Summary Into to bone development - human biology

Lecture 8

Bone development, Growth and Repair
- Bones forms by replacing existing connective tissues in the fetus
o Intramembranous bones
 Develop from sheet-like layers of undifferentiated connective tissue
 Turn into a cell type -> Osteoblasts -> bone builder
 Osteoclasts -> bone breaker
 Osteoblasts deposit a bony matrix around themselves in all directions
forming spongy bone
 Osteocytes is the mature type of Osteoblasts

o Endochondral
 Develop as hyaline cartilage models shaped like the future bones
 Cartilage is then replaced with bone tissues
 Most of the bone of the skeleton fall into this category
 Growth plate (Epiphyseal plates) is the place allow the bone to grow
longer
 Disintegrating cartilage is invaded by Blood vessels and osteoblasts that
first form spongy bone at the primary ossification center
 Secondary ossification center appears later in the epiphyses




 On X-ray: cartage will not show in white colour -> so if do not see gap in
x-ray, we can tell that this could be a grown-up

Homeostasis of Bone Tissue
- Osteoclasts resorb and osteoblasts deposit bone throughout life, in a process called
bone remodeling

, - An average of 3% to 5% of bone calcium is exchanged each year
- The remodeling process is controlled by hormones that regulate blood calcium level

Factoring affecting Bone development
- Nutrition: Vitamin D is needed for Ca absorption
o By Food
o By supplement
- Hormonal secretions:
o Growth hormone – stimulates division of cartilage cells of the epiphyseal plate
o Sex hormone – stimulate ossification of the epiphyseal plates to end growth in
height
- Physical exercise: muscle pull on bones at attachment sites, stress the bone -> increase
thickness and strength

Skeletal organization
- Axial skeleton – consists of the bony and cartilaginous parts that support the and
protect the head, neck and trunk
o Skull: cranium and facial bones
o Hyoid bone: supports the tongue and aids in swallowing
o Vertebral column
o Thoracic cage: ribs and sternum
- Appendicular skeleton – consists of the bones of the upper and
lower limbs
o Pectoral girdle: clavicle and scapula
o Upper limbs: humerus, ulna, radius, carpals, metacarpals,
and phalanges
o Pelvic girdle: 2 hip bones
o Lower limbs: femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges

Skull
- Made up of 22 bones
- Provide attachments for muscles and contains air filled paranasal sinuses that reduce its
weight and increase vocal resonance
o 8 cranial bones *Cranium bone – encloses and protects the brain*
 Frontal bone (include the supraorbital foramen)
 (coronal suture)
 Parietal bones x2 (Squamous suture) Temporal bone x2
 (lambdoid suture)
 Occipital bone