1C Skeletal System

Page 1: Title

  • Skeletal System Anatomy and Function of the Skeleton and Cartilage

  • Author: Christopher J. Kauhn, M.S.

Page 2: Introduction to the Skeletal System

  • The Skeletal System forms a solid framework of the body.

  • Composed of:

    • Bones

    • Cartilage

    • Ligaments

    • Associated tissues that stabilize or connect bones.

  • Origin of the word "skeleton": Greek word "skeletos" meaning dried.

Page 3: Structural Support of the Skeleton

  • Functions of the skeletal system:

    • Provides structural support for the body.

    • The outer periosteum attaches skeletal muscles.

    • Skeletal muscles connect to bones as tendons blend into the periosteal layer of bone tissue.

Page 4: Protection Provided by the Skeleton

  • The skeleton protects vital organs:

    • Brain is shielded by the skull.

    • Heart and lungs are guarded by the thoracic cage.

    • The pelvis safeguards parts of the digestive, urinary, and reproductive systems.

Page 5: Blood Cell Production

  • The skeleton manufactures blood cells through:

    • Hemopoiesis: the production process occurring in red bone marrow.

    • Red bone marrow contains hemopoietic stem cells that produce RBCs and WBCs.

Page 6: Bone Marrow Variants in Adults

  • Red bone marrow is widespread in children but replaced by:

    • Yellow (fatty) marrow in most adult bones.

  • In adults, red marrow persists in:

    • Hip bones, humerus, femur, and selected parts of the axial skeleton (skull, vertebrae, ribs, sternum).

Page 7: Storage Functions of the Skeleton

  • The skeleton works as a reservoir for:

    • Chemical substances: mainly calcium and phosphate.

    • Calcium is essential for:

      • Bone strength

      • Muscle contraction

      • Blood clotting

      • Nerve signaling.

    • Phosphorous essential for ATP utilization.

Page 8: Releases of Stored Materials

  • Over 90% of body's calcium and phosphate reserves are stored in the skeleton.

  • Reserves can be released into the bloodstream by breaking down bone.

  • Inadequate Vitamin D can lead to:

    • Low calcium and phosphate levels.

  • Rickets is a condition developing in children, resulting in overly flexible bones due to poor calcification.

Page 9: Types of Bones: Long Bones

  • Long bones: Length exceeds width characterized by:

    • Medullary (marrow) canal.

  • Examples:

    • Humerus, radius, ulna, femur, tibia, and fibula.

Page 10: Types of Bones: Short Bones

  • Short bones: Length equals width.

  • Examples:

    • Carpal bones (wrist) and tarsal bones (ankle).

Page 11: Types of Bones: Flat Bones

  • Flat bones: Expanded in 1 plane.

  • Examples:

    • Scapula, ileum of the hip, frontal bone of the skull.

Page 12: Types of Bones: Irregular Bones

  • Irregular bones: Do not fit into other categories.

  • Example: Vertebrae (oddly shaped processes and projections).

Page 13: Divisions of the Skeleton

  • Types of skeletons:

    • Axial Skeleton

    • Appendicular Skeleton

Page 14: Axial Skeleton Defined

  • The AXIAL SKELETON: occupies the central axis of the body.

  • "Axial" means to pivot.

Page 15: Components of the Axial Skeleton

  • The axial skeleton consists of:

    • Skull and hyoid (23 bones)

    • Vertebral column (26 bones)

      • 7 cervical vertebrae

      • 12 thoracic vertebrae

      • 5 lumbar vertebrae

      • 1 sacrum

      • 1 coccyx

    • Ribs and sternum (25 bones)

    • Bones of the middle ear (6 bones, 3 per side: Malleus, Incus, Stapes)

Page 16: The Appendicular Skeleton Defined

  • The APPENDICULAR SKELETON comprises the appendages including:

    • Upper limbs with associated shoulder bones

    • Lower limbs including hip bones.

Page 17: Bones of the Upper Limb

  • 64 bones include:

    • 2 Clavicles (collar bones)

    • 2 Scapulae (shoulder blades)

    • 2 Humerus bones (arms)

    • 2 Ulna bones, 2 Radius bones (forearms)

    • 8 Carpal bones (16 total)

    • 5 Metacarpal bones (10 total) (forming palms)

    • 14 Phalanges (28 total) (forming fingers)

Page 18: Bones of the Lower Limb

  • 62 bones include:

    • 2 Hip bones

    • 2 Femur bones (thighs)

    • 2 Patella bones

    • 2 Tibia bones & 2 Fibula bones (legs)

    • 7 Tarsal bones (14 total) (ankles)

    • 5 Metatarsal bones (10 total) (feet)

    • 14 Phalanges (28 total) (toes)

Page 19: Total Number of Bones

  • Adults have a total of 206 bones.

  • Some bones, e.g., sacrum and hip, are formed by individual bones that fuse during development.

  • Additional bones exist:

    • Sesamoid bones: located within tendons.

    • Ectopic bones: pathological formations within tissues.

Page 20: Long Bones Overview

  • Introduction to long bones.

Page 21: Long Bone Anatomy

  • Anatomy components include:

    • A. Epiphysis

    • B. Diaphysis

    • C. Compact bone

    • D. Spongy bone

    • E. Periosteum

    • F. Endosteum

    • G. Medullary cavity

    • H. Articular cartilage

    • I. Articular capsule

    • J. Epiphyseal disc

    • K. Metaphysis

Page 22: Structure of Long Bones

  • A. Epiphysis: Ends of long bone for joint formation.

  • B. Diaphysis: Shaft of long bone.

  • C. Compact bone: Appears solid and forms outer surface of bones.

    • Thicker in diaphysis and thinner at epiphysis.

Page 23: Spongy Bone and Periosteum

  • D. Spongy bone: Composed of thin plates meeting at angles with spaces between.

    • Found in the epiphysis.

  • E. Periosteum: Connective tissue sheath with:

    • Outer layer: Tough fibrous for tendon attachment.

    • Inner layer: Delicate cellular for growth in bone diameter.

Page 24: Endosteum and Its Importance

  • F. Endosteum: Thin cellular layer lining medullary cavity, destroying bone for marrow cavity growth and keeping bone light.

Page 25: Medullary Cavity Functions

  • G. Medullary (marrow) cavity: Long cavity in diaphysis containing red marrow (blood cell formation), yellow marrow (fat storage), or both.

Page 26: Articular Cartilage Role

  • H. Articular cartilage: Thin hyaline cartilage layer for plush joint movement.

Page 27: Articular Capsule Description

  • I. Articular capsule: Connects bones and encircles joint including joint cavity or synovial cavity.

    • Outer fibrous layer: Continuous with periosteum.

    • Inner synovial membrane: Vascular, produces synovial fluid for lubrication and nourishment.

Page 28: Epiphyseal Disc and Growth

  • J. Epiphyseal disc: Cartilaginous plate allowing growth in length; absent when growth is complete.

Page 29: Metaphysis Description

  • K. Metaphysis: Spongy bone at junction of diaphysis and epiphyseal disc; in adults, continuous with epiphysis.

Page 30: Overview of Cartilage

  • Introduction to cartilage.

Page 31: Composition of Cartilage

  • Cartilage: Tough connective tissue with cells in a firm gel-like substance.

    • More flexible than bone.

    • Commonly called gristle.

    • Lacks nerves and blood vessels (avascular).

  • Nutrients diffuse through intercellular substance.

  • Initially, the skeleton is cartilage before it's replaced by bone (ossification).

Page 32: Characteristics and Types of Cartilage

  • Classification of cartilage based on histological appearance of intercellular matrix.

Page 33: Hyaline Cartilage Features

  • Hyaline cartilage: Glass-like, translucent.

  • Examples include:

    • Embryo skeleton

    • Epiphyseal discs

    • Articular cartilages

    • Costal cartilages (ribs to sternum)

    • Larynx, trachea, bronchi

    • Nasal cartilages

Page 34: Fibrocartilage Examples

  • Fibrocartilage features and locations:

    • Interpubic disc

    • Intervertebral discs

    • Other anatomical sites related to lumbar vertebrae and pelvic region.

Page 35: Elastic Cartilage Overview

  • Elastic Cartilage examples include:

    • Auricle (external ear)

    • Auditory tube (inner ear to pharynx)

    • Epiglottis (flap preventing food from entering lungs).