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Bone Development. Unit 3, lesson 3. Bone Development. Osteogenesis (a.k.a. ossification ) is the process of bone tissue formation. In embryos this leads to the formation of the bony skeleton. In children and young adults, ossification occurs as part of bone growth.
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Bone Development Unit 3, lesson 3
Bone Development • Osteogenesis(a.k.a. ossification) is the process of bone tissue formation. • In embryos this leads to the formation of the bony skeleton. • In children and young adults, ossification occurs as part of bone growth. • In adults, it occurs as part of bone remodeling and bone repair.
Formation of the Bony Skeleton • Before week 8, the human embryonic skeleton is made of fibrous membranes and hyaline cartilage. • After week 8, bone tissue begins to replace the fibrous membranes and hyaline cartilage. • The replacement of fibrous membranes with bone is called INTRAMEMBRANOUS OSSIFICATION. • The replacement of hyaline cartilagewith bone is known as ENDOCHONDRAL OSSIFICATION
Growth in Bone Length • Epiphyseal cartilage of the epiphyseal plate divides to create more cartilage • Diaphyseal cartilage of the epiphyseal plate is transformed into bone. This increases the length of the shaft. • And you grow!!
At puberty, growth in bone length is increased dramatically by the combined activities of growth hormone, thyroid hormone, and the sex hormones. As a result osteoblasts begin producing bone faster than the rate of epiphyseal cartilage expansion. Thus the bone grows while the epiphyseal plate gets narrower and narrower and ultimately disappears. A remnant (epiphyseal plate) is visible on X-rays (do you see them in the adjacent femur, tibia, and fibula?)
VERTEBRAL COLUMN • Also called the spine, backbone, or spinal column • Functions to: • Protect the spinal cord • Support the head • Serve as a point of attachment for the ribs, pelvic girdle, and muscles • The vertebral column is curved to varying degrees in different locations • Curves increase the column strength • Help maintain balance in the upright position • Absorb shocks during walking, and help protect the vertebrae from fracture
VERTEBRAE • Composed of a series of bones called vertebrae (Adult=26) • 7 cervicalare in the neck (small) • 12thoracic are posterior to the chest cavity (medium) • 5lumbar support the lower back (large) • 1 sacrumconsists of five fused sacral vertebrae • 1 coccyx consists of four fused coccygeal vertebrae
SPINE CONDITIONS • Various conditions may exaggerate the normal curves of the vertebral column • Scoliosis – lateral imbalance of the spine (bent left or right) • Kyphosis – arch in the upper spine (ky = high) • Lordosis – arch in the lower spine (lor = low)
INTERVERTEBRAL DISCS • Found between the bodies of vertebrae • Functions to: • Form strong joints • Permit various movements of the vertebral column • Absorb vertical shock
Vertebral Column (Regions) • Cervical Region • Cervical vertebrae (C1–C7) • The atlas(C1) is the first cervical vertebra • The axis(C2) is the second cervical vertebra • Thoracic Region • Thoracic vertebrae (T1–T12) • Articulate with the ribs • Lumbar Region • Lumbar vertebrae (L1–L5) • Provide for the attachment of the large back muscles • Sacrum • The sacrum is a triangular bone formed by the union of five sacral vertebrae (S1–S5) • Serves as a strong foundation for the pelvis • Coccyx • The coccyx, like the sacrum, is triangular in shape • It is formed by the fusion of usually four coccygeal vertebrae • This is the “tail bone”
