Lung Development Flashcards
Lungs and GÌ tract derived from a pouch of the foregut called?
Respiratory diverticulum
Specilised endothelial derived from
Endoderm - outgrowth from GÌ Tract
Epithelial tissue buds from this
Budding process of epithelial tissue from endoderm is called?
Branching morphogenesis
Pseudoglangular phase
Tube epithelium
|
Bronchus (2 x L, 3 x R)
|
Bronchioles
|
Alveoli
Where key elements of lungs have formed: 8 weeks
Alveoli form?
16 weeks until approximately 8 years.
Canalicular phase
16 weeks
Terminal bronchioles form
Respiratory bronchioles form at
19 weeks
Terminal sac is formed at?
28 weeks
Alveolar sac forms?
From 16 weeks to 7/8 years
Maturation of alveoli not complete until?
7 years
Childhood asthma may resolve at this time
Lung buds are formed from ?
Endothelium
Cartilage and muscles derive from?
Surrounding mesoderm
Lungs grow to fill the pleural cavity
True or false?
True
Maturation of the lungs phases?
- Pseudoglandular period
- Canalicular period
- Terminal sac period
- Alveolar period
Name the period:
Branching has continued to form terminal bronchioles
No respiratory bronchioles or alveoli are present
Pseudoglandular period
5-16 wk
Name the period:
Each termina, bronchioles divides into two or more respiratory bronchioles, which in turn divide into three or six alveolar ducts
Canalicular period
16-26 wk
Name the period:
Terminal sacs (primitive alveoli) form, and capillaries establish close contact
Terminal sac period
26 wk to birth
Name the period:
Mature alveoli have well- developed epithelial endothelial (capillary) contact
Alveolar period
8 mo to childhood
What is Oesophageal atresia and Tracheoesophogeal fistulas?
- Fistula is the joining of the oesophagus to the trachea.
- 90% of cases the upper portion is a blind pouch (atresia)
- Cardio vascular defects often associated
What is defined as too much amniotic fluid in sac?
Polyhydramnios
Where the lung is formed is related to positional signalling from?
External RA
What are Wnts ?
Cell signalling molecules.
Involved in patterning, polarity, cell division and differentiation. Links to cancer
Importance of Wnts cells?
Wnt is important in determining how the lung tissue develops differently from the gut ie ciliated or squamous cell types.
Types of alveoli
Type I alveoli
Type II alveoli
Which type of alveoli epithelial cells appear in the alveoli, enabling an increase in surfactant production?
Type 2
What is Surfactant?
Surfactant is a phospho-lipid rich fluid which lines the interior of the alveoli and decreases surface-air tension, allowing the lung to inflate.
Phospholipid rich fluid which lines the interior of the alveoli and decreases surface-air tension, allowing the lung to inflate.
Surfactant
Production of surfactant is stimulated by
Increase in maternal and fetal cortisol levels
Preparation for labour occurs at ?
Week 34
What happens during preparation for l’about?
- lungs not air filled but fluid filled.
* Practice “breathing” pushes an exchange of “internal” lung fluid with the “external” amniotic fluid
What does the internal lung fluid contain?
- Chloride
- Surfactant
- phospholipids
Imitation of labour in fetal lung
- surfactant level increases
- Surfactant - A escapes into amniotic cavity
Initiation of labour in Amniotic cavity
Macrophages activated by exposure
Migrate across chorion
Initiation of labour in the uterus
- Interleukin 1B production which increases:
- Increased Prostaglandin (PG) production
What stimulates uterine contractions to Labour ?
PG - prostaglandins
How is lung fluid rapidly reabsorbed during parturition.?
- Triggered by increasing Cortisol and Thyroid Hormone
2. Physical expulsion from travel through the uterine canal
Water absorption during pregnancy
Chloride in secreted through Cl- channel. Causes water movement into lung spaces
Water absorption during labour
- Increasing TH and Cortisol stimulates transepithelial Na+ pump to pull Na + into the epithelial cells.
- Water follows and Na+ is pumped back out into spaces between the cells and water is removed.
When does the first birth happen after birth ?
10s postnatally
Water birth- on emergence from water
What happens at birth when breathing ?
Breathing inflates the lungs and triggers changes in the circulatory system.
What stimulates breath at birth ?
- Clearing of fluid
- High CO2 levels
- Temperature change (on head and umbilical cord)
- Vagal stimulation
Name the problem at birth:
Alveolar collapse. (collapsed lung) Not enough surfactant. Common with preterm births.
Atelactasis
Atelactasis can lead to?
Respiratory Distress Syndrome
Symptoms of Respiratory Distress Syndrome
20% of preterm deaths
- Tachypnoea (rapid breathing)
- Association with maternal diabetes mellitus
What is Transient tachypnea of new-born (TTNB) ?
0.5-4% of all neonates
Retention of lung fluid
Resolves with Oxygen therapy and antibiotic treatment.
Link to Caesarian births.
Why is Atelactasis common with preterm births?
Because type 2 alveolar cells are not producing surfactant until week 26, so there’s not enough surfactant tension as there’s no surfactant to line the inside of the alveoli - not enough cortisol
