Embryology Week 8

What arises from the ventral region of the sclerotome?

Vertebral bodies

Cartilaginous endplates

Some parts of the annulus fibrosis

How many sclerotomes make up the ventral region?

2

What arises from the dorsal region of the sclerotome?

Spinous process

Lamina

What arises from the central region of the sclerotome?

Superior and inferior articular processes (articular pillars)

Transverse processes

Proximal ribs

What arises from the lateral region of the sclerotome?

Distal ribs

Tendons for intrinsic muscles of the back

What is the AKA of the lateral region of the sclerotome?

syndetome

What arises from the medial region of the sclerotome?

Meninges (dura, arachnoid, pia mater)

Blood vessels of the meninges

What is the AKA of the medial region of the sclerotome?

Meningotome

What gives rise to the spinal cord?

Neural tube

What does the dermatome give rise to?

dorsal dermis

Where do the dermis of the lateral trunk and limbs come from?

Lateral plate mesoderm

What does the medial myotome give rise to?

Intrinsic back muscles

extensor muscles of the limbs

Which back muscles are not considered intrinsic?

Latissimus dorsi

Trapezius

What does the lateral myotome give rise to?

Muscles of the ventrolateral body wall

Flat abdominal muscles (external oblique, internal oblique, transversus abdominis muscle

Rectus abdominis and pyramidalis

Flexor muscles of the limbs

T or F: While the lateral myotome gives rise to the flexor muscles of the limbs, the medial myotome gives rise to the extensor muscles of the limbs

True

What do somitocoel cells give rise to?

Part of the annulus fibrosus

Facet joint articular surfaces

Proximal ribs

What gives rise to most of the annulus fibrosis?

Sclerotome cells

Where do the articular surfaces of the Z joint come from in general?

Sclerotome

How is the coronal plane best visualized?

A-P

How is the axial plane best visualized?

S-I

How is the sagittal plane best visualized?

L-M

Whe. does folding of the embryonic disc begin?

Week 4 gestation

What types of growth cause folding of the embryonic disc?

Lateral growth

Cranial-to-caudal growth

Which 2 planes do the embryonic disc fold in?

Sagittal plane

Axial plane

What directions does the embryonic disc fold downward in?

Laterally

Cranial-caudally

Which direction of folding is more dramatic?

Lateral folding

What type of folding creates the lateral folds?

Lateral folding

What type of folding creates the head fold and tail fold?

Sagittal plane folding

What is the AKA of sagittal plane folding?

cranial-to-caudal folding

What plane is transverse folding best observed in?

Transverse plane

Which structures' growth rate differences cause lateral folding?

Splanchnopleure - SLOW

amnion and somatopleure - FAST

What structure is the pivot point of lateral folding?

Splanchnopleure

What is created by the lateral folds coming together?

tube-within-a-tube body plan

What are the tubes (in the tube within a tube)

Neural tube

Gut tube

Where do the lateral folds not completely fold?

The halfway point at the level of the secondary yolk sac

What happens to the yolk sac as the lateral folds come together?

It has shrunken and no longer occupies the cranial or caudal regions of the embryonic disc

What forms at the region where the lateral folds do not fuse?

Umbilical cord

What does the umbilical cord swallow?

The stalk of the gut tube

What is the AKA of the stalk of the gut tube?

Vitelline duct

What does the region where the lateral folds do not fuse become in an adult?

umbilicus (belly button)

Which 3 structures are created by lateral folding?

Anterior body wall

Gut tube

Body cavity

What makes up the anterior body wall?

Anterior pelvic, abdominal, and thoracic walls

Umbilicus

What makes up the gut tube?

Foregut

Midgut

Hindgut

What forms the gut tube?

Splanchnopleure

Which cavities are formed from the body cavity?

Pericardial cavity

Pleural cavity

Peritoneal cavity

What are the 3 regions of the anterior body wall?

Thorax

Abdomen

Pelvis

What is the AKA of omphalocele?

Exomphalos

When do mature intestines normally return to the body cavity (after maturing inside the proximal umbilical cord)?

Week 10

What is the term for an umbilical hernia where the intestines fail to return to the body cavity?

Omphalocele

What type of hernia is an omphalocele?

Congenital umbilical hernia

What do the intestines pass through to reach the body cavity?

Umbilical ring

What covers herniated intestines in an omphalocele?

Amnion and parietal peritoneum

What is the term for the covering of an omphalocele?

Hernia sac

What can cause an omphalocele?

Teratogen exposure during the first 3 weeks gestation

What other abnormalities are present in 75% of babies with an omphalocele?

Trisomy 13

Beckwith-wiedmann syndrome

Exstrophy of the bladder

What is exstrophy of the bladder?

Bladder develops outside the body cavity and inside out

What are the 5 components of the pentalogy of Cantrell?

Defect of the anterior abdominal wall above the umbilicus

Anterior diaphragmatic defect

Defect in the sternum (sternal cleft)

Defect in the diaphragmatic pericardium

Congenital heart defects

What are types of anterior abdominal wall defects?

Gastroschisis

Omphalocele

What is an anterior diaphragmatic defect?

Hiatal hernia

What can a sternal cleft result in?

May lead to ectopia cordis

What congenital heart defects may be present in the pentalogy of Cantrell?

ASD

VSD

Ectopia cordis

What is complete pentalogy of Cantrell?

Born with all 5 defects

What is incomplete pentalogy of Cantrell?

Born with 2-4/5 defects

What is the incidence of incomplete pentalogy of Cantrell?

About the same as marfan's syndrome (0.01%)

What is the primary prenatal marker of an omphalocele?

alpha fetoprotein (AFP) in maternal blood serum

What imaging modality can be used to detect omphalocele?

Ultrasound