The Human Body Internal Structures!!
Body features
Although there is enormous variation between the external appearances of humans, all bodies contain the same basic features. The outward form of the body depends on the size of the skeleton, the shape of the muscles, the thickness of the fat layer beneath the skin, the elasticity or sagginess of the skin, and the person's age and gender.
Skeleton
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| Skeleton |
The skeleton is a mobile framework made up of 206 bone s, approximately half of which are in the hands and feet. Although individual bones are rigid, the skeleton as a whole remarkably flexible and allows the human body a huge range of movement. The skeleton serves as an anchorage for the skeletal muscles, and as a protective cage for the body's internal organs. Female bones are usually smaller and lighter than males bones, and the female pelvis is shallower and has a wider cavity.
Skull
The skull is the most complicated bony structure of the body but every feature serve a purpose. Internally, the main hollow chamber of the skull has three levels that support the brain, with every bump and hollow corresponding to the shape of the brain. Underneath and towards the back of the skull is a large round hole, the foramen magnum, through which the spinal cord passes. To the front of this are many smaller openings through which nerves, arteries, and veins pass to and from the brain. The roof of the skull is formed from the four thin, curved bones that are firmly fixed together from the age of about two years.
Spine
The spine has two main functions: it serves as a protective surrounding for the delicate spinal cord and forms the supporting back bone of the skeleton. The spine consists of 24 seperate differently shaped bones(vertebrae) with a curved, triangular bone (the sacrum) at the bottom. The top two vertebrae differ in appearance from the other and work as a pair: the first, called the atlas, rotates around a stout vertical peg on the second, the axis. This arrangement allows the skull to move freely up and down, and from side to side.
Brain
The brain is the major organ of the central nervous system and the control centre for all the body's voluntary and involuntary activities. It is also responsible for the complexities of thought, memory, emotion, and language. In adults, this complex organ is a mere 1.4kg (3 lb) in weight, containing over 10 thousand million nerve cells. Three distinct regions can easily be seen the brainstem, the cerebellum, and the large cerebellum. The brainstem controls vital body functions, such as breathing and digestion. The cerebellum's main functions are the maintenance of posture and the coordination of body movements. The cerebrum, which consists of the right and left cerebral hemisphere joined by the corpus callosum, is the site of most conscious and intelligent activities.
Heart
The heart is a hollow muscle in the middle of the chest that pumps blood around the body, supplying cells with oxygen and nutrients. A muscular wall, called the septum, divides the heart lengthways into left and right sides. At rest the heart beats between 60 and 80 times a minute; during exercises or at times of stress or excitement the rate may increase to 200 beats a minute.
Muscles
There are three main types of muscles: skeletal muscle ( also called voluntary muscle because it can be consciously controlled); smooth muscle ( also called involuntary muscle because it is not under voluntary control); and the specialized muscle tissue of the heart. Humans have more than 600 skeletal muscles, which differ in size and shape according to the jobs they do. Skeletal muscles are attached either directly or indirectly ( via tendons) to bones, and work in opposing pairs (one muscle in the pair contracts while the other relaxes) to produce body movements as diverse as walking, threading a needle, and array of facial expressions. Smooth muscles occur in the walls of the internal body organs and perform actions such as forcing food through the intestines, contracting the uterus (womb) in childbirth, and pumping blood through the blood vessels.
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Skull
 |
| Human being Skull |
The skull is the most complicated bony structure of the body but every feature serve a purpose. Internally, the main hollow chamber of the skull has three levels that support the brain, with every bump and hollow corresponding to the shape of the brain. Underneath and towards the back of the skull is a large round hole, the foramen magnum, through which the spinal cord passes. To the front of this are many smaller openings through which nerves, arteries, and veins pass to and from the brain. The roof of the skull is formed from the four thin, curved bones that are firmly fixed together from the age of about two years.
Spine
 |
| Spine |
The spine has two main functions: it serves as a protective surrounding for the delicate spinal cord and forms the supporting back bone of the skeleton. The spine consists of 24 seperate differently shaped bones(vertebrae) with a curved, triangular bone (the sacrum) at the bottom. The top two vertebrae differ in appearance from the other and work as a pair: the first, called the atlas, rotates around a stout vertical peg on the second, the axis. This arrangement allows the skull to move freely up and down, and from side to side.
Brain
 |
| Brain of human beings |
The brain is the major organ of the central nervous system and the control centre for all the body's voluntary and involuntary activities. It is also responsible for the complexities of thought, memory, emotion, and language. In adults, this complex organ is a mere 1.4kg (3 lb) in weight, containing over 10 thousand million nerve cells. Three distinct regions can easily be seen the brainstem, the cerebellum, and the large cerebellum. The brainstem controls vital body functions, such as breathing and digestion. The cerebellum's main functions are the maintenance of posture and the coordination of body movements. The cerebrum, which consists of the right and left cerebral hemisphere joined by the corpus callosum, is the site of most conscious and intelligent activities.
Heart
 |
| Heart of Human beings |
The heart is a hollow muscle in the middle of the chest that pumps blood around the body, supplying cells with oxygen and nutrients. A muscular wall, called the septum, divides the heart lengthways into left and right sides. At rest the heart beats between 60 and 80 times a minute; during exercises or at times of stress or excitement the rate may increase to 200 beats a minute.
Muscles
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| Human Body Muscles |
There are three main types of muscles: skeletal muscle ( also called voluntary muscle because it can be consciously controlled); smooth muscle ( also called involuntary muscle because it is not under voluntary control); and the specialized muscle tissue of the heart. Humans have more than 600 skeletal muscles, which differ in size and shape according to the jobs they do. Skeletal muscles are attached either directly or indirectly ( via tendons) to bones, and work in opposing pairs (one muscle in the pair contracts while the other relaxes) to produce body movements as diverse as walking, threading a needle, and array of facial expressions. Smooth muscles occur in the walls of the internal body organs and perform actions such as forcing food through the intestines, contracting the uterus (womb) in childbirth, and pumping blood through the blood vessels.
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