The human head contains 22 bones, consisting the cranium and the facial bones. The cranium is formed by 8 bones: the frontal bone, two parietal bones, two temporal bones, the occipital bone in the back, the ethmoid bone behind the nose, and the sphenoid bone.
The face consists of 14 bones including the maxilla (upper jaw) and mandible (lower jaw). (The skull has many little holes in its base which allow the cranial nerves to travel to their destinations.)
The cranium protects the brain, which, for an average adult male weighs about 1400 gram (49 oz). The brain of Russian novelist Turgenev, weighed 2021g (71 oz), Bismarck’s brain weighed 1807g (64 oz), while that of famous French statesman Gambetta was 1294g (46 oz).
Female average brain mass is slightly less than that of males. The largest woman’s brain recorded weighed 1742g (61 oz).
The human brain is the most complex organ in the human body and probably the most complex creation present on this universe. It is evident that, the world’s greatest man made wonders are a result of the human brain making it the most amazing feature in a human being. The human brain with its complexity acts like a storage device which holds safely a person’s most cherished memories. A person’s personality is by far influenced by the brain as well as generation of human consciousness which gives a person passion, motion and emotion. A command center for the central nervous system, the brain serves human beings with ample physical and cognitive abilities. This are just a few vital roles that the human brain performs but the most amazing thing about the human brain are the many facts that are less known by many people with a fully functional brain.
The thorax or chest (from the Greek thorax "breastplate, cuirass, corslet", via Latin: thorax) is a part of the anatomy of humans and various other animals located between the neck and the abdomen. The thorax includes the thoracic cavity and the thoracic wall. It contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain.
The contents of the thorax include the heart and lungs and the thymus gland); the (major and minor pectoral muscles, trapezius muscles and neck muscle); internal structures such as the diaphragm, esophagus, trachea and a part of the sternum known as the xiphoid process), as well as the content of the thoracic abdomen (stomach, kidney/adrenal, pancreas, spleen, and lower oesophagus). Arteries and veins are also contained – (aorta, superior vena cava, inferior vena cava and the pulmonary artery); bones ( the shoulder socket containing the upper part of the humerus, the scapula, sternum, thoracic portion of the spine, collarbone, and the rib cage and floating ribs). External structures are the nipples. The area exposed by open-necked shirts, the 'V of the chest' is sometimes the location of a light-induced skin disease polymorphous light eruption.
In the human body, the region of the thorax between the neck and diaphragm in the front of the body is called the chest. The corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to that part of the thoracic skeleton that encloses the heart and lungs. All the breadth of the shoulders is due to the shoulder girdle, and contains the axillae and the heads of the humeri. In the middle line the suprasternal notch is seen above, while about three fingers' breadth below it a transverse ridge can be felt, which is known as the sternal angle and this marks the junction between the manubrium and body of the sternum. Level with this line the second ribs join the sternum, and when these are found the lower ribs can often be counted. At the lower part of the sternum, where the seventh or last true ribs join it, the ensiform cartilage begins, and above this there is often a depression known as the pit of the stomach.
The skeleton of an adult human consists of 206 bones. It is composed of 270 bones at birth, which decreases to 206 bones by adulthood after some bones have fused together. It consists of 80 bones in the axial skeleton (28 in the skull and 52 in the torso) and 126 bones in the appendicular skeleton (32 × 2 in the upper extremities including both arms and 31 × 2 in the lower extremities including both legs). Many small and often variable bones, such as some sesamoid bones, are not included in this count.
The number of bones in the skeleton changes with age, as multiple bones fuse, a process which typically reaches completion in the third decade of life. In addition, the bones of the skull and face are counted as separate bones, despite being fused naturally. Some reliable sesamoid bones such as the pisiform are counted, while others, such as the hallux sesamoids, are not. Individuals may have more or fewer bones than this owing to anatomical variations. The most common variations include sutural (wormian) bones, which are located along the sutural lines on the back of the skull, and sesamoid bones which develop within some tendons, mainly in the hands and feet. Some individuals may also have additional (i.e. supernumerary) cervical ribs or lumbar vertebrae.
Your arm is made up of three long bones: your humerus in your upper arm and your ulna and radius in your lower arm. Your upper and lower arms are connected at your elbow by a hinge joint between your humerus and ulna. Your radius and ulna are linked at your elbow in a way that allows you to rotate your hand and forearm by more than 180 degrees. Your ulna bone forms the point of your elbow.
Your shoulder and arm bones have roughened patches on their surfaces where muscles are attached. When the muscles contract, this pulls the bone the muscles are attached to, making your arm move.
The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.
Skin has three layers:
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis.
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In human anatomy, the lower leg is the part of the lower limb that lies between the knee and the ankle, the thigh is between the hip and knee and the term "lower extremity" is used to describe the colloquial leg. The leg from the knee to the ankle is called the cnemis or crus. The calf is the back portion and the shin is the front. The tibia and fibula are the two bones of the crus.
Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism is not limited to the leg, however, but has also affected the location of the body's center of gravity, the reorganisation of internal organs, and the form and biomechanism of the trunk. In humans, the double S-shaped vertebral column acts as a shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization to support and locomotion — in orangutans the leg length is 111% of the trunk; in chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.
Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis.
Muscle tissues are derived from the mesodermal layer of embryonic germ cells in a process known as myogenesis. There are three types of muscle, skeletal or striated, cardiac, and smooth. Muscle action can be classified as being either voluntary or involuntary. Cardiac and smooth muscles contract without conscious thought and are termed involuntary, whereas the skeletal muscles contract upon command. Skeletal muscles in turn can be divided into fast and slow twitch fibers.
Muscles are predominantly powered by the oxidation of fats and carbohydrates, but anaerobic chemical reactions are also used, particularly by fast twitch fibers. These chemical reactions produce adenosine triphosphate (ATP) molecules that are used to power the movement of the myosin heads.
The term muscle is derived from the Latin musculus meaning "little mouse" perhaps because of the shape of certain muscles or because contracting muscles look like mice moving under the skin.