HESI A2 Exam: Skeletal System
• What are the dilated ends of bones called?
• What surrounds and protects the bone?
• What is the function of the Haversian canal?
• What type of bones are filled with marrow? Give an example of this type of bone.
• What type of bones protect internal organs? Example please.
• What differentiates rheumatoid arthritis from normal arthritis?
Parts of the Skeleton
There are two parts of the skeleton: the axial and the appendicular. The appendicular skeleton is composed of the limb bones, scapula, pelvis and clavicle. The axial skeleton consists of the skull, vertebrae, rib cage, and hyoid bone.
Types of Bone
Long bones are hollow, filled with marrow, and are longer than they are wide. The femur, tibia, fibula, metatarsals, humerus, radius and metacarpals are all long bones.
Short bones are wider than long. Examples include carpals and tarsals.
Flat bones provide protection to internal organs and examples include the sternum, ribs, and pelvis.
Irregular bones vary in shape. Examples include the bones of the vertebrae column, the skull, and the knee and elbow.
Spongy bone is less dense than compact bone, is located at the ends of bones, and contains bone marrow. Bone marrow is the site of red blood cell production.
Compact bone supports the body and stores calcium.
Ligaments attach bone to bone and tendons attach muscle to bone.
At the articulating ends of the bone is hyaline cartilage, which both prevents direct bone contact and cushions the joint.
Long bones have a cylindrical shaft, called the diaphysis.
They also have dilated ends, called the epiphyses.
The epiphyseal plate is the site of new bone growth. It’s a growth plate.
The periosteum is a growth plate and surrounds and protects the bone.
Structure of Bone
Osteoblasts build bone and osteoclasts break it down.
Osteocytes sense mechanical stress and regulate both osteoblasts and osteoclasts.
Haversian canals provide nutrients to the bone cells (the osteoblasts, osteoclasts, and osteocytes).
Volkmann canals connect the Haversian canals and enable nutrient exchange.
Canaliculi enable cellular communication.
Joints
Fibrous joints are held together by ligaments and cannot be moved. Bones in the skull are the most common example of a fibrous joint.
Synovial joints are ball and socket, hinge, and pivot joints. Types of synovial joints are found in the knee, elbow, hip and shoulder. The femur and the scapula are synovial joints.
Cartilaginous joints are found when two bones are connected by cartilage and are somewhat moveable. Cartilaginous joints could be joints found between vertebrae in the spine.
Arthritis
Rheumatoid arthritis is an autoimmune disease that is caused by immune cells attacking either the cartilage or joint lining.
Arthritis, on the other hand, develops when cartilage between joints breaks down over time.
Osteoarthritis is a degenerative joint disease characterized by the loss of cushioning cartilage.
Osteoporosis is caused by lack of calcium and vitamin D in the body and is also characterized by bone loss that occurs naturally in aging.
Ribs
The first seven pairs of ribs are called true ribs.
The eighth, ninth and tenth pairs are called false ribs.
The eleventh and twelfth pair are called floating ribs.
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