Embryology of Resp. System Flashcards
What week does gastrulation occur?
Week 3
Which 2 layers of the germ layer are most important for the development of the resp. system?
Endoderm and mesoderm
What does the endoderm form and what does the mesoderm form?
Endoderm: Epithelial lining and glands
Mesoderm: muscles, cartilage, connective tissue
What is needed for the appearance and location of the lung bud and what is it’s importance?
Retinoic acid: It is needed for the upregulation of the transcription factor TBX4 expressed in the gut tube
What is the role of TBX4?
Induces formation of lung bud and its continued growth and differentiation
How many pharyngeal arches , pouches, and clefts are there and where do they derive from?
5 pharyngeal arches: mesoderm
4 pouches: endoderm
4 pharyngeal clefts/grooves: ectoderm
What structure is derived from the 1st pharyngeal arch?
Mandibular (maxillary and mandibular processes)
What are the nerve supply derivatives of the 1st arch?
CN V : Trigeminal–> maxillary and mandibular divisions
What are the muscles of the 1st pharyngeal arch?
(MMATT)
Mastication (temporal, masseter, medial, lateral, pterygoids), Mylohyoid, Anterior belly of digastric, Tensor Palatine, Tensor tympani
What are the skeletal derivatives of the 1st pharyngeal arch
Premaxilla, maxilla, zygomatic bone, part of temporal bone, meckel cartilage, mandible malleus, incus, anterior ligament of malleus, sphenomandibular ligament
what is the derivative of the 2nd pharyngeal arch?
Hyoid
What is the nerve innervation from the 2nd pharyngeal arch?
Facial- CN7
What are the muscle derivatives of 2nd arch?
(Face posteriorly, side by side)
Facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi), posterior belly of digastric, stylohyoid, stapedius
What is the nerve innervation from the 3rd pharyngeal arch?
Glossopharyngeal -CN IX
What is the muscle derivative of 3rd pharyngeal arch?
Stylopharyngeus
What are the skeletal derivatives of the 3rd pharyngeal arch?
Greater horn and lower portion of body of hyoid bone
What are the skeletal derivatives of the 2nd pharyngeal arch?
stapes, styloid process, stylohoid ligament, lesser horn and upper portion of body of hyoid
What are the nerve derivatives of the 4th and 6th pharyngeal arches?
Vagus-X
4th: Superior laryngeal branch
6th: Recurrent laryngeal branch
What are the muscle derivatives of the 4th arch?
cricothyroid, levator veli palatini, constrictors of pharynx
What are the muscle derivatives of the 6th arch?
Intrinsic muscles of larynx
What are the skeletal derivatives of the 4th and 6th arch?
laryngeal cartilages: thyroid, criciod, arytenoid, corniculate, cuneiform
Which week does the trachea and lung develop ? Explain what happens during this week.
4th week
Edothelial cells coming off foregut forms lung bud. Tracheoesophageal groove forms, Bronchial bud forms, and tracheoesophageal septum forms
Which arches do the muscles and cartilage derive from?
4th and 6th
Explain role of tracheoesophageal septum
Separates the anterior lung bud (resp. diverticulum) from the posterior foregut
What takes place during week 5 of tracheal and lung development?
Tracheoesophageal septum closes
Endoderm from gut tube forms glands and epithelial lining
Splanchnic mesoderm forms muscles, cartilage, and CT
Stages of lung development starts
______ is the abnormal communication between trachea and esophagus due to defective development of the tracheoesophageal septum. May be associated with esophageal atresia
Tracheoesophageal fistula
-sometimes seen when the esophagus ends blindly
What else can be seen with TEF?
Poly-hydramnios
Baby can’t pass meconium
Baby will choke immediately during feeding
Cyanosis
Spina bifida
Renal anomalies
Why does the infant choke with TEF?
The choke due to accumulation of fluid in the mouth/resp. tract which may pass into the lungs- causes pneumonitis/ lung infection
____ forms the parietal pleura
Somatic mesoderm
____ forms the visceral pleura
Splanchnic mesoderm
_____ separates the pleural cavities from the pericardial cavity and fuses to form form fibrous pericardium
Pleuropericardial folds
_____ separates pleural cavities from the peritoneal cavity. They fuse with the septum transversum & dorsal mesentery of esophagus to form the posterolateral parts of the diaphragm
Pleural-peritoneal folds
When do the two folds form and where do they form from??
When the lung bud continues to grow into the pericardio-peritoneal canals; the two folds form in each canal
-forms from lateral walls of the canals
What are the 5 stages of lung development?
Embryonic
Pseudo-glandular
Canicular
Saccular (terminal sac)
Alveolar
Describe what takes place during pseudo-glandular stage and when does it take place?
Takes place during weeks 5-16
Primary left and right bronchi form–> Right splits into 3 lobar bronchi/ secondary bronchi & Left splits into 2 lobar/secondary bronchi–> Right and left lobar splits into tertiary bronchi–> Terminal bronchioles form for both
-Only conducting unit formed
Can a fetus born before 20 weeks survive?
NO
Describe what takes place during the canalicular stage and when does it take place?
Takes place during weeks 16-26
Terminal bronchioles become Resp. bronchioles–> Resp. bronchioles divide into 3-6 alveolar ducts —> angiogenesis and BLOOD AIR BARRIER forms–> Pneumocytes form (Type 1 and 2)—> Baby can survive with intensive care
Describe what takes place during the saccular stage and when does it take place?
Takes place during weeks 26 to birth
More resp bronchioles form, so more alveoli, more pulmonary capillaries form–> Type 1 cells perform gas exchange and type 2 cells form surfactant for preventing alveolar collapse
Describe what takes place during the embryonic stage and when does it take place?
Takes place during weeks 3-8
Organ start to develop and this when errors can occur
Describe what takes place during the alveolar stage and when does it take place?
Takes place from week 36 til ~ 8 years of age
Increase number of capillaries, increase number of alveoli, septa forms in alveoli to increase surface area, more surfactant
What takes place before birth
In utero breathing occurs via aspiration and expulsion of amniotic fluid–> increases resistance through gestation
What takes place after birth?
Fluid gets replaced with air–> decreased pulmonary vascular resistance
Describe Infant Resp Distress Syndrome and what is another name for it?
Another name: Hyaline membrane disease
-if baby is born premature not enough surfactant so increased surface tension, increased collapsing pressure so alveolar may collapse when born
What can treat Infant Resp. Distress?
Maternal steroid before birth: glucocorticoids which accelerates fetal lung movement and surfactant production, exogenous surfactant for infant
What factors influence normal development of lungs and what damages the factors?
Thoracic space for growth: congenital diaphragmatic hernia
Fetal breathing movements: having no air lungs at birth
Amniotic fluid volume: Oliogohydramnios
How do the lungs appear with Infant Resp. Distress?
They look quite dense and white due to collapse of lung tissue. Air in lung is small and chest xray has ground-glass appearnace
What is congenital lung cysts?
It is formed by the dilation of terminal bronchioles that may be due to disturbance in development during late fetal life. Cysts drain poorly so frequently causes chronic infection
What is agenesis?
Failure of lung bud to develop
-Unilateral agenesis : could live
What are the 2 portions of the diaphragm?
Peripheral: Muscular part (sternal costal lumbar)
Central : Aponeurotic part (central tendon)
Which cervical vertebrae keeps the “diaphragm alive”?
C3,C4,C5
What forms the diaphragm?
The septum transversum, pleuro-peritoneal membrane, Dorsal mesentery of esophagus
What nerve supplies the diaphragm?
Phrenic nerve
What forms the musculature part of the diaphragm?
Cervical myotomes: C3-C5
What forms the Central tendon?
Septum transversum
What forms the posterolateral parts of diaphragm?
Pleuro-peritoneal folds
What forms the crura of diaphragm?
dorsal mesentery of esophagus
What is a congenital diaphragmatic hernia?
-what causes it and what is the mortality rate ?
-which side of the chest is this most commonly seen?
-what type of defect is it: postero lateral or parasternal ?
When a hole/hernia in diaphragm allows the stomach and intestine to enter into the chest due to failure of pleuroperitoneal membranes to close the pericardioperitoneal canal
-Posterolateral
mortality rate: 76% due to pulmonary hypoplasia
Causes lung to not develop properly
seen on left side
What is pulmonary hypoplasia?
Caused by CDH: the lungs do not develop properly so they are small and cannot circulate oxygenated blood properly
Name 2 type of CDH
Retro/parasternal hernia
Postero-lateral hernia
What forms the alveoli?
The endoderm of the foregut
Explain how the larynx is formed?
After gastrulation around week 5, the laryngeal orifice forms and the endodermal cells invade the orifice and forms the vocal cord.
-The mesoderm forms the muscles and the cartilages
-It also forms the epiglottic swelling that forms above the orifice and the arytenoid swelling that forms above the orifice
Which week does the mature larynx form and what does the orifice become?
12 and laryngeal inlet
Name the epithelium around the larynx?
Psuedostratified ciliated columnar epithelium
Which germ layer does the vagus nerve derive from and what part of the larynx does it supply?
Mesoderm and it supplies the epithelial lining
Which week do all the lower resp. organs form?
4
Which end of the diverticulum forms the larynx?
Cranial end
What divides the lateral plate mesoderm into the somatic and splanchnic mesoderms?
Intra-embryonic coelom
