Noncardiac embryology

Question 0

Folding of intraembryonic ceolom

Answer 0

Lateral folds come together

Openings to extraembryonic ceolom -> join together to create future peritoneal cavity

Question 1

Intraembronic ceolom

Answer 1

Forms within lateral plate mesoderm (between parietal and visceral layers)
Runs up over cranial end of embryo
Open laterally to extraembryonic ceolom

Question 2

Partitions of intraembryonic ceolom

Answer 2

Cranial end (U) forms pericardial cavity/heart
“Pleuropericardial membrane” separates from
Lateral/vertical portions form two pleura
“Pleuroperitoneal membrane” separates from
Inferior portion forms peritoneal cavity (ie lateral holes that joined during lateral folding)

Question 3

Longitudinal folding of intraembryonic ceolom

Answer 3

Cranial end (U) will form pericardial cavity
Septum transversum is parietal mesoderm just dorsal to this
Both fold anterior and inferior until pericardium is in thorax
Septum transversum lies inferior to pericardium

Question 4

Formation of pleural cavities

Answer 4

Septum transversum divides pericardial and peritoneal cavities
Pericardioperitoneal cavities (2) run between (dorsal, like the middle of an old-school telephone receiver)
Pleuropericardial membranes divides pleural and pericardial
Pleuroperitoneal membranes divides pleural and peritoneal
Both membranes grow from parietal layer

Question 5

Origin of fibrous pericardium

Answer 5

Parietal layer of lateral plate
Projects from ventral-lateral wall ->
Pleuropericardial membranes
Fuse and become ->
Fibrous pericardium

Question 6

Formation of diaphragm

Answer 6

Septum transversum -> central tendon (came from cranial parietal layer and migrated with heart)
Pleuroperitoneal membranes - parietal layer, projects from dorsolateral wall, meet in middle
Dorsal mesentery of esophagus -> crura (back portion right behind esophagus)

Muscles =
Somites! hypaxial myoblasts of C3-C5 - migrate down with septum transversum - majority of musculature and strength (ie hernia)
Body wall - projects in to form edges

Phrenic nerve is C3-C5 -> musculature
Lungs expand to form costodiaphragmatic recess

Question 7

Longitudinal folding of gut tube

Answer 7

Forms foregut (cranial)
Midgut (connection to yolk sac)
Hindgut

Question 8

Origin of lung tissues

Answer 8

Foregut (endoderm) pushes out to form respiratory diverticulum
- Endoderm forms all epithelia!
Visceral layer of lateral plate mesoderm - pushed out (coats) endoderm, forms all muscle, vessels, cartilage, also visceral pleura
Parietal pleura forms from parietal layer of mesoderm

Question 9

Separation of trachea and esophagus

Answer 9

Tracheoesophageal ridge forms between respiratory diverticulum and foregut (future esophagus)
Errors can cause fistula or atresia (blind pouch)

Question 10

Development of lungs

Answer 10

Everything starts as respiratory diverticulum
Pushes out to form trachea, divides into bronchi and lung buds
Continues dividing and growing…

Question 11

Phrenic nerve

Answer 11

Originates at C3-C5 (origin of diaphragm somites)
Runs through fibrous pericardium
Anterior to root of lung and great vessels (“phrenic in phront”)
Innervates primarily diaphragm