The Skeletal System
Bone Classification
By shape
1)Long bones- femur/humerus-_____________________
2)Short bone-____________ - tarsal/carpal
3)Flat bones- parietal bone- __________________
4)Irregular bones-______________--variety of shapes vertebra
5)Round bones- patella- _______________associated with tendons and adjacent to
joints
Anatomy of a long bone
Epiphysis- end of bone that ______________ (forms a joint) with another bone
Periosteum- outer layer of a bone –______________, vascular-covers all parts of
bones except for the ________________________
Diaphysis- _________of the bone
Articular cartilage- hyaline cartilage that coats the articulated portion of the
epiphysis
Anatomy of a long bone
Diaphysis- composed of ___________- tightly packed- __________,continuous
extracellular matrix
Epiphysis- composed of ___________-branching bony plates- irregular connecting
spaces-keeps bones____________
Medullary cavity- composed of_____________–long tube in the __________-semi
rigid-hollow
Endosteum- _____layer of cells –lines the medullary cavity
Marrow- inside the _____________cavity
Microscopic Anatomy of a Bone
Remember
Osteocytes-___________________
Lacunae-surround the __________________
Canaliculi-channels in bone that allow ___________and cytoplasmic process is to
communicate between cells
Haversian canal or Osteon-inside are blood vessels/nerves
Lamellae-concentric layers around ____________canal
Bone Development and Growth
Bones form by replacing existing connective tissue in one of 2 ways:
1)Intramembranous Bones-originate between ________layers of connective tissues
2)Endochondral Bones-begin as masses of _____________that bone replaces later.
Intramembranous Bones
Broad, flat bones of the _________
During development, membranes like layers of _________________are located at
the sites of the __________________
1) Some primitive connective tissue cells _________and ______________into bone
forming cells called _____________________
2) Osteoblasts become_________ in the membrane and deposit
____________around themselves
3) Spongy bone tissue begins developing in all directions within the primitive
connective tissues
4) Over time, cells outside of the membranous tissues become the ______________
5) Osteoblasts on the inside of the ____________form a layer of
______________over the surface of the newly formed spongy bone
6) ______________________completely surrounds osteoblast(lacunae) it becomes
an osteocyte
Endochondral Bones
Most of the bones develop this way
They develop from masses of ______________shaped like future bony structures
In the long bone, the changes begin in the___________ of the diaphysis
1)Cartilage _________________down and disappears
2)periosteum forms from the _________________that encircles the developing
diaphysis
3) Blood vessels and osteoblasts from the periosteum __________the disintegrating
cartilage and spongy bone forms in its place ______________is called the primary
ossification center
4) Osteoblasts from the periosteum deposit a thin layer of _______________around
the primary ossification center
6) epiphyses of the developing bone remain _______________and continue to ____
7) Then ___________________appears in the epiphyses and spongy bone forms in
all directions
8) As spongy bone is ___________in the epiphysis and diaphysis a band of
cartilage called the _________________develops and remains between the 2
ossification centers
Ossification Centers
Epiphyseal Plate
 the cartilaginous cells of the epiphyseal plate include layers of
___________that are undergoing__________ and making new cells
9) As these cells ________and _________________forms around them, the
cartilaginous plate thickens, ________________the bone.
10) At the same time, ______________accumulate in the extracellular matrix
adjacent to the ___________cartilaginous cells and as the old extracellular matrix
____________ the cells begin to die
Epiphyseal(e pif a seal) Plate Damage
11) In time, large __________________called osteoblasts break down the calcified
extracellular matrix
12) These large cells originate in the ___________when certain single nucleated
white blood cells fuse
13) Osteoclasts ________________that breaks down the inorganic component of
the calcified matrix and their ____________________digest the organic components
14) After, osteoclasts remove the extracellular matrix, the ______________invade
the region and deposit new bone tissue in replace of the ___________________
Endochondral Bones
 A long bone continues to ___________while the cartilaginous cells in the
epiphyseal plates are _____________
 Once the ossification centers of the epiphysis and diaphysis meet, the
epiphyseal plates ossify and lengthening growth stops
 A developing long bone ___________as the compact bone is deposited on
the outside, just beneath the periosteum.
 As the ____________forms on the surface, osteoclasts ______other bone
tissue on the inside
The __________________becomes the medullary cavity
The bone in the central regions of the epiphyses and diaphysis remains __________
Endochondral Development
 Homeostasis of _____________________
After the intramembranous and endochondral bone form, the actions of the
_______________________continue to remodel them throughout your lifetime
Osteoclasts-__________________ bone matrix
Osteoblasts- ______________bone matrix
Hormones keep this cycle of ______________and ___________________
As a result, the total mass of bone tissue of an adult skeleton normally remains
nearly constant
___________of bone calcium is exchanged each year
Bone Fracture
1) Blood vessels within it and its periosteum
______________________________
2) Blood escapes from the broken vessels spreads through the
_______________and soon forms a blood clot or _______________________
3) Vessels in surrounding tissues dilate, ______________________the tissues
4) Within days or weeks the _________________________and large numbers of
osteoblasts from the _________________invade the hematoma
5)Osteoblasts divide rapidly in the regions close to the new blood vessels,
building spongy bone
6)Fibroblasts build masses of ______________________
7)Phagocytic cells begin to remove blood clot, dead , ______________
8) Osteoclasts appear and reabsorb bone fragments
9) In time, fibrocartilage fills the gap between the ends of the bones called a
cartilaginous callus
10) Cartilaginous callus breaks down and osteoblasts invade the area and bony
callus fills area
11) Most often more bone is produced than needed but the osteoclasts remove
the excess and the final result is a bone shaped like the old
Bone Function
 Shape, support and protect
 ________________________________
 House tissues that produce blood cells
 Store inorganic salts

Support and Protection
Examples
Ribs- protects the _______________________
Skull-protects ________________and brain
Pelvic girdle protects the ___________________and internal reproductive organs
Body Movement
Whenever limbs or other body parts move, ____________________interact as a
simple machine called a lever
Lever has 4 components
Fulcrum or pivot point
An object is moved against a resistance
A force that supplies ________________of the bar
Levers- the arm bending
The ____________ represents the rigid rods
The fulcrum is the ____________________
Hand moves against the ______________provided by the weight
Force is supplied by the _______________on the anterior side of the arm
Blood Cell Formation
____________________-- blood cell formation
Begins in the ___________________and continues then in your liver, spleen and
even later in your ___________________________
Marrow- soft, netlike mass of connective tissue found in the ________________of
the long bones
Marrow
Yellow and red
Red- forms the red blood cells (erythrocytes), white blood cells(leucocytes) and
blood platelets. Red color b/c of the red, oxygen carrying pigment ____________in
the red blood cells
In an infant, red marrow is found in most bones as you get older ______________
replaces most of it
Yellow-_____________, it is not active in blood cell formation
 In an adult, the red marrow is found in the ________________of ribs, skull,
sternum, clavicles, vertebrae and hipbones
If body needs more blood it can convert back into red marrow and revert back to
yellow if there is a surplus of blood
Storage of Inorganic Salts
 The extracellular matrix of bone tissue is rich in_____________, mostly
calcium phosphate
 When blood is ____________, parathyroid hormone stimulates the
osteoclasts to break bone down and release calcium salts from the
extracellular matrix into the blood
 A high blood calcium level will inhibit the
________________________________ form the thyroid gland will tell the
osteoblasts to make more bone tissue, storing calcium in the extracellular
matrix
 Maintaining adequate calcium levels is important to____________________,
nervous impulse conduction, blood clotting
Bone also contains_____, Na, K, CO3 ions and can accumulate Pb, Sr and Ra
Osteoporosis
 The skeletal system loses ______________________content as osteoclast
activity increases
 The infected bones fill with __________________that enlarge and fill with
fibrous and fatty tissue
 Bones can fracture because they are no longer able to hold the __________
Causes:
low intake of dietary calcium
_________________
Decrease in estrogen production
Genetic predisposition
Drinking _________________________