Embryology and Fetal Screening

Question 1

Describe the development of the blastocyst

Answer 1

-egg cell has thick white coat called zona pellucid and plasma membrane inside
-the sperm then goes through the plasma membrane and zona pellucid and merge the genetic information with the egg and it becomes a zygote
-the zygote then divides into two cells because it needs to grow really fast as it splits into half- this splitting in half is called cleavage
-they divide from 4-8-16 whilst staying in the zona pellucida
-it goes on and on and then it becomes a ‘morula’ and cleavage stage finishes
-whilst still in the zona pellucida, the cells become more closer and compacted
-some of the cells become different cells as they differentiate so the outer layer of cells (one type) is called trophoblasts and the inner cells (another type) is called embryo blasts
-ask of the cells then clump together leaving space on the other side and its called ‘inner cell mass’ as its all on one side and then the cavity on the other side is called a ‘blastocoel’
-this structure is then called blastocyst

Question 2

Describe the formation of the germ layers and the subsequent body tissue deriving from these layers

Answer 2

The germ layers form during the process of gastrulation, when the hollow ball of cells that constitutes the blastula begins to differentiate into more specialised cells that become layers across the developing embryo
1. Ectoderm;
2. Mesoderm;
3. Endoderm

Question 3

Describe the specific embryonic development stating the gestation period

Answer 3

month 1 - 5mm - 0.02g - heart is beating, main respiratory and gastrointestinal organs appear, neural tube appears (from which the nervous system develops), limb buds apparent
month 2- 28mm- 2.7g- endocrine glands appear, respiratory tree in place, vascular system laid down, heart development complete, skin, nails and sweat glands present in skin, cartilage models for bones appear, face has human profile
month 3- 78mm- 26g- blood cells produced in bone marrow, basic brain and spinal cord structure in place, classification of bones begins and muscles form, gonads appear (ovaries in females, testes in males)
month 4- 133mm- 150g- formation of hair, eyes and ears in place, rapid central nervous system development, joints formed
G - 346mm - 3.2kg- at birth, many systems immature but otherwise functional. Some important adaptions to independent life required e.g. in cardiovascular and respiratory function

Question 4

Describe the fetal screening procedure

Answer 4

With the application of physiology