Human Anatomy

1.Skeleton System:-

SKELETON SYSTEM

The human skeleton is the internal frameworks of our body. It is composed of 270 bones at birth , this total decreases to 206 bones by adulthood after some bones have fuse together. The bone mass in the skeleton reaches maximum density around age 30. The human skeleton can be divided into two skeleton,No 1-the axial skeleton and No 2- the appendicular- skeleton. The appendiculiarn skeleton,

The human skeletons 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 also subtle differences between sexes in the morphology of the dentition, skull, long bones, and pelves exist... In general. Female skeletal elements tend to be smaller and less robust than corresponding male elements. The human female pelvis is also different from that of males in order to facilitate childs birth. Unlike most other primates, human males do not have penile bones.

Divisions:

• Axial skeleton            

  

  AXIAL SKELETON

               

Main article:- 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 up-right posture of humans is maintained by the axial skeleton, which transmits the weight from the trunk, the head, and the upper-extremities down to the lower-extremities at the hip joints. The spine's bones are supported by many ligaments. The erectors spinae muscles  are useful for body balancing

• Appendicular skeleton          

  

  APPENDICULAR SKELETON

Main article: Appendicular skeleton
The appendicular skeleton (126 bones) is formed by the pectoral girdles, upper limbs,pelvis or pelvic-girdle, and a lower-limbs. Their functions are to make locomotion possible and to protect the digestion's major organs, excretion and reproduction.

Functions

SupportThe skeleton serves six major functions; support, movement, protection, production of blood cells, storage of minerals and endocrine regulation.

   1.   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, thelungs would collapse.

   2.   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.

   3.   Protection

The skeleton helps protect our many vital internal organs from being damaged.

• The skull protects the brain, the eyes, and the middle ears and inner ears.
• The vertebrae protect the spinal cord.
• The spine, sternum, and the ribcage protect the heart, lungs  and major blood vessels.
• The scapula and the clavicle protect the shoulder.
• The spine and the ilium protect the digestive and urogenital systems and the hip.
• The ulna and the patella protect the knee and the elbow respectively.
• The tarsals and the carpals protect the wrist and ankle respectively.

   4.   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 tibia and femur. In adults, it occurs mainly in the cranium, pelvis, vertebrae, and sternum.

   5.   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 andhydroxyapatite*, 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.

   6.   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

Anatomical differences between human males and females are highly pronounced in some soft tissues 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, long bones, dentition, and pelvis (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.

1.Skull

A variety of gross morphological traits of the human skull demonstrate sexual dimorphism, such as the nuchal crest, supraorbital margin, mastoid processes, supra-orbital ridge, and mental eminence.

2.Dentition

Human inter-sex dental dimorphism centers on the canines, but it is not nearly as pronounced as in the other great apes.

3.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.

4.Pelvis

Human pelvis exhibit greater sexual dimorphism than other bones, specifically in the size and shape of the pelvic cavity, greater sciatic notches, and the sub-pubic angle, ilia. 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.

Disorders

There are many classified skeletal disorders. One of the most common is osteoporosis. Also common is scoliosis, a side-to-side curve in the back or spine, often creating a pronounced "C" or"S" shape when viewed on an x-ray of the spine. This condition is most apparent during adolescence, and is most common with females.

1.Arthritis

Main article: Arthritis*

Arthritis is a disorder of the joints. It involves inflammation of one or more joints. When affected by arthritis, the joint or joints affected may be painful to move, may move in unusual directions or may be immobile completely. The symptoms of arthritis will vary differently between types of arthritis. The most common form of arthritis: Osteoarthritis can affect both the larger and smaller joints of the human skeletons. The cartilage in the affected joints will degrade, soften and wear away. This decreases the mobility of the joints and decreases the space between bones where cartilage should be.

2.Osteoporosis

Main article: Osteoporosis*

Osteoporosis is a disease of bone where there is reduced bone mineral density, increasing the likelihood of fractures.Osteoporosis is defined by the World Health Organization in women as a bone mineral density 2.5 standard deviationsbelow peak bone mass, relative to the age and sex-matched average, as measured by Dual energy X-ray absorptiometry, with the term "established-osteoporosis" including the presence of a fragility fracture. Osteoporosis is most common in women after menopause, when it is called "postmenopausal osteoporosis", but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking andmedications,, specifically glucocorticoids. Osteoporosis usually has no symptoms until a fracture occurs. For this reason, DEXA scans are often done in people with one or more risk factors, who have developed osteoporosis and be at risk of fracture.

Osteoporosis treatment includes advice to stop smoking, exercise regularly, decrease alcohol consumption, and have a healthy diet. Calcium supplements may also be advised, as may Vitamin D*. When medication is used, it may include bisphosphonates, Strontium ranelate, and osteoporosis may be one factor considered when commencing Hormone replacement therapy.