3.3 Bones, Muscles, Nerves, and Blood Vessels of Hands and Feet

Bones, Muscles, Nerves, and Blood Vessels of Hands and Feet

Quick Answer: The human hand contains 27 bones (8 carpals, 5 metacarpals, 14 phalanges), while the human foot contains 26 bones (7 tarsals, 5 metatarsals, 14 phalanges). Forearm bones are the radius (lateral / thumb side) and ulna (medial / pinky side). Lower leg bones are the tibia (medial weight-bearing shinbone) and fibula (lateral). Massage manipulations must always proceed from insertion to origin (distal to proximal). The median nerve innervates the thumb and first three fingers, traveling through the carpal tunnel; compression leads to Carpal Tunnel Syndrome (CTS). Major arteries supplying the extremities are the radial and ulnar arteries in the hand, and the anterior and posterior tibial arteries in the foot.

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1. Osteology: Bones of the Upper and Lower Extremities

Osteology is the scientific study of the anatomy, structure, and function of bones. Bones provide structural framework, protect delicate viscera, serve as levers for muscle action, produce red and white blood cells via marrow hematopoiesis, and store essential minerals (calcium and phosphorus).

┌────────────────────────────────────────┬────────────────────────────────────────┐
│         THE HAND & WRIST (27 BONES)    │         THE FOOT & ANKLE (26 BONES)    │
├────────────────────────────────────────┼────────────────────────────────────────┤
│ • Carpals (Wrist):         8 bones     │ • Tarsals (Ankle/Heel):    7 bones     │
│ • Metacarpals (Palm):      5 bones     │ • Metatarsals (Instep):    5 bones     │
│ • Phalanges (Digits):     14 bones     │ • Phalanges (Toes):       14 bones     │
│   - Thumb (Digit I):       2 phalanges │   - Great Toe (Digit I):   2 phalanges │
│   - Fingers II-V:          3 each (12) │   - Toes II-V:             3 each (12) │
│ TOTAL:                    27 BONES     │ TOTAL:                    26 BONES     │
└────────────────────────────────────────┴────────────────────────────────────────┘

Upper Extremity Osteology: Hand, Wrist, and Forearm

                          SKELETAL MAP OF THE HAND (27 BONES)

          [Distal]        Distal Phalanges (5)
                             ▲
                          Middle Phalanges (4)  [Thumb has NO middle phalanx!]
                             ▲
                          Proximal Phalanges (5)
                             ▲
          [Palm]          Metacarpals (I, II, III, IV, V) (5)
                             ▲
          [Wrist]         Carpal Bones (8 in 2 rows)
                          • Distal Row:   Trapezium, Trapezoid, Capitate, Hamate
                          • Proximal Row: Scaphoid, Lunate, Triquetrum, Pisiform
                             ▲
          [Forearm]       Radius (Thumb Side)  |  Ulna (Pinky Side)

1. The 8 Carpal Bones (Wrist):

   • Arranged in two transverse rows of four bones each, bound tightly by ligaments:
     • Proximal Row (Lateral / Thumb side to Medial / Pinky side):
       1. Scaphoid (Navicular): Boat-shaped; articulates with the radius; most commonly fractured carpal.
       2. Lunate: Crescent-shaped; articulates with the radius.
       3. Triquetrum (Triangular): Pyramidal bone on ulnar side.
       4. Pisiform: Small, pea-shaped sesamoid bone resting on the anterior surface of the triquetrum.
     • Distal Row (Lateral / Thumb side to Medial / Pinky side): 5. Trapezium (Greater Multangular): Four-sided irregular bone; articulates directly with Metacarpal I (thumb). 6. Trapezoid (Lesser Multangular): Wedge-shaped bone articulating with Metacarpal II. 7. Capitate: The largest carpal bone; forms the center of the carpal arch. 8. Hamate: Characterized by a prominent hook-like process (hamulus) on its palmar surface.
   • Classic Memory Mnemonic (Proximal to Distal, Lateral to Medial): Some Lovers Try Positions That They Cannot Handle (Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate).

2. The 5 Metacarpal Bones (Palm):

   • Five cylindrical bones forming the skeletal framework of the palm (metacarpus).
   • Numbered I through V starting laterally from the thumb (Metacarpal I) to the pinky (Metacarpal V).

3. The 14 Phalanges of the Hand (Digits):

   • Digits II through V (Index, Middle, Ring, Pinky) each possess 3 phalanges: Proximal, Middle, and Distal ($4 \times 3 = 12$ bones).
   • Digit I (Thumb / Pollex) possesses only 2 phalanges: Proximal and Distal (it has no middle phalanx).
   • Total phalanges in one hand: $12 + 2 = 14$.

4. Forearm and Arm Bones:

   • Radius: The lateral bone of the forearm on the thumb side. It is smaller at the elbow and wider at the wrist. During pronation and supination, the radius rotates across the stationary ulna.
   • Ulna: The medial, larger bone of the forearm on the little-finger (pinky) side. It forms the prominent olecranon process (the elbow point).
   • Humerus: The uppermost and largest bone of the arm, extending from the shoulder to the elbow.

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Lower Extremity Osteology: Foot, Ankle, and Lower Leg

                          SKELETAL MAP OF THE FOOT (26 BONES)

          [Distal]        Distal Phalanges (5)
                             ▲
                          Middle Phalanges (4)  [Great toe has NO middle phalanx!]
                             ▲
                          Proximal Phalanges (5)
                             ▲
          [Instep]        Metatarsals (I, II, III, IV, V) (5)
                             ▲
          [Ankle/Heel]    Tarsal Bones (7)
                          • Rearfoot:  Calcaneus (Heel), Talus (Ankle)
                          • Midfoot:   Navicular, Cuboid, 3 Cuneiforms (Medial, Int, Lat)
                             ▲
          [Lower Leg]     Tibia (Medial / Shin)  |  Fibula (Lateral)

1. The 7 Tarsal Bones (Ankle & Rearfoot):

   • Talus (Astragalus / Ankle Bone): Articulates superiorly with the tibia and fibula to form the true talocrural (ankle) joint; transmits the entire weight of the body from the leg to the foot.
   • Calcaneus (Heel Bone): The largest and strongest tarsal bone; forms the heel and serves as the insertion point for the massive Achilles tendon (tendo calcaneus).
   • Navicular: Boat-shaped bone on the medial midfoot between the talus and cuneiforms.
   • Cuboid: Cube-shaped bone located on the lateral aspect of the midfoot.
   • 3 Cuneiform Bones: Medial (First), Intermediate (Second), and Lateral (Third) cuneiforms, which articulate with metatarsals I, II, and III.

2. The 5 Metatarsal Bones (Instep):

   • Five long bones forming the midfoot/instep, numbered I through V from the medial great toe (Metatarsal I) to the lateral small toe (Metatarsal V). Metatarsal I is the thickest and bears significant weight during locomotion.

3. The 14 Phalanges of the Foot (Toes):

   • Toes II through V each possess 3 phalanges: Proximal, Middle, and Distal ($4 \times 3 = 12$).
   • Digit I (Great Toe / Hallux) possesses only 2 phalanges: Proximal and Distal ($12 + 2 = 14$).

4. Lower Leg Bones:

   • Tibia (Shinbone): The large, medial, primary weight-bearing bone of the lower leg. Its distal medial projection forms the medial malleolus (inner ankle bone).
   • Fibula: The long, slender, lateral bone of the lower leg. It does not bear direct body weight, but serves as a muscle attachment site and forms the lateral malleolus (outer ankle bone).
   • Patella (Kneecap): A large sesamoid bone embedded within the quadriceps tendon that protects the knee joint articulation.

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2. Myology: Muscle Actions & Extremity Musculature

Myology is the scientific study of the nature, structure, function, and diseases of muscles. Muscles constitute approximately 40% to 50% of human body weight and produce movement via active cellular contraction.

The Three Parts of a Muscle & Massage Rule

              ┌─────────────────────────────────────────────────┐
              │            THE THREE PARTS OF A MUSCLE          │
              ├─────────────────────────────────────────────────┤
              │ 1. ORIGIN:     Fixed, immovable attachment to   │
              │                skeletal bone or tissue.         │
              │ 2. BELLY:      Fleshy, contractile middle body. │
              │ 3. INSERTION:  Movable attachment point that is │
              │                pulled during contraction.       │
              └─────────────────────────────────────────────────┘

Universal Licensing Massage Rule: In professional manicuring, pedicuring, and esthetic bodywork, massage manipulations must ALWAYS be directed from the INSERTION toward the ORIGIN (distal toward proximal). Massaging toward the fixed origin prevents mechanical muscle strain, supports natural venous return, and facilitates lymphatic drainage.

Primary Functional Muscle Groups of the Extremities

Key Muscles of the Lower Leg & Foot in Pedicuring

• Tibialis Anterior: Situated on the anterior shin; dorsiflexes the foot (pulls toes upward toward shin) and inverts the foot.
• Gastrocnemius & Soleus: The powerful calf muscles forming the posterior lower leg; plantarflexes the foot (points toes downward like a ballerina) and inserts into the calcaneus via the Achilles tendon.
• Peroneus (Fibularis) Longus & Brevis: Lateral leg compartment; everts the foot (turns sole outward) and assists plantarflexion.
• Extensor Digitorum Longus: Extends the lesser toes upward and dorsiflexes foot.

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3. Neurology: Nerves of the Upper and Lower Extremities

Neurology is the scientific study of the structure, function, and pathology of the nervous system. The peripheral nervous system supplies motor control and sensory perception to the extremities.

                       PERIPHERAL NERVES OF THE UPPER EXTREMITY

                          Brachial Plexus (C5-T1)
                                    │
             ┌──────────────────────┼──────────────────────┐
             ▼                      ▼                      ▼
        MEDIAN NERVE           ULNAR NERVE            RADIAL NERVE
     • Passes through       • Passes medial elbow   • Passes lateral arm
       Carpal Tunnel          ("Funny Bone")          and dorsal forearm
     • Motor: Thumb thenar  • Motor: Intrinsic      • Motor: Extensors
     • Sensory: Palm,         hand muscles            of wrist/fingers
       Thumb, Digits II,    • Sensory: Pinky &      • Sensory: Dorsum of
       III, 1/2 of IV         medial 1/2 of IV        hand & thumb/index
             │                      │                      │
             └──────────────────────┴──────────────────────┘
                                    │
                          DIGITAL NERVE BRANCHES
                        (Sides & Tips of Fingers)

Upper Extremity Nerves

1. The Median Nerve:

   • Originates from the brachial plexus; travels down the midline of the anterior forearm.
   • Passes through the narrow, unyielding Carpal Tunnel beneath the fibrous flexor retinaculum at the wrist.
   • Innervation: Motor supply to forearm flexors and thenar muscles of the thumb; sensory supply to the palmar surface of the thumb, index finger, middle finger, and lateral half of the ring finger.
   • Clinical Focus — Carpal Tunnel Syndrome (CTS):
     • Caused by chronic compression and inflammation of the median nerve within the carpal tunnel.
     • Major occupational hazard for nail technicians resulting from repetitive hand motions, sustained forceful gripping of files/buffers, prolonged wrist flexion/hyperextension, and vibration from electric files.
     • Symptoms: Nocturnal burning, numbness, tingling (paresthesia) in the thumb, index, and middle fingers, progressing to loss of grip strength and thenar muscle atrophy.

2. The Ulnar Nerve:

   • Travels down the medial arm, crossing behind the medial epicondyle of the humerus (the cubital tunnel or "funny bone").
   • Innervation: Motor supply to intrinsic hypothenar and interosseous hand muscles; sensory supply to the little finger (pinky) and the medial (ulnar) half of the ring finger.

3. The Radial Nerve:

   • Travels down the posterior and lateral aspect of the arm and forearm.
   • Innervation: Motor supply to forearm extensor muscles (enabling wrist and finger extension); sensory supply to the dorsal aspect of the hand, back of the thumb, index finger, and proximal half of middle finger.

4. Digital Nerves: Sensory terminal branches that travel along both lateral margins of each finger, supplying exquisite tactile perception to the nail bed and fingertips.

Lower Extremity Nerves (Pedicure Considerations)

• Tibial Nerve (Posterior Tibial Nerve): Passes through the popliteal space behind the knee and down the deep posterior calf; divides at the ankle into the medial and lateral plantar nerves supplying the sole of the foot and toe flexors.
• Common Peroneal (Fibular) Nerve: Wraps around the fibular neck and bifurcates into:
  • Superficial Peroneal Nerve: Supplies lateral calf muscles and sensory branches to the top (dorsum) of the foot.
  • Deep Peroneal Nerve: Supplies anterior shin muscles (tibialis anterior) and sensory branches to the webspace between the first and second toes.
• Saphenous Nerve: Supplies cutaneous sensation to the inner (medial) leg and foot.
• Sural Nerve: Supplies sensation to the outer (lateral) calf, heel, and lateral margin of the foot and pinky toe.

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4. Angiology: Vascular Pathways and Blood Supply

Angiology is the scientific study of the circulatory and lymphatic systems. The vascular system delivers oxygenated blood, nutrients, hormones, and immune cells to tissues while removing carbon dioxide and metabolic byproducts.

┌────────────────────────────────────────┬────────────────────────────────────────┐
│      ARTERIAL SUPPLY TO THE HAND       │      ARTERIAL SUPPLY TO THE FOOT       │
├────────────────────────────────────────┼────────────────────────────────────────┤
│ • Brachial Artery (Upper Arm)          │ • Popliteal Artery (Behind Knee)       │
│   ├── Radial Artery (Thumb side/Pulse) │   ├── Anterior Tibial Artery           │
│   └── Ulnar Artery (Pinky side)        │   │   └── Dorsalis Pedis Artery (Top)  │
│        │                               │   └── Posterior Tibial Artery          │
│   ├── Superficial Palmar Arch          │       └── Plantar Arteries (Sole)      │
│   └── Deep Palmar Arch                 │            │                           │
│        └── Digital Arteries (Fingers)  │        └── Digital Arteries (Toes)     │
└────────────────────────────────────────┴────────────────────────────────────────┘

Upper Extremity Arterial System

• Brachial Artery: The principal artery of the upper arm; bifurcates just below the elbow crease (antecubital fossa) into the radial and ulnar arteries.
• Radial Artery: Travels down the lateral (thumb) side of the anterior forearm to the wrist. Its superficial position over the distal radius makes it the primary site for palpating the radial pulse. Supplies the lateral wrist, thumb, and deep palmar arch.
• Ulnar Artery: Travels down the medial (pinky) side of the forearm, providing blood to the medial forearm, wrist, and superficial palmar arch.
• Superficial & Deep Palmar Arches: Interconnected arterial networks in the palm that give rise to common and proper digital arteries, which branch along both lateral borders of each finger to supply the nail bed, matrix, and fingertip pulp.

Lower Extremity Arterial System

• Popliteal Artery: The continuation of the femoral artery behind the knee joint; branches into the anterior and posterior tibial arteries.
• Anterior Tibial Artery: Travels down the anterior shin compartment, crossing the anterior ankle joint where it becomes the Dorsalis Pedis Artery (a critical clinical pulse point on the top of the foot). Supplies the dorsal foot and toe digits.
• Posterior Tibial Artery: Travels down the posterior medial calf, passing behind the medial malleolus of the ankle; divides into the Medial and Lateral Plantar Arteries to supply the sole of the foot and plantar digital vessels.

Clinical Implications for Nail Technicians

• Diabetic & Neuropathic Precautions: Clients with diabetes mellitus, peripheral neuropathy, or peripheral arterial disease (PAD) often suffer from reduced extremity blood flow and diminished sensory feedback. Technicians must avoid vigorous deep-tissue pressure, never use sharp blades (such as credo blades/razors, which are strictly illegal in Georgia), and ensure water temperatures do not exceed 104°F (40°C).
• Venous & Lymphatic Return: Rhythmic, upward effleurage massage strokes on the arms and legs stimulate venous valves and lymphatic drainage, reducing pedal edema and soothing muscular fatigue.