Embryology

Question 1

Embryo >< Fetus

Answer 1

Embryo: 1st to 8 weeks -> organ development
Fetus: week 9 -> birth

Question 2

Phases of lung development

Answer 2

Embryonic:
gastrulation (week 3) -> 3 germ layers -> body folding ->  endodermal foregut -> respiratory diverticulum/lung bud (day 22) -> primary bronchiol buds (day 26_28) -> secondary bronchiole buds (week 5) 3 right and 2 left (will become the lobes) ->  tertiary bronchiole buds (week 6) ->  terminal bronchiole (week 16 - 4 months) 
Pseudoglandular:
-> respiratory bronchiole (week 28 - 7 months)
Canalicular:
-> terminal sacs (week 36 - 9 months) 
Alveolar:
-> mature birth

Question 3

Foregut

Answer 3

Develops esophagus, stomach, trachea and lungs

Defect -> GI and respiratory problems

Question 4

Amniotic fluid

Answer 4

contains poop and urine of foetus
Protective liquid in amniotic sac -> cushion for embryo
Facilitate exchange of nutrients, water and biochemical products
Amniotic fluid goes inside developing lungs as if inhaling and exhaling (week 26) -> practice breathing

Question 5

Neonatal. Preterm

Answer 5

New born
1st to 13th day of life outside the uterus
Preterm: before 37 weeks of gestation

Question 6

First Breath

Answer 6

During labor -> umbilical vessels constricted -> oxygenated blood flow goes down -> CO2 goes up -> acidosis goes up (pH down) -> respiratory center stimulation -> 1st Breath
1st Breath (within 10 seconds) -> lung inflate to full capacity -> lung pressure goes down blood flow resistance goes down -> pulmonary alveoli open -> alveolar capillaries fill with blood -> amniotic fluid drains and is absorbed
Vital to initiate transition of circulatory pattern !

Most force needed to inhale and then dicrease through time

Question 7

Circulation changes

Answer 7

before birth:
foramen ovale: a hole in between left and right atria
ductus arteriosus: duct between pulmonary trunk and aorto -> blood can bypass fetal lungs
ductus venosus: blood from umbilical vein to vena cava
after birth:
foramen ovale: first breath -> BP down in pulmonary system, right atrium and right ventricle -> BF reverse left atrium to right atrium through foramen ovale -> shunt gets blocked by 2 flaps -> after 1 year flaps fuse -> fossa ovalis
ductus arteriosus: constrict from O2 up. Blood from right ventricle can go to pulmonary arteries.
ductus venosus: deteriorates and become ligamentum venosum from atrophy (umbilical vein collapse)

Question 8

Umbilical cord

Answer 8

3 blood vessels
carry food and oxygen from placenta to fetus
carry waste from fetus to placenta
after birth: gets occluded after 20 min -> umbilical vessels collapse

Question 9

Placenta

Answer 9

Provides oxygen and nutrients to fetus
Removes waste from fetus
though the umbilical cord
inhibit metabolism of brown adispose fat and promote accumulation: fat consumed when cold
After birth: placenta delivered 5-30min after birth

Question 10

Surface tension

Answer 10

walls of alveoli lined by water -> forces to center -> collapse water molecules together. H+ with O-. Alveoli has air -> some water molecules cant bind to other water molecules -> too much cohesive tension -> pull closer together

Question 11

Laplace law

Answer 11

The Law of Laplace essentially states that the tension within the wall of a sphere filled to a particular pressure depends on the thickness of the sphere. Consequently, even at a constant pressure, the tension within a filled sphere can be decreased simply by increasing the thickness of the sphere’s wall.
P alveolus collapse: surface tension/ radius
Radius down, pressure up
exhale, pressure up -> inspiration difficult, compliance down

Question 12

Surfactant

Answer 12

phospholiprotein secreted by alveoly pneumocytes 2. (pneumocytes 1 are for gaz exchange)
line walls over water film -> surface tension down -> pressure down, compliance up
hydrophilic head towards water film, hydrophilic legs toward the center of the alveoli

alveoli radius deflated: higher density surfactant -> surface tension lower -> more compliance -> easy to inflate
alveoli radius inflate: lower density surfactant -> surface tension up -> less compliance -> recoil increase

=> surfactant makes it easier and faster to inhale/exhale

Question 13

Hyaline membrane disease

Answer 13

HMD
not enough surfactant -> alveolar collapse -> damaged cells accumulation: hyaline membrane
fibrin, debris, rbc, macophrages, neutophils

Question 14

Neonatal jaundice

Answer 14

yellowish discoloration of eyes due to high bilirubin levels.
red blood cells breakdown

Question 15

Fetal hemoglobin

Answer 15

HbF
different to HbA
2 alpha and 2 gamma compared to 2 alpha and 2 beta
-> higher affinity to O2 to keep maternal O2 in circulation system -> shift to right of saturation curve

embryo hemoglobin -> replaced by fetal hemoglobin -> adult hemoglobin