SKELETAL & MUSCULAR SYSTEM

Skeletal System

Compose of the bones and cartilages forming the framework of the human body.

Osteology

The study of bone structure and the treatment of bone disorder

Bone

a connective tissue consisting of cells and matrix made up of Collagen Fibers & Calcified Ground Substance

Collagen fibers

Made up of organic component

Responsible for its structural support and mechanical strength

Calcified ground substance

Made up of inorganic component

Responsible for making the bone strong and hard.

Calcium Phosphate

Forms hydroxyapatite crystals, the hard mineral compound that gives bones and teeth their structural strength and rigidity.

Calcium Carbonate

works alongside calcium phosphate as a key mineral component that gives bone matrix its hard, strong structural quality

Bone Ossification

begins during embryonic development and occurs through two primary processes: intramembranous ossification and endochondral ossification

Bone Development

Arise from mesenchymal cells

Intramembranous ossification

Bone formation

Endochondral ossification

Cartilage formation

Diaphysis

the long cylindrical, main portion of the bone

Epiphysis

the distal and proximal ends of the bone

Metaphysis

• In mature bone, where the diaphysis meets the epiphysis

• In growing bone, where the epiphyseal plate (hyaline cartilage) is located

• Age 18- 21, the bone stops to grow

Articular cartilage

reduces the friction and absorbs shock at freely movable joints

Periosteum

a dense irregular connective tissue with tough sheath that surrounds the bone’s surface

Medullary cavity

the space within the diaphysis that contains yellow bone marrow in adults

Endosteum

a single layer of connective tissue and bone - forming cells in the medullary cavity

Osteoblasts BLAST - IMMATURE CELLS

• Active in bone formation

• Occurs not only in initial bone formation but also during repair

• Secretes organic components in bone matrix

Osteoclasts DESTRUCTION

• Active in bone resorption

• Present in almost all bone cavities

• Function to cause resorption – DESTRUCTION OF BONE TISSUES

Osteocytes – ADULT/MATURE CELLS

• Principal cells in mature bone

• They are technically osteoblasts that are surrounded by bone matrix as bone is form

Compact Bone

Contains few spaces and is the strongest form of bone tissue. It is found beneath the periosteum of all bones and makes up the bulk of the diaphysis of long bones. Compact bone tissue provides protection and support and resists the stresses produced by weight and movement.

Spongy Bone

With many spaces hence, being called ‘spongy’. Doesn’t contain osteons

Trabeculae

the irregular thin columns similar to lamellae

Red bone marrow

where hemopoiesis/hematopoiesis takes place. Red blood cells and granular cells (megakaryocytes and leukocytes)are produced

Long bones

Typically, longer than wide. Have a shaft with heads at both ends. Contain mostly compact bone

femur, tibia and fibula, humerus, ulna and radius, and phalanges

Short bones

Generally, cube-shape. Contain mostly spongy bone

Carpals, tarsals

Flat bones

Thin and flattened. Usually curved. Thin layers of compact bone around a layer of spongy bone

Cranial, sternum, ribs

Irregular bones

complex shapes and cannot be grouped into any of the previous categories.

vertebrae, pelvic bone, certain facial bones, and the calcaneus.

Sesamoid bone

develop in certain tendons where there is considerable friction, tension, and physical stress

Patella

Bone Growth

• Epiphyseal plates allow for growth of long bone during childhood.

Zone of resting cartilage

cells do not function in bone growth but anchor the epiphyseal plate to the epiphysis of the bone.

Zone of proliferating cartilage

arranged like stacks of coins; these chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix.

Zone of hypertrophic cartilage

consists of large, maturing chondrocytes arranged in columns.

Zone of calcified cartilage

few cells thick and consists mostly of chondrocytes that are dead because the extracellular matrix around them has calcified

Parathyroid hormone of the parathyroid gland

• Released whenever there is decreased blood calcium level (HYPOCALCEMIA).

• This hormone stimulates bone resorption resulting to increased blood calcium.

Calcitonin hormone of the thyroid gland

• This hormone inhibiting bone resorption thus resulting to decreased blood calcium.

• Released whenever there is increased blood calcium level (HYPERCALCEMIA).

Fracture

• Break in the bone or cartilage. Nomenclature is based on severity, shape, or position of fracture line. Can be simple or compound (depending on skin breakage), and complete or incomplete (depending on extent through bone).

Open (compound) fracture

1. the broken ends of the bone protrude through the skin.

Closed (simple) fracture

1. does not break the skin.

Comminuted fracture

1. smaller bone fragments lie between the two main fragments.

Greenstick fracture

1. partial fracture in which one side bends and the other broken.

Impacted fracture

1.  one end of the fractured bone is forcefully driven to the interior of the other.

Pott's fracture

1. fracture of the distal end of the tibia.

Colles' fracture

1.  fracture of the distal end of the radius wherein the distal fragment is posteriorly displaced.

Stress fracture

1. microscopic bone fissures without any evidence of injury to other tissues.

Fracture Hematoma formation

1. Swelling and inflammation at the site of the fracture 6-8 hours after the onset of injury.

Fibrocartilaginous callus formation

1.  fibroblast and collagen fibers invade the fracture site.

Bony callus formation

1. 3-4 months the fibrocartilages are converted into spongy bones (bone callus).

Bone remodeling

dead portions of the original fragments of broken bone are gradually resorbed as osteoclasts that replaces the spongy bone callus into compact bone.

ARTHROLOGY

study of the joints

KINESIOLOGY

study of the motion of the body.

Fibrous Joints

fibrous connective tissue that holds the bone together.

Synarthroses

immovable fibrous joints (E.g., suture).

Cartilaginous Joints

the cartilage that holds the bone together.

Amphiarthroses

slightly movable cartilaginous joints (E.g., symphysis pubis and intervertebral disk).

Synovial Joints

• a synovial cavity with fluid in between bones.

Diarthroses

• freely movable synovial joints (E.g., shoulder joint, and hip joint).

Ball-and-socket

Allows movement in many directions (Examples: Shoulder joint, hip joint).

Hinge

• Allows movement in one direction (Examples: Knee, elbow, ankle, and interphalangeal joints).

Pivot

• Allows rotation around the length of bone (Examples: Atlanto-axial joint, Radioulnar joint).

Condyloid

• Allows movement in two directions (Examples: Wrist and metacarpophalangeal).

Saddle

• Like condyloid joint only with deeper articulating surface (Examples: carpometacarpal joint, metacarpal of the thumb).

Planar

• Flat or slightly curved articulated surfaces (Examples: intercarpal joints, intertarsal joints, sternoclavicular joints, acromioclavicular joints, sternocostal joints and vertebrocostal joints).

Muscular System

• Makes up 40 - 50% of total adult body weight.

Myology

study of the muscles.

Cardiac Muscular Tissue

• Appearance: Branched, striated, intercalated discs.

• Movement: Involuntary.

• Organs: Heart.

Smooth Muscular Tissue

• Appearance: Non-striated.

• Movement: Involuntary.

• Organs: Hollow organs (Digestive tract, blood vessels).

Skeletal Muscular Tissue

• Appearance: Striated.

• Movement: Voluntary.

• Organs: Attached to bone.

Electrical excitability

1. the ability to respond to certain stimuli by producing electrical signals called action potentials (impulses).

Contractility

1. the ability of muscular tissue to contract forcefully when stimulated by an action potential.

Extensibility

1. is the ability of muscular tissue to stretch, within limits, without being damaged.

Elasticity

the ability of muscular tissue to return to its original length and shape after contraction or extension.

Epimysium

1. The outermost layer of dense, irregular connective tissue, encircling the entire muscle.

Endomysium

1. Penetrates the interior of each fascicle and separates individual muscle fibers from one another.

Sarcolemma

1. plasma membrane of the muscle cells.

Transverse (T) tubule

1. tunnel in from the surface toward the center of each muscle fiber.

Sarcoplasm

1. cytoplasm of the muscle cells (contains Glycogen and Myoglobin).

Myofibrils

1. fine, threadlike structures in the sarcoplasm responsible for muscle contraction.

Sarcoplasmic Reticulum

1. fluid-filled system of membranous sacs that functions as the endoplasmic reticulum in the muscle cell.

Sarcomere

1. the structural and basic contractile unit of muscle.

Z discs

• Narrow, plate-shaped regions of dense material that separate one sarcomere from the next.

A band

• The dark, middle part of the sarcomere that extends the entire length of the thick filaments and also includes those parts of the thin filaments that overlap with the thick filaments.