Monday, 26 October 2015

Online Assignment - Skeletal System

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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