Cardiorespiratory Flashcards
At how many weeks of gestation do we see the formation of lung buds?
- 4 weeks
what are the 4 stages of lung development & when do they occur
- Psuedoglandular: week 5-17
- canalicular: week 15-25
- terminal sac period: 24-birth
- alveolar period: birth - 8 years
What occurs in the psuedoglandular phase/when does it occur
- begin development of the shape, no function yet
- form the acinus
- occurs in weeks 5-17
what is the functional unit of the lungs
- acinus
what occurs in the canalicular phase/when does it occur
- vascularization
terminal bronchioles give rise to respiratory bronchioles - alveolar ducts form by the end of this period
- 15-25 weeks
what occurs in the terminal sac period/when does it occur
- blood air barrier is formed formation of type 1
- epithelium - flat, squamous epithelium for exchange
- formation of type 2 epithelium - cuboidal, secrete surfactant
- 24 weeks - birth
what occurs in the alveolar period/when does it occur
- alveoli are present
- lungs continue to grow
- birth - 8
when does alveolar development take place; how many at birth; how many at 8 years
- last trimester, but mostly postnatally
- 20 million at birth
- 300 million at 8 years
what does lung weight best correlate with
- height
how does the respiratory rate/min change from birth
- decreases
how do measures of lung volume change after birth
- increase
what is the primary cause for preterm death
- infant respiratory distress syndrome
- due to surfactant deficiency or immature lung development
what stimulates a major increase in surfactant prior to birth
- increased catecholamines and glucocorticoids
At what week does the heart begin to form? When does it start to beat?
- 3 weeks; endothelial tubes begin to fuse forming the primitive heart
- 3 weeks + 1 day
What embryonic tissue does the heart originate from
mesenchyme??
what has occurred by week 6 in terms of the heart
- developed its general form minus the foramen ovale
what occurs by week 8 in terms of the heart
- blood vessels are formed
what vessels bring blood to the fetal heart, what takes blood away from the fetal heart
- 2 veins
- trunctus arteriosus
what structure provides O2 for the fetus
- placenta
which structure provides a connection between the umbilical vein and the IVC; when does this close/why
- Ductus venosus
- Closes within 1st 3 hrs
- due to decreased flow from umbilical vein (b/c it was cut)
which structure connects the two atria; when does it close/why
- foramen ovale
- closes after 3 days
- due to increased pressure in left atria
what structure connects the aorta and the pulmonary artery/when does it close
- ductus arteriosus
- closes after 1-2 days
- due to increased aortic pressure, increased atrial O2 and decreased prosteglandin
what makes up for the lesser O2 saturation in a fetus
- FHb has a greater affinity for O2 (O2 is 70% saturated, vs 97% saturated after birth
what structure assists in diverting blood through foramen ovale
- cista dividens
