The Skeletal System
Cervical region – the main function of the cervical spine is to support the weight of the head
Thoracic region –the main function of the thoracic spine is to protect the organs of the chest by providing attachment for the rib cage.
Lumbar region –the main function of the lumbar spine is to bear the weight of the body.
Sacral region –the main function of the sacrum is to provide attachment for the iliac (hip) bones and protect the pelvic organs.
Coccyx region –the four fused bones of the coccyx or tailbone don’t really have a function. It is an embryology remnant of a tail from our primate ancestors.
Types of Bones
Long Bones – These have a greater length than width, with growth plates (epiphysis) at either end, having a hard outer surface of compact bone and a spongy inner known as cancellous bone containing bone marrow. Examples of long bones would be: Tibia, Fibula, Femur, Humerus. But even some of the smallest bones in the body such as: Metacarpals, Metatarsals and Phalanges are long bones.
Short Bones – These are approximately as wide as they are long. The primary function of short bones is to provide support and stability with little movement. They consist of cancellous (spongy) bone surrounded in a thin layer of compact bone. Examples of short bones include: Tarsals and Carpals.
Flat Bones – These have a spongy middle between two layers of compact bone. They are found in areas which need protection and also in parts where broad muscle attachment is needed. In adults, the highest numbers of red blood cells are formed in flat bones. Examples of flat bones would include: Scapula, Sternum and Cranium. The Pelvis and Ribs are also classed as flat bones.
Irregular Bones – These bones do not fit into any category. They have lots of projections and grooves from which lots of muscles and ligaments attach. They primarily consist of cancellous (spongy) bone, with a thin outer layer of compact bone. Examples of Irregular bones would consist of: the Vertebrae, Sacrum and Mandible.
Sesamoid Bones – These resemble the shape of a sesame seed. They are small bones wrapped in tendons and give extra protection to joints. Examples of sesamoid bones would be the Patella and the base of the thumb.
Function of Skeletal System
1. Support - The skeleton is the framework of the body, it supports the softer tissues and provides points of attachment for most skeletal muscles.
2. Protection - The skeleton provides mechanical protection for many of the body's internal organs, reducing risk of injury to them. For example, cranial bones protect the brain, vertebrae protect the spinal cord, and the ribcage protects the heart and lungs.
3. Movement - Skeletal muscles are attached to bones, therefore when the associated muscles contract they cause bones to move.
4. Storage of Minerals - Bone tissues store several minerals, including calcium (Ca) and phosphorus (P). When required, bone releases minerals into the blood - facilitating the balance of minerals in the body.
5. Production of Blood Cells - Blood cells are made in the bone marrow by 'stem' cells. The bone marrow is the soft 'spongy' material in the centre of bones. The large flat bones such as the Pelvis and Sternum contain the most bone marrow.
6. Storage of Chemical Energy - With increasing age some bone marrow changes from 'red bone marrow' to 'yellow bone marrow'. Yellow bone marrow consists mainly of adipose cells, and a few blood cells. It is an important chemical energy reserve.
The skeleton of a newborn baby is made up of more than 300 parts, most of which are made of cartilage. Over time, most of this...