Bones
Mechanical Functions of Bones:
Protection:
•
•
•
•
•
At numerous places inside the body bones serve to protect important and
delicate organs.
o Ex. Brain is protected by skull
Shape:
Because of their rigid nature bones provide a framework around which
the body is built.
Bones are responsible for the shape and form of the human body
Movement:
Working with skeletal muscles, tendons, ligaments, and joints, the bones
form the moving machinery of the human body
The major role of bones in movement is that they act as levers, which
make use of the forces generated by skeletal muscles in a beneficial way
Synthetic Functions of Bones
Synthesis of blood cells
•
•
•
•
The major synthetic role of bones is to produce blood cells
The bones themselves are not capable of doing this. Instead, they house
the bone marrow, which contains hematopoietic stem cells, capable of
producing blood cells
In infants, bone marrow of all long bones is capable of synthesis,
however, as a person gets older, the red marrow turns into yellow fatty
marrow, which is no more capable of hematopoiesis
The red marrow in adults and older individuals is restricted to vertebrae
and heads of tibia and femur
Metabolic Functions of Bones
Mineral Storage
•
Bones serve as an important store house of minerals such as calcium and
phosphorus
Fat Storage
•
•
The yellow bone marrow of long bones act as a storage of fats
Role in acid-base balance
Bone buffers the blood against excessive pH changes by absorbing or
releasing alkaline salts
Frontal Bone
This bone forms the forehead
2 Parietal Bones
One bone from each side joins behind the
frontal bone to form the sides and roof of
the cranium
2 Temporal Bones
There are two temporal bones in all, one on
each side below the parietal bones
Occipital Bone
This is a single bone that is present at the
back of the cranium just behind the parietal
and temporal bones
Sphenoid Bone
This is a single bone that is situated at the
base of the skull in front of the temporal
bones and basilar part of the occipital bone
Ethmoid Bone
This is a light and spongy bone that is situated
in the anterior part of the base of the
cranium. It lies between the two orbits at
the roof of the nasal cavity separating the
brain from the nasal cavity
Mandible
This is the lower jawbone. It is U shaped and
the largest and strongest bone of the face.
The mandible consists of two halves that fuse
at the mental symphysis by the age of two
years
Each half of the mandible has a horizontal
body and a vertical ramus at the posterior
end of the body
Maxilla
The maxilla contributes to the roof of the oral
cavity and the lateral walls and floor of the
nasal cavity.
It also provides for the attachment of the
teeth of the upper jaw. It is actually two
bones that are fused along the palatal
fissure
2 Zygomatic Bone
There are two zygomatic bones one on each
side of the face forming the prominence of
the cheek.
Each bone also forms a part of the lateral side
and floor of each orbit.
Palatine Bone
The palatine is an L-shaped bone that is
situated between the maxilla and the
pterygoid process of the sphenoid.
It is located behind the nasal cavity and
hence, contributes to its floor and the
lateral walls.
Besides the nasal cavity, it also contributes to
the roof of the mouth as well as to the floor
of the orbit
Vomer
It is a thin, flat single bone that lies along the
midsagittal line.
It articulates with the ethmoid, the sphenoid,
the two palatine, and two maxillary bones
each (that is 6 bones in all)
2 Lacrimal Bones
There are two lacrimal bones in all, each lying
in the frontal part of the medial wall of the
orbit.
These are the smallest bones of the face and
each interacts with the frontal bone, the
ethmoid bone, the maxilla, and the inferior
nasal concha
2 Nasal Bones
These are 2 oblong bones placed side to side
that form the bridge of the nose
Inferior Nasal Concha
These are paired bones of the face that arise
from the maxillary bone and continues
horizontally along the lateral wall of the
nasal cavity. (Ahead of these bones are the
middle and the superior nasal conche that
are considered to be part of the cranium)
Vertebral Column
The vertebral column or the spinal column is
made of 33 small bones each of which is
known as a vertebra.
These vertebrae gives the vertebral column its
flexibility due to which we can bend
forwards and sideways
Cervical Vertebrate
The cervical vertebrae are the first 7 vertebrae that
are also the smallest of the true vertebrae.
They are different from those in thoracic and lumbar
regions in the fact that they have a hole or
foramen in each transverse process for the
vertebral process to pass through.
The skull is supported on the first cervical vertebra
which is known as the atlas.
The second cervical vertebra is the axis which forms
the pivot on which the atlas carrying the skull
turns.
The cervical vertebrae forms the neck
Thoracic Vertrbrae
There are 12 vertebrae in all the thoracic region that
come right after the cervical vertebrae. These are
larger than the cervical vertebrae but smaller than
those in the lumbar region.
The distinct features of these vertebrae are the presence
of the facets that provide the attachment of ribs
Each thoracic vertebra has facets on the side of the
bodies where heads of the ribs attach
Other than the last two vertebrae, all the rest of the ten
vertebrae have one facet on each of the transverse
process for articulation with tubercles of the ribs
Lumbar Vertebrae
The lumbar vertebrae consists of 5 vertebrae.
They lack the foramen on transverse process
that the cervical vertebrae have and the
facets on the body that characterize the
thoracic vertebrae
Sacral Vertebrae
5 sacral vertebrae fuse to form a triangular
bone called the sacrum in adults.
The sacrum fits between the two hip bones
and joins the spine and the pelvis together
Coccyx
The coccyx consists of 4 bones that fuse
together as one grows up
Coccyx can variably consist of 5 or 3 bones as
well
Shoulder
The shoulder is made of two bones that
together allow the attachment of the arm to
the body
Made up from the scapula and the clavicle
Scapula
The scapula is a flat triangular bone that
forms the posterior part of the shoulder
girdle.
It connects the humerus (upper arm) with the
clavicle.
It is what we commonly refer to as the
shoulder blade that provides for attachment
of the humerus
There are two shoulder blades
Clavicle
It is commonly called the collarbone.
It is a pair of small curved bones that join the
scapula and hence, the humerus to the
sternum.
Together the clavicle and the scapula form
the shoulder girldle
Thorax
The thorax is the portion below the neck that
encloses the heart and lungs
Sternum
This is a long T-shaped bone. It lies in the
front, central portion of the rib cage or the
chest and provides for the ribs and the
clavicle to attach.
It consists of three parts; the topmost part is
the manubrium to which the clavicle
attaches, followed by the body (to which
the ribs attach), and the end portion of the
sternum is the xyphoid process.
Ribs (12 pairs in all)
The first seven pairs are directly attached to
the sternum through cartilage.
The next three are attached to the sternum
through a common cartilaginous extension.
The last two pairs are known as the floating
ribs because although they start from the
thoracic vertebrae, they don not attrach to
the sternum
Hip Bone
This is an irregularly shaped bone that is constricted in
the middle and flares at both ends.
There are two hip bones that join together that along
with the sacrum and the coccyx form the pelvis.
Each hip bone has three parts: the ilium (flared, fanshaped superior portion of the hip bone), ischium
(lowest portion of the hip bone that curves forward and
meets the pubis to form the obturator foramen) , and
the pubis.
Hands
The bones of the hands can be divided into
those that make up the upper arm, the
lower arm, the wrist, the palm and the
fingers
Humerus
This is a single long bone of the upper arm.
It runs from the shoulder to the elbow.
The humerus connects the scapula to the
bones of the forearm
Radius
Radius is one of the bones of the forearm that
lies on the lateral side of the ulna (the other
bone of the forearm). It starts from the
lateral side of the elbow and continues to
the thumb side of the wrist
Ulna
This bone runs parallel to the radius along the
forearm.
It lies on the medial side of the body
Carpal Bones
These are the bones of the wrist. There are 7
carpal bones in each wrist which include:
Scaphoid bones
Lunate bones
Triquetral bone
Pisiform bone
Trapezium
Trapezoid bone
Capitate bone
Hamate Bone
•
•
•
•
•
•
•
•
Metacarpal Bones
These are the bones of the palms and there
are 5 metacarpal bones in every palm; one
corresponding to each digit
Phalanges
These are the bones of the fingers. There are
5 proximal phalanges in each hand that lie
in front of the metacarpals.
There are 4 intermediate phalanges in front of
the proximal phalanges, one on each finger
other than the thumb.
The last phalanges at the tip of each finger
are known as the distal phalanges. There is
5.
Legs
The bones of the legs can be studied as those
that make up the thigh, the lower half of
the legs, and the feet
Femur
This is the longest bone in the human body.
It is also known as the thigh bone.
The head forms the ball and socket joint at
the pelvic girdle.
Tibia
The tibia is the second longest bone in the human
body.
Along with the fibula, it forms the lower part of
the leg below the knee.
It articulates with the femur at its superior end
and with the talus at it inferior end.
Laterally, it articulates with the fibula.
The tibia is considered by many to be the
strongest bone of the body. It is commonly
known as the shin bone.
Fibula
The fibula is a long but thin bone that along
with the tibia forms the lower part of the
human leg.
It is attached to the tibia at both the ends.
Its upper end articulates with the tibia at the
back of its head whereas while attaching to
the tibia with its lower end, it angles
slightly forward.
The fibula is also known as the calf bone.
Patella
One on each leg, the patella is the knee cap.
It is a triangular bone that forms a protective
cap over the knee joint
Tarsal Bones
There are 7 tarsal bones in all that lie
between the tibia-fibula and the
matatarsals. They are:
Calneus (heel bone)
Talus
Navicular bone
Medial cuneiform bone
Intermediate cuneiform bone
Lateral cuneiform bone
Cuboid bone
•
•
•
•
•
•
•
Metatarsal Bones
There are 5 metatarsal bones in each foot,
one corresponding to each digit.
These lie between the tarsal bones and the
phalanges.
These may be considered to be equivalent to
the metacarpal bones of the hands.
Phalanges
They are the bones of the toes of the feet.
There are 5 proximal phalanges in each foot
that start from the metatarsals.
There are 4 intermediate phalanges, one on
each finger other than the big toe.
The last phalanges at which each toe ends are
known as the distal phalanges. They are 5 in
number.
These are the main bones present in the human
body. Other than these, there are 3 small bones
in each of the middle ear. They are the
malleus, incus and stapes. Our throat also has a
small bone - the hyoid bone.
These are the bones in the human body that
provide for various functions. As already said,
they mainly provide structural support and
protection to softer organs. However, the
bones of the middle ear help in conduction of
sound.