Biology 2401 By: Sedi Heydari

The skeletal system includes connective tissues such as bone, cartilage, tendons, and ligaments. These tissues are combined with the various types of muscle tissue to form the Musculo-Skeletal System. 1) Bone itself has five functions, including:  Movement  Support  Calcium Storage  Production of Red Blood Cells  Protection

 2) Cartilage serves as the fetal template for bone formation, and covers the ends of bone, most especially at the joints, or points of articulation.  3) Tendons connect muscles to bone  4) Ligaments connect bone to bone

 The adult human skeleton has 206 bones  Bones are making blood cells in the center of the bone.  Red marrow, white marrow, and yellow marrow (found in long bones).  Bone also functions as a site for mineral storage and blood cell formation.

A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood. Calcium is an important mineral that bone cells need to stay strong.

The axial skeleton includes the skull, the hyoid bone, the vertebral column (spine, sacrum, and coccyx), the sternum, and the ribs. Its components are aligned along the long axis of the body. The appendicular skeleton includes the bones of the upper extremities (arms, forearms, and hands), the pectoral (shoulder) girdle, the pelvic (hip) girdle, and the bones of the lower extremities (thigh, knee, leg, and foot). Its components are outside the body main axis.

 a. Long bones : main components of limbs, include the femur, humerus, radius and ulna, tibia and fibula.  b. Short Bones : include metacarpals of hands and metatarsals of feet  c. Flat Bones : includes cranial bones, innominates and scapula, offer protection and large muscle attachments  d. Irregular Bones : includes vertebra, carpals (hand) and tarsals (feet), many of the cranial bones. These bones are generally complex in design and serve specialized purposes

 "Articular capsules" surround the joints between the cartilages of the true ribs and the sternum (breastbone).  “Sternum" is the medical name for the breastbone, a long, narrow, flat plate that forms the center of the front of the chest.  “Tarsal bones"are The foot consists of an ankle, an instep, and five toes.

 “Carpal bones“ are the skeleton of the wrist consists of eight small "carpal bones" that are firmly bound in two rows of four bones each.  Ribs are flat, curved bones that form the framework of the chest and make up a cage to protect the heart, lungs and other upper organs.  Phalanges are the small bones that make up the skeleton of the fingers, thumb and toes. Each finger and smaller toe has three phalanges; the thumb and big toe each have two. The phalange nearest the body of the hand or foot is call the "proximal" phalange; the one at the end of each digit is the "distal" phalange; and, of course, when there are three, the middle one is called the "middle" phalange.

 “Femur" is the thigh bone, the longest bone in the body. The lower end joins the tibia (shin) to form the knee joint. The upper end is rounded into a ball (or "head" of the femur) that fits into a socket in the pelvis to form the hip joint.  Humerus is the bone of the upper arm. The smooth, dome-shaped head of the bone lies at an angle to the shaft and fits into a shallow socket of the scapula (shoulder blade) to form the shoulder joint.  Pelvis is a ring of bones in the lower trunk of the body, which is bounded by the coccyx (tail bone) and the hip bones. The pelvis protects abdominal organs such as the bladder, rectum and, in women, the uterus.

 Tibia is the inner and thicker of the two long bones in the lower leg. It is also called the shin bone. The tibia is the supporting bone of the lower leg and runs parallel to the other, smaller bone (the fibula) to which it is attached by ligaments.  Fibula is the outer and thinner of the two long bones of the lower leg. It is much narrower than the other bone (the shin), to which it runs parallel and to which it is attached at both ends by ligaments. The upper end of the fibula does not reach the knee, but the lower end descends below the shin and forms part of the ankle. Its main function is to provide attachment for muscles.

 Cartilage is all over our body. It covers bones and makes part of our nose as well as forms our ear lobes.  Cartilage: Not as strong as bone, but more flexible(Baby).  ~Has gel-like matrix containing collagenous and elastic fibers  ~Chondrocytes lie within lacunae that are irregularly grouped  ~Has no nerves  ~Great for padding joints  ~No blood vessels, so it heals slowly

When two or more bones meet, a joint is formed. They enable different body movements. There are 4 types of joints, the part of junction between 2 bones.  Ball and socket allows freedom of movement in several directions. It can be found between humerus & scapula; and femur & hipbone.  cartilaginous joints or Hinge joint allows movements in a single plane. An example of this joint can be found in your knee.  Pivot joining allows freedom of movement of somewhat between ball and socket & hinge joining. It can be found in your wrists and ankles.  fibrous joints or Joints of the skull are extremely strong and immovable.

 Arthritis and direct physical trauma to a joint are the causes of joint damage. Arthritis is a group of conditions where there is damage caused to the joints of the body.  The most common form of arthritis, osteoarthritis (also known as degenerative joint disease) occurs following trauma to the joint, following an infection of the joint or simply as a result of aging.  rheumatoid arthritis and psoriatic arthritis, which are autoimmune diseases in which the body is attacking itself.