Skeleton system- bones and their number with detailed description.

SKELETON
SYSTEM
PREPARED BY:
MS. BHARTI SHARMA
M.SC NURSING

SKELETON
 The skeleton is the bony framework of the body. It forms the
cavities & fossae ( depression or hollow) that protect some
structures from the joints & give attachment to the muscles.
 The skeleton is described in two parts: Axial (80) and Appendicular
(126) skeleton.
 The human skeleton consists of 206 bones, most of which are paired
with one member of each pair on the right and left sides of the body.
 The infants have more than 206 bones because some of their bones
( sacrum & coccyx) fuse later in life.

The Axial Skeleton:
 It consists of :
skull,
vertebral column,
sternum and
bones of ribs.

A. SKULL:
 Consist of two parts: Cranium and face.
 Formed by number of flat and irregular bones that provide a bony
protection for the brain.
 It has a base on which brain rest upon and vault that surrounds and
cover it.
 The only movable bone is the mandible / lower jaw.
 Lining of inner surface of skull is called as periosteum that forms
the outer layer of dura mater.
 In the mature skull the joints ( sutures) between the bones are
immovable (fibrous). The bones have numerous perforations (
foramina fissures) through which nerves, blood and lymph vessels
pass.

The bones of the
cranium are:-
 1 frontal bone
 2 parietal bones
 2 temporal bones
 1 occipital bone
 1 sphenoid bone
 1 ethmoid bone

SUTURES:
The sutures are the
immovable joints
between the bones of
the skull.
They are- coronal
suture, frontal sutures,
sagittal suture,
lambdoidal suture and
squamous suture.

FACE
 The skeleton of the face is
formed by 13 bones, in
addition to the frontal bone.
 They are-
2 Zygomatic
(cheek) bone
1 Maxilla
2 Nasal bones
2 Lacrimal bones
1 Vomer
2 Palatine bones
2 Inferior conchae
1 Mandible

HYOID BONE:
 This is an isolated horseshoe-
shaped bone lying in the soft
tissues of the neck just above
the larynx and below the
mandible.
 It does not articulate with any
other bone, but is attached to
the styloid process of the
temporal bone by ligaments.
 It support the larynx and gives
attachment to the base of the
tongue.

SINUSES:
 Sinuses containing air are
present in the sphenoid,
ethmoid, maxillary and frontal
bones.
 They all communicate with the
nasal cavity and are lined with
ciliated mucous membrane.
 Their functions are to give
resonance to the voice and to
reduce the weight of the skull,
making it easier to carry.

FUNCTIONS OF THE SKULL:
 The various parts of the skull have specific and different functions:
 The cranium protects the delicate tissues of the brain.
 The bony eye sockets provide the eyes with some protection against
injury and helps in eye movement.
 The temporal bone protects the delicate structures of the ear.
 Some bones of the face and the base of the skull give resonance to
the voice.
 The maxilla and mandible provide alveolar ridges in which the teeth
are embedded.
 The mandible is the only movable bone of the skull and help in
chewing food.

B. VERTEBRAL COLUMN:
 There are 26 bones in the vertebral column.
 24 separate vertebrae extend downwards from the occipital bone of
the skull; then there is the sacrum, formed from five fused vertebrae,
and lastly the coccyx, or tail, which is formed from between three to
five small fused vertebrae.
 The vertebral column is divided into different regions.
 The first seven form the cervical region; the next twelve vertebrae
are the thoracic spine, and next five the lumbar spine, the lowest
vertebrae of which articulates with the sacrum.
 Each vertebra is identified by the first letter of its region in the
spine, followed by a number indicating its position.

CHARACTERISTICS OF A TYPICAL
VERTEBRA:
 THE BODY : The body of each vertebra is situated anteriorly. The size varies
with the site. They are smallest in the cervical region and become larger towards
the lumbar region.
 THE VERTEBRAL (NEURAL) ARCH: This encloses a large vertebral foramen.
It is the area behind the body, and forms the posterior and lateral walls of the
vertebral foramen.
 The lateral walls are formed from plates of bone called pedicles, and the posterior
walls are formed from laminae.
 Projecting from the regions where the pedicle meets the lamina is a lateral
prominence called a transverse process, and where the two laminae meet at the
back is a process called the spinous process.

FEATURES OF THE VERTEBRAL
COLUMN:
 INTERVERTEBRAL DISCS: The bodies of adjacent vertebrae are
separated by intervertebral discs, consisting of an outer rim of
fibrocartilage and a central core of soft gelatinous material.
 They are thinnest in the cervical region and become progressively
thicker towards the lumbar region, as spinal loading increases.
 The posterior longitudinal ligament in the vertebral canal helps to
keep them in place. They have a shock- absorbing function and the
cartilaginous joints they form contribute to the flexibility of the
vertebral column as a whole.

INTERVERTEBRAL
FORAMINA:
 When two adjacent
vertebrae are viewed from
the side, a foramen
formed by a gap between
the vertebral pedicles can
be seen.
 Throughout the length of
the column there is an
intervertebral foramen on
each side between every
pair of vertebrae, through
which spinal nerves,
blood vessels and lymph
vessels pass.

CURVES OF THE VERTEBRAL
COLUMN:
When viewed from the side, the vertebral
column presents four curves: two primary
and two secondary.
 The fetus in the uterus lies curled up so
that the head and the knees are more or
less touching. This position shows the
primary curvature.
 The secondary cervical curve develops
when the child can hold up his head ( after
about 3 months) and the secondary curve
develops when he stands upright ( after 12
to 15 months). The thoracic and sacral
primary curves are retained.

FUNCTION OF THE VERTEBRAL COLUMN:
 Collectively the vertebral foramina form the vertebral canal, which
provides a strong bony protection for the delicate spinal cord lying
within it.
 The pedicles of adjacent vertebrae from intervertebral foramina, one
on each side, providing access to the spinal cord for spinal nerves,
blood vessels and lymph vessels.
 The numerous individual bones enable a certain amount of
movement.
 It supports the skull.
 The intervertebral discs act as shock absorbers, protecting the brain.
 It forms the axis of the trunk, giving attachment to the ribs, shoulder
girdle and upper limbs, and the pelvic girdle and lower limbs.

THORACIC / RIB CAGE:
The thorax is formed by sternum anteriorly, twelve pairs of ribs
forming the lateral bony cages, and the twelve thoracic vertebrae.
 STERNUM ( BREAST BONE) : This flat bone can be felt just
under the skin in the middle of the front of the chest.
 The manubrium is the uppermost section and articulates with the
clavicles at the sternoclavicular joints and with the first pairs of ribs.
 The body or middle portion gives attachment to the ribs.
 The xiphoid process is the tip of the bone. It gives attachment to the
diaphragm, muscles of the anterior abdominal wall and the linea
alba.

 RIBS: The 12 pairs of ribs from the lateral walls of the thoracic
cage. They are elongated curved bones that articulate posteriorly
with the vertebral column.
 Anteriorly, the first 7 pairs of ribs articulate directly with the
sternum and are known as the true ribs.
 The next 3 pairs articulate only indirectly and they are called false
rib. In both cases, costal cartilages, attach the ribs to the sternum.
 The lowest 2 pairs of ribs, referred to as floating ribs, do not join the
sternum at all, their anterior tips being free.
 The first rib is firmly fixed to the sternum and to the first thoracic
vertebra, and does not move during inspiration. Because it is a fixed
point, when the intercostal muscles contract, they pull the entire rib
cage upwards towards the first rib.

THE
APPENDICULAR
SKELETON:
The appendicular skeleton
consists of the shoulder girdle
with the upper limbs and the
pelvic girdle with the lower
limbs.

SHOULDER GIRDLE
AND UPPER LIMB:
The upper limbs forms a joint with the
trunk via the shoulder (pectoral) girdle.
SHOULDER GIRDLE: The shoulder
girdle consists of two scapulae and two
clavicles.
 CLAVICLE (COLLAR BONE):
The clavicle is an S- shaped long
bone. It articulates with the
manubrium of the sternum at the
sternoclavicular joint and forms the
acromioclavicular joint with the
acromion process of the scapula.
It provide the only
bony link between the upper limb and
the axial skeleton.

 SCAPULA ( SHOULDER
BLADE): The scapula is a
flat triangular-shaped bone,
lying on the posterior chest
wall superficial to the ribs
and separated from them by
muscles.
At the lateral angle is a
shallow articular surface, the
glenoid cavity, which, with the
head of the humerus, forms the
shoulder joint.
The prominent overhang,
which can be felt through the
skin as the highest point of the
shoulder, is called the acromion
process.

THE UPPER LIMBS:
 HUMERUS: This is the bone of
the upper arm. The head sits with
the glenoid cavity of the scapula,
forming the shoulder joint. Distal
to the head are two roughened
projections of bone, the greater
and lesser tubercles, and between
them there is a deep groove.
 The distal end of the bone presents
two surfaces that articulates with
the radius and ulna to form the
elbow joint.

ULNA AND RADIUS:
 These are the two bones of the
forearm. The ulna is longer
than and medial to the radius
and when the arm is in the
anatomical position.
 They articulate with the
humerus at the elbow joint, the
carpal bones at the wrist joint
and with each other at the
proximal and distal radioulnar
joints.

CARPAL (WRIST )
BONE
 There are eight carpal bones
arranged in two rows of four.
From outside inwards they are:
 Proximal row: scaphoid,
lunate, triquetral, pisiform
 Diatal row: trapezium,
trapezoid, capitate, hamate.
These bones are closely
fitted together and held in
position by ligaments that allow a
limited amount of movement
between them.

METACARPAL BONES:
These five bones form the palm of the
hand. They are numbered from the
thumb side inwards. The proximal ends
articulate with the carpal bones and the
distal ends with the phalanges.
PHALANGES:
There are 14 phalanges, three in
each finger and two in the thumb.
They articulate with the metacarpal
bones and with each other, by
hinge joints.

PELVIC GIRDLE AND LOWER LIMB:
The lower limbs forms a joint with the
trunk at the pelvic girdle.
 THE PELVIC GIRDLE:
The pelvic girdle is formed from two
innominate (hip) bones. The pelvis is the
term given to the basin-shaped structure
formed by the pelvic girdle and its
associated sacrum.
The pelvis is formed by the hip bones,
the sacrum and the coccyx. It is divided
into upper and lower parts by the brim of
the pelvis, consisting of the promontory of
the sacrum and the iliopectineal lines of
the innominate bones.

INNOMINATE (HIP) BONE:
Each hip bone consists of three fused bones:
the ilium, ischium and pubis.
The ilium is the upper flattened part of
the bone and it presents the iliac crest, the
anterior curve of which is called anterior
superior iliac supine. It forms sacroiliac joint
with sacrum.
The pubis is the anterior part of the bone
and it articulates with the pubis of the other
hip bone at the symphysis pubis.
The ischium is the inferior and posterior
part. The rough inferior projections of the
ischia, the ischial tuberosities, bear the
weight of the body when seated.
The union of the three parts takes place in the
acetabulum.

THE LOWER LIMB
FEMUR (THIGH BONE): The femur is
the longest and heaviest bone of the body.
The head is almost spherical and fits into the
acetabulum of the hip bone to form the hip
joint.
 The posterior surface of the lower third
forms a flat triangular area called
popliteal surface. The distal extremity has
two articular condyles, which, with the
tibia and patella, form the knee joint.
 The function of the femur is to transmit
the body weight of the body through the
bones below the knee to the foot.

PATELLA ( KNEE CAP):
Roughly triangular-shaped sesamoid bone associated with the
knee joint.

 TIBIA(SHIN BONE): The tibia is the
medial of the two bones of the lower leg.
The proximal extremity is broad and flat and
presents two condyles for articulation with
the femur at the knee joint.
The distal extremity of the tibia forms the
ankle joint with the talus and the fibula.
 FIBULA: The fibula is the long
slender lateral bone in the leg. The head
of the upper extremity articulates with
the lateral condyle of the tibia, forming
the proximal tibiofibular joint, and the
lower extremity articulates with the
tibia.It helps to stabilize the ankle joint.

 TARSAL (ANKLE) BONES: The seven
bones forming the posterior part of the
foot are the talus, calcaneus, navicular,
cuboid and three cuneiform bones. The
talus articulates with the tibia and
fibula at the ankle joint. The
calcaneous forms the heel of the foot.
The other bones articulate with each
other and with metatarsal bones.
 METATARSAL (BONE OF THE
FOOT): These are five bones,
numbered from inside out, which
form the greater part of the dorsum
of the foot. At their proximal they
articulate with the tarsal bones and at
the distal end with the phalanges.

 PHALANGES
( TOE
BONES):
There are 14
phalanges
arranged in a
similar manner to
those in the
fingers, i.e. two in
the great toe
(hallux) and three
in each of the toe.

Skeleton system- bones and their number with detailed description.

More Related Content

What's hot

Similar to Skeleton system- bones and their number with detailed description.

More from bhartisharma175

Recently uploaded

Skeleton system- bones and their number with detailed description.