Classification of bones (Skeleton):
I. According to their position in the body:
Functions of Skeletal system:
1. It provides a specific shape to the human body.
2. It provides the human body with a central axis.
3. It transmits and supports the human body weight.
4. It forms the joints of the locomotor system of the human body.
5. It protects the vital organs eg. the skull protects the brain
6. It provides a wide surface area for muscular attachment.
7. It forms the blood elements in the bone marrow.
8. It stores calcium salts.
Axial skeleton
- Skull,
- Mandible
- Sternum,
- Ribs
- Vertebral
column
vertebral column.
Appendicular
(peripheral)
skeleton
Bones of upper
and lower limbs
II. According to their shape:
Structure and
Site
Example of
bones
Function
1. Long bone In upper and lower
limbs
- Hummers
- Femur
Movement
2. Short bone In hand and foot - Carpal bone (in
hand)
- Tarsal bones in
foot
Resist compression
forces
3. Flat bone Skull Bones of skull roof Protection
4. Pneumatic
bone
- Bones containing
air called air
sinuses.
-They are present in
skull bones
surrounding the
nose.
Para-nasal sinuses
in the skull
1- They decrease the
weight of skull.
2- Resonance of voice.
5. Irregular bone Bones with
projecting processes
Vertebrae Muscle attachment
6. Sesamoid
bone
Small nodules of
bones which are
embedded in some
muscle tendons
near their insertion
or origin
Patella (largest
sesamoid bone),
embedded in the
tendon of the
quadriceps femoris
muscle in front of
knee joint.
They diminish friction
between tendons and
underlying bones
A.The Bones of the Upper Limb
Bone Site Structure Joints related
Clavicle Anterior bone of
shoulder girdle
- It is formed of medial
and lateral ends.
- It lies horizontally in the
human body.
1. Sternoclavicular joint: saddle synovial joint between
the medial end of the clavicle and the manubrium of
the sternum.
2. Acromioclavicular joint: plane synovial joint between
the lateral end of the clavicle and the acromial process
of the scapula.
Scapula Posterior bone
of shoulder
girdle
It is a triangular flat
bone.
1. Shoulder joint: Ball and socket synovial joint between
the glenoid cavity and the head of humerus.
2. Acromio-claviuclar joint: plane synovial joint
between the acromial process and the lateral end of
the clavicle.
Humerus
Bone of the arm
- It is formed of upper
end including head,
Shaft and lower end.
- It lies vertically in the
Human body.
1. Shoulder joint: as mentioned above.
2. Elbow joint: Hinge synovial joint between:
Lower end of humerus articulating with trochlear notch
of ulna and superior surface of head of radius.
Radius Lateral bone of
the forearm
- It is formed of upper
end including head,
shaft and lower end.
- It lies vertically in the
Human body.
1. Elbow joint: Mentioned before.
2. Superior radioulnar joint: It is pivot synovial joint
between the head of radius and ulna.
3. Wrist joint: It is ellipsoid synovial joint between lower
end of radius and carpal bones (scaphoid and lunate).
4. Inferior radioulnar: It is formed by head of ulna
articulating with the ulnar notch of radius.
Ulna Medial bone of
the forearm
- It is formed of upper
end including trochlear
notch, shaft and lower
end including head.
- It lies vertically in the
Human body.
1. Elbow joint: Mentioned above.
2. Superior radioulnar joint: Mentioned above.
3. Inferior radioulnar joint: Mentioned above.
Bones of
the hand
1. Carpus
(Bones of Wrist)
2.Metacarpus
(Bones of Palm)
3.Phalanges
Bones of
Fingers)
1. Carpus (8 bones)
2. Metacarpus
(5 bones)
3. Phalanges
(14 bones)
- In the medial 4 fingers there are 3 phalanges for each
finger (proximal, middle and distal) with 2 interphalangeal
joints in between.
- The thumb has 2 phalanges (proximal and distal) with
interphalangeal joint in between.
B.The Bones of the lower Limb
Bone Site Structure Joints related
Hip Bone of pelvic girdle - It is formed of
parts: ilium, ischium
and pubis.
-The 3 parts meet at
a cup-shaped
depression called
acetabulum.
1- Sacro-iliac joint: between the articular
surfaces of the ilium and sacrum.
2- Symphysis pubis: between the bodies of the
2 pubic bones.
3- Hip joint: between the acetabulum and the
head of the femur.
Femur Bone of the thigh - It is the longest and
strongest bone in the
human body
- It is formed of upper
end including the
head and lower end
including 2 condyles
and shaft.
1- Hip joint: Ball and socket synovial joint
between the head of femur and the
acetabulum.
2- Knee joint: Bicondylar synovial joint between
the condyles of femur above and the condyles
of tibia below and patella infront.
Fibula
Lateral bone of the
leg
- It is formed of upper
end including the head,
shaft and lower end
including the lateral
malleolus.
- It lies vertically in the
human body.
1. Superior tibiofibular joint: It is plane synovial joint
between the head of fibula and lateral condyle of
tibia.
2. Inferior tibiofibular joint: It is fibrous joint
(syndesmosis) between the lateral malleolus and
lower end of tibia.
3. Ankle joint: It is hinge synovial joint between the
lateral malleolus and talus of foot.
Patella It is the largest
sesamoid bone in
the body
is triangular in shape It articulates with the femoral condyles to form part of
knee joint.
Tibia Medial bone of the
leg
- It is formed of upper
end including 2
condyles, shaft and
lower end including the
medial malleolus..
- It lies vertically in the
human body.
1- Knee joint: The upper surfaces of tibial condyles
articulate with the femoral condyles.
2- Superior tibiofibular joint: A facet on the lateral
condyle of tibia articulates with head of fibula.
3- Inferior tibiofibular joint.: The lateral surface of
the lower end of tibia articulates with the lower end
of fibula.
4- Ankle joint: The inferior surface of the lower end of
tibia and the medial malleolus articulate with the
talus of the foot.
Bones of
the foot
1. The Tarsus:
2.Metatarsus:
skeleton of middle
part of the foot, The
3- Phalanges:
skeleton of the toes.
1. The Tarsus: 7 bones
arranged into two rows.
2.Metatarsus: 5 bones
- Each toe has 3 phalanges except the big toe which
has 2 phalanges.
- Each tarsal bone is formed of base, shaft and head.
C.Thoracic Cage
Boundaries:
1. Anteriorly: Sternum.
2. Posteriorly: 12 thoracic vertebrae.
3. On both sides: 12 pairs of ribs with their costal cartilages.
I. The Sternum
It has 3 parts:
A- Manubrium:
- It articulates with the body of the sternum to form Manubriosternal angle (sternal angle).
- It articulates with the clavicle forming sternoclavicular joint and with first and second
costal cartilages.
B- Body:
- Above: it articulates with manubrium above and with xiphoid process below.
- Laterally: it articulates with 2-7 costal cartilages.
C- Xiphoid process:
- Above: it articulates with the body of the sternum.
- On both sides: it articulates with 7th costal cartilages.
II. The Ribs
They are 12 pairs of ribs, they are classified into:
1- True ribs: The upper 7 ribs are attached to the sternum by costal cartilages.
2- False ribs: The lower 5 ribs are not attached to the sternum.
3- Floating: Ribs: The last 2 ribs "No. 11 and 12". They have free anterior ends (not
attached anteriorly).
III. The Vertebral Column
Average adult length:
A- In male: about 70 cms.
B- In female: about 65 cms.
Components of the vertebral column:
1. Vertebrae: comprise about 3/4 of its length. They are divided into:
a- Separate vertebrae: 7 cervical, 12 thoracic and 5 lumbar.
b- Fused vertebrae: 5 sacral vertebrae (sacrum) and 3(±1) coccygeal vertebrae
(coccyx).
2. Intervertebral discs: comprise about 1/4 of its length, each disc is formed of 2 parts:
D. The Skull
The skull is the skeleton of head, it is formed of 21 bones (5 single and 8 paired)
articulating together, by fibrous joints called sutures.
1- Frontal, 2 parietal and occipital.
2- Three sutures:
a- Sagittal suture: Between the 2 parietal bones.
b- Coronal suture: Between the frontal and the 2 parietal bones.
c- Lambdoid suture: Between the occipital and the 2 parietal bones.
3- Two points:
a- Bregma: Between the coronal and sagittal suture, it the site of the anterior
fontanelle in the foetus which ossifies at 18 months after birth.
b- Lambda: Between the lambdoid suture and the sagittal suture, it the site of the
posterior fontanelle in the foetus which ossifies at the 3 months after birth.
The Mandible
It is the skeleton of the lower jaw which is formed of a body and 2 rami.
The junction between the ramus and the body of mandible called angle of
mandible.
The skull
4. ARTICULAR SYSTEM (JOINTS)
The joint is the contact between two bones or more together:
Classification of Joints
There are 3 types of joints.
I. Fibrous Joints:
Fixed joints in which the surfaces of bones are connected together by fibrous tissue.
There are 3 types:
Syndesmosis Gomphosis Sutures
Present in inferior tibio-
fibular joint.
The lower end of tibia
and fibula are
connected together by
fibrous tissue called
interosseous ligament
Present in teeth.
The roots of teeth are
connected to their
sockets in mandible
and maxilla by fibrous
tissue called
periodontal ligament.
Present in skull.
The bones of skull are
connected together by a
thin layer of fibrous tissue
called sutural ligament.
They obliterated in old
age
II. The Cartilaginous Joints: In these joints the surfaces of the articulating bones
are connected together by cartilagenous tissue.
They are 2 types:
a- Primary cartilaginous joint: It is a temporary joint formed of plate of hyaline
cartilage between the articulating bones (epiphysis and diaphysis).
Site: At the ends of the growing long bones between the epiphysis and diaphysis.
It is immobile joint which disappears in adulthood by ossification.
b- Secondary cartilaginous joint: The articulating bones are separated by a disc
of white fibrocartilage which is permanent. The surfaces of the articulating bones
are covered by a thin layer of hyaline cartilage. It is slightly mobile joint present
in the midline.
Sites: Intervertebral discs and symphysis pubis.
III. Synovial Joints: They are freely mobile joints present mostly in the limbs
Characteristics (structure) of synovial joints:
A- Fibrous capsule: The synovial joint is surrounded completely by a strong fibrous
capsule which is lined by synovial membrane. This capsule is supported and
strengthened by strong ligaments.
B- Articular cartilage: Hyaline cartilage covers the articular surfaces of bones. It is
very smooth and is lubricated by the synovial fluid. It has no blood and nerve supply.
C- Joint cavity: It is a potential cavity containing very small amount of synovial
fluid.
D- Synovial membrane: Thin, moist and glistening membrane that covers all
structures inside the joint except the articular surfaces, it also lines the fibrous
capsule. It secretes and absorbs the synovial fluid.
E- Synovial fluid:
Pale yellow viscous fluid similar to egg-albumin. It has 3 functions:
1- Lubricates the articular cartilage. 2- Reduces erosion of articular cartilage.
3- Helps nutrition of articular cartilage.
F- Ligaments:
Extracapsular and intracapsular ligaments which support and strength the joint.
Types (varieties) of Synovial Joints
According to the
axis of movement. According to shape of the articular surface
I. Uni-axial joints 1- Hinge e.g. elbow joint-ankle joint
2- Pivot e.g. superior R.U. joint
II. Bi-axial joints
1- Condylar e.g. knee - T.M. joint
2- Ellipsoid e.g. wrist joint
3- Saddle e.g. carpometacarpal joint of thumb-
sternoclavicular joint
III. Multi-axial joints Ball and socket e.g. Hip-shoulder
IV. Non-axial joints Plane joints e.g. superior tibio-fibular joint.
Movements of the Synovial Joints
1- Flexion: Approximation of two ventral aspects (bending).
2- Extension: Straightening; the two ventral surfaces move away from each other.
3- Abduction: Movement of the limb away from the middle line. In the fingers
moving away from the middle finger, in the toes moving away from the 2
nd toe.
4- Adduction: Movement of the limb towards the middle line. In the fingers moving
towards the middle finger, in the toes moving towards the second toe.
5- Rotation: Medial or lateral rotation of the limb around a vertical axis.
6- Circumduction: Combination of all above movements.
7- Supination: The lateral rotation of the forearm.
8- Pronation: The medial rotation of the forearm.
9- Inversion: The sole of foot is directed inwards.
10- Eversion: The sole of foot is directed outwards.
11- Opposition: The thumb is opposing (come in contact) the other 4 fingers.