By

Dr. Noura El Tahawy

http://www.slideshare.net/nmohmed

Functions� Support

� Protection

� Assistance in movement

� Mineral homeostasis

� Blood cell production

� Triglycerides storage

Functions of bones1. Bones form the skeleton which is the framework of the body.

2. The skeleton supports the softer tissues and provides points of attachment

for most skeletal muscles.

3. The skeleton provides mechanical protection for many of the body's

internal organs, reducing risk of injury to them. It forms boundaries of

cranial, thoracic and pelvic cavities. Thus it protects the brain, lungs, heart

etc.

4. Bones permit movement of the body as a whole or part of the body, by

formation of joints, which are moved by muscles.

5. Bone tissues store several minerals, including calcium and phosphorus.

When required, bone releases minerals into the blood facilitating and

maintaining the balance of minerals in the body.

6. Bone contains red bone marrow in which blood cells develop.

7. Bone acts as an important chemical reserve. With advancing age, some

bone marrow changes from red bone marrow to yellow bone marrow

which consists mainly of adipose cells and a few blood cells.

Components � Skull

� Vertebral column

� Auditory ossicles

� Hyoid

� Ribs

� Sternum

Components � Upper limb bones

� Pectoral (shoulder) girdle

� Lower limb bones

� Hip girdle

Types of bones� Long bone

� Short bone

� Flat bone

� Irregular bone

� Seasamoid bone

Types of bones

Long bone � Greater length than width

� Mostly compact bone tissue

� Curved

� Vary in size

� Includes:

Femur Ulna

Tibia Radius

Fibula Phalanges

Humerus

Long bone: Femur

Forms of bone

Short bones� Cube shaped

� Equal lenghth and width

� Mostly spongy, except on surface it is compact

� Includes:

carpal bone (except pisiform)

tarsal bones (except calcaneus)

Flat bones� Thin

� 2 layers of compact surrounding a spongy layer

� Large areas for muscle attachment

� Includes:

Cranial bones

Sternum

Ribs

Scapulae

Irregular bones� Complex shape

� Amount of spongy and compact varies

� Includes:

Vertebrae

Hip bone

Certain facial bones

Calcaneus

Sesamoid bones� Develop in certain muscles tendons

� Protect the tendons from excessive wear

Structure of bone� Diaphysis

� Epiphysis

� Metaphysis

� Articular cartilage

� Periosteum

� Medullary cavity

� Endosteum

Structure of

bone:

Spongy bone tissue

Types of ossification

By

DR. Noura El Tahawy

Bone formation� Intramembranous ossification

(flat bones)

� Endochondral ossification

(long bones)

Bone Growth & Remodeling

Growth

Appositional Growth = widening of bone

� Bone tissue added on surface by osteoblasts of the periosteum

� Medullary cavity maintained by osteoclasts

Lengthening of Bone

� Epiphyseal plates enlarge by chondroblasts

� Matrix calcifies (chondrocytes die and disintegrate)

� Bone tissue replaces cartilage on diaphysis side

Endochondral ossification

Endochondral ossification

� Endochondral ossification is the gradual replacement of

cartilage by bone during development. This is responsible

for formation of most of the skeleton. Osteoblasts arise in

regions of cartilage called ossification centers. They

develop into osteocytes, which are mature bone cells,

embedded in the calcified (hardened) part of the bone

known as the matrix.

Intramembranous ossification

� Intramembranous ossification is the transformation of the

mesenchyme, embryonic cells, into bone. During early

development, the embryo consists of three primary cell layers,

ectoderm on the outside, mesoderm in the middle and

endoderm on the inside. Mesenchyme cells constitute part of

the embryo's mesoderm and develop into connective tissue

such as bone and blood. The bones of the skull derive directly

from mesenchyme cells by intramembranous ossification.

� Most bones arise from a combination of intramembranous

and endochondral ossification. Mesenchyme cells develop

into chondroblasts and increase in number by cell division.

Chondroblasts enlarge and excrete a matrix which hardens due

to presence of inorganic minerals. Chambers form within the

matrix and osteoblasts and blood-forming cells enter these

chambers. The osteoblasts then secret minerals to form the

bone matrix.

Vertebral Column

Vertebral Column

Vertebra

Typical vertebra

�Skull

�Skull

Ribs

Sternum

Upper limb bones� Humerus

� Ulna and radius

� Carpal bones

1- Scaphoid 2- Lunate

3- Triquetrum 4- Pisiform

5- Trapezium 6- Trapezoid

7- Capitate 8- Hamate

� Metacapals

� phalanges

Pectoral girdle� Clavicle

� Scapulae

Bones of the upper

limb

Lower limb bones� Femur � Tibia � Fibula � Tarsal bones

1- Talus 2- Calcaneum3- Navicular 4- Cuboid5- Medial cuniform6- Intermediate cuniform7- Distal cuniform

� Metatarasals� Phalanges

Hip girdle � Hip bone

1- ilium

2- pubis

3- sacrum

Bones of the lower limb

Bones of the lower limb

Bones of the foot

Bones of the foot

Thanks

http://www.slideshare.net/nmohmed