Embryology 1 Flashcards
What are the two methods of dating a pregnancy
- Menstrual age
- Fertilisation age
Who uses the menstrual age method
What does the method rely on
How is it split
Clinicians
The woman’s last menstrual cycle
Three equal trimesters
Why is the menstrual age cycle 40 weeks long
1st 2 weeks due to ovulation
Who uses the fertilisation age method
How many weeks of pregnancy does it include
How many periods is it split into
Embryologists
38 weeks
3 periods
What are the three periods of the fertilisation age method
- Early development (ED)
- Embryonic period (E)
- Foetal period (F)
What happens in the early development period (fertilisation age)
- Cell division
- Pre-embryonic
- Foetus termination due to environmental factors
What happens in embryonic period (fertilisation age)
- Organogenesis
- Most susceptible to environmental factors since organs still forming
Eg teratogens
What happens in the foetal period (fertilisation age)
- Parturition lost likely
What are the know causes for human birth defects
- Genetics
- Environmental
What are the genetic causes for human birth defects
- Monogenic
- Chromosomal
What is a monogenic cause
Defective gene on autosome
What are chromosomal causes
Numerical Structural
What are the effects of Trisomy 21, Down’s syndrome
- Growth retardation
- Intellectual retardation
- Craniofacial abnormalities
- Congenital heart defects
What are the environmental causes of human birth defects
- Infections
- Chemical
- Deficiency
- Maternal disease
- Physical
What are the infectious agents that cause human birth defects and how does the baby get them (infections)
Cross the placenta
- Toxoplasmosis
- Rubella
- Cytomegalovirus
- Herpes virus
- Zika virus
What causes toxoplasmosis (infections)
- Parasite
- Cat faeces and uncooked meat
- Usually asymptomatic
What are the congenital malformations of toxoplasmosis (infections)
- Inflammation of retina
- Hearing loss
- Enlarged liver spleen
- Hydrocephaly
- Microcephaly
When is rubella likely to happen
How can it be reduced
(Infection)
1st 3 months
MMR vaccine
What are the congenital malformations dues to rubella (infection)
- Cloudy cornea
- Intellectual disability
- Microcephaly
Heart defects
How is cytomegalovirus transmitted (infection)
Viral, via bodily fluids
Usually asymptomatic
What are the congenital malformations of cytomegalovirus (infection)
- Inflammation of retina
- Enlarged spleen or liver
- Mineral deposits on the brain
- Microcephaly
- Psychomotor retardation
What causes Herpes (infection)
- Herpes simplex
- Herpes zoster
Wha causes chickenpox and when is it most dangerous (infection)
- Varcellar zoster virus
- 13-20 weeks or just before birth to two days after
What are the congenital malformations of herpes virus (infection)
- Segmental skinloss
- Limb hypoplasia
- Microcephaly
- Visual defects
What is the cause of Zika virus and how is it transmitted (infection)
Mosquito
Via bodily fluids
What are the symptoms of Zika virus (infection)
- Fever
- Rash
- Joint pain
- Red eyes
What are the congenital malformations of Zika virus (infection)
- Microcephaly
- severe cognitive disabilities
What are the chemical causes of human birth defects
- Thalidomide
- Alcohol
What does thalidomide cause and what is it used to treat
Shortened or absent limb
Leprosy and HIV
What is foetal alcohol syndrome associated with
- Prenatal & postnatal growth retardation
- Intellectual disability
- Impaired motor ability & coordination
What is the most common deficiency that causes human birth defect
Folic acid deficiency
What does folic acid deficiency cause and how can the risk be reduced
- Malformation in CNS
- OTC supplements reduce malformation risk by 60%
What are congenital malformations of folic acid deficiency
- Spina bifida
- Anencephaly
What is the most common maternal disease that causes human birth defect
Diabetes mellitus
What happens in diabetes mellitus
- Cellular structural defects
- Cellular physiology change
What are the congenital malformations of diabetes mellitus
- Macrosomia
- Ventricular septal defects
- Spines bifida
- Renal agenisis
What does radiation do to the foetus
- Cell death
- Chromosome changes
- CNS damage
- Most sensitive 1st trimester
What are the congenital malformations of radiation
- Microcephaly
- Mental and cognitive disabilities
- Haemopoietic malignancies and leukaemia
What happens in fertilisation
- Fimbriae sweep oocyte into unsterile tube
- Capacitation of sperm in female tract
- Acrosome reaction
- Formation of zygote
- Fusion of pronuclei
Where does fertilisation take place
Ampulla of uterine tube
What happens in acrosome reaction
- Capacitated sperm passes through corona radiate
- Acrosome releases enzymes —> sperm penetrates zone pellucida
- Cortical reaction —> zona pellucida becomes impenetrable
What happens in acrosome reaction
- Capacitated sperm passes through corona radiate
- Acrosome releases hydrologic enzymes —> sperm penetrates zona pellucida
- Cortical reaction —> zona pellucida becomes impenetrable
What happens in cleavage
Zygote cells divide
Does the size of zygote change in cleavage
No. Blastomeres get smaller
How is morula formed
- 16-32 cells
- Inner cell mass
- Outer cell mass
What does inner cell mass develop into
Embryo proper, embryoblasts
What does outer cell mass develop into
Placenta, trophoblasts
How is the blastocyst formed
- Fluid-filled cavity
- Cells separated: compact mass; thinner outer layer
- Blastocyst hatch & implantation happens
When is fluid-filled cavity formed
Day 5
When does blastocyst hatch and implant
Days 5 & 6
