The
Skeletal
System
Honors A&P
Do Now:

How would your life be different if you had an
exoskeleton (skeleton on the outside)?
Name the bones:
1. Frontal
2. Maxillary
3. Mandible
4. Vertebrae‘
5. Clavicle
6. Humorous
7. Sternum
8. Rib
9. Radius
10. Ulna
11. Coxal/pelvic girdle
12. Sacrum/coccyx
13. Carpals
14. Metacarpals
15. Phalanges
16. Femur
17. Patella
18. Fibula
19. Tibia
20. Tarsals
21. Metatarsals
22. phalanges
Functions





Support
 Structural support
 Framework for attachment
Protection
 Surrounds soft tissues and organs
Storage
 Calcium and phosphate reserve
 Energy reserves (triglycerides in yellow marrow)
Hematopoeisis
 Rbc, wbc, and platelet production in red marrow
Hormone production


Osteocalcin – regulates bone formation
Leverage for movement
 Change magnitude and direction of forces generated by skeletal
muscles
 Tendons connect muscle to bone
Classification of Bones

Axial vs. Appendicular skeletons

Long Bones



Short Bones



Cube shaped
 Ex. Carpals, tarsals
Sesamoid bones
 Form in tendon
 Ex. Patella & psiform
Flat Bones



Longer than they are wide
Ex. Limb bones
Thin and broad
Ex. Ribs, sternum, scapulae, ribs, cranial bones
Irregular Bones

Complex shapes

Ex. Vertebrae and hips
What is NOT part of the Appendicular
skeleton?
1.
2.
3.
4.
5.
Hip
Scapula
Fibula
Coccyx
Clavicle
20%
1
20%
20%
2
3
20%
4
20%
5
What is the tailbone called?
1.
2.
3.
4.
5.
6.
7.
Sacrum
Coccyx
Patella
Scapula
Clavicle
Hyoid
Talus
14%
1
14%
2
14%
14%
14%
3
4
5
14%
14%
6
7
What is the shin bone called?
1.
2.
3.
4.
5.
6.
7.
8.
Sacrum
Patella
Tibia
Fibula
Radius
Ulna
Talus
Calcaneous
12%
1
12%
2
12%
12%
12%
12%
3
4
5
6
12%
12%
7
8
What type of bone is a rib?
1.
2.
3.
4.
5.
Long
Short
Flat
Irregular
Sesmoid
20%
1
20%
20%
2
3
20%
4
20%
5
What type of bone is a phalange?
1.
2.
3.
4.
5.
Long
Short
Flat
Irregular
Sesmoid
20%
1
20%
20%
2
3
20%
4
20%
5
What type of bone is a patella?
1.
2.
3.
4.
5.
Long
Short
Flat
Irregular
Sesmoid
20%
1
20%
20%
2
3
20%
4
20%
5
What type of bones are the tarsals?
1.
2.
3.
4.
5.
Long
Short
Flat
Irregular
Sesmoid
20%
1
20%
20%
2
3
20%
4
20%
5
Features of Long Bones

Diaphysis

Central shaft of thick collar of compact bone

Medullary Cavity



Compact bone







Covers outer surface of bone w dense irregular
tissue
Inner layer osteoblasts and osteoclasts
Secured by Sharpey’s fibers (collagen)
Nutirent foramen (formina)


Network of bony rods w/ spaces
Found in epiphysis
Periosteum


Expanded ends covered w/ articular cartilage
Epiphyseal line in adults is remnant of
epiphyseal plate
Spongy (cancellous) bone


Dense/solid
Found in diaphysis
Epiphysis


Contains Yellow Bone marrow
Loose connective tissue
Opening in periosteum for bv, nerrves, and lymph
vessles
Endosteum

Layer of osteoblasts that lines marrow cavity
Skeletal Cartilage



Skeletal Cartilage

Consists of mostly water

Avascular, no nerves

Surrounded by perichondrium (dense
irregular) w/bv
Types

Hyaline

Most abundant

Articular cartilage , costal cartilage
nasal cartilage, and respiratory
cartilage

Elastic

External ear & epiglottis

Fibrocartilage

Highly copmressable

Mensci & vertebral discs
Growth

Flexible matrix to accomadate mitosis

Appositional growth – from
perichondrium

Interstitial growth – from chondrocytes
within
Microscopic Features of Compact Bone

Haversian system (aka
osteons)


Lamella



connect bv of periosteum to
haversian canal
Osteocytes


blood vessels and nerve fibers
Perforating canals (aka
Volkmanns canals)


concentric matrix tube
Twister resistor
Haversian (central) canal


arranged in cylinders
reside in lacunae
Canaliculi

connect lacunae to central canal
Microscopic Features of Bone (cont’d)

Spongy Bone

Found in flat, short and irregular bones and
epiphysis of long bones

Trabecule (rods create network)





Lamellae arrangemnet
No central haversian cancal
All 3 bone cell types
In flat bones, the spongy bone is called
dipole
Chemical composition

Inorganic: 65% mineral salts –
Hydroxyapatite


Calcium Phosphates account for hardness
Other 1/3 Osteoid - organic
components

Cells, collagen, and ground substance
Bone Cytology

Osteogenic cells (osteoprogenitor)


Osteoclasts





produce new bone (osteogenesis) , collagen
promotes Ca deposits in bone matrix
Osteocytes




giant multinucleated cells that secrete acids and enzymes to dissolve bony matrix
and release Ca (osteolysis)
Secrete lysosomal enzymes to digest organic matrix and HCl to make Ca
soluable
Phagocytic digestion
Osteoblasts


bone stem cells
Mature bone cells occupy lacunae
Monitor and maintain bone matrix
Stimulate osteoblasts and osteoclasts
Periosteal and endosteal cells

Flat cells on bone surface
Compact Bone vs. Spongy Bone
(Ground bone)
(Cancellous bone)
Note the absence of osteons in
spongy bone
The outer covering of each bone, made
from fibrous connective tissue, is called
1.
2.
3.
4.
5.
Epiphysis
Diaphysis
articular cartilage
Periosteum
Endosteum
20%
1
20%
20%
2
3
20%
4
20%
5
Which cells are responsible for
building new osseous tissue?
1.
2.
3.
4.
5.
6.
7.
Osteocytes
Osteoclasts
Osteoblasts
Osteogenic cells
Perisoteal cells
Endosteal cells
Macrophages
14%
1
14%
2
14%
14%
14%
3
4
5
14%
14%
6
7
Which tissue type houses red bone
marrow?
1.
2.
3.
4.
5.
6.
Compact bone
Periosteum
Diaphysis
Osteon
Spongy bone
Lamella
17%
1
17%
2
17%
17%
3
4
17%
5
17%
6
Which tissue type has lamellae?
1.
2.
3.
4.
Compact bone
Spongy bone
All of the above
None of the above
25%
1
25%
25%
2
3
25%
4
Spongy bone contains all of the
following except
1.
2.
3.
4.
trabeculae.
collagen fibers.
true osteons.
hydroxyapatite
25%
1
25%
25%
2
3
25%
4
Do Now:



List 4 things in your car….
Complete the following sentence for each
item:
A ___(item)____ is like the skeletal system
because_________________
Ossification (Osteogenesis): Bone Formation

Begins at 6 weeks
(in utero)



Composed of fibrous
membranes and
hyaline cartilage
Flexible and resilient
to accommodate
mitosis
Intramembranous
Ossification

Bone develops within
membranes of
connective tissue

Cranial bones &
clavicles
Mesenchymal cells
form fiberous
connective
membranes

Endochondrial Ossification
Bone replaces cartilage
1.
Primary Ossification center –
infiltrated w/bv causing
mesenchymal cells to become
osteoblasts
2.
Bone Collar forms from osteoblasts
3.
Chondroctyes within shaft enlarge
and calcify and die… opening up a
cavity
4.
Periosteal bud (bv, nerves,
osteoblasts, redmarrow elements)
invades internal cavity


5.
6.
osteoclasts erode calcified matrix
osteoblasts secrete trabeculae
Diaphysis elongates – by hyaline
cartilage followed by ossification
Epiphysis ossify from secondary
ossification centers where spongy
bone is retained
Bone Growth

Post-natal growth of long bones




Growth in width (thickness)


Cells at epiphyseal plate rapidly divide pushing epiphysis away from diaphysis
Cartilage is replaced by bone on diaphysis side, and requires continues remodeling
Epiphyseal plate closure occurs at about 18 in females and 21 in males
Osteoblasts in periosteum secrete bone on external surface as osteoclasts remove bone on the
endosteal surface
Hormonal Regulation

Growth hormone (hGH) stimulates growth at epiphyseal plate

Sex hormones promote gender specific development of the skeleton
Which of these statements is not true
about intramembranous bones?
1.
2.
3.
4.
They begin with a
cartilage model.
They form between
flat sheets of
connective tissue.
Skull bones are
formed in this way.
Osteoblasts deposit
new bone along
blood vessels within
the layers
25%
1
25%
25%
2
3
25%
4
When cartilage is produced at the epiphyseal side
of the metaphysis at the same rate as bone is
deposited on the opposite side, bones
1.
2.
3.
4.
5.
become shorter.
become thicker.
become more
porous and
weaker.
grow wider.
grow longer.
20%
1
20%
20%
2
3
20%
4
20%
5
Intramembranous ossification
1.
2.
3.
4.
is the most common way
bones are formed.
begins within a
connective tissue
membrane.
is responsible for long
bone formation.
begins with a
cartilaginous precursor.
25%
1
25%
25%
2
3
25%
4
Osteocytes maintain contact with the
blood vessels of the central canal
25%
25%
25%
25%
through
1.
2.
3.
4.
periosteum.
interstitial
lamellae.
concentric
lamellae.
canaliculi.
1
2
3
4
Bone Homeostasis

Remodeling

Every week recycle 5-7% of bone mass



Bone deposit occurs at injured or stressed sites



Spongy bone 3-4 years
Compact bone 10 years
Vit C, D,A, Ca, P, Mg, Mn are needed
Bone resorption – osteoclasts
Wolf’s Law – bone grows or remodels in
response to the demands placed on it

Long bones thickest in middle where bending stress
Bony projections where muscles attach

Inactivity (even brief) causes atrophy (degeneration)


Prenatal Requirements

Prenatal – minerals absorbed from mother (often loses
bone mass)

Consume Ca and P from diet

Vitamin D3 allows absorption of Ca and P
Vitamin A and C needed for osteoblast activity

Homeostasis and Mineral Storage

Calcification – deposition of
calcium salts, regulated by hormones




99% Ca deposited in skeleton
Ca+ ions used Nervous &
Muscular System
Ca absorbed from intestine
under control of vitamin D
Ca ion conc.regulated

Parathyroid hormone (PTH)


elevate Ca levels in body fluids
(bones become weaker)
Calcitonin

depresses Ca levels in body fluids
(bones become stronger)
Injury and Repair




Fracture – any crack or break in a bone
Healing can take from 4 months to over a year!
Fracture hemotoma – large blood clot closes injured bv
External and internal calluses – thickenings resulting
from mitotic divisions
Classification of Fractures

Displaced (not aligned) or Non-displaced (normal
position)

Complete (through) or incomplete

Linear (parallel) or transverse (perp to bone)

Compound (open sticking through skin) or simple
(closed)
Types of Fractures
Comminuted – 3 or more fragments
Compression – crushed (vertebrae)
Spiral – due to twisting (athletes)
Depression – skull
Greenstick – children (partial
break/bend)
http://www.youtube.com/watch?v=us
n8ltc1FWU&playnext=2&list=PL27A7
948A76FDD768
Fracture Repair

Reduction – realignment of broken bone ends



Hematoma forms




Capillaries grow into hemotoma, phagocytic cells clean area
Fibroblasts secrete collagen
Chondroblasts secrete matrix, psteoblasts form spongy bone
Bony callus forms


Bv rupture and hemmorhage, clot forms, bone cells die
Fibrocartilage callus forms


Closed – physician positions bones and immobilizes
Open – bones secured w/pins or wires
Trabeculae appear, endochondrial ossification
Bone remodeling occurs

Excess removed, compact bone replaces shaft walls
What is a complete break of a bone
and it sticking through the skin?
1.
2.
3.
4.
5.
Dislocation
Greenstick
Compound
Fracture
Sprain
Simple Fracture
20%
1
20%
20%
2
3
20%
4
20%
5
Aging and Skeletal System





Reduction in bone mass occurs between ages 30 40
Women lose ~8% skeletal mass per decade
Men lose ~3% per decade
Epiphyses, vertebrae, and jaws most vulnerable
Osteoperosis – decrease in estrogen increases
osteoclast activity (so does smoking); other causes
include lack of Ca+ in diet, inactive lifestyle, and
certain medications
Which of the following factors is
NOT believed to affect bone growth?
1.
2.
3.
4.
5.
Exercise and gravity
Genetic factors
Stimulation by hormones such
as growth hormone,
testosterone, thyroid
hormone, and estrogen
Increased intake of protein
Diet deficiencies in vitamins D
and C, and minerals such as
calcium
20%
1
20%
20%
2
3
20%
4
20%
5
How would increasing the proportion of organic
molecules to inorganic components in the bony
matrix affect the physical characteristics of bone?
20%
1.
2.
3.
4.
5.
20%
20%
2
3
20%
20%
The bone would be less
flexible.
The bones would be
more brittle.
The bones would be
more flexible.
The bones would be less
compressible.
The bones would be
stronger.
1
4
5
Mary is 50 years old. During a checkup, a bone scan
reveals that portions of her skeleton show signs of
osteoporosis. Her physician suggests hormone therapy
after reviewing the test results. What hormone is
25%
25%
25%
25%
prescribed for Mary?
1.
2.
3.
4.
Parathyroid
hormone
Calcitonin
Estrogen
Growth hormone
1
2
3
4
Bone Markings
Bone Markings