Chapter 5 - Development

Question 1

Pre-embryonic stage

Answer 1

• conception to day 14

- fertilization in ovum

Question 2

blastocyst

Answer 2

• pre-embryonic stage
• solid sphere of cells with cavity inside
• when cavity forms in fertilized egg
• outer layer will become fetal contribution of placenta
• inner cells will become embryo(embryonic disk)
• implants into the endometrium of the uterus

Question 3

embryonic disk

Answer 3

2 layers:

1) ectoderm
2) endoderm

Question 4

embryonic stage

Answer 4

Day 15 to eighth week

- organs are formed

Question 5

ectoderm

Answer 5

sensory organs, epidermis, nervous system

Question 6

mesoderm

Answer 6

dermis, muscles, skeleton, excretory and circulatory

Question 7

endoderm

Answer 7

gut, liver, pancreas, respiratory

Question 8

Fetal

Answer 8

9th week to birth

- nervous system develops and myelination begins

Question 9

Neural plate

Answer 9

longitudinal thickening of ectoderm

- forms on the surface of embryo(head to tail)

Question 10

Neural fold

Answer 10

edges of the plate fold toward each other

Question 11

Neural tube

Answer 11

formed when neural folds touch(day 21)

• first closes in cervical region
  - rostrally –> caudally
• neuropores = openings of the tube
• superior neuropore closes = day 27
• inferior neuropore closes = day 30
• neural tube(day 26):
  1) marginal layer(outer) = white matter(axons and glial cells)
  2) mantle layer(inner) = cell bodies and gray matter

Question 12

Neural crest

Answer 12

adjacent cells that separate from tube and remaining ectoderm
- tube and crest go inside embryo and covered by ectoderm(epidermal skin)

Question 13

schlerotome

Answer 13

anteromedial part of somites

- vertebrae and skull

Question 14

myotome

Answer 14

posteromedial part

- muscles

Question 15

dermatome

Answer 15

lateral part

- dermis

Question 16

ventral section

Answer 16

motor plate –> ventral horn

• axons from cell bodies –> myotome
• myotome:
  1) embryologic section of somite
  2) group of muscles innervated by nerve
  
  • cell bodies in dorsal root ganglia

Question 17

conus medullaris

Answer 17

end of the spinal cord(L1 to L2)

Question 18

conus equina

Answer 18

lumbosacral nerve roots extending inferior to end of spinal cord

Question 19

filum terminale

Answer 19

end of dura, pia, and glia

Question 20

hindbrain

Answer 20

myelencephalon = lower section
metencephalon = upper section

• medulla, pons, cerebellum

Question 21

midbrain

Answer 21

connects 3rd and 4th ventricles

Question 22

forebrain

Answer 22

diencephalon = thalamus and hypothalamus
midline cavity –> third ventricle
telencephalon = anterior part(cerebral hemispheres)
central cavity –> lateral ventricles
- hemispheres expand ventrolaterally –> temporal lobe
- C-shaped

Question 23

neurons migrate by

Answer 23

1) sending process to brain surface and follow process

2) climb along radial glia

Question 24

glia

Answer 24

long cells that stretch from center of brain to surface

Question 25

growth cone

Answer 25

forward end process that samples environment

Question 26

neuronal death

Answer 26

failed to make optimal connections or too inactive

Question 27

myelin sheath

Answer 27

insulation for axons - lipids and proteins - begins fetal month 4 --> 3rd year of life

Question 28

growing into deficit

Answer 28

nervous system damage that occurred earlier is not evident until damaged system would normally become functional

Question 29

Nervous system disorders

Answer 29

CNS most susceptible from day 14 --> week 20

Question 30

Anencephaly

Answer 30

Neural tube defect - formation of brain stem without cerebral and cerebellar hemisphere(die before birth) - cranial end of tube does not close and no forebrain - detected by: 1) maternal blood 2) amniotic fluid 3) ultrasound - causes: 1) chromosome abnormalities 2) maternal nutrition deficiencies 3) hyperthermia

Question 31

Arnold-Chiari malformation

Answer 31

deformity of hindbrain | - type 1 and 2

Question 32

Type 1 Arnold-chiari malformation

Answer 32

herniation of cerebellar tonsils through foramen magnum - mostly no symptoms - if symptoms, in adolescence, head and neck pain - hydrocephalus = excess of CSF - sensory and motor disorders - malformation of lower cranial nerves

Question 33

Type 2 Arnold-chiari malformation

Answer 33

malformation of brainstem and cerebellum - extension of medulla and cerebellum through foramen magnum - associated with meningomyelocele = nonclosure of neural tube

Question 34

Spina bifida

Answer 34

inferior neuropore does not close - vertebrae do not close around tube = bony defect at distal end of tube - maternal nutritional deficits

Question 35

spina bifida cystica

Answer 35

meninges and spinal cord through posterior opening of vertebrae 3 types: meningocele, meningomyelocele, myeloschisis

Question 36

Meningocele

Answer 36

meninges through posterior opening

Question 37

meningomyelocele

Answer 37

neural tissue with meninges protruding outside of the body - abnormal growth of spinal cord - LE dysfunction - cognitive dysfunction(abstract, visual, visual-motor)

Question 38

myoloschisis

Answer 38

neural folds do not close | - malformed spinal cord open to surface

Question 39

Tethered spinal cord

Answer 39

spinal cord adheres to lower vertebrae causing traction - dermatome and myotome deficits in LE - pain in saddle region signs: - progressive LE weakness, deterioration in walking, back and leg pain, excessive muscle resistance to stretch, scoliosis, foot deformity

Question 40

spinal muscular atrophy

Answer 40

``` autosomal recessive disorder - motor neurons with cell bodies in spinal cord degenerate Type 1(most severe) Type 2(intermediate) Type 3(less severe) ```

Question 41

Forebrain malformation

Answer 41

1 cerebral hemisphere instead of 2 - facial abnormalities - holoprosencephaly(genetic) - genetic testing and ultrasound

Question 42

Intellectual Disability

Answer 42

abnormalities of dendritic spines

Question 43

cerebral palsy

Answer 43

movement and postural disorder caused by damage to developing brain - types: spastic, dyskinetic, ataxic, hypotonic, mixed