Embryo 2 Flashcards
The respiratory system comes from ___ endoderm. Specifically, it comes form the ___ ____ (the __ ___)
- Forgut
- Primitive Pharynx
- 6th Arch
Laryngotracheal groove
gives rise to larynx and trachea
Laryngotracheal Diverticulum–2 other names
- forms during week 4
1. Lung Buds (inferior portion)
2. Respiratory Diverticulum
The trachea is ___ to the esophagus.
anterior
How do we separate the larynx/trachea from the esophagus?
We have the tracheoesophageal folds fuse to form a tracheoesophageal septum (occurs in the 5th week)
What is the function of the bilateral arytenoid swellings?
- Give rise to cartilage (NC covered with cartilage)
- They are endodermal covered mesenchyme (NC derived) from the 6th arch
- Fuse to form a T shape, which forms the glottis
What structure/arch does the epiglottis arise from?
- Hypobranchial Eminence
2. Arch 4
What is/why do we need recanalization?
- Process of apoptosis that is complete in the 10th week
2. Endoderm grows, and covers the glottis; forms the laryngeal ventricles, vocal folds, and vestibular folds
Laryngeal Atresia
- obstruction of upper fetal airway that results from a failure of recanalization
- asphyxia at birth, and emergency tracheotomy is required
- can be detected with ultrasound/corrected prior to birth
Laryngeal Webs
- incomplete atreseia due to tissue between vocal folds
- presents with respiratory distress, unusual cry, & stridor
- due to failure of recanalization
Laryngomalacia
- aka “Congetial laryngeal stridor”
- collapse of supraglottic structures during inspiration
- fairly common; mxn is unknown
What gives rise to the trachea/its parts?
- Endoderm: epithelium and glands; pulmonary epithelium (lungs)
- Splanchnic Mesoderm: cartilage rings, CT of BVs, smooth muscle
Tracheoesophageal Fistula: cause
- week 5: tracheoesophageal fold problem
- Esophageal atresia + Tracheoesophageal fistula
- abnormal passage between the trachea + esophagus
Esophageal atresia
blind end esophagus
Tracheoesophageal Fistula: clinical presentation
- with feedings, babies will cough/gag a lot because food gets into the airway
- can be cyanotic
- dianosed by putting tube down (should be 17cm to stomach, but their’s will could at 12 cm)
What’s unique about H-type Tracheoesophageal Fistula?
- it is hard to diagnose; can be diagnosed as late as 4-5
- will have increased respiratory infections
What week do lung buds form?
week 4
When/what do lung buds divide into, which then divide into?
- Primary Bronchial buds (primary bronchi)–wk 5
- Secondary bronchial buds (3 on right, 2 on left)–wk 6
Tertiary bronchial buds (10 right, 9 left–wk 7
What space/tissue type are the bronchial buds growing in?
- Pericardial perineal canals
2. Splanchnic Mesoderm
When do the terminal bronchioles form? What do we have now?
by week 24 (17 orders of branches have occurred)
officially have our conduction system–woohoo
What are the four stages of lung development? Weeks? Overlap…why?
- a. Pseudoglandular (wk 5-17)
b. Canalicular (wk 16-25)
c. Terminal Sac (wk 24-birth)
d. Alveolar (wk 32-8yrs) - They overlap because race, gender, region…all matter
What happens to an infant born in the Pseudoglandular stage?
- they die
- in this stage, terminal bronchioles are formed, and surrounded by CT from Splanchnic Mesoderm
- the players are there, but they are not interacting correctly
What happens to an infant born in the Canalicular stage?
- MAY survive (wk 16-21 will not; wk 22+ may survive)
- branching leads to respiratory bronchioles–>primordial alveolar ducts; have terminal sacs
- vessels (capillaries) are much closer to terminal sacs
Terminal sacs are…
primitive alveoli
What happens to an infant born in the Terminal sac stage?
- they WILL survive because gas exchange is made possible due to squamous epithelium producing Type I and secretory epithelial cells producing Type II
- Lymphatic capillaries are now in contact with the squamous epithelium
Atelectasis
collapse of the alveoli
What happens to an infant born in the Alveolar stage?
- they are surviving
- formation of alveolocapillary membrane
- formation of primitive alveoli (95% after birth; done 3yr)
The alveolocapillary membrane is made of…
endoderm and mesoderm
What are FBMs? When do they occur? Why do they occur?
- Fetal Breathing Movements
- In utero with sufficient force to cause aspiration of amniotic fluid
- Primes lungs so they’re ready for birth
What 3 things are necessary for normal lung development?
- Adequate amniotic fluid
- Thoracic space for growth
- FBMs
What has to happen with intra-alveolar fluid?
- it must be cleared
- in vaginal birth, pressure on chest helps to expel fluid through the mouth or nose
- in C-section birth, fluid enters lympathics, pulmonary capillaries, arteries, and veins
What is Oligohydramnios?
- inadequate amniotic fluid
- retards lung development, and increased risk of pulmonary hypoplasia (if oligohydramnios occurs prior to 26 weeks)
Hiland Membrane Disease
- aka Respiratory Distress Syndrome
- Occurs due to lack of surfactant during the terminal sac stage
- symptoms: tachypnea, nasal flaring, suprsternal/intercostal/subcostal retractions, grunting, cyanosis
- chest x-ray will show low lung volumes, diffuse reticulogranular ground glass appearance (fuzzy)
Congenital Diphragmatic Hernia: PE findings
- barrel shaped chest
- scaphoid appearing abdomen
- absense of breath sounds on ipsilateral side
- if herniation is on the left, heart sounds will be on the right
Congenital Diphragmatic Hernia is caused by…
- failure of septum transverse and pluerperitoneal folds to meet
- should fuse by week 6; left folds slower than the right
- Foramen of Bochdalek
Tracheoesophageal Fistula: Signs/Symptoms
- Prentally: polyhydramnios
2. Birth: coughing, gagging, cyanosis, vomiting, voluminous oral secretions, possible respiratory distress
Congenital Lung Cysts
-cysts filled with fluid or air due to disturbance in bronchial development during later fetal life
