Skeletal System Overview

Skeletal System Overview

• The skeletal system is composed of bones, joints, cartilage, and ligaments
• It is divided into two parts: the axial skeleton (skull, vertebral column, rib cage) and the appendicular skeleton (limbs)

Functions of Bones

• Provide support for the body
• Protect soft organs, such as the brain and spinal cord, and thoracic organs
• Facilitate movement with skeletal muscles
• Store minerals, primarily calcium and phosphorus, and fat in the marrow cavity
• Produce blood cells through hematopoiesis

Bone Types and Structures

• The adult skeleton contains 206 bones.
• Bone tissue is classified into two types: compact bone, which is dense and homogeneous, and spongy bone, which has a porous structure.

Classification of Bones by Shape

• Long bones are longer than they are wide, with a shaft and heads at both ends.
• Example: femur, humerus
• Short bones are roughly cube-shaped.
• Example: bones of the wrist and ankle
• Flat bones are thin and flattened, usually curved.
• Example: cranial bones, ribs, sternum
• Irregular bones have complex shapes.
• Example: vertebrae, hip bones

Skull Bones

• The skull is made up of many bones that articulate with each other through sutures.
• Important bones include:
  • Frontal bone
  • Parietal bones
  • Temporal bones
  • Sphenoid bone
  • Ethmoid bone
  • Maxilla
  • Mandible
  • Nasal bone
  • Zygomatic bones
  • Lacrimal bones
  • Vomer

Paranasal Sinuses

• These are hollow cavities within several skull bones surrounding the nasal cavity.
• Functions include lightening the skull and contributing to resonance and amplification of the voice.

The Hyoid Bone

• This is the only bone in the body that does not articulate with another bone.
• It anchors the tongue and aids in swallowing and speech.

The Fetal Skull

• The fetal skull is large relative to the infant's body, making up 1/4 of the total body length.
• Fontanels, fibrous membranes that connect cranial bones, are present in the fetal skull.
• Fontanels allow for compression during birth and brain growth during pregnancy and infancy. They ossify within 24 months after birth.

The Vertebral Column

• The vertebral column, also known as the spine, consists of 26 bones (vertebrae).
• It has four curvatures:
  • Cervical curvature (concave)
  • Thoracic curvature (convex)
  • Lumbar curvature (concave)
  • Sacral curvature (convex)
  • Coccyx curvature (convex)
• The primary curvatures, thoracic and sacral, are present at birth.
• The secondary curvatures, cervical and lumbar, develop after birth.

A Typical Vertebra

• Each vertebra has a body, vertebral arch, vertebral foramen, transverse processes, spinous process, and superior and inferior articular processes.

Important Vertebrae

• Atlas (C1): The first cervical vertebra, supports the skull.
• Axis (C2): The second cervical vertebra, allows for rotation of the head.

Types of Joints

• Joints are the junctions between bones.
• They allow for movement and flexibility.
• Joints are classified based on their degree of movement:
  • Nonaxial: No movement.
  • Uniaxial: Movement in one plane.
  • Biaxial: Movement in two planes.
  • Multiaxial: Movement in three planes.
• Common types of joints include:
  • Condylar joint (biaxial)
  • Saddle joint (biaxial)
  • Ball-and-socket joint (multiaxial)

Inflammatory Conditions Associated with Joints

• Bursitis: Inflammation of a bursa, often caused by trauma or friction.
• Tendonitis: Inflammation of tendon sheaths.
• Arthritis: A group of over 100 inflammatory or degenerative diseases of the joints.
  • It is the most widespread crippling disease in the United States.
  • Symptoms include pain, stiffness, and swelling.

Clinical Forms of Arthritis

• Osteoarthritis: The most common type of arthritis, often related to aging.
• Rheumatoid arthritis: An autoimmune disease that targets the joints, often causing symmetrical inflammation and leading to deformities.

Explore the essentials of the skeletal system, which includes its composition, functions, and classifications. This quiz covers the axial and appendicular skeleton, various bone types, and their shapes, providing a comprehensive understanding of this vital system in the human body.