9-12: sexual differentiation, buds for all teeth form, GI activity, face and neck, urogenital tract, RBC production in liver, urine excretion, gender determined week 12, limbs lengthen, digits form, movement of limbs, kicks, swallowing reflex
-Weeks 13-16: fine hair (lanugo), bones harden, active mvmt, sucking motions, amniotic fluid swallowed, external genitalia, nails, weight quadruples, fetal mvmt felt (quickening)
-Weeks 17-20: rapid brain growth, heart tones, kidneys secret urine, vernix caseosa forms, thick hair, brown fat to maintain temp, nails, muscles
-Weeks 21-24: brows and lashes, hand grasp, startle reflex, alveoli, lungs produce surfactant
-Weeks 25-28: fetus reaches length of 15 in, eyelids open, fingerprints set, subq fat, blood formation in bone marrow, head-down position, response to light and sound, sucks thumb, shuts eye
-Weeks 29-32: body fat, CNS, rhythmic breathing, pupillary light reflex, storage of Fe, Ca, P
-Weeks 33-38: testes, lanugo disappears, strong hand grasp reflex, body fat, earlobes, nails, breast buds, mother supplies antibodies, full term at 38 weeks, head-down position
Fetal stage
-End of 8th week until birth
-Average pregnancy is 280 days from 1st day of LMP
-Longest period
Embryonic layers
-Ectoderm
-Mesoderm
-Endoderm
Ectoderm
-Forms CNS, special senses, skin, glands
-Outside protective layers
Mesoderm
-Forms skeletal, urinary, circulatory, and reproductive organs
-Internal body systems
Endoderm
-Forms respiratory system, liver, pancreas, and digestive system
-Epithelial lining of organs
Fxns of the placenta
-Interface btwn mother and fetus
-Making hormones to control mother’s physiology
-Protecting fetus from immune attack from mother
-Removing waste products from fetus
-Inducing mother to bring more food to the placenta
-Producing hormones that mature into fetal organs
-Precursor is trophoblasts
Oligohydramnios vs hydramnios
-Oligohydramnios: amniotic fluid < 500 mL at term
-Hydramnios: amniotic fluid > 2,000 mL at term
Hormones produced by placenta
-hCG (present in pregnancy tests)
-Human placental lactogen (hPL) or human chorionic somatomammotropin (hCS)
-Estrogen
-Progesterone
-Relaxin
Umbilical cord
-Formed from the amnion
-Lifeline from the mother to the growing embryo
-Contains 1 large vein and 2 small arteries
-Wharton jelly surrounds the vein and arteries to prevent compression
-At term, the average umbilical cord is 22-in long and about 1-in wide
Role of amniotic fluid
-Helps maintain a constant body temperature for the fetus
-Permits symmetric growth and development
-Cushions the fetus from trauma
-Allows umbilical cord (no nerve endings) to be mostly free of compression
-Promotes fetal movement to enhance musculoskeletal development
Fetal circulation
-Blood from placenta to and thru the fetus then back to placenta
-Oxygenated blood must travel thru shunts to reach fetus
-Highly oxygenated blood to heart, brains –> shunts away from lungs, liver
-Large volumes of oxygenated blood are not needed d/t placenta taking over fxns of lungs and liver
-Blood w/ highest oxygen content goes to heart, head, neck, upper limbs
-Blood w/ lowest oxygen content goes to placenta
Shunts during fetal life
-Ductus venosus
-Ductus arteriosus
-Foramen ovale
Shunt closure
-Supposed to be open during fetal development for circulation
-When baby gasps after birth, shunts should close
-If shunts don’t close, a murmur will be heard
-Not a problem if as/s
-Problem is deoxygenated and oxygenated blood mix and cause cyanosis or fatigue
Ductus venosus
Connects umbilical vein to inferior vena cava
Ductus arteriosus
Connects main pulmonary artery to aorta
Foramen ovale
Anatomic opening btwn R and L atrium
Genetics and advances in genetic knowledge
-Pharmacogenomics: study of genetic and genomic influences on pharmacodynamics and pharmacotherapeutics
-Perinatal care
-Genetic testing
-Gene therapy
Genetics vs genomics
-Genetics: scrutinizes fxns of single genes and their role in inheritance
-Genomics: address genes and their interrelationships
Human Genome Project
-International 13-year effort started in 1990 to produce a comprehensive sequence of human genome
-Goal: map, sequence, determine fxn of all human genes
-Genome: person’s genetic blueprint determining genotype and phenotype