Introduction: The Human Skeleton
Below our skin and muscle lies our extremely intricate bone structure, the internal framework of the human body. Composed of three hundred five bones at birth, a number which decreases as the human body ages due to the fusion of some bones together to roughly two hundred six, the human skeleton is of a marvelous complexity and has multiple functions: Support, movement, protection, mineral storage, endocrine regulation and the production of blood cells.
What exactly are bones?
Bones are a type of connective tissue containing cells, extracellular matrix and minerals. They are a composite of both organic and inorganic materials. The inorganic material that a skeleton stores is calcium phosphate, magnesium and sodium – other elements also found in small amounts are potassium, and chlorine.
The cells making up a bone are:
- Osteoblasts: Found on the surface of the bone. They create the matrix and assist in precipitating mineral.
- Osteocytes: They aid in bone development and later are buried in the lacunae of the matrix and are in charge of tissue maintenance.
- Osteoclasts: Giant cells, usually seen in areas where bone is being resorbed.
There are two types of bone tissue, one is spongy (trabecular) and the other is compact (densely mineralized). A general rule is that the outside portions of the bone organ are compact whereas much of the interior is made up of the porous, spongy bone. Spongy bones, however, constitute the bony tissue at the initial development of bone. Compact bones must replace the spongy types, at some areas.
Sexual Dimorphism in the Human Skeleton
While sexual dimorphism is not as pronounced between the two human genders as in other primate species it does exist, subtle as it is. Skeletal gender differences in bone growth are traditionally attributed to stimulatory “male” androgen action as opposed to inhibitory “female” estrogen action on periosteal bone formation. According to recent studies, however, skeletal sexual dimorphism is not only determined by androgen action in male and estrogen action in females respectively but also by complex gender and time-specific interactions between sex hormones, GH-IGFI, and mechanical loading. Differences between the two sexes include generally wider but not thicker bones for males compared to females, and subtle differentiation in the morphology of the skull, dentition, long bones and pelvis. The pelvis, notably, is different in females in order to facilitate childbirth.
Division of the Human Skeleton
Experts currently divide the human skeleton into two separate parts, the axial skeleton and the appendicular skeleton, by virtue of their different functions. The axial skeleton consists of the bones of the skull, the ossicles – the “inner ear” -, the hyoid bone, a horse-shoe shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage, the rib cage, the sternum and the vertebral column. In total, the axial skeleton consists of eighty bones. Its name, “axial” is derived from the word axis, referring to the fact that this part’s bones are located close or along the central “axis” of the body. Our upright posture is maintained by the axial skeleton, as it transmits the weight from the head, the trunk and the upper limbs down to the lower extremities at the hip joints.
The appendicular skeleton has a significantly higher number of bones than the axial, numbering one hundred twenty six. These include the pectoral girdles, arms and forearms, hands, pelvis, thighs and legs, feet and ankles. All these bones remain unfused – unlike those of the axial skeleton – and thus allow for a much greater range of motion. Functionally, the appendicular skeleton is involved in locomotion of the axial skeleton and manipulation of objects in the environment – through the lower and upper limbs respectively.
Combining these two parts together forms the complete human skeleton, numbering two hundred six bones in total in the human body.
Which human body is the strongest?
According to the BBC, the leg bones collectively, part of the appendicular skeleton, are the strongest bones in the human body because they are used to support the entirety of the human body’s substantial weight. Of these, a single bone, the femur or thigh bone is the longest, heaviest and strongest. It is considered a major component of the appendicular skeleton.
During a great number of activities, including running, jumping, walking and standing all of the human body’s weight is supported by the femurs. Extreme forces constantly get inflicted upon the femur because of the strength of the hip and thigh muscles that act on it in order to move the human leg. It is structurally classified as a long bone. It is almost perfectly cylindrical in the greater part of its extent.
In the erect posture it is not vertical, being separated above from its fellow by a considerable interval, which corresponds to the breadth of the pelvis, but inclining gradually downward and medialward, so as to approach its fellow toward its lower part, for the purpose of bringing the knee-joint near the line of gravity of the body. The degree of this inclination varies in different people, and generally greater in females than males.
The strength of the femur is so strong that it can withstand extreme forces, rising up to the staggering number of two thousand and five hundred pounds. Only disastrous events such as car accidents or falls from very high heights can cause it to break. In case it breaks, it naturally takes many months to heal.
The human skeleton is an immensely complex and intricate system that would definitely humble a great number of man-made machines. It is divided in two distinct parts, the axial and the appendicular, with each of them serving different functions. Out of the grand total of two hundred and six bones in the human body, the strongest and longest one is the femur, alternatively called the thigh bone. The femur supports the totality of the human weight and is able to withstand extremely high levels of force, only breaking in cases of misfortune, like a car accident.