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our supporting structure

The skeletal system includes:

bones and associated cartilage, tendons and ligaments

Why are bones resilient?

because of their elastic protein matrix, and strong because of mineral salts deposited in this matrix

The skeleton works together with ____
to create movement


Bones are made of ______ _______

living tissues

The stone like appearance comes from _________________

mineral salts like calcium phosphate

The 5 functions of the skeletal system are: ___________________

Support surrounding tissues
Protect vital organs
Provide levers for muscles to pull on generating movement
Manufactures blood cells (hematopoiesis)
Stores mineral salts (calcium, phosphorus) and fats

Poiesis means: __________


The skeletal systems connective tissues are: ___________



Environment in which bone develops in fetus
found at ends of bones and in joints
Provides smooth surface for bone to bone areas


attach bones to bones


attach muscles to bones

Bone develops from: _____________

osteoblast cells

Osteoblast cells originate in the: ___________________

periosteum and endosteum of the bone.

Osteoblasts mature to become: ____________


Deposition of bone depends on: ____________

strain or pressure on the bone (exersize)

Step 1: Broken Bones

A broken bone stimulates osteocytes (mature osteoblasts) to proliferate.

Step 2: Broken Bones

They secrete large quantities of protein matrix, to form new bone

Step 3: Broken Bones

Osteoclasts are present in bone cavities, derived from the immune system they cause bone reabsorbtion, and remodelling.

Step 4: Broken Bones

Osteoclasts remove bone from the inner side and so remodel bone as after a break and can make a crooked bone straight

The two types of ossification are: _______ and _______

(both result in cancellous and compact bone)

Maintaining Bone requires calcium whose concentration is controlled by 2 hormones of the endocrine system:



causes calcium release into blood


results in calcium storage in bones

What happens to excess calcium?

excreted by kidneys and digestive system

Cancellous bone means: _______

spongy bone

Intramembranous Ossification

Dense connective tissue membrane is replaced by inorganic salts like calcium, forming bones.
This connective membrane becomes the periosteum, over a layer of compact and a layer of spongy bone.
Only cranial bones are formed this way, complete ossification of the skull is not complete until fontanels close after birth.

Endochondral Ossification

This is when bone develops inside cartilage environment.
Osteoblasts become completely surrounded by protein matrix and become mature bone cells or osteocytes
Produces all other bones of the body


forming new bones
By end of 3 months fetus skeleton is completely formed but mostly cartilage
Begins ossification and grows as osteoblasts invade cartilage

Compact bone

Dense and strong
Contain "Haversian canals"
Blood vessels run parallel to surface of the bone
These are surrounded by concentric rings of bone (lamella)
Between rings of bone are Lacunae cavities containing osteocyte connected to the central haversian canal by canaliculi.
Horizontal open areas contain blood vessels and fluid that nourish bone cells (osteocytes)

Functions of havesian cannals:

dense and strong with Haversian systems of central canals surrounded by rings of bone. Rings separated by lacunae, connected by canniculi. Horizontally blood vessels run through these canals bathing osteocyte with 02 and food, excreting waste

. Cancellous or spongy bone

Found at ends of long bones and forms the center of all other bones
Spongy appearance created by meshwork of bone (trabeculae) with spaces filled with bone marrow

What else does Cancellous bone do?

Function as open spaces where bone marrow filled with red bone marrow performs hemapoesis. In adults found in vertebrae, sternum, pelvis, end of humerus (upper arm) and femur (thigh). Areas decrease with age.

Bone Marrow is found in:

the spaces of certain spongy or cancellous bones

Red marrow whose functions is...

Hematopoiesis (formation of RBC, WBC & Platelets). Contains blood cells in all stages of development.

Red marrow is found in the:

ribs, sternum, vertebrae, and pelvis

Yellow Marrow is:

connective tissue containing fat cells.

Yellow Narrow is found:

chiefly in shafts of long bones.

Bones are classified by these 4 shapes:


Structure of a long bone includes:

Epiphyseal growth line


shaft filled with yellow marrow


flared portion



Epiphyseal Growth Line

where longitudinal growth occurs

Longitudal growth of bones for girls stops at what age?


Longitudal growth of bones for boys stops at what age?


Maturation and remodeling of skeleton continues till _____ for women and men.

21 years

Short bones

Lack a long axis- consist of spongy cancellous bone covered by thin compact layer.

Shaort bones have a:

Somewhat irregular shape.

Short bones are NOT:

merely shorter versions of long bones.

Flat Bones:

Thin bones found wherever need for extensive muscle attachment.

The shape of a flat bone is:

usually curved

Where do you find flat bones?

sternum, ribs, scapula, parts of pelvic bones skull

What shape do irregular bones have?

Very irregular

Examples of irregular bones are:

vertebrae, ossicles of ear

Irregular bones are:

Spongy bone enclosed by thin layers of compact bone.

What shape is a Sesamoid bone?

small rounded bones

Sesamoid bones are:

enclosed in tendon and fascial tissue

Sesamoid bones are found:

located adjacent to joints

Examples of the Sesamoid bones are:

Patella is largest, some wrist and ankle bones

Processes are:

any obvious boney prominences

Examples of Processes are:

spine, condyle, tubercle, trochlea, trochanter, crest, line, head, neck


any depressions or cavity in or on a bone
suture, foramen, meatus, sinus, sulcus

Functions of fossa and processes include:

muscle attachment, articulation, passageways

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