Bone DevelopmentUnit 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.1. The replacement of fibrous

membranes with bone is called INTRAMEMBRANOUS OSSIFICATION.

2. The replacement of hyaline cartilage with 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!!

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?)

At puberty, growth in bone length is increased dramatically by the combined activities of growth hormone, thyroid hormone, and the sex hormones.

• 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

VERTEBRAL COLUMN

Vertebral Column

• Composed of a series of bones called vertebrae (Adult=26)– 7 cervical are in the neck (small)– 12 thoracic are posterior to the chest cavity (medium)– 5 lumbar support the lower back (large)– 1 sacrum consists of five fused sacral vertebrae– 1 coccyx consists of four fused coccygeal vertebrae

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)

• Found between the bodies of vertebrae• Functions to:– Form strong joints– Permit various movements of the vertebral

column– Absorb vertical shock

INTERVERTEBRAL DISCS

Vertebral Column

• 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”

Vertebral Column (Regions)

Vertebral Column

So what is back pain?

Seriously…what is back pain?