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Skeletal

System

 

I).  Function

A).  support

B).  protection

C).  movement

D).  mineral storage

E).  blood cell formation   

II). Skeletal Cartilage:  Hyaline Cartilage

A). articular cartilage

B). costal cartilage

C). nasal cartilage

long bone anatomy

III). Long Bone Anatomy:

A). diaphysis

B). epiphysis

The epiphysis is usually covered in articular cartilage

C). epiphyseal line or plate:

IV). Bone Structure

A). compact bone

structural units called osteons.

Ostean consists of long cylinders that run parallel to the long axis of the bone.

osteon

Structure of an osteon

1). lamella:  concentric ring

2). haverson’s canal: runs through the core .

3). perforating canals: Connect the Haverson’s canals

4). lacuna: contain osteocytes (mature bone cells)

Types of osteocytes

i). osteoblasts: build bone

ii). osteoclasts: consume or remove bone

 B). spongy bone

honeycomb or network of flat pieces filled with:

1). red bone marrow:

2). yellow bone marrow:

C). periosteum

The periosteum is supplied with nerve fibers, lymphatic vessels and blood vessels, which enter the bone.

It also contains osteoblasts (bone builders) & osteoclasts (bone breakers)

 

V). bone development

A). osteogenesis: Bone tissue formation

1. cell types

i. oseteoblasts: build calcium matrix

ii. osteoclasts: reabsorb calcium matrix

 

2. ossification: formation of bone

Ossification Replacing cartilage with bone matrix

bulletIntramembranous Ossification occurs in flat bones only
bulletEndochondral ossification occurs in long bones and all other bones

3). Differences between Intramembranous Ossification & Endochondral Ossification

a. long bones ossify along hyaline cartilage models

 b. flat bones follow membrane like layers of unspecified connective tissue.

 

c. flat bones ossify inside with spongy bone and work outward to compact bon

d.  long bones ossify on the outside with compact bone and move inward to spongy bone.

 

B). Intramembranous Ossification of flat bones

1). An ossification center appears in the connective tissue.

2). A bone matrix is secreted in the fibrous membrane.

3). Woven bone and periosteum form.

4). Bone collar of compact bone forms and red bone marrow appears.

     

 

C). Endochrondral Ossification

1). Formation of hyaline cartilage model

2). A bone collar forms around the diaphysis of the hyaline cartilage

3). Cartilage in the center of the diaphysis calcifies and then cavitates

4). The periosteal bud invades the internal cavity and spongy bone forms.   

                            The bud contains a nutrient artery and osteoclasts

5). The diaphysis elongates and a medullary cavity forms

6). The epiphysis ossify.

*Hyaline cartilage remains on the growth plate and the articulating surface.

 

VI). Bone Remodeling

Weekly recycle 5% to 7% of bone mass. With a replacement of spongy bone every 4 years and a replacement of compact bone every 10 years.

 
bullet

osteoblasts:   Bone deposit occurs at injury sites and for strengthening

bullet

osteoclasts:   Bone resorption

 

Controlled by:

1). Negative feedback

Ca++loop that maintains blood calcium.

It involves the hormones: Parathyroid Hormone and Calcitonin.

PARATHYROID HORMONE

if blood Ca++ is low

 ß

Parathyroid Hormone is released

 ß

Ca++ is reabsorbed from bone by osteoclasts

 

CALCITONIN HORMONE

if blood Ca++ is high

 ß

 Calcitonin is released

 ß

Ca++ is absorbed into the bone by osteoblasts

 

2). Mechanical & gravitational forces.

Wolf’s Law

Bone grows where stressors are placed on it.

 

VII). Bone Fractures

A).  Classification of fractures

1). non-displaced fractures

2). displaced fractures

3). complete fracture

4). incomplete fracture

5). open (compound) fracture

6). closed (simple) fracture

7). closed reduction

8). open reduction

 

B).  Types of fractures

1). green stick

2). partial or fissure

3). comminuted fracture

4). depressed

5). transverse fracture

6). oblique fracture

 

VIII). Repair of Fractures

STEP1:  A hematoma forms over the fracture site.

STEP2:  Fibrocartilaginous callus formation.

STEP3:  Bony callus formation

STEP4:  Bone remodeling

Mnemonic

Go C3PO

 

(use 3 Cs)

 

Greenstick
Open
Complete
Closed

Comminuted
Partial
Other

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