Basic Embryology of Head and Neck 1 Flashcards
describe the embryo
what is the head and tail end of an embryo called? what is the front and back called?
head = cranial region
tail = cordal region
front = ventral
back = dorsal
what are the 3 planes to the body?
transverse - cutting laterally
sagittal - straight down the middle
coronal - cutting middle from anterior to posterior
what 2 techniques are used to date a pregnancy?
- menstrual age
- fertalisation age
describe using the menstrual age to date a pregnancy.
- from the woman’s last period
- not very accurate
- period cycles aren’t always the same
- split into 3 equal terms
- first, second and third trimester
describe using the fertilisation age to date a pregnancy.
- the date of conception
- only able to tell if u know the date
- split into 3 terms
- early development - 3 weeks - cell division
- embryonic period - 8 weeks - organogenesis
- foetal period - 38 weeks
what does monogenic and chromosomal defect mean?
monogenic - defective gene on autosome
chromosomal - change in chromosome number or structures
Trisomy 21 - Downs Syndrome is a congenital malformation. Why does it occur and what are the effects?
3 copies of chromosome 21 rather than 2
- growth and intellectual retardation
- craniofacial abnormalities
- congenital heart defects
define teratogen
environmental factor which causes defects in embryo
list 5 different teratogens and give examples
- chemical (pharmaceutical)
- thalidomide and alcohol - deficiencies
- folic acid - maternal disease
- diabetes - physical
- radiation - infection TORCH
- toxoplasmosis
- other - hep B, syphilis
- rubella
- cytomegalovirus
- herpes
give 5 teratogens.
- chemical (pharmaceutical)
- thalidomide
- alcohol - deficiencies
- folic acid - maternal disease
- diabetes - physical
- radiation - infectious - TORCH
- toxoplasmosis
- other - hep b, syphilis
- rubella
- cytomegalovirus
- herpes
what stages is the embryo at highest risk?
3-5 weeks
between which periods are embryos more at risk to teratogens?
3-5 weeks
what is Toxoplasmosis? state where it is found and its symptoms.
parasite
cat faeces or raw/uncooked meat
- inflammation of retina and eye
- hearing loss
- enlarged liver spleen
- hydrocephaly
- microcephaly
what is Rubella? state how it comes about and its symptoms.
German measles
infection passes over first 3 months
- cloudy cornea
- intellectual disability
- microcephaly
- heart defects
what is Cytomegalovirus? state how it comes about and its symptoms.
virus
infection via body fluids, crosses the placenta
- inflammation of retina
- enlarged liver or spleen
- mineral deposits on brain
- microcephaly
- psychomotor retardation
what is Herpes? state where it is found and its symptoms.
virus
most dangerous 13-20 weeks or 2 days postpartum
- scarring
- limb hypoplasia
- microcephaly
- visual defects
what is the Zika virus? state where it is found and its symptoms.
virus from mosquitoes, passes through bodily fluids
patient - fever, rash, joint pain, red eyes
embryo - microcephaly and severe cognitive disabilities
describe thalidominde
- prescribed for morning sickness
- lead to short/absent limbs of babies
- now used for leprosy and HIV
describe foetal alcohol syndrome
clear link between congenital abnormality and alcohol use
- intellectual disability
- impaired motor ability and coordination
- growth retardation
facial features
- small eyes
- smooth philtrum over lip
- thin upper lip
describe the effect of radiation on embryos
- most sensitive in first trimester
- cell death
- chromosome changes
- microcephaly
- mental and cognitive disabilities
- haemopoietic malignancies
- leukaemia
describe the effect of diabetes mellitus on an embryo.
- cellular structure defects
- macrosomia - very large baby
- ventricular septal defects
- spina bifida
- renal agenesis
describe the effect of folic acid deficiency
reduce risk of malformation by 60%
spina bifida
anencephaly
outline the gametogenesis
- fertilisation requires 2 gametes - 2 sex cells produced from gametogenesis
- gametes start off as a diploid cell
- meiosis - split into 2 = haploid cells
- 2 rounds of mitosis
forms 4 daughter cells, each with 1/2 DNA
outline fertilisation
- takes place at the ampulla of the uterine tube
- egg goes into the uterine tube
- sperms undergoes capacitation
- acrosome releases enzymes
- sperm is able to penetrate the zona pellucid
- sperm initiates cortical reaction
- zona pellucida then becomes impenetrable again
- male and female gamete fuse = zygote
how does a zygote develop to a pre-implantation blastocyst?
zygotę travels down fallopian tube
becomes a morula
- when it reaches the uterus
= morula becomes a blastocyst
