md2 cas2 block exam msk system

What is endochondral ossification and which bones does it form?

Endochondral ossification is the process where bone forms by replacing a pre-existing hyaline cartilage template. It forms all long bones of the limbs, vertebrae, ribs, pelvis, and the base of the skull.

What are the steps in endochondral ossification?

1. Mesenchymal cells condense. 2. Differentiate into chondrocytes. 3. Form a cartilage model. 4. The primary ossification center forms in the diaphysis. 5. Secondary ossification centers form in the epiphyses after birth.

What is intramembranous ossification and which bones does it form?

Intramembranous ossification is the process where bone forms directly from mesenchymal tissue without a cartilage template. It forms the flat bones of the skull vault, clavicle, mandible, and maxilla.

In the case of achondroplasia, which type of ossification is defective?

Endochondral ossification is defective in achondroplasia.

Which ossification type is spared in achondroplasia?

Intramembranous ossification is spared.

What are the five zones of the growth plate from the epiphysis to the metaphysis?

1. Reserve (resting) zone. 2. Proliferating zone. 3. Hypertrophic zone. 4. Provisional calcification zone. 5. Primary spongiosa.

What is the SALTER mnemonic for Salter-Harris growth plate fractures?

S — Slipped (Type I). A — Above (Type II). L — Lower (Type III). T — Through all three zones (Type IV). E/R — Ram/ERasure (Type V).

What does the Apical Ectodermal Ridge do in limb development?

The Apical Ectodermal Ridge is a thickened band of ectoderm that secretes fibroblast growth factors to stimulate mesoderm proliferation and drive proximal-to-distal limb growth.

What drug causes phocomelia and what is its mechanism?

Thalidomide causes phocomelia by inhibiting angiogenesis and interfering with fibroblast growth factor signaling during embryonic limb development.

What are the histological differences between skeletal, cardiac, and smooth muscle?

Skeletal muscle is striated, multinucleated, and has peripheral nuclei. Cardiac muscle is striated with intercalated discs and a central nucleus. Smooth muscle is non-striated with a single central nucleus.

What are satellite cells in skeletal muscle responsible for?

Satellite cells are responsible for muscle regeneration after injury.

What is the difference between Haversian canals and Volkmann's canals?

Haversian canals run longitudinally along the bone and contain blood vessels, while Volkmann's canals run transversely and connect Haversian canals.

List the three types of cartilage and where they are found.

Hyaline cartilage (Type II collagen) is found in joints and fetal skeleton. Fibrocartilage (Type I collagen) is found in intervertebral discs and pubic symphysis. Elastic cartilage (Type II collagen and elastin) is found in the ear and epiglottis.

What are the cell markers for osteoblasts and osteoclasts?

Osteoblasts: alkaline phosphatase (ALP), osteocalcin; originate from mesenchymal stem cells. Osteoclasts: tartrate-resistant acid phosphatase (TRAP); originate from monocyte/macrophage precursors.

What is woven bone versus lamellar bone?

Woven bone has irregularly arranged collagen fibers and is structurally weak. Lamellar bone has collagen arranged in parallel sheets and is structurally strong.

What are glycosaminoglycans (GAGs)?

GAGs are long chains of repeating disaccharides that are negatively charged and help retain water in connective tissues.

What is elastin and how does it differ from collagen?

Elastin provides tissue elasticity and is rich in proline and desmosine; collagen resists tension and has a different structural organization.

Describe the difference between superficial and deep fascia.

Superficial fascia contains loose connective and adipose tissue while deep fascia consists of dense, inelastic connective tissue that wraps around muscles.

What are the steps in collagen synthesis?

1. Pro-alpha chain synthesis. 2. Hydroxylation. 3. Glycosylation. 4. Triple helix formation (procollagen). 5. Secretion. 6. Cleavage to tropocollagen. 7. Cross-linking.

Which step in collagen synthesis is defective in scurvy?

Step 2 (hydroxylation) is defective due to Vitamin C deficiency.

What are the major collagen types and their locations?

Type I: found in bone, tendons. Type II: found in cartilage. Type III: found in blood vessels and granulation tissue. Type IV: found in basement membranes.

Describe the collagen defect in Vascular EDS and its risks.

Type III collagen is defective, leading to spontaneous ruptures of vessels; it's dangerous due to the risk of arterial dissection.

Which collagen type is defective in Alport syndrome?

Type IV collagen is defective, causing renal symptoms and hearing loss.

What are the three forms of Vitamin D?

Form 1: Cholecalciferol (D3) produced in skin; Form 2: 25-hydroxyvitamin D3 (Calcidiol) produced in liver; Form 3: 1,25-dihydroxyvitamin D3 (Calcitriol) produced in kidney.

What stimulates renal 1-alpha-hydroxylase?

Parathyroid hormone, low serum phosphate, and low serum calcium stimulate it.

What does parathyroid hormone do to calcium and phosphate?

It increases calcium and decreases phosphate in the blood.

Does parathyroid hormone deposit or mobilize calcium from bone?

It mobilizes calcium from bone through osteoclast activation.

What does RANKL do and what is osteoprotegerin?

RANKL activates osteoclasts while osteoprotegerin is a decoy receptor that prevents RANKL from activating osteoclasts.

What is McArdle disease and its characteristic feature?

A glycogen storage disease caused by muscle glycogen phosphorylase deficiency, causing exercise intolerance and 'second wind phenomenon'.

Describe the difference between Menkes and Wilson disease regarding copper metabolism.

Menkes disease causes copper deficiency due to defective absorption, while Wilson disease causes copper accumulation due to defective excretion.

What are the lab values in osteoporosis?

All normal — calcium, phosphate, parathyroid hormone, and alkaline phosphatase are normal.

What markers are expected in Paget disease of bone?

Massively elevated alkaline phosphatase; calcium and phosphate are normal.

What is excitation-contraction coupling in skeletal muscle?

An action potential travels down the motor neuron, triggers acetylcholine release, leading to muscle contraction through calcium release.

What are Type I, Type IIa, and Type IIb muscle fibers?

Type I: slow oxidative, endurance; Type IIa: fast oxidative-glycolytic, moderate endurance; Type IIb: fast glycolytic, high power but fatigable.

Describe the differences between Myasthenia Gravis and Lambert-Eaton syndrome.

Myasthenia Gravis: post-synaptic antibodies cause weakness worsening with use. Lambert-Eaton: pre-synaptic calcium channels affected, weakness improves with use.

What does botulinum toxin do?

Botulinum toxin cleaves SNARE proteins to prevent acetylcholine release at neuromuscular junctions, causing flaccid paralysis.

What is the mechanism behind malignant hyperthermia?

Uncontrolled calcium release from the sarcoplasmic reticulum, triggered by certain anesthetics in susceptible individuals.

How do you reverse non-depolarizing neuromuscular blockers?

Use neostigmine or sugammadex to reverse the effects.

What is the mechanism of organophosphate poisoning?

It irreversibly inhibits acetylcholinesterase, leading to acetylcholine accumulation.

What is the most commonly fractured bone in the body?

The clavicle.

What fracture risks avascular necrosis and why?

Scaphoid fracture due to its retrograde blood supply.

Differentiate Colles fracture from Smith fracture.

Colles fracture: distal radius fracture with dorsal angulation. Smith fracture: distal radius fracture with volar angulation.

What is a Bennett fracture?

An intra-articular fracture of the base of the first metacarpal.

What is the brachial plexus formation mnemonic?

Real Teenagers Drink Cold Beer = Roots, Trunks, Divisions, Cords, Branches.

What is Erb's palsy caused by?

Injury to the C5 and C6 roots of the brachial plexus.

What is Klumpke's palsy and its presentation?

Caused by injury to C8 and T1 roots, leading to claw hand presentation.

What nerve injury results in inability to abduct the shoulder?

Axillary nerve injury.

What does injury to the radial nerve at midshaft cause?

Wrist drop and sensory loss in the dorsal hand.

What does anterior interosseous nerve injury cause?

Inability to make an 'OK' sign; no sensory loss.

What does median nerve injury at the wrist cause?

Loss of thenar muscles and sensory loss in the lateral 1.5 fingers.

What is ulnar nerve injury at the elbow's effect?

Claw hand and sensory loss in the medial 1.5 fingers.

What are the thenar muscles and their innervation?

Abductor pollicis brevis, opponens pollicis, flexor pollicis brevis; innervated by the median nerve.

What are the contents of the carpal tunnel?

9 flexor tendons and the median nerve.

What are the SITS muscles of the rotator cuff?

Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.

What is the painful arc sign?

Pain during 60-120 degrees of shoulder abduction due to impingement.

What is the mechanism of anterior versus posterior shoulder dislocations?

Anterior dislocation from abduction and external rotation; posterior dislocation from adduction and internal rotation.

What is a Monteggia fracture?

Fracture of the ulna with dislocation of the radial head.

What are the contents of the cubital fossa laterally to medially?

Radial nerve, bicipital aponeurosis, biceps tendon, brachial artery, median nerve.

What nerve supplies serratus anterior?

Long thoracic nerve.

What causes winged scapula?

Injury to the long thoracic nerve.

What is Poland syndrome?

Congenital condition characterized by the absence of the pectoralis major muscle.

What is the anatomical snuffbox and what passes through it?

The radial artery passes through it; borders consist of abductor pollicis longus and extensor pollicis brevis.

What is the danger layer of the scalp?

The loose areolar tissue layer; infections can spread through this layer.

What nerve innervates facial expression muscles?

Facial nerve (cranial nerve VII).

What is the most common cause of Bell's palsy?

Herpes simplex virus type 1 activation.

Where does the spinal accessory nerve run and what happens if injured?

It runs in the posterior triangle of the neck and injury causes trapezius paralysis.

What are the vertebral levels of diaphragm openings?

T8 (IVC), T10 (esophagus), T12 (aorta).

What is the phrenic nerve and its function?

C3, C4, C5 nerve roots supply the diaphragm and carry sensory fibers.

What is the intercostal neurovascular bundle arrangement?

VAN: Vein, Artery, Nerve from superior to inferior along the costal groove.

What is flail chest?

When three or more consecutive ribs are fractured in two or more places causing paradoxical movement.

Which nerve root is compressed by an L4-L5 disc herniation?

L5 nerve root is compressed.

What triad characterizes cauda equina syndrome?

Bilateral leg weakness, saddle anesthesia, bladder and bowel dysfunction.

Which artery is at risk in a femoral neck fracture?

The medial femoral circumflex artery.

What is a supracondylar femur fracture?

Fracture just above the femoral condyles, risk to the popliteal artery.

What nerve is injured at the fibular neck?

The common peroneal nerve.

Which fracture is associated with a calcaneus fracture?

Compression fracture of L1 vertebra.

What is the Trendelenburg sign?

Contralateral pelvis drops when standing on one leg; indicates hip abductor weakness.

What is the unhappy triad of the knee?

Tear of the anterior cruciate ligament, medial collateral ligament, and medial meniscus.

What are the four compartments of the leg?

Anterior, lateral, superficial posterior, deep posterior compartments.

What are the 6 P's of compartment syndrome?

Pain, Paresthesia, Pressure, Pallor, Paralysis, Pulselessness.

What is slipped capital femoral epiphysis?

Slippage of the femoral head due to growth plate issues, common in obese adolescents.

What is Legg-Calvé-Perthes disease?

Avascular necrosis of the femoral head in children.

What is Osgood-Schlatter disease?

Traction apophysitis of the tibial tubercle in active adolescents.

What is developmental dysplasia of the hip?

Hip joint abnormalities from shallow acetabulum to dislocation.

What is in the superficial perineal pouch in males?

Bulb of the penis, crura of corpora cavernosa, muscles like bulbospongiosus.

What is the course of the pudendal nerve?

Exits pelvis through the greater sciatic foramen, crosses ischial spine, re-enters via lesser sciatic foramen.

What is the levator ani muscle?

Main pelvic floor muscle that supports pelvic organs.

What are the four pelvic types?

Gynecoid, Android, Anthropoid, Platypelloid.

What is the difference between indirect, direct, and femoral hernias?

Indirect: through deep inguinal ring. Direct: bulges through Hesselbach's triangle. Femoral: through femoral canal.

What is the pathogenesis of rheumatoid arthritis?

T-cell activation and cytokine production leading to pannus formation and joint erosion.

What antibodies are present in rheumatoid arthritis?

Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP), with anti-CCP being more specific.

Which are the three hand deformities in rheumatoid arthritis?

Ulnar deviation, boutonniere deformity, swan neck deformity.

What are the seronegative spondyloarthropathies?

Ankylosing spondylitis, psoriatic arthritis, reactive arthritis, enteropathic arthritis.

What are the features of psoriatic arthritis?

Asymmetric oligoarthritis, distal interphalangeal joint involvement, sausage digits.

What triad characterizes reactive arthritis?

Conjunctivitis, urethritis, asymmetric oligoarthritis.

What is enteropathic arthritis?

Arthritis associated with inflammatory bowel disease.

What is osteomalacia?

Insufficient mineralization of newly formed bone matrix, often due to vitamin D deficiency.

What is bursitis?

Inflammation of a bursa, often due to repetitive motion or mechanical irritation.

What is adhesive capsulitis (frozen shoulder)?

Progressive capsule fibrosis of the glenohumeral joint leading to reduced shoulder movement.

What is Dupuytren's contracture?

Progressive fibrosis of the palmar fascia resulting in flexion contractures of fingers.