Skeletal System: Bone Growth, Structure, and Joints Study Guide

Chapter 6: Bone Growth and Physiology

Appositional vs. Interstitial Bone Growth

Bone growth occurs through two primary mechanisms: appositional growth (increase in bone diameter) and interstitial growth (increase in bone length).

• Appositional growth: New bone tissue is added to the surface of existing bones, increasing thickness.

• Interstitial growth: Occurs at the epiphyseal plate, allowing bones to lengthen during development.

• Example: Long bones such as the femur grow in length via interstitial growth and in width via appositional growth.

Periosteum and Endosteum Anatomy & Physiology

The periosteum and endosteum are connective tissue membranes covering the outer and inner surfaces of bones, respectively.

• Periosteum: Dense fibrous membrane covering the bone's outer surface; contains osteoblasts for bone growth and repair.

• Endosteum: Thin membrane lining the medullary cavity; involved in bone remodeling.

Hormonal Effects on Bone Physiology

Various hormones regulate bone growth and maintenance.

• Growth hormone: Stimulates bone growth during childhood.

• Parathyroid hormone: Increases blood calcium by stimulating bone resorption.

• Calcitonin: Lowers blood calcium by inhibiting bone resorption.

• Sex hormones (estrogen, testosterone): Promote bone growth and epiphyseal plate closure.

Bone Markings and Anatomy

Bones have various markings that serve as attachment points for muscles, ligaments, and tendons.

• Foramen: Opening for nerves and blood vessels.

• Process: Projection for muscle attachment.

• Fossa: Depression for articulation.

Epiphyseal Plate Function

The epiphyseal plate (growth plate) is a region of cartilage that allows for longitudinal bone growth during development.

• When growth is complete, the plate ossifies and becomes the epiphyseal line.

Red and Yellow Bone Marrow

Bone marrow exists in two forms: red marrow (hematopoietic) and yellow marrow (fat storage).

• Red marrow: Produces blood cells; found in flat bones and the ends of long bones.

• Yellow marrow: Stores fat; found in the medullary cavity of long bones.

Types of Bone Cells

Bone tissue contains several cell types, each with specific functions.

• Osteoblasts: Build new bone matrix.

• Osteocytes: Mature bone cells maintaining bone tissue.

• Osteoclasts: Break down bone matrix for remodeling.

Compact vs. Spongy Bone

Bones are composed of compact bone (dense, strong) and spongy bone (porous, lightweight).

• Compact bone: Forms the outer layer; provides strength.

• Spongy bone: Found at bone ends; contains red marrow.

Bone Remodeling and Ossification

Ossification is the process of bone formation, while remodeling maintains bone strength and mineral homeostasis.

• Intramembranous ossification: Forms flat bones (e.g., skull).

• Endochondral ossification: Forms long bones from cartilage models.

Bone Density and Wolff's Law

Wolff's Law states that bone adapts to the loads under which it is placed.

• Bone density increases with mechanical stress and decreases with inactivity.

• Peak bone density is typically reached in early adulthood.

Functions of the Skeletal System

The skeletal system serves several vital functions:

• Support

• Protection of internal organs

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphorus)

• Blood cell production (hematopoiesis)

Chapter 7: Bone Identification and Axial Skeleton

Major Bones and Their Locations

Students should be able to identify all major bones, except the six middle ear bones.

• Axial skeleton: Skull, vertebral column, rib cage.

• Appendicular skeleton: Limbs, pelvic and pectoral girdles.

Pelvic Bones and Articulations

The pelvic bones form the pelvis and articulate to support body weight and protect organs.

• Pelvic girdle: Consists of ilium, ischium, and pubis.

• Bones fuse together to form the pelvis.

Skull Sutures and Cranial Bones

Sutures are immovable joints between skull bones.

• Major sutures: coronal, sagittal, lambdoid, squamous.

• Cranial bones: Frontal, parietal, temporal, occipital, sphenoid, ethmoid.

Weight-Bearing Bones and Functions

Some bones are specialized for weight bearing and support.

• Lower extremity: Femur is the primary weight-bearing bone.

• Spinal cord: Protected by vertebrae; vertebral column supports body weight.

Sella Turcica and Nasal Conchae

The sella turcica is a depression in the sphenoid bone housing the pituitary gland. The nasal conchae are bony structures in the nasal cavity.

• Superior and Middle Nasal Conchae: Located in the ethmoid bone.

• Sella turcica: Important for endocrine function.

Axial vs. Appendicular Skeleton

The skeleton is divided into two main parts:

• Axial skeleton: Skull, vertebral column, rib cage.

• Appendicular skeleton: Limbs and girdles.

Anatomy of the Ankle (C1) and Nasal Conchae

• Ankle bones: The talus and calcaneus are key components.

• Nasal conchae: Superior and middle conchae are part of the ethmoid bone; inferior concha is a separate bone.

Chapter 8: Joints and Ligaments

Types of Joints

Joints, or articulations, connect bones and allow for movement. There are several types:

• Fibrous joints: Immovable (e.g., sutures in the skull).

• Cartilaginous joints: Slightly movable (e.g., intervertebral discs).

• Synovial joints: Freely movable (e.g., knee, shoulder).

Joint Mobility and Spine Anatomy

The spine contains joints with varying degrees of mobility.

• Cervical spine: Most mobile region of the vertebral column.

• Example: Atlantoaxial joint allows head rotation.

Ligaments of the Knee

Ligaments are strong bands of connective tissue stabilizing joints.

• Anterior cruciate ligament (ACL): Prevents anterior displacement of the tibia.

• Posterior cruciate ligament (PCL): Prevents posterior displacement of the tibia.

• Medial and lateral collateral ligaments: Provide side-to-side stability.

Joint Movements

Joints allow for various movements, classified as:

• Flexion/Extension

• Abduction/Adduction

• Rotation

• Circumduction

Table: Types of Joints and Their Mobility

Joint Type	Mobility	Example
Fibrous	Immovable	Sutures of the skull
Cartilaginous	Slightly movable	Intervertebral discs
Synovial	Freely movable	Knee, shoulder

Additional info: Academic context and definitions have been expanded for clarity and completeness.