Lab Practical 2 Study Guide: Bones, Bone Structure, and Joints

Bones and Bone Structure

Types of Bone Cells

Bone tissue is maintained and remodeled by several specialized cells, each with distinct functions:

• Osteoblasts: Cells responsible for bone formation; they synthesize and secrete the bone matrix.

• Osteocytes: Mature bone cells that maintain the bone matrix and communicate with other bone cells.

• Osteoclasts: Large, multinucleated cells that break down bone tissue during bone remodeling.

• Osteoprogenitor cells: Stem cells that differentiate into osteoblasts.

Longest Bone in the Body

• Femur: The femur is the longest and strongest bone in the human body, located in the thigh.

Bone Orientation and Anatomical Terms

Understanding anatomical directions is essential for identifying bones:

• Medial: Toward the midline of the body.

• Lateral: Away from the midline.

• Superior: Above or toward the head.

• Inferior: Below or toward the feet.

Parts of a Long Bone

Long bones have distinct structural regions:

• Diaphysis: The shaft; composed mainly of compact bone.

• Epiphysis: The ends; contain spongy bone and red bone marrow.

• Metaphysis: The region between diaphysis and epiphysis; includes the growth plate.

• Medullary cavity: Central cavity containing yellow bone marrow.

Types of Bone Tissue

• Compact bone: Dense, forms the outer layer of bones.

• Spongy bone: Porous, found in the epiphyses and inside flat bones.

Vertebrae: Number and Features

The vertebral column consists of several types of vertebrae:

• Cervical: 7 vertebrae (C1–C7)

• Thoracic: 12 vertebrae (T1–T12)

• Lumbar: 5 vertebrae (L1–L5)

• Sacral: 5 fused vertebrae (sacrum)

• Coccygeal: 3–5 fused vertebrae (coccyx)

Special vertebrae:

• Atlas (C1): Supports the skull; allows nodding motion.

• Axis (C2): Has the dens (odontoid process); allows rotation of the head.

Articular Cartilage

• Definition: Smooth, white tissue covering the ends of bones in joints.

• Type: Made of hyaline cartilage.

• Function: Reduces friction and absorbs shock in joints.

Bone That Does Not Articulate With Any Other Bone

• Hyoid bone: Located in the neck; does not form joints with other bones.

Bone Composition

• Matrix: Primarily composed of calcium phosphate (hydroxyapatite) and collagen fibers.

• Cells: Osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells.

Joints and Movements

Classification of Joints

Joints are classified by structure and function:

• Fibrous joints: Bones joined by fibrous tissue; no movement (e.g., sutures in the skull).

• Cartilaginous joints: Bones joined by cartilage; limited movement (e.g., intervertebral discs).

• Synovial joints: Freely movable; contain a synovial cavity (e.g., knee, shoulder).

Examples of Joint Types

Joint Type	Example	Movement
Hinge	Elbow	Flexion/Extension
Ball-and-socket	Shoulder, Hip	Multiaxial (all directions)
Pivot	Atlas-Axis	Rotation
Saddle	Thumb (carpometacarpal)	Flexion/Extension, Abduction/Adduction
Plane	Intercarpal	Gliding
Condyloid	Wrist	Flexion/Extension, Abduction/Adduction

Types of Joint Movements

• Abduction: Movement away from the midline.

• Adduction: Movement toward the midline.

• Flexion: Decreasing the angle between bones.

• Extension: Increasing the angle between bones.

• Rotation: Turning a bone around its axis.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

Bone Marrow

Red vs. Yellow Bone Marrow

Type	Location	Function
Red Bone Marrow	Epiphyses of long bones, flat bones	Produces blood cells (hematopoiesis)
Yellow Bone Marrow	Medullary cavity of long bones	Stores fat (adipose tissue)

Example: In adults, red bone marrow is found mainly in the pelvis, ribs, sternum, and vertebrae, while yellow marrow fills the shafts of long bones.

Additional info: Red marrow is more abundant in children, gradually replaced by yellow marrow with age.