Basic Embryology of Head and Neck 1

Question 1

describe the embryo

Question 2

what is the head and tail end of an embryo called? what is the front and back called?

Answer 2

head = cranial region
tail = cordal region

front = ventral
back = dorsal

Question 3

what are the 3 planes to the body?

Answer 3

transverse - cutting laterally
sagittal - straight down the middle
coronal - cutting middle from anterior to posterior

Question 4

what 2 techniques are used to date a pregnancy?

Answer 4

1. menstrual age
2. fertalisation age

Question 5

describe using the menstrual age to date a pregnancy.

Answer 5

• 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

Question 6

describe using the fertilisation age to date a pregnancy.

Answer 6

• 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

Question 7

what does monogenic and chromosomal defect mean?

Answer 7

monogenic - defective gene on autosome

chromosomal - change in chromosome number or structures

Question 8

Trisomy 21 - Downs Syndrome is a congenital malformation. Why does it occur and what are the effects?

Answer 8

3 copies of chromosome 21 rather than 2
- growth and intellectual retardation
- craniofacial abnormalities
- congenital heart defects

Question 9

define teratogen

Answer 9

environmental factor which causes defects in embryo

Question 10

list 5 different teratogens and give examples

Answer 10

1. chemical (pharmaceutical)
   - thalidomide and alcohol
2. deficiencies
   - folic acid
3. maternal disease
   - diabetes
4. physical
   - radiation
5. infection TORCH
   - toxoplasmosis
   - other - hep B, syphilis
   - rubella
   - cytomegalovirus
   - herpes

Question 10

give 5 teratogens.

Answer 10

1. chemical (pharmaceutical)
   - thalidomide
   - alcohol
2. deficiencies
   - folic acid
3. maternal disease
   - diabetes
4. physical
   - radiation
5. infectious - TORCH
   - toxoplasmosis
   - other - hep b, syphilis
   - rubella
   - cytomegalovirus
   - herpes

Question 11

what stages is the embryo at highest risk?

Answer 11

3-5 weeks

Question 12

between which periods are embryos more at risk to teratogens?

Answer 12

3-5 weeks

Question 12

what is Toxoplasmosis? state where it is found and its symptoms.

Answer 12

parasite

cat faeces or raw/uncooked meat

• inflammation of retina and eye
• hearing loss
• enlarged liver spleen
• hydrocephaly
• microcephaly

Question 13

what is Rubella? state how it comes about and its symptoms.

Answer 13

German measles

infection passes over first 3 months

• cloudy cornea
• intellectual disability
• microcephaly
• heart defects

Question 14

what is Cytomegalovirus? state how it comes about and its symptoms.

Answer 14

virus

infection via body fluids, crosses the placenta

• inflammation of retina
• enlarged liver or spleen
• mineral deposits on brain
• microcephaly
• psychomotor retardation

Question 15

what is Herpes? state where it is found and its symptoms.

Answer 15

virus

most dangerous 13-20 weeks or 2 days postpartum

• scarring
• limb hypoplasia
• microcephaly
• visual defects

Question 16

what is the Zika virus? state where it is found and its symptoms.

Answer 16

virus from mosquitoes, passes through bodily fluids

patient - fever, rash, joint pain, red eyes

embryo - microcephaly and severe cognitive disabilities

Question 17

describe thalidominde

Answer 17

• prescribed for morning sickness
• lead to short/absent limbs of babies
• now used for leprosy and HIV

Question 18

describe foetal alcohol syndrome

Answer 18

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

Question 19

describe the effect of radiation on embryos

Answer 19

• most sensitive in first trimester
• cell death
• chromosome changes
• microcephaly
• mental and cognitive disabilities
• haemopoietic malignancies
• leukaemia

Question 20

describe the effect of diabetes mellitus on an embryo.

Answer 20

• cellular structure defects
• macrosomia - very large baby
• ventricular septal defects
• spina bifida
• renal agenesis

Question 21

describe the effect of folic acid deficiency

Answer 21

reduce risk of malformation by 60%

spina bifida
anencephaly

Question 22

outline the gametogenesis

Answer 22

• 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

Question 23

outline fertilisation

Answer 23

• 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

Question 24

how does a zygote develop to a pre-implantation blastocyst?

Answer 24

zygotę travels down fallopian tube
becomes a morula
- when it reaches the uterus
= morula becomes a blastocyst