Support

Protect

Body Movement

Hemopoiesis

Mineral Storage

Acid-Base Balance

External and Internal surfaces of flat bone are composed of compact bone, which is dense, rigid, hard, and unyielding.

Middle layer is spongy bone with a diploe layer. (Diploe- honeycomb trabeculae). Shock absorption. No marrow cavity.

Shaft(diaphysis)

Epiphyses

Articular Cartilage (hyaline)

Periosteum

Epiphyseal Plate or line

Long Bones

Cylinder of Compact Bone

Contains marrow (medullary cavity) which is lined with endosteum

Long Bones

Enlarged proximal and distal ends.

Spongy bone covered with layer of compact.

Where joints are covered with articular cartilage to absorb shock (no bone on bone) and create less stress.

Long Bones

peri- around           steum- bone

covers remainder of bone

highly sensitive with nerve activity

outer fibrous layer of collagen fibers continuous with tendons

perforating (Sharpey's) fibers penetrate bone matrix

inner osteogenic layer important for healing and growth

Long Bones

Depends on age

Long Bones

depends on age

Epiphysis (2)

Diaphysis

Periosteum and Articular Cartilage

Compact Bone

Spongy Bone

Medullary Cavity or Marrow Cavity

Yellow Marrow

Endosteum

Nutrient Foramen

Osteoblasts

Osteoclasts

Osteogenic Cells

Osteocytes

Osteogenic Cells

reside in endosteum, periosteum, or central canals

pre-cursor/stem cells/will become something

arise from fibroblasts and become only source for new osteoblasts

multiply continuously and differentiate into amitotic osteoblasts in response to stress or fractures

can only come from osteogenic cells

form and help mineralize organic matter of matrix

creates hardness/firmness

are former osteoblasts that have become trapped in the matrix they formed

in lacunae connected by gap junctions inside canaliculi

signal osteoclasts and osteoblasts about mechanical stresses

develop in bone marrow by the fusion of 3-50 of the same stem cells (osteogenic) that give rise to monocytes found in blood

reside in pits called resorption bays that they have eaten into the surface of the bone (so they can dissolve bone cells)

tear down/remodel bone tissue

Concentric Lamellae

Lacunae

Canaliculi

Perforating (volkman's) Canal

Osteon (blood vessel inside)

Central Canal (Haversian)

Compact Bone

where blood vessels and nerves pass

vertical

Compact Bone

crosses matrix and feeds into central canals

perforates side

Compact Bone

channels, provide nourishment

connect the osteocytes

Communicate between concentric rings

lateral extensions

Compact Bone

space for osteocytes

Compact Bone

Concentric rings

Compact Bone

bone cells

maintain bony matrix

star-shaped; looks like nerve cell

Spongelike appearance formed by rods and plates of bone called trabeculae; spaces filled with red bone marrow

Trabeculae have few osteons or central canals

Provides strength with little weight

Blood and Bone marrow

no osteocyte is far from blood or bone marrow

Soft tissue that occupies the medullary cavity of a long bone or the spaces in the trabeculae of spongy bone

Red

Yellow

Gelatinous

looks like thick blood

mesh of reticular fibers and immature cells

Hemopoietic

found in vertebrae, ribs, sternum, pelvic girdle, and proximal heads of femur and humerus of adults

fatty marrow of long bones in adults

DOES NOT make blood

storage of minerals

created in old age

yellow marrow replaced with reddish jelly

Produces flat bones of skull and clavicle only!

Fibrous membrane develops directly into bone

How all other bones are made

bones start out as cartilage and turn into bones

Has a cartilage phase that IMO did not have

6 step process

Primary Ossification Centers Step 1

taking the cartilage and transforming it to bone

formation of the primary ossification center, bony collar, and periosteum

fills medullary cavity with blood to start the activity in bone

vascular invasion, formation of primary marrow cavity, and appearance of secondary ossification center

Secondary Ossification Center built

enlargement of marrow cavity in epiphysis

establish epiphyseal plate

growth at ends of bones; not in middle

Begins to form in the epiphyses near time of birth

Same stages occur as in primary ossification center

result is center of epiphyseal cartilage being transformed into spongy bone

Hyaline cartilage remains on joint surface as articular cartilage, junction of diaphysis and epiphysis, and each side of epiphyseal plate has a metaphysis

Bone elongation

transitional zone between head and shaft of developing long bone- 5 zones

1) reserve cartilage

2) proliferation

3) hypertrophy

4) calcification

5) deposition

Zone of reserve cartilage

chodrocytes multiply forming columns of flat lacunae

chondro = build

cyte = cell

cell enlargement

hyper = increase

trophy = size

chodrocytes die and columns fill with osteoblasts

osteons formed and spongy bone is created

Bone grows by both appositional growth and by interstitial growth from the cartilage within the bone

athletes or active adults have greater bone mass and density

bones increase in length by interstitial growth of the epiphyseal plate

an open epiphyseal plate has room to grow, but once plate closes and it become an epiphyseal line, the plate cannot grow any longer

in late teens, early 20's- growth plates begin to close in different bones (cartilage depleted and replaced with spongy bone; now called epiphyseal line)

bones increase in width

osteoblasts lay down matrix in layers parallel to the outer surface

osteoclasts dissolve bone on inner surface

bone marrow cavity widens as diameter of bone increases

if one outpaces the other, bone deformities can occur (osteoporosis, Paget disease)

Always Remodeling- bone is dynamic and active tissues all life long

Every week recycle 5-7% of bone mass

Each day 1/2 gram of Ca++ may leave/enter the skeleton

spongy bone is replaced every 3-4 years

compact bone is replaced every 10 or so years

mineral deposits (Ca++ and Pi) made when bone is injured or strength is needed- needed to rebuild

Diet of bones = vitamin C, C, A, and several minerals (Ca++)

dissolving via osteoclasts

bone remodeling is based on the amount of Ca++ and Pi deposition vs. resorption

can be performed by 3 hormones: calitonin, calcitriol, and the parathyroid hormone

happens because of mechanical and gravitational forces (Wolff's Law)

needs Ca++ and Pi to rebuild

Depends on Dietary intake, waste removal, and mineral exchange

based on the amount of Ca++ and Pi deposition vs. their resorption

bone is the reservoir for Ca++ and Pi

Ca++ and Pi homeostasis is vitally important for muscle contraction, blood clotting, nerve communication, etc.

**all about the Ca++ and Pi laid down and removed**

is a normal response

Bone accommodates the forces applied to it by altering its amount and distribution of mass (SAID principle)

SAID = Specific Adaptations to Impose Demands

when body cannot keep up to demands, injuries occur

Perfect ex. of form of the bone follows functional experience

Ex) greater trochanter vs. greater tubercle: trochanter is a huge process that gets bigger from muscles pulling on it

Long Bones are thickest midway along diaphysis

Curved bones are thickest where they tend to buckle

Trabeculae form struts along lines of compression

Large bony projections occur where heavy muscles attach

All match the demands placed upon it

1 hormone that regulates homeostasis of bone

formed from vitamin D produced by the skin -> liver -> kidneys

kidney makes calcitriol

Function: increase blood Ca++ conc. ; makes sure there is enough Ca++ in circulating blood

If constantly lacking calcitriol, bones soften

acts as a hormone but is considered a vitamin (usually added to your diet especially if you don't get much sunlight)

Secreted by thyroid gland (found in neck) when Ca++ conc. rises too high

Functions(2):both lower Ca++ in blood

1) reduces osteoclast activity by as much as 70% in 15 min.

2) Within an hour increases the # and activity of osteoblasts

Important role in children; little effect in adults- deficiency not known to cause disease in adults

Secreted by the parathyroid glands

Released when Ca++ blood level too low

4 Functions: to raise Ca++ levels

Correction for Hypercalcemia

Correction for Hypocalcemia

• 20 or more hormones, vitamins, and growth factors not well understood
• Bone growth especiall rapid at puberty

- hormones stimulate proliferation of osteogenic cells and chondrocytes in growth plate

-adolescent girls grow faster than boys and reach their full height earlier (estrogen has stronger effect)

-males grow for a longer time

• growth ceases when plates close

-steroids may cause premature closing and short adult stature

hema = blood

toma = pool/packet

broken vessels from a blood clot pool form granulated tissue

not used in elderly due to risks of long-term confinement to bed, otherwise cast immobilization

hip fractures are pinned and early walking is encouraged

• Most common bone disease
• Trabeculae thins
• Bones lose mass & become brittle due to loss of both organic matrix and minerals
  
  • -risk of hip fracture, wrist and vertebral column
  • post hip fracture 20% mortality rate
  • deformities in bone are common as well

• Postmenopausal white women at greatest risk

ERT (Estrogen Replacement Theory) slows bone resoprtion, but best treatment is prevention (exercise and Ca++ intake) 1,000 mg/day ages 25-40

Risks: smoking, diabetes, poor diet in Ca++, Vitamin D & C

No cure, can slow its progression