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Bones of lower limbs

Femur (Thigh Bone)

  • Only bone in the thigh

  • Heaviest and strongest bone in the body

  • Landmarks:

    • Patellar Surface: Anteriorly on the distal femur

    • Greater and Lesser Trochanter: Site for muscle attachment

    • Femoral Slant: The femur slants medially to align knees with the body’s center of gravity (more noticeable in females due to a wider pelvis)

Leg Bones

  • Tibia (Shin Bone) and Fibula

  • Connected by interosseous membrane

  • Proximal End Features:

    • Medial and Lateral Condyles: Articulate with the distal end of the femur to form the knee joint

    • Patellar Ligament attaches to the tibial tuberosity

  • Distal End Features:

    • Medial Malleolus: Inner ankle bulge (Tibia)

    • Lateral Malleolus: Outer part of the ankle (Fibula)

Feet

  • Consists of Tarsals, Metatarsals, and Phalanges

  • Functions:

    1. Supports body weight

    2. Acts as a lever for walking/running

  • Tarsus (7 Tarsal Bones): Posterior half of the foot

    1. Body weight carried by Calcaneus (heel bone) and Talus

  • 5 Metatarsals

  • 15 Phalanges: Similar to fingers; 3 per toe except for the big toe (which has 2)


Types of Synovial Joints

  • Ball and Socket Joint - Multiaxial

  • Plane Joint - Nonaxial

  • Hinge Joint - Uniaxial

  • Pivot Joint - Uniaxial

  • Condyloid Joint - Biaxial

  • Saddle Joint - Biaxial


Muscular System

Types of Muscle Tissue

  • Skeletal Muscle

    • Striated, voluntary

    • Attached to bones, responsible for movement

    • Activated by reflexes

    • Fibers are enclosed in endomysium, bundled into fascicles by perimysium, and covered by epimysium

    • Tendons: Attach muscle to bones; provide durability and conserve space

  • Smooth Muscle

    • No striations, involuntary

    • Found in walls of hollow organs (e.g., stomach, bladder, respiratory passages)

    • Spindle-shaped with a single nucleus

    • Slow, sustained contractions

  • Cardiac Muscle

    • Found only in the heart

    • Striated but involuntary

    • Has interwoven muscle fibers arranged in spirals for efficient pumping

Muscle Functions

  1. Produce movement

  2. Maintain posture

  3. Stabilize joints

  4. Generate heat

5 Golden Rules of Muscle Activity

  1. All muscles cross at least one joint

  2. Bulk of muscle lies proximal to the joint crossed

  3. Muscles have two attachments: origin and insertion

  4. Muscles pull, never push

  5. Muscle insertion moves toward origin during contraction


Types of Body Movements

  • Flexion: Decreases joint angle, bringing two bones closer together

  • Extension: Increases joint angle (opposite of flexion)

  • Rotation: Moving around a longitudinal axis (e.g., atlas around dens of axis)

  • Abduction: Moving limb away from midline

  • Adduction: Moving limb toward midline

  • Circumduction: Combination of all movement types (mainly found in ball and socket joints)

Special Movements

  • Dorsiflexion/Plantarflexion: Upward/downward foot movement

  • Inversion/Eversion: Turning sole medially/laterally

  • Supination/Pronation: Rotation of forearm (supination = radius and ulna parallel, pronation = radius crosses ulna)

  • Opposition: Thumb movement to touch fingertips


Types of Skeletal Muscles

  • Prime Mover: Muscle causing movement (e.g., biceps)

  • Antagonist: Reverses prime mover’s motion (e.g., triceps)

  • Synergist: Aids prime mover

  • Fixator: Stabilizes joints for efficient movement


Anabolic Steroids

  • Used for medical recovery and muscle growth

  • Recreational use can enhance muscle mass but has serious side effects:

    • Short-term risks: Acne, liver tumors, aggression, heart enlargement

    • Long-term risks: Baldness, stunted growth, testicular shrinkage, infertility


Head and Neck Muscles

Facial Muscles

  • Frontalis: Raises eyebrows, wrinkles forehead

    • Origin: Cranial aponeurosis

    • Insertion: Skin of eyebrows

  • Orbicularis Oculi: Closes eyes, blinking, winking

  • Orbicularis Oris: Closes mouth, protrudes lips

  • Buccinator: Flattens cheeks, holds food while chewing

    • Origin: Maxilla and mandible

    • Insertion: Orbicularis oris

  • Zygomaticus: Raises corners of mouth (smiling)

    • Origin: Zygomatic bone

    • Insertion: Angle of the mouth

Chewing and Neck Muscles

  • Masseter: Elevates mandible (jaw closing)

    • Origin: Zygomatic process

    • Insertion: Mandible

  • Temporalis: Assists masseter in closing jaw

  • Platysma: Pulls corners of mouth downward (sagging face)

    • Origin: Chest connective tissue

    • Insertion: Area around mouth

  • Sternocleidomastoid: Two-headed muscle responsible for neck flexion

    • Origin: Sternum and clavicle

    • Insertion: Mastoid process