Embryology 01-02 - Limb Development - Msk

Front 1

What are the layers of the embryo in week 3?

Back 1

Trophoblst(forms syncytiotrophoblast(secretes hhCG) + cytotrophoblast(secretes enzymes that break down ECM)), embryoblast (epiblast + hypoblast)

Front 2

What are the layers of bilaminar germ disc?

Back 2

Aka embryoblast = epiblast(lines amniotic cavity) + hypoblast (lines blastocyst cavity)

Front 3

What happens on day 16?

Back 3

Gastrulation -> epiblasts migrate inward -> divides down -> makes trilaminar germ disc = ectoderm (epiblast cells that didn’t migrate)+ mesoderm(cells that end up on the middle) + endoderm(pushes hypoblast out of the way)

Front 4

On day 17 what does the intraembryonic mesoderm develops into?

Back 4

1. Paraxial mesoderm(forms axial skeleton, voluntary musculature and part of the dermis), 2. intermediate mesoderm(will form the urinary system and parts of the genital system), 3. lateral plate mesoderm(will split into somatic and splanchnic mesoderm)

Front 5

Mesenchyme

Back 5

Precursor to connective tissue

Front 6

What day mesoderm forms the somitomeres?

Back 6

Day 20 - paraxial mesoderm -> forms somitomeres (rostral (superior ) to caudal (inferior) sequence

Front 7

What are the number of somites in the paraxial mesoderm?

Back 7

Occipital = 4, cervical = 8, thoracic = 12, lumbar = 5, sacral = 5, coccygeal = 8-10

Front 8

What parts of the somite become sclerotome?

Back 8

Ventral and medial parts of somite dissociate and shift position -> turns into sclerotome; dorsal lateral region -> forms dermomyotome; ventral medial region -> forms sclerotome

Front 9

What does the sclerotomes form?

Back 9

Bone(ie rib cage), cartilage, ligaments, etc

Front 10

What does the dermomyotome form?

Back 10

Dermotome -> dermis + subcutaneous tissue, myotome -> skeletal muscle

Front 11

What are the connective tissue cells?

Back 11

1. Fibroblasts, 2. osteoblasts, 3. chondroblasts

Front 12

What is the 2 ways bones develop?

Back 12

1. Intramembranous = fibrous CT -> bone, 2. endochondral = cartilage -> CT -> bone

Front 13

Somatic layer of lateral plate mesoderm

Back 13

Forms sternum and limb bones

Front 14

Neural crest

Back 14

Forms Bones of the skull

Front 15

Somitomeres

Back 15

Forms cranial vault and base of skull

Front 16

What embryonic tissue does skeletal muscle come from?

Back 16

Mesoderm -> paraxial mesoderm -> Myoblasts come together -> forms syncitial (multinucliated) -> forms actin + myosin

Front 17

What does the myotome develop into?

Back 17

1. Epimere -> forms erector spinae (deep back muscles), multifidus, all innv by dorsal rami. 2. Hypomere - forms everything else -> intercostal muscles, abdominal wall muscles, and muscles in the limb -> innv by ventral rami

Front 18

What do the lateral segments of the hypomere form?

Back 18

Cervical - scalenes, geniohyoid, prevertebral, thoracic - intercostals + transversus thoracicis, abdominal - obliques, lumbar - quadratus lumborum, sacral - pelvic diaphram

Front 19

What do the ventral segments of the hypomere form?

Back 19

Ventral segments = infrahyoid muscles and rectus abdominis

Front 20

Poland syndrome -

Back 20

Underdevelopment/absence of chest muscle (ie Missing right pectoralis major)

Front 21

Prune belly

Back 21

Missing abdominal wall muscles-> see intestines thru stomach

Front 22

Arhrogyposis multiplex congentia(AMC)

Back 22

Missing muscles around the joint -> stiff ness and contractures

Front 23

Pt w/missing half a diaphram?

Back 23

Congenital absence of the diaphragm

Front 24

Which sclerotomes make up the atlas? axis

Back 24

C1 + C2 sclerotomes = atlas; C2+ C3 = axis(aka the caudal portion of each sclerotome proliferates and proceeds to the cranial half of inferior sclerotome) -> newly formed vertebral body = INTERSEGMENTAL; Myotomes + nerves = SEGMENTAL

Front 25

Spina bifida oculta

Back 25

Missing vertebral arches

Front 26

Spina bifida meningocele

Back 26

Meninges + CSF

Front 27

Spina bifida meningomyelocele

Back 27

Spinal cord + meninges + CSF

Front 28

Congenital scoliosis

Back 28

Asymmetric fusion of vertebra -> half a vertebra missing -> abdnormal curvature of vertebral column

Front 29

What are accessory ribs?

Back 29

Rib at C7 or L1

Front 30

Klippel-feil anomoly (brevicollis)

Back 30

Short neck due to absence or fusion of cervical vertebrae(ie fusion of C5,C6,C7)

Front 31

Upper limb - DAY?

Back 31

Day 26

Front 32

Lower limb - day?

Back 32

Day 28

Front 33

What stimulates the somatic layer of lateral plate mesoderm to envaginate?

Back 33

Somites -> stimulate somatic layer of lateral plate mesoderm to evaginate -> froms a core of mesenchyme covered by surface ectoderm

Front 34

What does the lateral plate mesoderm form in the limb?

Back 34

1. Bones, 2. tendons, 3. ligaments, 4. cartilage, 5. fascia, 6. joints, 7. vessels, 8. dermis

Front 35

What embryonic tissue forms the epidermis of the limbs?

Back 35

apical ectodermal ridge -> epidermis -> forms fingers and toes

Front 36

What embryonic tissue forms the muscles in the limb?

Back 36

Somites

Front 37

What embryonic tissue forms the motor nerves in the limbs?

Back 37

Neuroectoderm

Front 38

What embryonic tissue forms the sensory nerve and melanocytes in the limbs?

Back 38

Neural crest

Front 39

What embryonic tissue contributes to limb bud growth?

Back 39

Proliferation of mesenchyme

Front 40

What is the function of Homeobox (HOX) genes?

Back 40

1. Axis (front to back, left to right), 2. patterning

Front 41

Function of AER(apical ectodermal ridge)

Back 41

Causes adjacent cells to remain undifferentiated -> allows proximal to distal axis

Front 42

Zone of polarizing Activity - function

Back 42

Anterior to posterior axis determination

Front 43

What is bad about retinoic acid in teenagers?

Back 43

Teenager -> perscribed retinoic acid for acne ->interferes w/signaling in developing limbs (careful when giving to teenagers who are pregnant) -> might get no arm or legs baby!!!

Front 44

What are hand and foot plates?

Back 44

Distal ends of limb buds flatten into paddle like plates -> end of 6th week mesenchyme in HAND -> forms digital rays (finger buds) -> end of 7th week mesenchyme in FOOT -> forms digital rays (toe buds)

Front 45

How do the fingers form

Back 45

AER (apical ectodermal ridge ) -> induces mesenchyme to form bones; Loose CT is inbetween each ray(ie webbed fingers) -> cell death occurs -> forms notches between each digit -> separates digits

Front 46

What is the 1st bone to ossify?

Back 46

Clavicle is first to ossify -> then femur

Front 47

What embryonic tissue forms synovial joints?

Back 47

Interzonal mesenchyme -> synovial joints -> peripherally = capsule + ligaments, centrally = forms a cavity -> forms synovial membrane; joint movement -> mesenchyme disappears from articular cartilage

Front 48

What is the initial direction limbs are in at 7th week?

Back 48

Flexor compartment = ventral and medial, extensor compartments = dorsal and lateral

Front 49

Flexor compartment rotation of limb development

Back 49

Face ventral and medial -> laterally rotates 90 °

Front 50

Extensor compartment of limb development

Back 50

Face dorsal and lateral -> medially rotates 90 °

Front 51

Spinal levels of -upper limb?

Back 51

C5->T2

Front 52

Spinal levels of - lower limb?

Back 52

L2-S2

Front 53

Which axons grow out first from the posterior root ganglion?

Back 53

Motor axons grows out first -> peripheral processes extend from posterior root ganglion neurons and use motor axons as a guide to their target

Front 54

What is the initial blood supply of limb buds?

Back 54

Limb buds are initially supplied by dorsal intersegmental arteries that arise from dorsal aorta

Front 55

What consists of the primordial vascular pattern?

Back 55

Primary axial arteries and branches; axial artery drains -> into marginal sinus -> peripheral vein,

Front 56

What initial blood artery becomes the brachial and then turns into common interosseous artery?

Back 56

Axial (not axillary) artery

Front 57

How is the radial and ulnar arteries form?

Back 57

Radial and ulnar arteries arise as secondary branches of the brachial

Front 58

What is the fate of the median artery?

Back 58

Median artery (also a secondary branch) -> degenerates

Front 59

What is the embryonic origin of axial artery?

Back 59

Axial artery in the lower limb begins as the "ischiadic" artery

Front 60

What is the embryonic origin of anterior and posterior tibial atery?

Back 60

Anterior and posterior tibial artery arise as secondary branches

Front 61

What is the fates of primary axial vessel?

Back 61

Primary axial vessel becomes 1. artery to the sciatic nerve, 2. part of politeal, 3. part of fibular

Front 62

What drug used in 1957-1961 and causes limb defects?

Back 62

thalidomide

Front 63

Limbs are bowed and short, disturbance of endochondral ossification at epiphyseal plates

Back 63

Achondroplasia

Front 64

Lethal skeletal dysplasia, death of respiratory failure, fibroblast growth factor receptor deficiency

Back 64

Thanatophoric dysplasia

Front 65

Deficient in type I collagen

Back 65

Osteogenesis imperfecta

Front 66

Amelia

Back 66

Absence of entire limbs

Front 67

Meromelia

Back 67

Absence of a part of a limb

Front 68

Absence of central digits -> failure of digital rays to form

Back 68

Cleft hand or foot (aka lobster claw deformity)

Front 69

Absence of radius

Back 69

Congenital absence of radius -> hand moves laterally

Front 70

Shortness of digits, associated w/short stature

Back 70

Brachydactyly

Front 71

Supernumery digits, extra digits is usually useless

Back 71

polydactyly

Front 72

Fusion of 2 fingers/toes

Back 72

syndactyly

Front 73

Defect involving talus that prevents normal weight bearing

Back 73

Congenital club foot

Front 74

Laxity of joint capsule of femur or defect of acetabulum

Back 74

Congenital dislocation of hip