Understanding the Skeletal System

Skeletal System Roles

• Protection of internal organs from injury.
• Body support that provides a framework.
• Attachment points for muscles.
• It serves as a storehouse for essential nutrients.
• Formation of blood cells.

Axial vs. Appendicular Skeleton

• The axial skeleton consists of 80 bones, including 26 vertebral, 1 hyoid, 22 skull, 6 auditory, and 25 ribs.
• The appendicular skeleton consists of 126 bones, 64 in the upper extremity and 62 in the lower extremity.

Bone Composition

• Bones are composed of 50% water and 50% organic and inorganic material.
• Bone elements include phosphorus, zinc, calcium, magnesium, fluorine, iron, and chlorine.
• Bones resist compression and tension.
• Bones are bound by joints through ligaments.
• Muscles attach to bones through tendons to facilitate movement.

Bone Types

• Long bones are found in the arms and legs.
• Short bones are located in the wrists and ankles.
• Flat bones include those of the skull, ribcage, and shoulder blade.
• Irregular bones comprise the vertebrae.
• Sesamoid bones are wrapped within tendons, such as the patella.

Long Bone Anatomy

• Cancellous bone is a spongy, porous type of bone.
• Compact bone is dense and strong.
• The medullary cavity contains bone marrow.
• The periosteum is the outer membrane covering the bone.
• Cartilage provides a smooth surface for joint movement.
• The epiphysis is the end of a long bone.
• The diaphysis is the shaft of a long bone.

Joint Types

• Fibrous joints unite two bones with connective tissue, allowing no movement.
• Cartilaginous joints unite bones with cartilage, permitting very little movement

Synovial Joints

• Synovial joints are the body's main functional joints and are freely mobile.
• Joints are contact points between two or more bones.
• Ligaments are strong, elastic bands that hold bones together at joints.
• Joints with no movement have connective tissue between the bones.
• Joints with slight movement have cartilage connecting the articulating bones.
• Joints with free movement have a joint capsule, synovial membrane, cavity, and layer of cartilage.

Synovial Joint Types

• Ball and Socket joints, like the hip joint, allow movement in all directions.
• Hinge joints, like the elbow joint, allow bending and straightening.
• Saddle joints, like the thumb joint, allow back-and-forth and side-to-side movement.
• Gliding joints, like the wrist joint, allow bones to slide over each other.
• Pivot joints, like the neck joint, allow rotational movement.

Synovial Joint Characteristics

• A synovial joint features a synovial cavity.
• Articular cartilage and an articular capsule are always present.
• The synovial membrane secretes synovial fluid, which forms a thin, viscous film over surfaces.
• Synovial joints often contain ligaments and articular discs.
• Bursae are sac-like structures that reduce friction in joints, common in the shoulder and knee.

Tendons and Ligaments

• Tendons consist of collagen bundles (white, fibrous protein), attach muscle to bone, and are vascular.
• Ligaments are tough bands of white, fibrous tissue, attach bone to bone, and are avascular.

Common Skeletal Injuries and Conditions

• Strains, pulls, and tears describe injuries to joint tissues.
• Tendinitis is the inflammation of a tendon.
• Dislocations occur when a bone is displaced from its original location.
• Separations involve the tearing and separation of fibrous ligaments that bind bones.
• Cartilage injuries refer to torn cartilage.
• Shin splints are stress fractures in the lower leg bones, often due to overpronation (flat feet).

Skeletal System Diseases

• Osteoporosis is a loss of minerals and a decrease in bone density due to increased osteoclast activity, often related to low calcium intake.
• Rickets and Osteomalacia involve demineralization of bone due to Vitamin D deficiency.
• Gout (Gouty Arthritis) is inflammation within joints causing pain and discomfort, caused by high levels of protein in the diet leading to uric acid buildup.

Fractures

• A fracture is any break in a bone diagnosable via X-rays.
• Partial fractures are incomplete breaks, like cracks.
• Complete fractures are complete breaks into two or more pieces.
• Closed (simple) fractures do not break through the skin.
• Open (compound) fractures have broken bone ends that protrude through the skin.
• Fracture repair involves hematoma formation, new blood vessel formation, bony callus of spongy bone, and eventual bone healing.

Dislocation Injuries

• Dislocation is an injury where bone ends are forced from their normal joint positions.
• A dislocation causes temporary joint deformation and immobilization.
• Dislocations commonly occur in the shoulders and fingers.
• Suspected dislocations require medical attention for relocation.

Muscular System Functions

• Movement includes breathing, eating, and the beating of our hearts.
• Provides support.
• Produces heat.
• There are over 600 muscles in the human body.

Muscle Tissue Types

• Skeletal muscles are voluntary, striated, and attach to bones through tendons and other tissues.
• Cardiac muscles are involuntary, striated, and found exclusively in the heart.
• Smooth muscles are involuntary, non-striated, and surround the body’s internal organs.

Muscle Fibre Properties

• Irritability refers to a muscle's ability to respond to stimuli.
• Contractibility refers to a muscle's ability to shorten in length.
• Elasticity refers to a muscle's ability to stretch and return to its normal position.
• Extensibility refers to a muscle's ability to extend in length.
• Conductivity refers to a muscle's ability to transmit nerve impulses.

Skeletal Muscle Anatomy

• Perimysium binds muscle fibres together.
• Epimysium envelops the entire muscle.
• Endomysium surrounds each muscle fibre with connective tissue.

Naming Muscles

• Muscles are named by action/function (Flexion/Extension).
• Muscles are named by the direction of fibres (Rectus/Transversus).
• Muscles are named by the location (Anterior/Posterior).
• Muscles are named by the number of divisions/heads.
• Muscles are named by shape: Deltoid/Trapezius
• Muscles are named by points of attachment: Sternum/Clavicle/Mastoid process

Muscle Attachment

• Indirect attachment involves the epimysium extending past the muscle as a tendon, attaching to the periosteum of bone.
• Direct attachment involves the epimysium adhering to and fusing with the periosteum.

Muscle Origin and Insertion

• Origin is the proximal attachment, where the muscle attaches to the least moveable area of the axial skeleton.
• Insertion is the distal attachment, where the muscle attaches to the bone that is moved most.
• Function is the action/motion the muscle performs when activated.

Key Muscles

• Sternocleidomastoid: muscles of the neck
• Erector Spinae Group: muscles of the vertebral column
• Rectus Abdominis, External Obliques: muscles of the abdomen
• Bicep Brachii (anterior), Tricep Brachii (posterior): muscles of the elbow flexors/extensors
• Quadricep group (anterior), Hamstring Group (posterior): muscles of the thigh
• Tibialis Anterior (anterior), Gastrocnemius and Soleus (posterior): muscles of the extrinsic foot
• Trapezius: muscles of the upper back
• Deltoids: muscles of the shoulders
• Pectoralis Major: muscles of the pecs (chest)
• Latissimus Dorsi: muscles of the lower back
• Adductor group: muscles of the hip
• Gluteus Maximus: muscles of the glute

Muscle Injuries

• Contusion (bruise) occurs when a muscle is subject to a sudden, strong, compressive direct blow resulting in muscle tissue damage.
• Strain occurs during sprinting, jumping, or rapid muscular contraction or overstretching, leading to excessive tensile force.
• Laceration occurs when skin, tissue, and/or muscle is torn or cut open, varying in depth, length, and width.

Soft Tissue Injury Grades

• Grade I strain involves only a few muscle fibres being stretched or torn, with normal strength despite tenderness and pain.
• Grade II strain is a moderate strain with more injured fibers, severe muscle pain, tenderness, mild swelling, noticeable strength loss, and sometimes a bruise.
• Grade III strain is a serious injury causing complete muscle function loss due to a full rupture/tear, often with a "pop," pain, swelling, tenderness, and discoloration.

R.I.C.E. Principle

• Rest the injured site for a minimum of 24-72 hours to limit inflammation and encourage healing.
• Ice helps reduce inflammation by causing vasoconstriction to reduce bruising.
• Compression reduces blood flow and inflammation using compression of the blood and lymphatic vessels.
• Elevation involves placing the injured extremity above the heart to decrease hydrostatic pressure and reduce excessive interstitial fluid.