9.1 Flashcards
Define the pre-embryonic, embryonic and fetal periods.
PE: Fertilisation –> 2 weeks
E: 3 –> 8 weeks
F: 9 –> 38 weeks
What is a crown rump length and how does it change in pregnancy?
Measurement of human embryo length from top of head to bottom of buttocks.
Increases rapidly in the pre-embryonic, embryonic and early fetal periods.
Describe weight gain of fetus during pregnancy?
Slow at first but increases rapidly in the mid and late fetal periods.
At what week is the head half of the crown rump length.
9
What proportion of the crown rump length is the head at healthy birth?
Approx 1/4 of body
What process occurs as an early fetus, late fetes and embryo in terms of weight gain?
Embryonic period - Intense morphogenesis and differentiation with little weight gain and placaental growth most significant
Early fetus - protein deposition
Late fetus - adipose deposition
When does the specialisation of the lungs occur? When do they become viable? Implication
Embryonic development only creates airway, no gas exchange parts.
Specialisation for function in fetal period
Viable only after 24 weeks
–> Pre term survival
What are the 4 stages of development of the respiratory system? Name and period.
Pseudoglandular stage: 8 - 16 weeks
Canalicular: 16 - 26 weeks
Terminal Sac stage: 26 - Term
Alveolar period: Late fetal - 8 years
What occurs in the pseudo glandular stage?
Duct systems form within bronchi pulmonary segments created during the embryonic period.
Bronchioles develop.
What occurs in the canalicular stage?
Formation of respiratory bronchioles - Budding from bronchioles More vascular Some terminal sacs May be viable
What occurs in the terminal sac stage?
Terminal sacs begin to bud from the respiratory bronchioles Some primitive alveoli Differentiation of pneumocytes Type 1 - gas exchange Type 2 - surfactant production
When do most alveoli form?
95% post-natally
How are the lungs prepared to assume full birder immediately after birth?
Breathing movement - conditioning of respiratory musculature.
Fluid filled - crucial for normal lung development.
What are corticospinal tracts required for and when do they begin to form?
Required for coordinated voluntary movement and begin to form in 4th month.
When does myelination of the spinal cord and the brain begin?
Spinal cord - 20th week
Brain - 36th week (9th month)
When does the fetus begin to move?
8
What changes occur in the brain during the fetal period?
Cerebral hemispheres become largest part of brain.
Gyri and sulci form after 5 months as brain grows faster than head.
Differentiation of cortex in cerebrum and cerebellum
Formation and myelination of nuclei and tracts
Relative growth of the spinal cord and vertebral column.
At what week is maternal awareness of fetal movement?
17 onwards
What senses mature first?
Hearing and taste before vision.
Organ of corgi developed at 5 months, tertian immature at birth.
When is the definitive fetal heart rate achieved?
After 15 weeks.
When is the ascent of the kidneys complete and when does fetal kidney function begin?
Week 10
When are the renal pelvis and calyces present?
Week 23
What is a major contribution of amniotic fluid
Fetal urine
What occurs in the absence of fetal kidney function?
Oligohydramnios
