Conception, Embryology And Pre-conception LO

Question 1

Describe the development of the blastocyst

Answer 1

• cell division becomes asymmetrical
• cells polarise
• lose their totipotency and begin to differentiate
• implants at day 6

Question 2

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

Answer 2

The three germ layers form around week 3
- ectoderm: nervous system, retina of eye, special sense cells epidermis
- mesoderm: connective tissue, heart, spleen, muscles, skull
- endoderm: lungs, trachea, liver, pancreas, bladder, alimentary canal

Question 3

Discuss specific embryonic development stating the gestation period

Answer 3

Month 1
- 0.02g and 5mm
- heart beating
- main respiratory and GI organs appear
- neural tube appears
- limb buds apparent
Month 2
- 2.7g and 28mm
- 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
- 26g and 78mm
- blood cells produced in bone marrow
- basic brain and spinal cord structure in place
- ossification of bones begins and muscles form
- ovaries/testes appear
Month 4
- 150g and 133mm
- formation of hair
- eyes and ears in place
- rapid central nervous system development
- joints formed
Month 9 (birth)
- many systems immature but functional
- some important adaptations to independent life requires e.g. in cardiovascular and respiratory function

Question 4

Discuss the application of physiology to fetal screening procedures

Answer 4

• antenatal screening is used to identify any possible risks to the mother or fetus during pregnancy or to identify health issues that will affect the baby
• ULTRASOUND IMAGING: pregnant people are routinely given 2 ultrasound scans during their pregnancy
  > a dating scan: carried out between 8-14 weeks. Used to determine stage of pregnancy ad due date. Used with tests for marker chemicals which vary during pregnancy
  > anomaly scan: carried out between 18-20 weeks. May detect serious physical abnormalities
  -BLOOD AND URINE TESTS: regular checks are carried out to monitor concentrations of marker chemicals which can identify possible conditions. These chemicals vary normally during pregnancy. This is why they are used in conjunction with scans, as measuring chemicals at the wrong time can lead to a false positive result.
  > changing chemistry in blood and urine can be used to indicate pre-eclampsia and Down syndrome
• there are two main types of diagnostic testing. Normally carried out between 14-16 weeks. Cells obtained can curried to produce a karyotype, which can then be used to diagnose a range of conditions
  > amniocentesis - uses a small amount of amniotic fluid to check for genetic disorders
  > chronic villus sampling (CVS) - test a sample of cells from the mothers placenta for genetic disorders

Question 5

Define the term blastocyst

Answer 5

A hollow ball of 70-100 cells

Question 6

Define the term zygote

Answer 6

Growth of a new human being begins when an ovum is fertilised by a spermatozoon. The resulting cell is called Zygote. A zygote has 46 chromosomes

Question 7

Define the term embryo

Answer 7

The first 8 weeks of development is called the embryonic period and the developing ‘baby’ is described as an embryo

Question 8

Define the term foetus

Answer 8

Name for the developing ‘baby’ after 8 weeks

Question 9

Define the term gestation

Answer 9

The period between fertilisation and birth (normally around 40 weeks)