Topic 3 Embryology, Down syndrome and spinabifida

Question 1

List the 3 germ layers and the systems that arise from them

Answer 1

Ectoderm
Sensory organs
Epidermis of skin
Nervous system

Mesderm
Dermis
Muscles
Skeleton
Excretory system
Circulatory system

Endoderm
Gut 
Liver
Pancreas
Respiratory system

Question 2

Aetiology or cause of Down syndrome

Answer 2

Down syndrome (trisomy 21)
Each human cell has 46 chromosomes (23 pairs)
Gametes have 23 chromosomes
Individual has an extra copy of chromosome 21
(3 copies)

Can be due to a robertsonian translocation that occurs when it is glued to another chromosome

Question 3

Usual features of Down syndrome

Answer 3

Low muscle tone (hypotonia) cerebellar and UMN damage

A face that appears flatter with eyes slanting upwards
Small ears and a wider neck than usual
A crease across the palm of the hand and a gap between the first and second toes (sandal gap sign)
Flat feet
Atlantoaxial instability
Health problems, heart, digestive system and general development
Cognitive impairments ( IQ < 70)

Possible additional impairments
Epilepsy, visual impairments, hearing impairments, hernias, marked succeptibility to respiratory infections

Question 4

How is down syndrome diagnosed

Answer 4

How is it diagnosed?
Chromosome testing using a blood sample
Prenatal testing (screening or diagnostic)

Screening tests give a risk estimate of the probability that the baby has a health problem.
-Ultrasounds, non invasive prenatal testing( 1st and 2nd trimester screening)
Diagnostic tests give a more accurate result as they are directly testing the baby, may lead to loss of the baby in a small number of cases
Ultrasounds, chorionic villus sampling(CVS) and amniocentesis