Musculoskeletal System Development PDF

Development of the Musculoskeletal System Terminology and Concepts: Proficiently communicate in the medical community by practicing anatomical terminology and recalling basic anatomical concepts to demonstrate your knowledge. Histology: Interpret micrographs by recognizing important...

Development of the Musculoskeletal System Terminology and Concepts: Proficiently communicate in the medical community by practicing anatomical terminology and recalling basic anatomical concepts to demonstrate your knowledge. Histology: Interpret micrographs by recognizing important components of cells and tissues to more fully understand how organs and organ systems function. Embryology: Trace the development of major organ systems and structures by recalling the major events and processes of embryological development to more fully understand the organization of the developed body and the connections between organ systems.  Lecture Learning Objectives 1. Recall the processes of myogenesis, 7. For the axial musculoskeletal system: including the origin of CT coverings a. List the three locations, and resulting skeletal structures, that form through sclerotome 2. Link chondrogenesis to the development of migration into the trunk bone and three types of cartilage b. Describe how vertebral bodies form from presented in Block 2 material adjacent somites and allow for spinal nerve growth 3. Compare and contrast intramembranous c. Describe how the migration of dermatomes and endochondral bone formation, and myotomes leads to patterns of focusing on innervation and muscle action in hypaxial and epaxial muscles a. The embryonic origin of tissues d. Link Block 2 muscles to their hypaxial and b. The steps involved in each type of osteogenesis epaxial divisions c. How these processes maintain bone marrow 8. Link/chart the muscles and bones of the cavities after birth head to their embryonic origins and type of 4. Identify and define the two types of bone bone formation growth and describe the processes for each 9. Describe limb development focusing on: 5. Identify the zones of endochondral bone Identifying and comparing proximodistal, growth in the histology slide anteroposterior, and dorsovental growth 6. Link the subdivisions of somites to the Major events in weeks ​4-7 musculoskeletal components they will form Limb rotation Formation of joints Muscle, Cartilage, and Bone Formation  LO 1 Myogenesis Muscle Fibers a. Form from mesodermal cells Overlying Connective b. Mesenchymal cell bodies and Tissue nuclei elongate and differentiate into myoblasts Endomysium- formed by external lamina of muscle c. Cells fuse to form elongated, fibers and reticular fibers multinucleated myotubes d. Myotubes differentiate to form striated muscle fibers Perimysium and Some progenitor cells remain on epimysium- produced by periphery of fibers and form satellite cells fibroblasts e. Muscle fibers are surrounded by external laminae, separating them from Most muscles are formed surrounding CT by birth and all by the end of the first year  LO 2 Chondrogenesis Begins during Week 5 a. Mesenchyme condenses to form chondrification centers b. Cells differentiate forming chondroblasts, mitotically divide c. Chondroblasts secrete extracellular matrix d. Chondroblasts become Interstitial mitotic chondrocytes in lacunae activity ceases in mature cartilage Junqueira's Basic Histology (2018), Mesher  LO 3 Osteogenesis Bone develops in CT: mesenchyme and cartilage Bone will continue to be replace throughout life by osteoblasts and osteoclasts A. Intramembranous bone formation (direct) Bone develops in mesenchyme- unorganized CT - from membranous sheaths Forms most axial bones B. Endochondral bone formation (indirect) Bone develops from cartilaginous models Forms most appendicular bones Before We are Born, Moore et al., 2011  Intramembranous Mature Ossification center LO 3 bone Ossification 1. At ossification centers, mesenchyme condenses (CM) and becomes highly vascularized (V) Woven 2. Some cells differentiate into bone osteoblasts (O) and deposit osteoid 3. Inorganic matrix (hydroxyapatite) is deposited on osteoid, organized into woven bone (B) 4. Trapped osteoblasts become osteocytes 5. Woven bone matures into layered lamellar bone on periphery to form surface plates of compact bone Between surface plates, bone remains Distal tibia with pathological spiculated to form spongy bone woven bone Within trabecular bone, mesenchyme differentiates into bone marrow  LO 3 Endochondral Ossification a. During week 5 of development, mesenchymal cells form models of hyaline cartilage, surrounded by perichondrium b. Osteoblasts in cellular layer of perichondrium form a thin overlying layer- bone collar- around the diaphysis c. In central diaphysis, chondrocytes hypertrophy (increase in size) Bone collar cuts off nutrient supply to chondrocytes and apoptosis occurs (cell death) leaving empty cavities; forms marrow cavity d. Blood vessels penetrate periosteum and bone color and, brining osteoprogenitor (d) cells, to form primary centers of ossification Osteoprogenitor cells become osteoblasts or hematopoietic cells (blood cells in bone marrow) e. Ossification occurs: osteoblasts deposit bone matrix (osteoid and hydroxyapatite), replacing cartilage Most diaphyses are ossified at birth Wk 5 UNSW Website Junqueira's Basic Histology (2018), Mesher  LO 3/4 Endochondral Ossification Secondary Centers of Ossification a. Form in epiphyses after birth Develop in a similar manner to primary centers, on previous slide b. Trabecular bone remains instead of medullary cavity formation ____________________________________ As bone continues to develop after birth, Cartilage only remains in two locations a. Growth/epiphyseal plates b. External epiphyses as articular cartilage Bone spicules in medullary cavity increase in size due to osteoblastic activity Resorption of bone by osteoclasts maintain the presences of spongy bone and size of cavity Junqueira's Basic Histology (2018), Mesher Bone Growth  LO 4 Bone Growth A. Periosteal/appositional growth Growth in diameter Occurs in compact bone along diaphyseal shaft B. Endochondral/interstitial growth Growth in length Occurs at epiphyseal plate at ends of bone Junqueira's Basic Histology (2018), Mesher  LO 4 Periosteal/Appositional Growth Occurs between diaphyseal bone and periosteum/endosteum Osteoblasts from osteogenic/cellular layer of periosteum build osteons, forming compact bone Osteoblasts from endosteum form trabecular bone surrounding medullary cavity Osteoclasts resorb bone to maintain medullary cavity  LO 4/5 Endochondral/Interstitial Growth Occurs at epiphyseal plate which is displaced proximally or distally, lengthening Epiphyseal plate 1. Chondrocytes in epiphyseal plate proliferate (undergo mitosis), pushing 1 older cells from metaphysis towards the diaphysis 2. Chondrocytes hypertrophy then apoptosis occurs, leaving enlarged 2 empty openings 3 3. Surrounding matrix (cartilage) hardens through calcification 4. Calcified cartilage ossifies (becomes 4 bone) Vascular invasion brings osteoprogenitor cells- will deposit bone on cartilaginous matrix (ossification) What is a possible outcome of trauma to the epiphyseal plate? Junqueira's Basic Histology (2018), Mesher  1 LO 4/5 1. Reserve cartilage- small chondrocytes at end of bone 2. Zone of proliferation- stacked chondrocytes 3. Zone of hypertrophy- enlarged 4 spaces 1 2 5 2 3 3 4 4. Zone of calcified cartilage- empty, large lacunae 5. Zone of ossification- 5 osteoprogenitor and osteoblasts surrounded by osteoid Musculoskeletal Embryology  Development of Somites Develop from intraembryonic mesoderm which is subdivided based on location and developmental trajectory a. Lateral plate mesoderm b. Intermediate mesoderm c. Paraxial mesoderm Located on adjacent to notochord Differentiates to form pairs of cuboidal bodies called somites Form in cranial to caudal direction 1. Sclerotome- bone and cartilage 2. Myotome- skeletal muscle 3. Dermatome- dermis embryology.med.unsw.edu.au Before We are Born (2020), Moore  LO 6 Differentiation of Somites Transverse section through embryo Begins during 4th week of development in mesoderm of trilaminar embryo Paraxial mesoderm→ Somites A. Dermomyotome Dermatome- Dermis and accessory organs Folded embryo Myotome- migrate and form muscle B. Sclerotome: migrate and form bone and CT UNSW Website Patterned Development Patterned Development Development of the Axial Musculoskeletal System  LO 7a Development of the Trunk Mesodermal cells from the sclerotome These condensed cells form the migrate and condense in three areas: centrum (vertebral body), vertebral around the notochord arches, and the costal processes around the neural tube (future ribs). into the lateral body wall. Harrell, K. M., & Dudek, R. (2019). Lippincott¯ illustrated reviews: anatomy, 1e. Lippincott Williams & Wilkins, a Wolters Kluwer business. https://premiumbasicsciences-lwwhealthlibrary-com.forward.marian.edu/book.aspx?bookid=2793&sectionid=0  LO 7b Development of Trunk Cells of the centra (future vertebral body) will be separated (von Ebner fissure) by developing spinal nerves which will grow towards and into myotomes (future axial muscle) The cranial portion of each sclerotome will fuse with the caudal portion of the adjacent, inferior sclerotome Harrell, K. M., & Dudek, R. (2019). Lippincott¯ illustrated reviews: anatomy, 1e. Lippincott Williams & Wilkins, a Wolters Kluwer business. https://premiumbasicsciences- Spinal nerves will continue to grow lwwhealthlibrary- com.forward.marian.edu/book.aspx?bookid=2793 towards myotome &sectionid=0  LO 7c Development of Trunk- Myotomes Myotomes divide and migrate, taking along spinal nerve branches Creates pattern innervation to muscle groups Myotomes will form Epaxial division muscles Hypaxial division muscles  LO 7c Myotome Divisions Epaxial division Muscles dorsal to vertebral column Carry dorsal ramus of spinal nerves Hypaxial division Muscles ventral to vertebral column4 Carry ventral ramus of spinal nerves Epaxial Most go on to form non- Hypaxial segmented muscles, but some reflect somite organization and remain segmented (ex., intercostals) Before We Are Born, Moore et al., 2020  LO 7c Epaxial Division Posterior, segmented muscles of the main body axis, extensor muscles of neck and vertebral column What are some examples of neck or vertebral extensors? Gray’s Basic Anatomy (2018). Drake et al. Epaxial Hypaxial Before We Are Born, Moore et al., 2020  LO 7c Hypaxial Division Anterior/ventral, segmented muscles of the main body axis, flexor muscles of neck and vertebral column a. Cervical myotomes form muscles of the neck Scalene muscles Longus colli, longus capitis Infrahyoid muscles Geniohyoid Epaxial b. Thoracic myotomes form anterolateral Hypaxial axial muscles Lateral and ventral flexors of the vertebral column c. Lumbar myotomes Quadratus lumborum d. Sacrococcygeal myotome Pelvic diaphragm  Think- Pair- Share How does this patterned development aid in the interpretation of symptom presentation? How do muscle reflexes (e.g., patellar ligament reflex) relate to segmentation and migration of muscles and their innervation?  LO 8 Development of the Crania The neurocranium develops from the sclerotome Most viscerocranial elements are derived from neural crest cells (head mesenchyme) that migrate into pharyngeal arches embryology.med.unsw.edu  LO 8 Development of Neurocranium From paraxial mesoderm> somite > sclerotome Endochondral Base of cranium- Occipital Sphenoid Ethmoid Temporal- all parts except squama Intramembranous Calvaria Frontal Parietal Squama of temporal Before We are Born (2019), Moore et al.  LO 8 Development of Viscerocranium Mostly from neural crest cells Nearly all intramembranous Maxilla Mandible Nasal bone Zygomatic Before We are Born (2019), Moore et al.  LO 8 Head, Neck, and Tongue Muscles- Migrating Hypaxial Cells Occipital myotomes form muscles of the face and deep neck Cells migrate into pharyngeal arches Pharyngeal arches form during 4th week; cells migrate here to form structures Form muscles of facial expression, mastication, pharynx, and larynx Cells migrate from occipital divisions to also form the muscles of the tongue Musculoskeletal Limb Development  LO 9 Development of the Limbs Limbs will develop in weeks 4 through 8 Begin as limb buds; upper limbs develop slightly ahead of the lower limbs Grow from lateral plate mesoderm- specifically somatopleure Myogenic precursor cells in limb buds Migrate into limb buds dermamyotome and undergo epitheliomesenchymal transformation via induction Cells will proliferate causing limb buds to grow  LO 9 Development of the Limbs Limb buds grow on three axes Proximodistally Apical ectodermal ridge (AER) induces growth and development in limb mesenchyme Anteroposteriorally Zone of polarizing activity is induced by AER to control anterior/posterior limb patterning (radial/ulnar) Dorsoventral Induced by dorsal and ventral epidermis of limb buds, respectively Future flexors and extensors Mesenchymal cells proximal to AER differentiate into blood vessels and cartilaginous bone models https://en.wikipedia.org/wiki/Zone_of_polarizing_activity  LO 9 Development of the Limbs Week 4 Limb buds first appear Week 5 Limb buds are present Week 6-7 Hand and foot plates develop Digital rays form AER at the tip of each digital ray induces primordia of bones (phalanges) Apoptosis of loose mesenchyme between developing digits occurs Cartilaginous models are formed End of week 7 Limb rotation occurs  LO 9 Limb Rotation Prior to rotation, dermatomes, myotomes, and their innervation have straight segmentation patterns Beginning of week 7, limbs are extended ventrally: Orientation Digit 1 cranial Flexors mm. ventral Digit 5 caudal Extensors dorsal End of week 7, rotation of the limbs occur Upper limb rotates 90 degrees laterally Lower limb rotates 90 degrees medially “thumbs out, knees in”  LO 9 Development of the Limbs Week 9 Synovial joints form Week 12 + Osteogenesis of long bones is occurring All limb bones form through endochondral ossification Grow in size via appositional and endochondral growth Bone modeling occurs in a proximal distal direction As long bones form, myoblasts aggregate and form large muscle masses Separate into dorsal (extensor) and ventral (flexor) components in both limbs  LO 9 Development of Joints Week 6 Interzonal (condensed) mesenchyme forms Week 8 Have the appearance of adult joints Fibrous joints Interzonal mesenchyme between developing bones differentiates into dense CT Cartilaginous joints Interzonal mesenchyme between developing bones differentiates into hyaline cartilage or fibrocartilage Synovial joints Interzonal mesenchyme 1. Differentiates into joint capsular ligaments 2. Degenerates forming joint cavity 3. Differentiates into synovial membrane Before We are Born (2019), Moore et al. LO 10  Think-Pair- Share Using the information provided on bone development, what steps do you think are involved in the healing of bone?