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