Anatomy of the Face, Axilla, Hand, and Thorax: Nerves, Blood Vessels, and Regions

Posted on May 19, 2024 in Biology

Face: Regions, Blood Vessels, and Nerves

Regions

  • Forehead: Frontal bone + frontal eminence & glabella
  • Nasal Region: Nasal apparatus formed by nasal bones & cartilage
  • Periorbital Region: Maxilla + zygomatic bone
  • Perioral & Chin: Surround the mouth, mandibular bone & maxilla
  • Oral Region: Orifice of mouth, upper & lower lip

Nerves

All Are Cranial Nerves

I. Sensory

  • Trigeminal nerve separates into 3 branches before leaving the middle cranial fossa.
  • Ophthalmic nerve (V1): Scalp & forehead, eyelids, and cornea
  • Maxillary nerve (V2): Lower eyelid and cheeks, upper lip, upper teeth, and gums
  • Mandibular nerve (V3): Lower lip, lower teeth & gums, chin, and jaw. Also carries pain and temperature from the mouth.
  • Trigeminal ganglia is within Meckel’s cave and analogous to dorsal root ganglia.

II. Motor Innervation

  • V3 mandibular nerve
  • Facial nerve to the muscles of facial expression
  • Motor root of trigeminal nerve/mandibular nerve: Mastication muscles
  • Facial nerve forms the geniculate ganglion prior to entering the facial canal.

Blood Vessels

Arterial Supply

  • From branches of the external carotid artery.
  • They pass through deep structures of the neck and appear at the lower mandible border.
  • From there they go upward & medially.
  • I. Facial artery divides into:
    1. Inferior labial branch: Upper lip
    2. Superior labial branch: Supplies lower lip & nasal septum
    3. Lateral nasal branch: Lateral surface & dorsum of nose
  • II. Transverse facial artery: Superficial temporal artery, through parotid gland
  • III. Maxillary artery divides into:
    1. Infraorbital artery: Lower eyelid & upper eyelid
    2. Buccal artery: Blood to buccinator muscle
    3. Mental artery: Supplies chin
  • IV. Ophthalmic artery (from internal carotid) divides into:
    1. Zygomaticofacial artery: Face & zygomatic bone
    2. Dorsal nasal artery: Supplies dorsum of the nose

Venous Drainage

  • Mainly through the jugular vein
  • I. Facial vein:
    • From the medial corner of the orbit
    • Drains eyelid, external nose, lip, cheek, and chin
  • II. Transverse facial vein:
    • Accompanies the transverse facial artery
    • Empties into the superficial temporal vein
  • III. Intracranial venous connection:
    • Ophthalmic vein
    • Intraorbital foramen
    • Deeper face regions

Axilla

Topography

  • Made of clavicle, scapula, upper thoracic wall, humerus, and muscles.
  • Superior wall: Outer border of 1st rib, superior border of scapula, posterior clavicle
  • Anterior: Pectoralis major, pectoralis minor, subclavius
  • Posterior: Subscapularis, teres major, latissimus dorsi
  • Inferior: Skin (armpit)
  • Lateral: Intertubercular sulcus
  • Medially: Serratus anterior & ribcage

Contents

  • Axillary artery & branches
  • Axillary vein & tributaries
  • Infraclavicular brachial plexus
  • 5 axillary lymph nodes
  • Long thoracic & intercostobrachial nerves
  • Axillary fat & alveolar tissue
  • Proximal part of biceps & coracobrachialis muscle

Topography of Arm & Forearm

StructureBoundariesImportance
Anterior (flexor) Arm– Medial & lateral intermuscular septa + humerus
– Anterior/lateral/medial: Brachial fascia		– Flexor muscles (biceps, brachialis)
– Innervated: Musculocutaneous nerve
Anterior Forearm– Medial & lateral: Intermuscular septa
– Radius & ulna		– Flexor of hand (pronator teres)
– Median nerve, ulnar nerve
Cubital Fossa– Shallow depression on anterior elbow
– Superior: Epicondyle
– Medial: Pronator teres
– Lateral: Brachioradialis medial border		– Medial cubital vein crosses here
– Is site for phlebotomy
Posterior Arm– Intermuscular septa & humerus
– Brachial fascia		– Posterior compartment of the arm
– Radial nerve
– Deep brachial artery
Posterior Forearm– Antebrachial fascia– Extensor muscles of hand & wrist
– Superficial & deep radial nerve
Posterior Axillary Fold– Fold of skin and muscle with teres major & latissimus dorsi– Posterior extent of floor of axilla

Hand: Veins, Arteries, and Nerves

Arteries

  • Radial & ulnar artery
  • Form vascular arches (superficial & deep) in palm.
  • 1. Ulnar artery + superficial palmar arch:
    • Medial side of wrist
    • Distally swings laterally across palm forming the superficial palmar arch.
    • Then joined with palmar branch of radial artery.
    • Superficial palmar arch gives rise to palmar digital arteries and common palmar digital arteries.
  • 2. Radial artery & deep palmar arch:
    • Curves in lateral wrist, deep plane of palm through back of hand.
    • Passes between metacarpal bones and forms deep palmar arch.
    • Forms deep palmar branch of ulnar artery.
    • Gives rise to”princeps pollicis arter” and”radialis indicis artery” which supply the thumb and index finger, respectively.

Veins

  • Interconnected network of deep & superficial veins
  • Deep veins follow arteries
  • Superficial veins drain dorsal venous network on back of metacarpal bones
  • 1. Cephalic vein:
    • From lateral side of dorsal venous network
    • Over anatomical snuffbox
  • 2. Basilic vein:
    • Medial side of dorsal venous network
    • Dorsomedial aspect of forearm

Nerves

  • Ulnar, median, and radial nerves
  • All help in cutaneous and general innervation.
  • Ulnar nerve innervates intrinsic muscles of the hand except for the three thenar muscles and 2 lateral lumbricals.
  • Radial nerve only innervates skin on the dorsolateral side of the hand.

Topography of Thigh

StructureBoundariesSignificance
Adductor Canal– Musculo-fascial canal
– Boundaries:
1. Anterior: Sartorius
2. Lateral: Vastus medialis
3. Posterior: Adductor longus & adductor magnus
– Starts proximal to inferior angle of femoral triangle		– Large neurovascular bundle
– Contains femoral artery & vein, saphenous nerve
Adductor Hiatus– Gap between adductor magnus and femur– Femoral artery & vein become popliteal artery & vein
Anterior Compartment of Thigh– Anterior & lateral: Fascia lata– Contains extensor muscles of the knee
– Includes quadriceps femoris muscle and sartorius muscle
Femoral Triangle– Musculo-fascial triangle on anterior thigh
– Boundaries:
1. Superior: Inguinal ligament
2. Medial: Adductor longus
3. Lateral: Sartorius		– Contains femoral artery, vein, and nerve
Medial Compartment of Thigh– Anterior: Lateral intermuscular septum
– Posterior: Medial intermuscular septum		– Contains muscles that flex the knee
– Includes semimembranosus, semitendinosus, and biceps femoris muscles
Saphenous Hiatus– Opening in fascia lata inferior to inguinal ligament
– Lateral to pubic tubercle		– Site of passage of greater saphenous vein

Anatomy & Principles of Somatic & Visceral Sensory Fibers

Sensory Nerves

  • Afferent division of PNS transmits signals to CNS.
  • Cell bodies of sensory neurons are located in ganglia.

General Visceral Afferent Fibers

  • Nerves from viscera, glands, & blood vessels to CNS
  • Part of ANS but not divided into sympathetic and parasympathetic.
  • Input from cerebrum, hypothalamus, and other areas
  • Without ANS, homeostasis is limited.
  • ANS reflexes:
    1. Sensory receptor
    2. Sensory associated motor neuron
    3. Effector cells

General Somatic Afferent Fibers

  • GSA are afferent fibers from spinal ganglia.
  • Conduct impulses of pain, touch, and temperature from body to posterior roots.
  • 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)

Anatomy & Principles of Segmental Innervation of Limbs, Thorax & Abdomen

Spinal Nerves & Segments

  • All 31 spinal nerve pairs exit via vertebral column.
  • Exceptions: 1st pair and sacrum.
  • Sacrum nerves exit through sacral foramina.
  • 31 Spinal Segments:
    • 8 Cervical nerves (C1 exception) (C1-C8)
    • 12 Thoracic nerves (T1-T12)
    • 5 Lumbar nerves (L1-L5)
    • 5 Sacral nerves (S1-S5)
    • 1 Coccygeal region

Dermatomes

  • Part of skin supplied by a single spinal cord level, by 1 spinal nerve.
  • Relaying sensation (including pain) from skin to brain.
  • In abdomen & thorax, dermatomes are disc-like.
  • In arms & legs, they are longitudinal.

Myotomes

  • Skeletal muscle innervated by 1 spinal cord level, by 1 spinal nerve.

Sensory Innervation of Thorax, Abdomen, and Pelvic Viscera

I. CN X (Vagus)

  • From medulla between pyramid and inferior cerebellar peduncle.
  • Passes through mediastinum on way to abdominal cavity.
  • In thorax, provides parasympathetic innervation.
  • Carries visceral afferent from thorax.
  • Visceral afferent to CNS.
  • Branches to esophagus, cardiac plexus, pulmonary plexus.

II. Phrenic Nerve

  • Origin: C3-C5 cervical nerves.
  • Phrenic nerves descend through the thorax.
  • Supply motor & sensory to diaphragm.
  • Innervate somatic afferent fibers.

III. Sensory Innervation of Abdominal Viscera

  • Abdominal viscera (GI tract)
  • Visceral afferent: Sensory info to CNS
  • Components of afferent fibers:
    1. Posterior root of spinal cord
    2. Splanchnic nerves

IV. Enteric System

  • Motor & sensory in 2 interconnected plexuses in GI tract.
  • Controls contraction & relaxation of intestinal smooth muscle, secretion, and blood flow.

V. Sensory Innervation of Pelvic Viscera

  • Sympathetic & parasympathetic course to spinal cord.
  • Afferent nerves enter at lower thoracic & lumbar levels.
  • Sympathetic nerves carry pain from cervix.
  • Parasympathetic nerves carry pain from bladder and urethra.
  • GVA fibers from organs in pelvis.
  • Sensory axons run along ANS with ANS plexus.

Neuroanatomy of Pain in Spinal Cord & Brainstem/Cortex

Spinothalamic Pathway (STT)

  • For sensation & perception.
  • To the brain.
  • Divisions:
    1. Lateral STT: Pain & temperature
    2. Anterior STT: Light touch, pressure, tickle, itch
  • STT carries affective sensation (sensation & compulsion to act).
  • Decussation occurs at spinal cord instead of brainstem.
  • Nuclei are located in dorsal horn of spinal cord.
  • Path:
    1. Pseudounipolar neurons: Dorsal spinal cord
    2. Nucleus proprius
    3. Tract cells
    4. Decussate in spinal cord via”anterior white commissure & anterolateral corne”
    5. Travel up to brainstem
    6. Pain travels contralaterally

Lateral Spinothalamic Tract

  • Afferent, poorly myelinated posterior fibers.
  • Bifurcates in posterolateral tract (Lissauer’s tract).
  • Fibers originating here cross in white commissure to opposite side.
  • Ascends in the lateral funiculus to thalamus (second neuron).
  • Pathway carries pain & temperature, exteroceptive & proprioceptive impulses.
  • Division is somatotopical (sacral & lumbar are dorsolateral, thoracic & cervical are ventromedial).
  • Pain sensation fibers are superficial.
  • Temperature sensation fibers lie deeper.

Skin: Blood Vessels & Nerves

Vasculature of Dermis

  • Highly vascularized connective tissue.
  • Provides mechanical support and tensile strength.
  • Muscular arteries supply blood to the skin.
  • Small arteries, veins, and capillaries maintain vasculature of dermis.
  • Small blood vessels form deep plexus in reticular dermis and superficial plexus.
  • Extensive network of papillae under epidermis for nutrient delivery.
  • Anastomoses in deep layer of dermis.
  • Vasculature is coiled.
  • Glomus bodies regulate temperature.
  • Under autonomic nervous system control.

Innervation of Dermis

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