Essentials of Human Anatomy & Physiology, 7 th ed. by Elaine N. Marieb Chapter 5 The Skeletal System: Anatomy Chapter 5 The Skeletal System: Anatomy

 Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments  Divided in two: Axial skeleton: bones that form the longitudinal axis of the body (skull, vertebrae, sternum, ribs, hyoid bone) Appendicular skeleton: bones of the limbs and girdles Skeletal System: Anatomy

Bones of the Human Body  The adult skeleton has 206 bones  Two basic types of osseous (bone) tissue: 1. Compact bone Homogeneous, smooth, dense 2. Spongy bone Small needle-like pieces of bone Many open spaces Skeletal System: Anatomy

compact bone spongy bone

Microscopic Anatomy of Bone Skeletal System: Anatomy

Osteon (AKA Haversian System) A unit of bone consisting of a central canal and matrix rings Central canal (AKA Haversian canal) Opening in the center of an osteon Carries blood vessels and nerves Perforating canal (AKA Volkman’s canal) Canal perpendicular to the central canal Carries blood vessels and nerves Central canal Perforating canal Skeletal System: Microscopic Anatomy

Lacunae Cavities containing mature bone cells (osteocytes) Arranged in concentric rings called lamellae Skeletal System: Microscopic Anatomy

Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system Skeletal System: Microscopic Anatomy

Classification of Bones on the Basis of Shape Skeletal System: Anatomy

Long bones  Typically longer than wide  Have a shaft with heads at both ends  Contain mostly compact bone Examples: Femur, humerus The human femur – the longest bone in the body. Skeletal System: Classification of Bones

Short bones  Generally cube-shaped  Contain mostly spongy bone Examples: Carpals, tarsals Sesamoid bones are a special type of short bone that form within tendons (Ex: patella or kneecap) Skeletal System: Classification of Bones

Flat bones  Thin and flattened  Usually curved  Thin layers of compact bone around a layer of spongy bone Examples: Skull, ribs, sternum (breastbone) Skeletal System: Classification of Bones

Irregular bones  Irregular shape  Do not fit into other bone classification categories Examples: Vertebrae and hip bones Skeletal System: Classification of Bones

Gross Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone Epiphysis (Pl. epiphyses) Ends of the bone Composed of a thin layer of compact bone filled with spongy bone Skeletal System: Long Bones

Structures of a Long Bone Periosteum Outside covering of the diaphysis Fibrous connective tissue membrane Sharpey’s fibers Secure periosteum to underlying bone Arteries Supply bone cells with nutrients Skeletal System: Long Bones

Articular cartilage Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces Skeletal System: Long Bones Structures of a Long Bone

Medullary cavity (AKA Yellow Marrow cavity) Cavity of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation) in infants (Red marrow in spongy bone if adults) Skeletal System: Long Bones Structures of a Long Bone

Epiphyseal plate (AKA growth plate) a flat plate of hyaline cartilage in young, growing bone that causes lengthwise growth; turns into the epiphyseal line in adult bone (by the end of puberty) Skeletal System: Long Bones Structures of a Long Bone

Growth plates under the X-ray

Bone Markings  Surface features of bones  Sites of attachments for muscles, tendons, and ligaments  Passages for nerves and blood vessels  Categories of bone markings Projections and processes – grow out from the bone surface Depressions or cavities – indentations Skeletal System: Anatomy

Joint = Articulation = Arthrosis Definition: A point of contact between two bones, between bone and cartilage, or between bone and teeth Skeletal System: Joints

Structural Classification of Joints  Fibrous joints  Generally immovable  Cartilaginous joints  Immovable or slightly moveable  Synovial joints  Freely moveable

Fibrous Joints = generally immovable  Bones united by fibrous connective tissue  Examples  Sutures  Syndesmoses  Allows more movement than sutures  Example: distal end of tibia and fibula  Gomphoses between tooth and its socket

Cartilaginous Joints = slightly movable  Bones connected by cartilage  Examples  Pubic symphysis  Intervertebral joints

Synovial Joints = freely movable  Articulating bones are separated by a synovial (joint) cavity  Synovial fluid is found in the joint cavity

Features of Synovial Joints  Articular cartilage (hyaline cartilage) covers the ends of bones  Joint surfaces are enclosed by a fibrous articular capsule  Have a synovial cavity filled with synovial fluid surrounded by synovial membrane  Ligaments reinforce the joint

Structures Associated with the Synovial Joint  Bursae – flattened fibrous sacs  Lined with synovial membranes  Filled with synovial fluid  Not actually part of the joint  Tendon sheath  Elongated bursa that wraps around a tendon

The Synovial Joint Figure 5.28

Types of Synovial Joints Based on Shape Figure 5.29a–c

Types of Synovial Joints Based on Shape Figure 5.29d–f