Development/Developmental Disorders

Question 1

Gastrulation

Answer 1

• phase in development during which the single layered blastula is reorganized into three germ layers (trilaminar)
• begins with formation of Primitive Streak (13-14 days)

Question 2

3 Germ Layers

Answer 2

Ectoderm (nervous tissue, skin)
Mesoderm (CT, musculoskeletal)
Endoderm (visceral linings)

Question 3

Neurulation (creates 3 things)

Answer 3

• Starts at 18 days
• Begins with formation of a neural plate
• Accomplishes 3 things: 1. Creates neural tube 2. creates neural crest 3. creates epidermis

Question 4

Neural Plate

Answer 4

• thickening of ectoderm caused when cuboidal epithelial cells become columnar (formation of neural plate is beginning of neurulation)
• invaginates into mesoderm and edges approximate to form neural tube

Question 5

Neural Tube

Answer 5

• formed from neural plate, gives rise to CNS

- formed by day 20

Question 6

Neural Crest (6 things)

Answer 6

• migrates away from dorsal surface of neural tube, gives rise to diverse set of cell types
• becomes DRG, ANS ganglia, adrenal medulla, pigmented cells of skin/retina, pia matter, post lobe pituitary

Question 7

Epidermis

Answer 7

covers neural tube once created

Question 8

Implantation of the blastula occurs on Day ___

Answer 8

6

Question 9

Primitive Streak

Answer 9

• 13-14 days
• invagination of cells to form the 3 germ layers
• Beginning of gastrulation

Question 10

Primary Vesicle Stage

Answer 10

• begins when neural tube is fully closed (28 days)

- formation of prosencephalon, mesencephalon, rhombencephalon

Question 11

Rhombencephalon

Answer 11

hindbrain

Question 12

Mesencephalon

Answer 12

midbrain

Question 13

Prosencephalon

Answer 13

forebrain

Question 14

Cervical flexure

Answer 14

when mesen folds onto rhomben

Question 15

Secondary Vesicle Stage

Answer 15

• 6 weeks
• prosencephalon becomes telencephalon (cerebral hemisphere) and diencephalon (thalamus)
• mesencephalon stays the same
• rhombencephalon becomes metencephalon (cerebellum, pons) and myelencephalon (medulla oblongata)

Question 16

3 months

Answer 16

• telencephalon grows lateral, posterior over diencephalon

- peak of neural cell proliferation

Question 17

6 months

Answer 17

• start to see sulci

- glial cell proliferation at peak

Question 18

mantle layer of neural tube

Answer 18

-becomes grey matter, where neurons form

Question 19

Marginal layer of neural tube

Answer 19

-becomes white matter (myelinated axons)

Question 20

Basal plate & Alar plate of neural tube

Answer 20

basal plate forms ventral horn

alar plate forms dorsal horn

Question 21

Surface ectodern

Answer 21

becomes epidermis, lens of eye

Question 22

Somites

Answer 22

-each somite is divided into sclerotome, dermatome, and myotome

Question 23

Myotome (2 parts)

Answer 23

supplied by one spinal nerve
2 parts:
1. epaxial division (dorsal rami - extensors of neck and back)
2. hypaxial (ventral rami - neck, prevertebral, and limb ms)

Question 24

Occipital Myotomes (postotic)

Answer 24

give rise to muscles of tounge supplied by hypoglossal nerve

Question 25

Preotic Myotomes

Answer 25

- cranial to occipital myotomes | - extra-ocular muscles of eye ( CN 3, 4, 6)

Question 26

Otic Somites

Answer 26

balance/equilibrium, hearing

Question 27

Pharyngeal (branchial) arches

Answer 27

- form in utero (week 4) as a series of mesodermal outpouchings on sides of developing pharynx - form visceral structures

Question 28

Myeloschisis (3 types)

Answer 28

- developmental anomoly characterized by a cleft spinal cord - neuroplate fails to form complete tube - spina bifida, anencephaly, Arnold-Chiari syndrome

Question 29

Spina Bifida (5 types)

Answer 29

- most common form myeloschisis | - occulta, meningocele, meningomyelocele, syringomyelocele, myelocele

Question 30

Spina Bifida Occulta

Answer 30

- failure of neural arches of vertebrae to fuse dorsally | - still have complete NS, get dimple in back with hair

Question 31

Meningocele

Answer 31

- subarachnoid space bulges through unfused neural arches (dura and arachnoid bulge out) - cyst made of dura and arachnoid passes through hole in vertebrae, filled w fluid - surgically repaired - can also happen in cranial meninges (named for location on skull)

Question 32

Meningomyelocele

Answer 32

- caudal spinal cord and nerve root bulge though arch | - surgically repaired (if not problems with posture, bladder)

Question 33

Syringomyelocele

Answer 33

- dorsal 1/2 of cord bulges out in cyst | - not compatible with life

Question 34

Myelocele

Answer 34

-enitre cord bulges out, exposed to environment (no cyst)

Question 35

Arnold-Chiari Syndome

Answer 35

-congenital anomoly in which cerebellum and medulla protrude into SC through foramen magnum

Question 36

Anencephaly

Answer 36

- congenital absence of cranial vault | - defect in development of rostral neural tube -- cerebral hemispheres don't develop

Question 37

Meningocephalocele

Answer 37

- protrusion of part of cerebellum, covered by meninges and skin - defect at foramen magnum

Question 38

Meningohydroencephalocele

Answer 38

-protrusion of part of occipital lobe containing part of posterior horn of lateral ventricle -defect at posterior fontanelle