Limbs and Back: Week Five Flashcards
What is the meaning of Amelia?
Total absence of limbs
What is the meaning of Meromelia?
Partial limb loss
What is the meaning of sirenomelia?
Fusion of limbs
What is mutated in Marfan’s syndrome?
FBNI gene. This is autosomal dominant.
What is the difference between dominate and recessive?
Dominant is one gene and recessive is two genes.
What is the meaning of ectrodactlyly?
Total absence of digits
What is the meaning of syndactyly?
Failure of differentiation
What is the meaning of brachydactyly?
Shortened digits
What is the meaning of macrodactyly?
Enlarged digits
What does the Sclerotome form?
Vertebrae and ribs
What is the function of Neurotrophin-3?
Directs the dermatome to become the dermis.
Which two protien combine to activate MYOD?
Wnt (activating) and BMP (inhibitory)
What is the function of sonic hedgehog and noggin?
Induce Sclerotome function
What does the lateral somitic frontier separate?
The somites and the lateral plate mesoderm. It separates the two domains: primaxial and abaxial.
Where is are the primaxial and abaxial domains located?
The primaxial is the region around the neural tube. The abaxial is the parietal layers of the lateral plate.
Name some muscles that are derived from the primaxial layer
Scalene, Geniohyoid, paravertebral, intercostal, rhomboids, levator scapular, latissimus dorsi
Name some muscles that are derived from the abaxial layer
Infrahyoid, pectoralis major and minor, external and internal oblique, transverse abdominus, sternalis, rectus abdominus, pelvic diaphragm, distal limb muscles
Where does the latissimus dorsi derive from?
Primaxial layer
Where do the rhomboids derive from?
Primaxial layer
Were does the levator scapula derive from?
Primaxial layer
Where do the intercostal derive from?
Primaxial layer
Where does the pectoralis major and minor derive from?
Abaxial layer
Where does the external and internal oblique derive from?
Abaxial layer
The primaxial area has somite derived cells. What does the Abaxial area contain?
Parietal layer of the lateral plate and somites that have migrated across.
What is the difference between epaxial and hypaxial?
Abaxial is innervated by the dorsal primary rami. Hypaxial is innervated by ventral primary rami.
What does the hypaxial area form?
Diaphragm, abdomen, and limbs
What does the epaxial area form?
Vertebra, ribs and skull
What are limb buds and when do they become visible?
They are undifferentiated mesoderm which is covered in ectoderm. Appear at day 24.
When does limb morphogenesis occur?
Week 4-8
Where does the upper limb buds originate from?
Ventrolateral body wall
The appearance of mesenchyme is the first sign of condensation. Where does mesenchyme differentiate from?
Dorsolateral mesoderm of somites. It is also from parietal layer of lateral plate.
What shape is the ectoderm that surrounds the mesenchyme core of limb buds?
Cuboidal
What is the undifferentiated ectoderm at the dorsal border called?
The apical ectodermal ridge
What is the function of FGF10?
Limb outgrowth.
What does the dorsal ectoderm express?
Signalling molecule called radical fringe.
What does the ventral ectoderm express?
Transcription factor called engrailed-1
What is the function of FGF4 and FGF8?
Maintenance of undifferentiated zone
Which end does retonic acid start differentiation?
Proximal
What does the AER promote and prevent?
Promotes mitosis and prevents differentiation.
What is polydactyly a mutation of?
HOX genes
The terminal portion of buds will become flattened to hand-plates and footplates. They are separated by proximal segments by constriction. A second constriction will divide them into digits. At which week does this usually occur at?
6
The development of the limb proceeds proximodistally into three parts. What are the three parts and what do they compose of?
Stylopod: humerus and femur
Zeugopod: Radius, Ulna, Tibia, Fibula
Autopod: carpals, metacarpals, digits, tarsals, metatarsals
What is the positioning of limbs regulated by?
HOX genes is a craiocaudal sequence (9-13)
What transcription factor is produced in forelimb?
TBX-5
What transcription factor is produced in hindlimb?
TBX-4 and PITX1
By what day is digit separation complete?
Day 56
The limbs rotate during week seven. Which way do the upper and lower limbs rotate?
Lower limb: medially
Upper limb: laterally
At what week do cartilage models form?
6
when does ossification begin?
Week 8
Where is BMP4 secreted and what is its function?
Secreted by ectoderm and induces production of WNT by dorsal neural tube.
Where is sonic hedgehog derived from?
Notochord and floor or neural tube
Which mesoderm are voluntary head Muslces derived from?
Paraxial mesoderm
What is Sarcopenia?
The loos of skeletal mass and strength due to aging.
What is Cachexia?
Severe muslce wasting due to disease
What is indirect fracture healing?
This is the formation of bone via a process of differential tissue formation until skeletal continuity is restored.
What is the first stage of indirect fracture healing?
Fracture Hematoma and Inflammation: Broken vessels form a clot and there is swelling and inflammation. Platelets and immune cells are involved and this process occurs 6-8 hours after injury.
What is the second stage of indirect fracture healing?
Fibrocartilage Callus: new capillaries organise the hematoma into granulation tissue, forming a procallus. Fibroblasts and oestrogenic cells invade. Chondrocytes make fibrocartilage and collagen is produced. Collagen helps bind bone together. This last 3 weeks.
What is the third stage of indirect fracture healing?
Bone hard callus: osteoblasts make woven bone and this occurs around 3 weeks after injury. This lasts around 3-4 months.
What is the fourth stage of indirect fracture healing?
Bone remodelling: osteoclasts remodel wove bone into compact bone and trabecular bone. This lasts up to 6 months.