the human axial and appendicular skeletal

• The human skeletal system is a complex structure with two distinct divisions composed of fused and individual bones supported by -ligaments -tendons -muscles -cartilage.
• Humans are born with over 300 bones, but many of the bones fuse between birth and the end of maturity and remain with the average number of 206 bones in an adult skeleton.
• Bones have three different layers made from three different kinds of cells.
• The general structure of bones is a combination of a protein called collagen and a molecule called calcium phosphate that weave together to form a strong and lightweight structure.
• Bones are composed of four types of cells. These are:

  1.Osteoblasts

  2. Osteocytes

  3.Osteoclasts

  4.Osteoprogenitor
• Osteoblasts involve in new bone formation.
• Osteocytes are mature bone cells that help to mature bones of newborns.
• Osteoclasts break down bones and help them to form into correct shapes.
• Osteoprogenitor are important in repair of fracture.
• Based on their shapes, there are four different types of bones in the human body:

  1.Long bones

  2. Short bones

  3. Flat bones

  4. Irregular bones

  5. Sesamoid bones
• Long bones have long and thin shapes.
• Short bones have squat and cubed shapes.
• Flat bones have flattened and broad surfaces.
• Irregular bones have shapes that do not conform to the above three types. it have complex shape which helps protect internal organ. it vary in shape and structure, therefore do not fit into any other categories.
• Sesamoid bones are small, flat bones and are shaped similarly to a sesame seed
• Functions of bones:

  1.Support body and helping move

  2. Protecting the internal organs

  3. Producing blood cells

  4. Storing and releasing fat

  5. Storing and releasing minerals
• Support body and helping move: bones hold up body stability, keep from collapsing to the ground, movement and body posture.
• Protecting the internal organs: bones keep organs to be safe from hard impacts, punctures, and other forms of injury (ribs protect the heart and lungs, and the skull protects the brain).
• Producing blood cells: certain types of bones make platelets, red blood cells, and white blood cells inside bones.
• Storing and releasing fat: certain bones store fat and release when body needs energy.
• Storing and releasing minerals: bones store necessary minerals when the levels are too high in the blood and release minerals when the body needs them (calcium, phosphorus, and vitamin D).
• The axial skeleton is the one that consists of the skull, trunk, and pelvis bones of the medial core of the body.
• Skull

  • Composed of cranium bones fitting together at joints (sutures)
  • Facial bones forming the lower front part
• Facial bones


  • Eye
  • Ear
  • Nose
  • Mouth cavities
• Axial skeleton includes - the jaw or mandible - the upper jaw or maxilla - the zygomatic or cheekbone - the nasal bone.
• The rib cage (thoracic cage) forms the thorax (chest) portion of the body and consists of 12 pairs of ribs with costal cartilage and the sternum
• An appendicular skeleton is the portion of the skeleton that consists of 126 bones out of a total of 206 bones and supporting appendages.
• The appendicular skeleton includes


  • Skeletal elements
  • Limbs
  • Shoulder-supporting girdle
  • Pectoral
  • Pelvic girdle
  • Joined appendages
• Total number of bones in the human body = axial + appendicular = 80 + 126 = 206
• Joints are the parts of the body where two or more bones meet with binding tissues and allow the body to produce movements
• Types of joints

  1.The ball and socket joint

  2. Hinge joints

  3. Condyloid joints

  4. Pivot joints

  5. Gliding joints

  6. Saddle joint
• The ball and socket joint: the rounded head of one bone sits in the cup of another bone to permit movement in all directions (shoulder and hip joints).
• Hinge joints: like a door, a joints that opens and closes in one direction along one plane only (elbow and knee joints).
• Condyloid joints: joints that do not rotate but allow movements (finger and jaw).
• Pivot joints are rotary or trochoid joints in which one bone swivels in a ring (ulna, radius, and neck).
• Gliding joints: a plane joint that allows only limited movement by slipping smooth surfaces over one another (wrist joint).
• Saddle joint: enables movement back and forth, side to side, and cannot rotate (thumb base)