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RS Embryology

Respiratory System Embryology

What prominences form the nose? Maxillary Frontonasal Medial nasal Lateral nasal
The nasal pits (openings of the nose) are found: Between the medial and lateral nasal prominences
At the end of the fourth week, the facial prominences are formed by: The first pair of pharyngeal arches
The facial promincences consists primarily of: Neural-crest derived mesenchyme
The frontonasal prominence is formed by: Proliferation of mesenchyme ventral to the brain vesicles
What structure constitutes the upper border of the stomodeum? The frontonasal prominence
On both side of the frontonasal pominence there are local thickenings of surface ectoderm called: The nasal (olfactory) placodes
The nasal placodes originate under influence of the Ventral portion of the forebrain
During the fifth week, the nasal placodes invaginate to form Nasal pits (the nostrils)
When the nasal pits are formed they: Create a ridge of tissue that surrounds each pit and from the nasal prominences
The frontal facial prominence gives rise to: The nasal septum
The medial nasal prominences gives rise to: The crest and tip of the nose
The lateral nasal prominences give rise to: The alae of the nose
Olfactory pit gives rise to: the nostril and then invaginates to give the vestibule
During the following 2 weeks, the maxillary prominences grow medially, causing: Medial nasal prominences to compress medially and the cleft between the medial nasal prominence and the maxillary prominence is lost The two fuse
The oronasal membrane between the oral cavity and the nasal cavity ruptures, creating a communication. When does this communication close? When the palate is formed
The rupture of the oronasal membrane gives rise to The primitive choanae posteriorly
When the primary and secondary palates form, what else forms? The definitive choanae, leading into the nasopharynx
The paranasal sinuses form as: invaginations in the lateral nasal wall forming ducts
How do these sinuses reach the skull bones? Proliferation of cells and canalization take place. Eventually the canalization (diverticula) reaches one of the skull bones (frontal, ethmoidal, maxillary, and sphenoid) and forms a cavity in it
They reach their maximum size during: puberty and contribute to the definitive shape of the face
The structure formed by the two merged medial and maxillary prominences is the Intemaxillary segment
The intermaxillary segment is composed of: a) a labial component b) an upper jaw component c) a palatal component
The labial component of the intermaxillary segment forms: the philtrum of the upper lip
The upper jaw component of the intermaxillary segment forms: carries the four incisor teeth
The palatal component of the intermaxillary segment forms: The triangular primary palate
The secondary palate develops from the maxillary prominences The main part by two shelflike outgrowths from the prominences (The palatine shelves)
The palatine shelves appear in which phase of development: the sixth week of development
The palatine shelves are directed: obliquely and downwards towards the tongue
The palatine part of the maxilla is called: The secondary palatine In the 7th week, the palatine shelves ascend to attain a horizontal position above the tongue and fuse-form the secondary palatine
Fusion occurs between the primary and the secondary palates. As a result of this fusion, what structure is formed? The incisive foramen The hard palate
Any defect in fusion between primary and secondary palates will lead to: Cleft palate Cleft lip
Cleft lip and palate can be: Unilateral or bilateral Complete or partial
The respiratory system begins developing from the anterior surface of the foregut
The entire respiratory tract begins as Respiratory diverticulum, which forms at the fourth week of development
The respiratory diverticulum is also called the Lung bud
Why is the respiratory diverticulum also called the Lung bud? It will give the tracheal bud, then two lung buds
All lining epithelium of the respiratory system is originally: Endodermal
All cartilages, muscles, and connective tissues are originally splanchnic mesodermal
As the respiratory diverticulum forms, what structures appear? The tracheoesophageal ridges
The tracheoesophageal ridges develop internally, until they form a Tracheoesophageal septum, that separates the trachea from the esophagus
Abnormalities in partitioning of the esophagus and trachea by the tracheoesaphageal septum result in Esophageal atresia with or without tracheoesaphageal fistulas (TEF)
What is the most common abnormality in formation of the TE septum? Proximal esophageal atresia with distal tracheoesophageal fistula
What other types are there? Two-sided atresia without fistula. H-shaped fistula. These account for 4% of cases. Other types account for 1%
Other birth defects accompany TEFs. The most important are cardiac anomalies (in 33% of cases)
What other anomalies accompany TEF? • Vertebral anomalies • Anal atresia • Renal anomalies or agenesis
Clinical consequences/complications of TEF: 1. Pneumonia 2. Air can reach the stomach, leading to apparent distention of the stomach during crying 3. Polyhydramnios: excessive amniotic fluid around the baby
The internal lining (epithelium) of the larynx originates from Endoderm
Cartilages, muscles and connective tissue of the larynx originate from Mesenchyme (mesoderm) of the fourth and sixth pharyngeal arches
The laryngeal orifice changes in appearance from a slit like opening to A T-shaped opening
The mesenchyme (mesoderm) of the fourth and sixth pharyngeal arches transforms into: The thyroid, cricoid, and arytenoid cartilages
Laryngeal epithelium proliferates rapidly resulting in temporary occlusion in the lumen of the larynx. This is directly followed by vacuolization and recanalization that produce: A pair of lateral recesses, the laryngeal ventricles
These recesses, the laryngeal ventricles. are bounded by folds of tissue that differentiate into the False and True vocal cords
All laryngeal muscles are innervated by branches of the Vagus nerve
The superior laryngeal nerve innervates derivatives of the Fourth pharyngeal arch Cricothyroid muscle through its external branch
The recurrent laryngeal nerve innervates derivatives of the sixth pharyngeal arch
Larynx Anomalies: Laryngeal atresia (congenital high airway obstruction syndrome/chaos) Can lead to fetal ascites Accompanied by accumulation of serous fluid in the chest. Prenatal ultrasonography permits diagnosis
During its separation from the foregut, the lung bud forms: the trachea and two lateral outpocketings, the bronchial buds
The spaces for the lungs are called the: pericardioperitoneal canals
Where are the pericardioperitoneal canals located? They lie on each side of the foregut and are gradually filled by the expanding lung buds
The pleuroperitoneal space will be formed after the pericardioperitoneal canal and will give rise to the pleural and peritoneal spaces
The visceral pleura is derived from the splanchnic mesoderm
The parietal pleura is derived from the somatic mesoderm
While all of these new subdivisions are occurring and the bronchial tree is developing, the lungs assume A more caudal position
Maturation of the lungs is divided into 4 periods, which are: 1) Pseudoglandular period 2) Canalicular period 3) Terminal sac period 4) Alveolar period (POSTNATAL)
Duration of pseduoglandular period; Week 5-16
Duration of canalicular period: Week 16-26
Duration of terminal sac period: Week 26-birth
Duration of alveolar period: 8 months-10 years
Are mature alveoli present before birth? No They mature after birth and develop by increasing in number ONLY and not in size.
Cells surrounding the respiratory bronchioles during the canaclicular period are: Cuboidal
Cells surrounding the respiratory bronchioles during the terminal sac period are: Cuboidal cells become very thin (simple squamous)
Cells surrounding the respiratory bronchioles during the alveolar period are: Thin squamous epithelial cells (Type I cells)
At the end of the sixth month, which type of alveolar cells develop? type II alveolar cells develop and produce surfactant
The amount of surfactant in the fluid increases particularly during the last two weeks before birth
Fetal breathing movements begin before birth and cause aspiration of amniotic fluid
When respiration begins at birth most of the lung fluid is: Rapidly resorbed by the blood and lymph capillaries A small amount is probably expelled via the trachea and bronchi during delivery
What are the possible anomalies of the lung? 1) IRDS 2) Blind- ending trachea with absence and agenesis of single or both lungs 3) Abnormal (extra) divisions of the bronchial tree 4) Ectopic lung lobe 5) Congenital cysts of the lung 6) Lung hypoplasia
IRDS counts for what percentage of deaths among newborns? 20%
How does intrauterine asphyxia play a role in IRDS? By producing irreversible changes in type II cells thus inhibiting surfactant production
How is IRDS treated? Administration of artificial surfactants along with oxygen treatment of mothers with premature labor with glucocorticoids Put in an incubator Thyroxin is an important stimulator of surfactant production
Ectopic lung lobes arise from The septum between the trachea and esophagus They could form in other sites than the chest
Congenital cysts of the lung are formed by: dilation of terminal or larger bronchi
These congenital cysts might give the lung, what appearance? Honeycomb
Lung hypoplasia occurs along with: congenital diaphragmatic hernia
This congenital diaphragmatic hernia allows the Abdominal viscera to enter the pleural cavity
Lung hypoplasia is more common on which side: The left side
Fate of infants with CDH: Death due to pulmonary insufficiency
What is Oligohydramnios? A condition in pregnancy characterized by a deficiency of amniotic fluid
When oligohydroamnios is severe, what effect does this have on the lung? Lung development is retarded Severe pulmonary hypoplasia
What is the purpose of the lung float test? To determine whether or not the infant was stillborn If it was the lungs will be firm and heavy and sink
Cells during canilicular and terminal sac period: Cuboidal to simple squamous
Origins of all of the components of the RS: Splanchnic mesoderm -->All cartilages, muscles, and connective tissues + visceral pleura Somatic mesoderm --> Parietal pleura Endoderm --> All lining epithelium Neural-crest derived mesenchyme --> facial prominences
Events and the week in which they appear: 4th-->First pair of pharyngeal arches form the facial prominences Resp. diverticulum formed 5th--> nasal pits formed During the 6th and 7th --> Maxillary + medial nasal prominences fuse Palatine shelves appear --> fuse to form secondary palate
Created by: Ulaisl



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