Embryo - Respiratory System Flashcards
What do the Coelomic clefts split into?
Coelomic clefts appear in the lateral plate mesoderm & split it into:
-
somatic layer (somatopleure)
- gives rise to parietal layer of serous pericardium, pleura and peritoneum
-
splanchnic layer (splanchnopleure)
- gives rise to visceral layer of serous pericardium, pleura and peritoneum
What is the result of the formation of head fold?
-
Pericardioperitoneal canals
- come to sides of foregut
-
Peritoneal cavity
- lies dorsally to sides of gut
-
Pericardial cavity
- comes ventrical to foregut
Note:
- 3 cavities are still continuous
- 2 folds develop:
- Pleuropericardial fold
- Pleuroperitineal fold
What happens during formation of lateral folds?
A) endoderm lining inside of yolk sac
- mesoderm surrounding outside
B) formation of intra-embryonic coelomic cavity
- 2 lateral folds fuse to form 1 cavity
- splits off yolk sac & leaves umbilical attachment to gut
C) Splanchnic mesoderm surrounding coelomic cavity
- forms parietal layer evenualy
The pericardial, pleural & peritoneal parts form one continous coelomic canal until which week?
7th week!
Partitioning of the Coelomic canal:
-
Pericardio-peritoneal canals
- lung buds grow into these
- 2 pairs of folds are formed from lateral wall of canals
-
Pleuropericardial folds (membranes)
- separate pleural cavity from pericardial cavity
- fuse w/ each other to form = fibrous pericardium
-
Pleuroperitoneal folds (membranes)
- separate pleural cavitities from peritoneal cavity
- form the posterolateral part of diaphragm
What are the 5 major developmental components of the Diaphragm?
-
Central tendon (aponeurotic)
- forms from septum transversum
-
Posterlateral parts
- from pleuoperitoneal folds
-
Peripheral part (muscular)
- from sidewall mesenchyme (abd muscles)
-
Crura
- from dorsal mesentery of esophagus
- right/left crus = attach pleura to lumbar vertebrae
-
Musculature
- fr__om C3-5 myotomes
What are the positional changes of the diaphragm?
Week 4
- Septum transversum = near C3-5 & somite 1
- this explains innervation of phrenic nerve
Week 8
- Septum transversum = diaphragm is now mid-thoracic
Full-term
- Septum transversum = diaphragm is now at L1
- descends due to growth on dorsal side
- phrenic nerve descended too
What are the common sites of hernia through diaphragm?
Congenital hiatal hernia
-
esophageal hiatus = abnormally large
- most commonly seen in adults due to:
- chronic stress, smoking
- weak musculature
- most commonly seen in adults due to:
Congenital diaphragmatic hernia
- large posterolateral defect (pleuroperitoneal fold)
- more common on left side
- abdomen = empty when flat
- abdominal contents go into thorax –> via defective hold in diaphragm
- lung = compressed (hypoplastic)
Note:
-
3 NORMAL openings in diaphragm:
- Inferior Vena Cava (T8)
- Esophagus (T10)
- Abdoninal aorta (T12)
What is eventration of diaphragm?
Basics:
- caused by defective musculature in 1/2 of diaphragm
Result:
-
Paradoxical Respiration
- 1/2 diaphragm goes up w/ contraction during inspiration
- Presents similar to congenital diaphragmatic hernia
- hypoplasia
What are the 3 major structures of Respiratory primordium?
-
Foregut
-
Respiratory diverticulum
- dev. from FLOOR of the pharnyx
- Tracheosophageal septum
- btw. respiratory divertculum & esophagus
- defect –> abnormal connect of trachae & esophagus
-
Respiratory diverticulum
-
Midgut
- lateral fold –> supplied by superior mesentric a.
-
Hindgut
- tail fold –> supplied by inferior mesentric artery.
What is important about the larygotracheal tube in relation to the dervations of larnyx, trachea, bronchi components?
Basics:
- cranial part –> larynx
- LT-tube (below larynx) forms –> trachea
- lower end of LT tube –> divides into 2 bronchial (lung buds)
- form bronchi
Derivations of Larnyx:
-
epithelium of larynx gives rise –>
- endodermal lining
-
laryngeal cartilages –>
- 4th & 6th pair of pharyngeal arches
-
EXCEPT the epiglottis –>
- dev from hypo(pharyngeal)branchial eminence
-
laryngeal muscles –>
- mesenchyme (mesoderm) in 4th & 6th arches
Derivation of Trachea:
-
epithelial lining & glands –>
- endoderm of LT-tube
-
CT, cartilage muscles, blood vessels –>
- splanchnic mesoderm (surrounding LT-tube)
Derivation of Bronchi:
-
bronchial epithelium & glands –>
- from endoderm of LT tube
-
muscles & cartilages –>
- from surrounding splanchnic mesoderm
What are the 4 stages of maturation of lungs?
-
Pseudoglandular (5-16 wks)
- lung resembles compound exocrine gland
- terminal bronchiole ONLY
- cuboidal epithelium
-
Canalicular (16-24 wks)
- lumen of conducting sys enlarges
- terminal branch –> respiratory bronchiole
- cuboidal epithelium
- Type II alveoli - start secreting surfactant
-
Terminal sac (24 wks - birth)
- respiratory –> subdivide to terminal sacs
- cuboidal epithelium –> flat
- associate w/ blood & lymph
- respiratory –> subdivide to terminal sacs
-
Alveolar (Birth - 8 yrs)
- epithelium –> thinner (Type I pneumocytes)
- capillaries protrude into alveolar sacs
- form blood-air barrier
- mature alveolus
Note:
- if baby is born before 24th week, will likely not survive
- poor respiratory sys development
What are the 3 factors important for lung development?
- Thoracic space for growth
- Fetal breathing movements
- not continuous –> intermediate
- needed for conditioning of muscles
- Amniotic fluid volume
Note:
- If we do not have this, we get pulmonary hypoplasia
What are 3 important clinical pathologies?
-
Tracheo-esophageal fistula
- incomplete separation of laryngotracheal tube from pharynx & esophagus
- abnormal communication w/ esophagus & trachea
-
Respiratory Distress Syndrome (HMD)
- aka: hyalane membrane disease
- lack of surfactant (type II pneumocytes)
-
Hypoplasia of the lung
- associated w/
- congenital diaphragmatic hernia
- oligohydramnios ( not enough amniotic fluid)
- associated w/
