EXAM II Cole

Question 1

What is a herniated disc?

Answer 1

Protrusion of nucleus pulposus, may compress spinal nerves

Question 2

What are the 3 types of Congential Scoliosis?

Answer 2

Hemivertebrae caused by failure to form

Block Vertebrae and Unsegmented Bar due to failure of segmentation

Unsegmented bar with Hemivertebrae

Question 3

What are the subtypes of Hemivertebraes under Congenital scoliosis?

Answer 3

Semisegmented (not a full wedge that’s inserted)

Fully segmented

Wedge Vertebrae (full wedge)

These occur due to a failure in the formation of vertebrae

Question 4

What condition is seen here?

Answer 4

Semisegmented vertebra caused by a failure of formation of the vertebrae.

Congenital scoliosis

Question 5

Where are ribs derived from?

Answer 5

Condensed mesenchyme lateral to the body of the vertebra (from sclerotome)

Question 6

What forms during axial skeletogenesis?

Answer 6

Vertebral column

Thorax

Ribs and Sternum

All derived from sclerotome

Question 7

Where is the sternum derived from and what’s it developed from?

Answer 7

Derived from sclerotome

Develops from cartilaginous sternal bars in ventral body wall and fuse in cranial-caudal direction

Question 8

What are 3 defects of the sternum?

Answer 8

Pectus carinatum

Pectus excavatum

Sternal cleft

Question 9

What is Pectus carinatum?

Answer 9

Overgrowth of cartilage causing sternum to protude

Most common in males; esp during growth spurt

Can occur congenitally or genetic disorders

Question 10

What is pectus excavatum?

Answer 10

Possibly caused by an overgrowth of costal cartilage which restricts the expansion of ribs and pushes sternum inward

More common in males

Question 11

What is a sternal cleft?

Answer 11

When the sternum doesn’t fuse at the midline causing a sunken chest

Question 12

What is a sternal foramen?

Answer 12

A hole found in the sternum; caused by an anomaly of ossification

Mistaken for a bullet wound

Common acupuncture point, directly over the heart

Question 13

Which set of genes regulates the positioning of limbs along the craniocaudal axis?

Answer 13

HOX genes

Question 14

Which gene initiates the outgrowth of limbs in the forelimb?

Answer 14

TBX5 and FGF factor

Top

​Both are secreted by lateral plate mesoderm cells

Question 15

Which gene initiates limb outgrowth in the hindlimb?

Answer 15

TBX4 and FGF

Both are secreted by lateral plate mesoderm cells

Question 16

Define meromelia, what is it caused by?

Answer 16

Part of limb is missing

Caused by arrest or failure of development due to TBX4,5 genes

Question 17

Define amelia

Answer 17

When a complete limb is missing

Question 18

Define phocomelia

Answer 18

Where the feet and hands arise close to the trunk

Problem with TBX4,5 gene expression

Question 19

Define Mesomelia

Answer 19

Shortened forearm or leg elements

The forearm (radius/ulna, tibula/fibula) is shortened compared w/ humerus

Problem with expression of TBX4,5 signals

Question 20

Define radial club hand

Answer 20

Congenital absence or hypoplasia of radial structures of forearm and hand

Treatment includes stretching exercies and casting

Question 21

What is AER and how is it initially formed?

Answer 21

Apical Ectodermal Ridge - thickened ectoderm on apex

Induced by BMPs after limb outgrowth is initiated

SLPM - somatic lateral plate mesoderm

Question 22

Which regions control limb tissue differentiation?

Answer 22

Apical Ectodermal Ridge (AER)

Zone of Polarizing Activity (ZPA)

….and Progress Zone (PZ) = mitosis and limb lengthening

Question 23

What does the AER express once it’s established?

Answer 23

AER = initial part of limb formation

FGF signals that maintain the Progress Zone (proliferating/motitic mesenchyme cells adjacent to the ridge)

SHH (secreted by ZPA) controls the signaling patterns of FGFs

Question 24

What initiates expression of SHH?

Answer 24

Retinoic Acid

Question 25

What cells produce retinoic acid? (limb formation)

Answer 25

Mesodermal cells located at the base of limb bud

Question 26

Which areas do the following control during limb development

AER

SHH and RA

Answer 26

AER = proximal/distal, dorsal/ventral

SHH and RA = preaxial/postaxial

Question 27

Which signals direct organization of limb bud and patterning of digits?

Answer 27

SHH

Question 28

Define Polydactyly/Supernumerary digits

Answer 28

Extra digits; usually medial or lateral

In foot: lateral

Dominant trait; genetics

Caused by misexpression of RA/SHH or duplication of AER

Question 30

What are the effects of Thalidomide?

Answer 30

Disrupts AER signaling the FRG signal

Causes a small amount of limb growth that ends once a hand or foot develops

Question 31

Define Syndactyly

Answer 31

Webbed fingers/toes

Most common limb abnormality

Failure of programmed apoptosis to separate the digits

Simple dominant or simple recessive

More frequent b/w 3,4 fingers and 2,3 toes

Question 32

Define Brachydactyly

Answer 32

Short digits

Uncommon

Question 33

Cleft Hand/Foot

Answer 33

Lobster-claw (fusion of digits or loss of middle digit)

Question 34

Sirenomelia

Answer 34

“Mermaid Syndrome”

Fusion of either the skin or limbs

Question 35

Achondroplasia

Answer 35

Most prevalent form of dwarfism

Mutation of FGF gene

Abnormal cartilage that’s laid down, pathologic changes at epiphyseal plate, zones of proliferation and hypertrophy are narrow and disorganized

Autosomal dominat

Question 36

Osteogenesis Imperfecta

Answer 36

Brittle bone disease

Mutation on collagen that’s laid down

Kids can be misdiagnosed

Question 37

Talipes Equinovarus

Answer 37

Club foot - most common type

Sole of foot turned medially and is inverted

Question 38

Flexible Talipes Equinovarus

Answer 38

Abnormal positioning or restricted movement of lower limbs in utero

Feet are structurally normal

Usually correct spontaneously

Usually due to in-utero crowdness

Question 39

Rigid Talipes Equinovarus

Answer 39

Abnormal development of the ankle and foot joints during 6th and 7th week

Bony deformities, usually in talus

Usually during bone development