INTRODUCTION
Skeletal muscles plays a major role in locomotion and movement.There are
skeletal muscles in which the muscles are attached to skeleton by tendons. The
skeletal muscle is of two types axial skeleton and appendicular skeleton .
There are 206 bones in our skeletal system. The human skeleton serves six major
functions and they are support ,movement,protection, production of blood
cells,storage of ions and endocrine regulationThe study of human bones probably
started in ancient Greece under Ptolemaic kings due to their link to Egypt.
Herophilos, through his work by studying dissected human corpses in Alexandria
is credited to be the pioneer of the field. His works are lost but are often
cited by notable perons in the field such as Galen and Rufus of Ephesus.
HUMAN SKELETAL SYSTEM
The human skeleton is the internal framework of the body. It is composed of
270 bones at birth – this total decreases to 206 bones by adulthood after some
bones have fused together. The bone mass in the skeleton reaches maximum
density around age 30. The human skeleton can be divided into the axial
skeleton and the appendicular skeleton. The axial skeleton is formed by the
vertebral column, the rib cage and the skull. The appendicular skeleton, which
is attached to the axial skeleton, is formed by the pectoral girdle, the pelvic
girdle and the bones of the upper and lower limbs.The human skeleton serves six
major functions; support, movement, protection, production of blood cells,
storage of ions and endocrine regulation. The human skeleton is not as sexually
dimorphic as that of many other primate species, but subtle differences between
sexes in the morphology of the skull, dentition, long bones, and pelves exist.
In general, female skeletal elements tend to be smaller and less robust than
corresponding male elements within a given population. The human female pelvis
is also different from that of males in order to facilitate child
birth.[citation needed] Unlike most primates, human males do not have penile
bones.
Divisions
Axial skeleton
The axial skeleton (80 bones) is formed by the vertebral column (32–34
bones; the number of the vertebrae differs from human to human as the lower 2
parts, sacral and coccygeal bone may vary in length), the rib cage (12 pairs of
ribs and the sternum), and the skull (22 bones and 7 associated bones).The
upright posture of humans is maintained by the axial skeleton, which transmits
the weight from the head, the trunk, and the upper extremities down to the
lower extremities at the hip joints. The bones of the spine are supported by
many ligaments. The erector spinae muscles are also supporting and are useful
for balance. A human is able to survive with just the axial portion of their
skeleton
APPENDICULAR SKELETON
The appendicular skeleton (126 bones) is formed by the pectoral girdles,
the upper limbs, the pelvic girdle or pelvis, and the lower limbs. Their
functions are to make locomotion possible and to protect the major organs of
digestion, excretion and reproduction
FUNCTIONS
The skeleton serves six major functions; support, movement, protection,
production of blood cells, storage of minerals and endocrine regulation.
Support
The skeleton
provides the framework which supports the body and maintains its shape. The
pelvis, associated ligaments and muscles provide a floor for the pelvic
structures. Without the rib cages, costal cartilages, and intercostal muscles,
the lungs would collapse. Movement
The joints between bones allow movement, some allowing a wider range of
movement than others, e.g. the ball and socket joint allows a greater range of
movement than the pivot joint at the neck.
Movement is powered by skeletal muscles, which are attached to the skeleton at
various sites on bones. Muscles, bones, and joints provide the principal
mechanics for movement, all coordinated by the nervous system. It is believed
that the reduction of human bone density in prehistoric times reduced the
agility and dexterity of human movement. Shifting from hunting to agriculture
has caused human bone density to reduce significantly.
Protection
The skeleton helps protect our many vital internal organs from being
damaged.The skull protects the brain, the eyes, and the middle and inner
ears.The vertebrae protect the spinal cord.The rib cage, spine, and sternum
protect the lungs, heart and major blood vessels.
Blood cell production
The skeleton is the site of haematopoiesis, the development of blood cells
that takes place in the bone marrow. In children, haematopoiesis occurs
primarily in the marrow of the long bones such as the femur and tibia. In
adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.
Storage
The bone matrix can store calcium and is involved in calcium metabolism,
and bone marrow can store iron in ferritin and is involved in iron metabolism.
However, bones are not entirely made of calcium, but a mixture of chondroitin
sulfate and hydroxyapatite, the latter making up 70% of a bone. Hydroxyapatite
is in turn composed of 39.8% of calcium, 41.4% of oxygen, 18.5% of phosphorus,
and 0.2% of hydrogen by mass. Chondroitin sulfate is a sugar made up primarily
of oxygen and carbon.
Endocrine regulation
Bone cells release a hormone called osteocalcin, which contributes to the
regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases
both the insulin secretion and sensitivity, in addition to boosting the number
of insulin-producing cells and reducing stores of fat.
Sex differences
During construction of the York to Scarborough Railway Bridge in 1901,
workmen discovered a large stone coffin, close to the River Ouse. Inside was a
skeleton, accompanied by an array of unusual and expensive objects. This chance
find represents one of the most significant discoveries ever made from Roman
York. Study of the skeleton has revealed that it belonged to a woman.
Anatomical differences between human males and females are highly
pronounced in some soft tissue areas, but tend to be limited in the skeleton.
The human skeleton is not as sexually dimorphic as that of many other primate
species, but subtle differences between sexes in the morphology of the skull,
dentition, long bones, and pelves (sing. pelvis) are exhibited across human populations.
In general, female skeletal elements tend to be smaller and less robust than
corresponding male elements within a given population.
Skull
A variety of gross morphological traits of the human skull demonstrate
sexual dimorphism, such as the nuchal crest, mastoid processes, supraorbital
margin, supraorbital ridge, and mental eminence.
Dentition
Human inter-sex dental dimorphism centers on the canines, but it is not
nearly as pronounced as in the other great apes.
Long bones
Long bones are generally larger in males than in females within a given
population. Muscle attachment sites on long bones are often more robust in
males than in females, reflecting a difference in overall muscle mass and
development between sexes. Sexual dimorphism in the long bones is commonly
characterized by morphometric or gross morphological analyses.
Pelvis
Human pelves exhibit greater sexual dimorphism than other bones,
specifically in the size and shape of the pelvic cavity, ilia, greater sciatic
notches, and the sub-pubic angle. The Phenice method is commonly used to
determine the sex of an unidentified human skeleton by anthropologists with 96%
to 100% accuracy in some populations.
CONCLUSION
Skeletal system is important for
human. However, “the human body is not designed to last forever” (Weber, Z.,
and Prof. Ying, S., 2005),bone fractures may occur in sometimes on a normal person caused by some accidents or bone defects that
born with affect a person’s life. Therefore, artificial bones are used to solve
these problems. Artificial bones play an important role in bone grafting. It is
used to replace the bones that are fractured in order to perform normally in
daily life. Although artificial bones may have some impacts on human body, but
they can help a lot of people in order to achieve their goal and fulfill one’s
dream.
REFERENCE
· Functional zoology- prof. K.K.Bhaskaran
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