Bones and Bone Structure

Major Bones and Their Parts

This section covers the identification and features of major bones in the human body, including their anatomical landmarks and functions.

• Radius and Ulna: The two long bones of the forearm. The radius is lateral (thumb side), and the ulna is medial (pinky side) in anatomical position.

• Fibula: The slender lateral bone of the lower leg, parallel to the tibia.

• Mandible: The lower jawbone, notable for the mandibular foramen (passage for nerves), mental foramen (anterior opening for nerves/vessels), condyle (articulates with temporal bone), and alveolar process (holds teeth).

• Skull Bones: Includes the palatine (posterior part of hard palate), maxillae (upper jaw), zygomatic (cheekbone), occipital (back of skull), foramen magnum (large opening for spinal cord), and sphenoid bone (central skull base).

• Hyoid Bone: U-shaped bone in the neck, not articulating with other bones; important in forensic identification of strangulation.

• Xiphoid Process: Inferior tip of the sternum; landmark for CPR hand placement.

• Glenoid Cavity: Socket in the scapula for the humerus (shoulder joint).

• Pubic Symphysis: Cartilaginous joint uniting left and right pubic bones.

• Acetabulum: Hip socket for femoral head.

Example: The foramen magnum is a critical landmark for the passage of the spinal cord from the brain to the vertebral column.

Bone Microstructure

• Osteon: The functional unit of compact bone, consisting of concentric lamellae around a central canal.

• Central Canal: Contains blood vessels and nerves.

• Lacunae: Small spaces housing osteocytes (bone cells).

Example: Osteons are visible in cross-sections of compact bone under the microscope.

The Axial and Appendicular Skeleton

Skull and Facial Bones

• Sutures: Immovable joints between skull bones. Examples include coronal, sagittal, lambdoid, and squamous sutures.

• Sella Turcica: Depression in the sphenoid bone housing the pituitary gland.

• Crista Galli: Vertical projection of the ethmoid bone, attachment for brain membranes.

• Nasal Bones: Form the bridge of the nose.

Vertebrae

• Body: The thick, anterior portion of a vertebra that bears weight.

• Spinous Process: Posterior projection for muscle/ligament attachment.

• Vertebral Canal: Passage for the spinal cord formed by vertebral foramina.

• Intervertebral Cavity: Space between vertebrae for intervertebral discs and nerves.

Thorax

• Costal Cartilage: Hyaline cartilage connecting ribs to the sternum.

• Floating Ribs: The 11th and 12th pairs of ribs, not attached to the sternum.

• Sternum: The breastbone, consisting of the manubrium, body, and xiphoid process.

Wrist and Ankle Bones

• Carpals: Eight small bones forming the wrist.

• Tarsals: Seven bones forming the ankle.

• Calcaneus: The heel bone, largest tarsal.

• Capitate: Largest carpal bone in the center of the wrist.

• Talus: Tarsal bone that articulates with the tibia and fibula.

• Metacarpals: Five bones forming the palm of the hand.

The Tissue Level of Organization

Types of Epithelial Tissue

Epithelial tissues cover body surfaces, line cavities, and form glands. They are classified by cell shape and layers.

• Simple Squamous Epithelium: Single layer of flat cells; allows diffusion and filtration. Found in alveoli and capillaries.

• Simple Cuboidal Epithelium: Single layer of cube-shaped cells; functions in secretion and absorption. Found in kidney tubules.

• Simple Columnar Epithelium: Single layer of tall, column-like cells; lines digestive tract.

• Stratified Squamous Epithelium: Multiple layers; protects against abrasion. Found in skin, vagina, and esophagus.

Example: The lining of the trachea contains goblet cells (secrete mucus) and cilia (move mucus).

Other Tissue Types

• Adipose Tissue: Stores fat, insulates, and cushions organs.

• Cartilage: Flexible connective tissue found in joints, ear, nose, and respiratory tract.

Blood

Components of Blood

• Plasma: The liquid matrix of blood, containing water, proteins, nutrients, and waste products.

• Erythrocytes (Red Blood Cells): Carry oxygen; appear red under the microscope.

• Leukocytes (White Blood Cells): Defend against infection; appear purple in stained slides.

Summary Table: Key Structures and Their Functions

Additional info:

• Knowing left/right orientation of bones is important for anatomical identification.

• The xiphoid process is a critical landmark for CPR; improper hand placement can cause injury.

• The hyoid bone is unique in not articulating with other bones and is often examined in forensic cases of suspected strangulation.