4- Respiratory Embryology Flashcards
The respiratory system starts as a median outgrowth, called the ________ ________. This is found in the floor of the caudal end of the foregut/primordial pharynx, which is inferior to the 4th pharyngeal arches.
Laryngotracheal Groove
The primordium of the _________ _________ develops caudal to the 4th pharyngeal pouches.
Tracheobronchial Tree
The endoderm of the Laryngotracheal Groove will give rise to what?
Pulmonary Epithelium
Glands of Larynx
Trachea
Bronchi
The Laryngotracheal Groove will evaginate to form the _________ _________ (lung bud).
Laryngotracheal Diverticulum
This is what forms the CT, cartilage, and smooth muscle in the structures formed by the endoderm of the Laryngotracheal Groove (Pulmonary Epithelium, Glands of Larynx, Trachea, and Bronchi). It also surrounds the foregut.
Splanchnic Mesoderm
The Laryngotracheal Diverticulum elongates and is invested with _______ _______. The distal end then enlarges to form a globular ________ ________, which is the origin of the respiratory tree.
Splanchnic Mesenchyme
Respiratory Bud
Tracheoesophageal Folds develop and fuse to form the _________ _________ at the end of the 5th week.
Tracheoesophageal Septum
The Tracheoesophageal Septum divides the cranial portion of the foregut into a ventral part and dorsal part. What do each of these parts give rise to?
Ventral Part = Laryngotracheal Tube (Primordium of Larynx, Trachea, Bronchi, and Lungs)
Dorsal Part = Primordium of Oropharynx and Esophagus
What makes the epithelial lining of the Larynx?
Endoderm of Laryngotracheal Tube (Cranial End)
What makes the cartilages of the Larynx?
Mesenchyme of 4th and 6th pairs of Pharyngeal Arches (NCC derived)
In the development of the Larynx, mesenchyme produces paired arytenoid swellings, which convert the primordial glottis into a…
T-shaped Laryngeal Inlet
The Laryngeal epithelium proliferates and occludes the Laryngeal lumen, but it recanalizes by the ______ week.
10th
Laryngeal _________ form during recanalization, which are bounded by folds of mucous membranes to form _______ _______ and ________ ________.
Ventricles
Vocal Folds (Cords)
Vestibular Folds
The Epiglottis develops from the ________ ________, which is produced from mesenchyme of the 3rd and 4th pharyngeal arches.
Hypopharyngeal Eminence
What do Laryngeal muscles develop from?
Myoblasts of 4th and 6th Pharyngeal Arches
The Larynx is in a (LOW/HIGH) position in the neck of the neonate. Laryngeal (ASCENT/DESCENT) occurs over the first 2 years.
High
Descent
The Epiglottis is in contact with the _______ ______, and separates the respiratory and digestive tracts.
Soft Palate
This is a rare birth defect, resulting from failure of recanalization of the Larynx. There is an obstruction of the upper fetal airway, or Congenital High Airway Obstruction Syndrome (CHAOS Syndrome).
Laryngeal Atresia
In Laryngeal Atresia, the airways become dilated and the lungs are enlarged and filled with fluid. The _________ is flatted or inverted and there is fetal ascites and/or hydrops. Treatment is by ________ _______ of the Laryngeal web.
Diaphragm
Endoscopic dilation
In the development of the trachea, the __________ _________ gives rise to the Trachea and two Primary Bronchial Buds.
Laryngotracheal Diverticulum
In the development of the trachea, endoderm differentiates into what?
Tracheal Epithelium & Glands
Pulmonary Epithelium
In the development of the trachea, the Splanchnic Mesenchyme develops into what?
Tracheal Cartilages
CT
Muscle
This is the term for an abnormal connection between the Trachea and Esophagus due to the failure of the foregut endoderm to proliferate rapidly enough in relation to the rest of the embryo. It is the most common congenital anomaly of the lower respiratory tract.
Tracheoesophageal Fistula
Tracheoesophageal Fistula occurs in 1 of 3000-5000 births, and 85% of cases are associated with _________ ________, or blind esophagus.
Esophageal Atresia
What are symptoms of a Tracheoesophageal Fistula?
– Cannot swallow
– Frequently drool saliva
– Immediately regurgitate food when fed
– GI contents may reflux through fistula into trachea and lungs
– Polyhydramnios (excess amniotic fluid)
In a Tracheoesophageal Fistula, Polyhydramnios can occur because…
- Fluid cannot enter the stomach/intestines for absorption
- - Fluid not transferred for disposal via the placenta
During the 4th week, the distal end of the Laryngotracheal Diverticulum enlarges to form the _________ ________.
Respiratory Bud
The Respiratory Bud grows ventrocaudally and bifurcates, forming the…
Primary Bronchial Buds
The Primary Bronchial Buds grow laterally into…
Pericardioperitoneal Canals
The Primary Bronchial Buds branch beginning in the 5th week, and form the _______ _______ _______. These then give rise to _______ _______ _______.
Secondary Bronchial Buds
Tertiary Bronchial Buds
The branching pattern of the lung endoderm is regulated by…
Splanchnic Mesenchyme
What is the pathway for branching, starting with the Main Bronchi?
Main Bronchi – Secondary Bronchi – Lobar – Segmental – Intrasegmental Branches
These develop during the 7th week and consist of segmental Bronchi and mesenchyme.
Bronchopulmonary Segments
As lungs develop, they acquire a layer of _______ _______ (from the Splanchnic portion of the Lateral Plate Mesenchyme).
Visceral Pleura
The thoracic body wall becomes lined by a layer of _______ _______ (from the Somatic portion of the Lateral Plate Mesoderm).
Parietal Pleura
What is the space between the Parietal and Visceral Pleura called?
Pleural Cavity
List the periods of lung maturation from least to most developed.
Pseudoglandular
Canalicular
Terminal Sac
Alveolar
This period of lung maturation looks like exocrine glands. All major elements of the lung have formed, except those involved with gas exchange. The fetus cannot survive.
Pseudoglandular (5-17 weeks)
This period of lung maturation overlaps Pseudoglandular. There is vascularization and Respiratory Bronchioles develop. Primordial alveolar and sacs are present (primitive alveoli). 50/50 chance for survival.
Canalicular (16-25 weeks)
This period of lung maturation includes numerous alveoli and a thin epithelium with increased vascularization. There are Type I Pneumocytes, Type II Pneumocytes (Surfactant), and Lymphatic capillaries. Gas exchange can occur and survival is probable.
Terminal Sac (24 weeks - Birth)
This period of lung maturation contain an Alveolocapillary Membrane, primitive alveoli (as well as more formed), and mature alveoli.
Alveolar (32 weeks - 8 years)
Approximately 95% of mature alveoli develop postnatally and alveolar development is largely completed by age ______. New alveoli are added until year ______.
3
8
As the bronchi develop, Splanchnic Mesoderm is critical because it develops what 3 things?
1) Cartilaginous plates (bronchial)
2) Bronchial smooth muscle and CT
3) Pulmonary CT and capillaries
These are essential for normal lung development. It is an intermittent pattern that conditions respiratory muscles and is used during fetal monitoring and as a predictor of fetal outcome in pre-term delivery.
Fetal Breathing Movements (FBMs)
_________ _________ _________ are forceful enough to cause aspiration of amniotic fluid and helps to stimulate lung development. At birth, aeration of the lungs requires rapid replacement of intra-alveolar fluid with air.
Fetal Breathing Movements (FBMs)
At birth, what are the 3 ways intra-alveolar fluid can be cleared (so air can get in)?
1) Released from mouth/nose by pressure on the fetal thorax during vaginal delivery
2) Pulmonary capillaries, arteries, and veins
3) Lymphatics
This occurs in 1 out of 15,000 births and is the complete absence of a lung or a lobe and accompanying bronchi, due to Respiratory Bud failure to split into Right and Left Bronchial Buds.
Pulmonary Agenesis
***Unilateral Agenesis refers to just one lung begin absent
This is the term for insufficient amniotic fluid production (<500mL). It is typically associated with renal agenesis or failure. If severe or chronic, then it can retard lung development.
Oligohydramnios
This occurs in 14 out of 10,000 births and is a restriction of the fetal thorax (from uterine pressure). There is decreased hydraulic pressure on the lungs and affects stretch receptors and lung growth. Risks of this increase significantly with Oligohydramnios at <26 weeks.
Pulmonary Hypoplasia
This is the atypical physical appearance of a baby due to Oligohydramnios experienced when in the uterus. It includes clubbed feet, pulmonary hypoplasia and cranial anomalies related to the Oligohydramnios.
Potters Sequence
This affects approximately 2% of neonates and accounts for 50-70% of deaths in premature infants. It includes rapid, labored breathing developed shortly after birth. Surfactant deficiency is a major cause.
Respiratory Distress Syndrome
Respiratory Distress Syndrome (RDS) can be caused by surfactant deficiency. Lungs are under inflated and alveoli contain a fluid that resembles a “glassy membrane”. This is called ________ ________ _________. There are also irreversible changes in the ________ alveolar cells, making them incapable of producing surfactant.
Hyaline Membrane Disease
Type II
What neonatal pathology is being describe by the following symptoms:
- Tachypnea
- Nasal Flaring
- Suprasternal, Intercostal, or Subcostal Retraction
- Grunting
- Cyanosis
Respiratory Distress Syndrome
These are filled with fluid or air and are thought to be formed by the dilation of Terminal Bronchi. There is a disturbance in Bronchial development during late fetal life. May exhibit wheezing, cyanosis, and difficulty breathing.
Congenital Lung Cysts
