Musculoskeletal and Dermatology Physiology

• From surface to base:
• -Stratum Corneum (keratin)
• -Stratum Lucidum
• -Stratum Granulosum
• -Stratum Spinosum (spines = desmosomes)
• -Stratum Basale (stem cells)

"Californias Like Girls in String Bikinis"

• Sebaceous Glands
• Eccrine Glands
• Apocrine Glands

• -Holocrine (rupture of plasma membrane) secretion of sebum
• -Associated with hair follicle

• -Secrete sweat
• -found throughout the body

"Eccrine glands are Everywhere"

• -Secrete milky viscous fluid
• -Found in axillae, genitalia and areolae
• -Not functional until puberty
• -Malodorous because of bacterial action

• "Zona Occludens"
• -apical surface of cells?

• Function:
• -prevents paracellular movement of solutes

• Structure:
• -claudins
• -occludins

• "Zonula Adherens"
• -found below tight junctions

• Function:
• -forms "belt" connecting actin cytoskeletons of adjacent cells

• Structure:
• -CADherins (Ca²⁺ dependent adhesion proteins)

• Disease:
• -loss of E-cadherin promotes metastasis

"Macula Adherens"

• Function:
• -structural support between cells

• Structure:
• -via keratin interactions

• Disease:
• -Pemphigus Vulgaris (autoantibodies)

• Function:
• -permit electrical and chemical communication between cells

• Structure:
• -connexins (channel proteins)

• Function:
• -connect basal cells to underlying basement membrane

• Structure:
• -via keratin interactions

• Disease:
• -Bullous pemphigoid (autoantibodies)
• "hemidesmosomes are down bullow"

• -membrane proteins that maintain integrity of basement membrane
• -bind to laminin in basement mebrane

"Saddle nerve block"

-relieve pain of delivery

Landmark = ischial spine

2/3 of the way from the umbilicus to ASIS

McBurney's point

Iliac Crest

SItS (small t for teres minor)

• Supraspinatus
• Infraspinatus
• Teres Minor
• Subscapularis

Innervated by C5-C6

• Function:
• -abducts arm initially (before deltoid)

Most common rotator cuff injury

• Function:
• -laterally rotates arm

Pitching injury

• Function:
• -adducts and laterally rotates arm

• Function:
• -medially rotates and adducts arm

"Slide Left Tiny Pinky, Here Comes The Thumb"

• Scaphoid
• Lunate
• Triquetrium
• Pisiform
• Hamate
• Capitate
• Trapezoid
• Trapezium

• Scaphoid:
• -most commonly fractured carpal bone
• -prone to avascular necrosis due to retrograde blood supply

• Lunate:
• -dislocation may cause acute carpal tunnel syndrome

• "Randy Travis Drinks Cold Beer"
• -Roots
• -Trunks
• -Divisions
• -Cords
• -Branches

-Long Thoracic Nerve

• -Dorsal Scapular Nerve
• -Suprascapular Nerve

-Lateral Pectoral

• -Upper Subscapular Nerve
• -Thoracodorsal Nerve
• -Lower Subscapular Nerve

• -Medial Pectoral
• -Medial Brachial Cutaneous
• -Medial Antebrachial Cutaneous

• -Musculocutaneous
• -Axillary
• -Median
• -Radial
• -Ulnar

• Innervates:
• -serratus anterior (abduction above horizontal position)

• Palsy:
• -scapular winging
• -can be injured during mastectomy (winging and ipsilateral lymphedema

• Innervates:
• -Levator Scapulae
• -Rhomboids

• Innervates:
• -supraspinatus
• -infraspinatus

• Innervates:
• -Pectoralis Major

• Innervates:
• -subscapularis

• Innervates:
• -Latissimus Dorsi

• Innervates:
• -Subscapularis
• -Teres Major

• Innervates:
• -Pectoralis Major
• -Pectoralis Minor

• Innervates:
• -sensory to medial arm

• Innervates:
• -sensory to medial forearm

• -C7 root
• -Upper trunk
• -Axillary nerve
• -Radial nerve (spinal groove)
• -Median nerve
• -Ulnar nerve
• -Deep branch of radial nerve
• -Anterior Interosseus nerve
• -Recurrent branch of median nerve

• Nerve Roots:
• -C5-C7
• -terminal lateral cord

• Innervates:
• 1. MOTOR (flexion of arm at elbow):
• -Biceps
• -Brachialis
• -Coracobrachialis

• 2. SENSORY
• -Lateral forearm

• Typical Injury:
• -upper trunk compression

• Nerve Roots:
• -C5, C6
• -Posterior Cord

• Innervates:
• 1. MOTOR:
• -deltoid (abduction of arm at shoulder)

• 2. SENSORY:
• -over deltoid

• Typical Injury:
• -fractured surgical neck of humerus

• Injury Sign:
• -atrophied deltoid

• Nerve Roots:
• -C5-C8, T1
• -Terminal lateral and medial cords

• Innervates:
• 1. MOTOR:
• -Thenar Muscles (opposition of thumb)
• -FDS, FDP 2 and 3, FPL (lateral finger flexion)
• -FCR (radial wrist flexion)
• -PT, PQ (forearm pronators)

• 2. SENSORY:
• -dorsal and plamar aspects of lateral 3.5 fingers
• -thenar eminence

• Typical Injury:
• -Proximal lesion: fracture of supracondylar humerus
• -Carpal tunnel syndrome 
• -Superficial laceration of recurrent branch of median nerve

• Injury Sign:
• -Ape hand (loss of thumb opposition)
• -Pope's Blessing Hand

• Nerve Roots:
• -C5-C8, T1
• -Terminal posterior cord

• Innervates:
• 1. MOTOR:
• -Brachioradialis
• -Extensors of wrist and fingers
• -Supinator
• -Triceps
• "BEST extensors"

• 2. SENSORY:
• -posterior arm
• -dorsoradial hand and thumb

• Typical Injury:
• -Fracture at midshaft of humerus (spiral groove)
• -"Saturday night palsy" (extended compression of axilla by chair or crutches)

• Injury Signs:
• -Wrist drop

• Nerve Roots:
• -C8, T1
• -terminal medial cord

• Innervates:
• 1. MOTOR:
• -FCU (ulnar wrist flexion)
• -Ulnar FDP (medial finger flexion)
• -Intrinsic hand muscles

• 2. SENSORY:
• -Medial 1.5 fingers (dorsal and palmar)
• -hypothenar eminence

• Typical Injury:
• -Proximal lesion: fracture of medial epicondyle of humerus "funny bone"
• -Distal Lesion: trauma to heel of hand, fracture to hook of hamate

• Injury Signs:
• -radial deviation of wrist upon wrist flexion

• C6: A-OK
• C7: flipping off
• 

• Thenar
• Hypothenar
• Dorsal Interosseous
• Palmar Interosseus
• Lumbricals

• Innervation:
• -median nerve

• Muscles:
• -Opponens pollicis
• -Abductor pollicis brevis
• -Flexor pollicis brevis

"OAF"

• Innervation:
• -Ulnar nerve

• Muscles:
• -Opponens digiti minimi
• -Abductor digiti minimi
• -Flexor digiti minimi

"OAF"

• Innervation:
• -Ulnar nerve

• Function:
• -abduct the fingers

DAB= Dorsals ABduct

• Innervation:
• -Ulnar nerve

• Function:
• -adduct the fingers

PAD = Palmar ADduct

• Innervation:
• -Median Nerve (radial: first and second)
• -Ulnar nerve (ulnar: third and fourth)

• Function:
• -flex MCP joint
• -extend DIP and PIP joints
• "Queen's wave"

• Obturator
• Femoral
• Common Peroneal
• Tibial
• Superior Gluteal
• Inferior Gluteal

• Nerve Roots:
• -L2-L4

• Innervates:
• 1. MOTOR
• -Thigh adductors (External obturator, Adductor lungs, Adductor brevis, Adductor Magnus, Gracilis)

• 2. SENSORY:
• -medial thigh

• Typical Injury:
• -anterior hip dislocation

• Nerve Roots:
• -L2-L4

• Innervates:
• 1. MOTOR:
• -Quadraceps (Rectus femoris, Vastus lateralis, Vastus medialis, Vastus intermedius)
• -Function: Thigh Flexion and Leg extension

• 2. SENSORY:
• -anterior thigh
• -medial leg

• Typical Injury:
• -pelvic fracture

• Nerve Roots:
• -L4-S2

• Innervates:
• 1. MOTOR
• -Anterior compartment of leg
• -Lateral compartment of leg
• -Foot eversion and dorsiflexion
• -toe extension

• 2. SENSORY:
• -Anterolateral leg and dorsal aspect of foot

• Typical Injury:
• -trauma or compression of lateral aspect of leg
• -fibula neck fracture

• Signs of Injury:
• -foot drop
• -foot slap
• -steppage gait

"PED = Peroneal Everts and Dorsiflexes; if injured foot dropPED"

• Nerve Roots:
• -L4-S3

• Innervates:
• 1. MOTOR
• -Posterior leg
• -foot inversion
• -foot plantarflexion
• -toe flexion

• 2. SENSORY:
• -sole of foot

• Typical Injury:
• -knee trauma

TIP "Tibial Inverts and Plantarflexes, If injured can't stand on TIPtoes"

• Nerve Root:
• -L4-S1

• Innervation:
• 1. MOTOR:
• -thigh abduction

• Typical Injury:
• -posterior hip dislocation
• -polio!

• Injury Sign:
• -positive Trendeleburg sign: contralateral hip drops when standing on leg ipsilateral to side of lesion

• Nerve Root:
• -L5-S2

• Innervation:
• 1. MOTOR

• Typical Injury:
• -posterior hip dislocation

• Injury Signs:
• -can't jump, climb stairs, rise from seated position
• -can't push inferiorly (downward)

• Muscles:
• -Rectus femoris
• -Vastus medialis
• -Vastus intermedius
• -Vastus lateralis
• -Sartorius

• Function:
• -extend the knee joint
• -flexion of the hip

• Blood Supply:
• -Femoral artery

• Innervation:
• -Femoral nerve

• Muscles:
• -Gracilis
• -Adductor Magnus
• -Adductor Brevis
• -Adductor Longus

• Function:
• -adduction of the leg

• Blood Supply:
• -Obturator Artery

• Innervation:
• -Obturator nerve

• Muscles:
• -Biceps Femoris
• -Semitendinosus
• -Semimembranosus

• Function:
• -extension of the hip
• -rotation of the hip

• Blood Supply:
• -perforating arteries (from deep artery of the thigh)

• Innervation:
• -sciatic nerve

• Muscles:
• -Tibialis anterior
• -Extensor digitorum longus
• -Extensor hallucis longus
• -Fibularis

• Function:
• -dorsiflexion
• -foot inversion

• Blood Supply:
• -anterior tibial artery
• Innervation:
• -deep fibular (peroneal) nerve

• Muscles:
• -Fibularis longus
• -Fibularis brevis

• Function:
• -foot eversion

• Blood Supply:
• -fibular artery

• Innervation:
• -superficial fibular nerve

• Muscles:
• -Gastrocnemius
• -Soleus
• -Plantaris

• Function:
• -plantarflexion

• Blood Supply:
• -posterior tibial artery

• Innervation:
• -Tibial nerve

• Muscles:
• -Flexor digitorum longs
• -Flexor hallucis longus
• -Tibialis Posterior
• -Popliteus

• Function:
• -plantar flexion

• Blood Supply:
• -Posterior tibial artery

• Innervation:
• -Tibial nerve

1. AP depolarization opens presynaptic voltage gated Ca²⁺ channels, inducing NT release

2. NT binds to postsynaptic membrane leading to muscle cell depolarization that the motor end plate

3. Depolarization travels along muscle cell and down the T tubule

• 
• 4. Depolarization of voltage-sensitive Dihydropyridine receptor results in opening of the ryanidine receptor on the sarcoplasmic reticulum (mechanically coupled or CICR).
• -induces Ca²⁺ release from sarcoplasmic reticulum

5. Released Ca²⁺ binds troponin C causing a conformational change that moves tropomyosin out of the myosin-binding groove on actin filaments

• Z line:
• -forms the borders of the sarcomere
• -Z is the last letter of the alphabet, Z band is the last part of the sarcomere

• M line:
• -in the Middle of the sarcomere
• -within the H band

• A band:
• -entire length of a single thick filament
• -A band is Always the same length

• I band:
• -only actin (thin filament)
• -I is a thin letter

• H band:
• -only myosin (thick filament)
• -H is a thick letter

Contraction results in shortening of H and I bands and between the Z lines (HIZ shrinkage)

A band remains the same length

Slow Twitch, Red Fibers

Increased mitochondria and myoglobin concentration → ↑ oxidative phosphorylation

Allows for sustained contraction

"1 slow red ox"

Fast Twitch, White Fibers

Decreased mitochondria and myglobin concentration → ↑ Anaerobic glycolysis

Weight training results in hypertrophy of fast twitch fibers

• 
• 1. "Cocked State"
• -ATP hydrolysis cocks the myosin head (not attached to actin)

• 2. "Cross-Bridged State"
• -Ca2+ binds troponin C, causing conformational change
• -this displaces tropomyosin and allows the myosin head to bind actin

• 3. "Power Stroke State"
• -Pi is release changing myosin head conformation and causing the power stroke

• 4. "Released State"
• -ADP dissociates and ATP binds myosin head, causing release from actin filament
• -lack of ATP causes rigor mortis

1. AP depolarizes SM membrane

2. Voltage gated Ca²⁺ channels open leading to increased Ca²⁺ in the cytoplasm

3. Ca²⁺ binds calmodulin and activates MLCK

4. MLCK phosphorylates actin leading to cross-bridge formation and muscle contraction

• Inhibition of Smooth Muscle contraction:
• -NO activates GC, activates cGMP which inhibits MLCK

• Location:
• -bones of axial and appendicular skeleton
• -base of skull

1. Cartilaginous model of bone is made by chondrocytes

2. Osteoclasts and osteoblasts later replace with woven bone and then remodel to lamellar bone

• Woven bone:
• -haphazard arrangement of collagen fibers
• -weak
• -in adults occurs after fractures and in Paget's disease

• Lamellar bone:
• -collagen arranged in sheets
• -strong

• Location:
• -calvarium
• -facial bones

1. Woven bone formed directly without cartilage

2. Later remodeled to lamellar bone

• Function:
• -blasts build bone
• -secrete collagen and catalyze mineralization

• Origin:
• -differentiate from mesenchymal stem cells in periosteum

• Function:
• -multinucleated cells that dissolve bone by secreting acid and collagenases

• Origin:
• -differentiate from monocytes/macrophages

• Low-Intermittent levels
• -anabolic effects (building bone) on osteoblasts and osteoclasts (indirect)

• Chronic high levels:
• -ie: primary hyperparathyroidism
• -catabolic effects (osteitis fibrosa cystica)

• Function:
• -inhibits apoptosis in bone-forming osteoblasts
• -induces apoptosis in bone-resorbing osteoclasts

• Estrogen Deficiency:
• -ie: surgical, postmenopausal
• -excess remodeling cycles and bone resorption lead to osteoporosis