Embryoloy And Fetal Screening Flashcards
Define terms used when discussing embryology
Blastocyst: a hollow ball of 70-100 cells
Zygote: growth of a new human being begins when an ovum is fertilised by a spermatozoon. Result = zygote. Has 46 chromosomes
Embryo: the first 8 weeks of development are called the embryonic period and the developed gene ‘baby’ is described as an embryo
Fetus: name for the developing ‘baby’ after 8 weeks
Gestation: the period between fertilisation and brith (normally around 40 weeks)
Describe the development of the blastocyst
The zygote is firmly embedded in uterine lining 10 days after fertilisation, signalling beginning of pregnancy
They loose their totipotency and begin to differentiate
Undergoes rapid and repeated cell divisions, and by the time it implants in the endometrium it has become a blastocyst
Containing an inner mass of cells, which develops into the fetus, and its amniotic sac. The outer cell mass is known as the trophoblast which develops into the placenta
Discuss the formation of the germ layers and the subsequent body tissue deriving from these layers
The three germ layers form around week 3
Ectoderm: nervous system, retina of the eye, special sense cell epidermis
Mesoderm: connective tissue, heart, spleen, muscles, skull
Endoderm: lungs, trachea, liver, pancreas, bladder, alimentary canal
Discuss specific embryonic development stating the gestation period
Month 1: heart beating. Main respiratory and gastrointestinal organs appear.
Month 2: endocrine glands appear. Respiratory tree in place. Vascular system laid down. Heart development complete. Skin, nails and sweat glands present in skin. Face has human profile
Month 3: blood cells produced in bone marrow. Basic brain and spinal cord structure in place. Ossification of bones begins and muscles forms. Gonads appear.
Month 4: formation of hair. Eyes and ears in place. Rapid CNS development. Joints formed
Month 9: many systems immature but functional
