Osseous Tissue and the Skeletal System
Functions Support Storage- minerals and fats Blood cell production- red and
white Protection Leverage
Bone Shapes Long bones- long and slender, ex.
Arm, forearm, thigh, and leg Flat bones- have thin almost
parallel surfaces, ex. Sternum, ribs, scapula
Osseous Tissue and Bone structure Compact bone- dense solid bone, surface Spongy bone- open network, interior Long bone
Diaphysis (shaft) is surrounded by compact bone, which around the yellow marrow cavity
Epiphysis- contains the spongy bone and red bone marrow
Metaphysis- narrow zone between
MarrowYellow marrow- stores fat cellsRed marrow- stores red, white,
and stem cells
Matrix of bone Calcium crystals- hard but inflexible, good
at withstanding compression Collagen fibers- very strong under tension
(pulling), stronger than steel Crystals form on fiber network,
combination makes bone strong, somewhat flexible, and resistant to shattering
Cells in bone Osteocytes- mature bone cell, maintain
protein and mineral content Osterblasts- immature bone cells, produce
new bone matrix Osteoprogenitor cells- stem cells that
produce osteoblasts Osteoclasts- remove bone matrix to
release Ca and phosphate Osteoblasts continually create new bone,
while the osteoclasts breakdown bone
Bone Growth and Development Bony skeleton begins to grow 6 weeks after
fertilization, cartilage at first Ossification- process of replacing existing tissue
with bone Intramembranous Ossification- bone is formed
directly from fibrous connective tissue, flat bones of the skull
Endochondral Ossification- bone is formed by replacing cartilage, most bones develop this way
Bone Growth Osteoblasts continually add bone at the
diaphysis side of the metaphysis At the epiphysis side of the metaphysis new
cartilage is formed So as the both occur bone gets longer During puberty, sex hormones stimulate
osteoblasts to produce bone faster than cartilage, so the epiphyseal cartilage gets smaller and bone gets longer, this happen until around 25 until there is no cartilage left
Appositional Growth Increases the diameter of bone Osteoprogenitor cells become osteoblasts
and grow new matrix Fun fact: About 1/5 of your skeleton is
recycled and replaced each year!
Effects of exercise on bones Exercise creates an electrical field in
bone, and stimulates osteoblasts to make new bone
More powerful muscles corresponds to larger bumps on bones
Heavily stressed bones become thicker and stronger compared to bone w/no stress which becomes brittle and weak
Hormonal & Nutritional Effects on bone Must have Calcium and phosphate in diet Calcitriol, helps w/ absorption of ca from
digestive tract (made from vitamin D) Vitamin C is essential for building of collagen Vitamin A stimulates osteoblast activity, B and K
help make proteins Growth hormone- stimulate growth Thyroxine- increase rate of osteoblast activity