Human Skeletal System

Skeletal System

• The skeletal system consists of 206 bones and a few cartilages, divided into axial and appendicular skeleton.
• The axial skeleton includes 80 bones along the main axis of the body.

Axial Skeleton

• The skull is composed of 22 bones, including cranial and facial bones.
• Cranial bones protect the brain, while facial bones form the front part of the skull.
• The hyoid bone is present at the base of the buccal cavity.
• The middle ear contains three tiny bones called ear ossicles.
• The skull articulates with the vertebral column through occipital condyles.
• The vertebral column is made up of 26 vertebrae, divided into cervical, thoracic, lumbar, sacral, and coccygeal regions.
• The vertebral column protects the spinal cord, supports the head, and serves as the attachment point for the ribs and back muscles.

Vertebral Column

• The cervical region has 7 vertebrae.

Thorax

• The sternum is a flat bone on the ventral midline of the thorax.
• There are 12 pairs of ribs, with the first seven pairs being true ribs, attached to the thoracic vertebrae and sternum.

Appendicular Skeleton

• Each limb is made up of 30 bones.
• The hand (forelimb) bones include the humerus, radius, ulna, carpals, metacarpals, and phalanges.
• The leg (hind limb) bones include the femur, tibia, fibula, tarsals, metatarsals, and phalanges.
• The knee is covered by the patella.
• The pectoral girdle articulates the upper limbs with the axial skeleton and consists of the clavicle and scapula.
• The pelvic girdle articulates the lower limbs and is formed by the fusion of the ilium, ischium, and pubis bones.

Joints

• Joints are points of contact between bones or bones and cartilage.
• Joints can be fibrous, cartilaginous, or synovial.
• Fibrous joints do not allow movement, while cartilaginous joints permit limited movement.
• Synovial joints have a fluid-filled cavity, allowing considerable movement.
• Examples of synovial joints include ball and socket, hinge, pivot, gliding, and saddle joints.

Disorders of the Muscular and Skeletal System

• Myasthenia gravis is an autoimmune disorder affecting the neuromuscular junction.
• Muscular dystrophy is a degenerative disorder.
• Tetany is rapid spasms in muscles due to low calcium levels.
• Arthritis is inflammation of joints.
• Osteoporosis is a disorder characterized by decreased bone mass.
• Gout is inflammation of joints due to uric acid crystal accumulation.