Embryology
Which embryologic structure gives rise to skeletal muscle?
a) Intermediate mesoderm
b) Paraxial mesoderm → somites → myotome
c) Lateral plate mesoderm
d) Neural crest
b) Paraxial mesoderm → somites → myotome
Skeletal muscle develops from myotomes derived from paraxial mesoderm.
Which sarcomere component remains the same length during contraction?
a) I-band
b) H-zone
c) A-band
d) Z-line
c) A-band
The A-band (myosin length) stays constant; the I-band and the H-zone shorten during contraction
During smooth muscle contraction, calcium binds to _____ forming a complex that activates Myosin-Light-Chain Kinase, enabling actin-myosin interaction and muscle contraction.
a) troponin
b) calmodulin
b) calmodulin
Which nerve is most commonly injured in midshaft humerus fractures?
a) axillary
b) musculocutaneous
c) radial
d) ulnar
c) radial
the radial nerve runs in the spiral groove of the humerus and is vulnerable in midshaft fractures
When doing the McMurray Test, pain/click on internal rotation means ____ tear; pain/click on external rotation means ____ tear
a) lateral meniscus tear, medial meniscus tear
b) medial meniscus tear, lateral meniscus tear
a) lateral meniscus tear, medial meniscus tear
What structure deepends the shoulder socket for stability?
a) glenoid labrum
b) subacromial bursa
c) glenohumeral ligament
d) deltoid tendon
a) glenoid labrum
it's a fibrocartilaginous rim that deepends the glenoid cavity, improving shoulder stability
What is the origin of osteoclasts?
a) Mesenchymal stem cells
b) Fibroblasts
c) Monocyte-macrophage lineage
d) Chondrocytes
c) Monocyte-macrophage lineage
Osteoclasts differentiate from myeloid progenitors and are responsible for bone resorption
Which muscle fiber is the most fatigue-resistant and uses oxidative metabolism?
a) Type I
b) Type IIA
c) Type IIB
d) Type IV
a) Type I
Type I fibers are red, slow-twitch fibers that rely on aerobic respiration and resist fatigue
During smooth muscle relaxation, endothelial nitric oxide synthase converts which amino acid into NO?
a) L-Lysine
b) L-arginine
b) L-arginine
NO can then diffuse into smooth muscle cells, activate cGMP, then Myosin-LIght-Chain-Phosphatase, myosin gets dephosphorylated and then muscle relaxes
What movement is impaired with damage to the axillary nerve?
a) elbow flexion
b) shoulder abduction
c) wrist extension
d) forearm pronation
b) shoulder abduction
The axillary nerve innervates the deltoid, which abducts the shoulder from 15-90 degrees
What is the function of the deltoid ligament of the ankle?
a) resists eversion
b) resists inversion
c) stabilizes fibula
d) allows plantarflexion
a) resists eversion
the strong medial deltoid ligament stabilizes the ankle and prevents excessive eversion
Which radioulnar joint is responsible for spinning (rotation)?
a) proximal radioulnar
b) distal radioulnar
a) proximal radioulnar
other is pronation/supination
Which type of bone formation occurs without a cartilage model?
a) endochondral ossification
b) lamellar bone remodelling
c) intramembranous ossification
d) synchrondosis formation
c) intramembranous ossification
flat bones (eg skull, clavicle) form directly from mesenchyme without a cartilage precursor
What is the primary collagen type in articular cartilage?
a) Type I
b) Type II
c) Type III
d) Type IV
b) Type II
Type II collagen predominates in hyaline cartilage, including articular cartilage
In skeletal muscle contraction, action potential travels down a motor neuron, opening Ca channels and releasing ACh, then muscle depolarizes, intracellular calcium concentration increases and Calcium binds to troponin C, shifting tropomyosin and exposing myosin-binding sites on _____
Actin
What structure passes through the carpal tunnel but is spared in sensory loss?
a) ulnar nerve
b) palmar cutaneous branch of the median nerve
c) superficial radial nerve
d) dorsal branch of the ulnar nerve
b) palmar cutaneous branch of the median nerve
It travels outside the tunnel, so sensation over the thenar eminence is preserved in carpal tunnel syndrome
What is the most commonly sprained ligament in the ankle?
a) calcaneofibular ligament
b) posterior talofibular ligament
c) anterior talofibular liagament
c) anterior talofibular liagament
The elbow joint is a uniaxial synovial hinge joint. Which articulation of the elbow joint is primarily involved in flexion & extension?
a) humeroulnar joint
b) humeroradial joint
c) proximal radioulnar joint (pivot joint)
a) humeroulnar joint
What bone formation marker measures osteoblast activity?
a) PTH
b) ALP
c) ALT
b) ALP
Alkaline phosphatase measures osteoblast activity. Osteocalcin is also secreted by osteoblasts, and Pro-peptides of Type 1 collagen is an indirect marker of osteoblast function
Which joint is classified as synchrondosis?
a) Pubic symphysis
b) Intervertebral disc
c) Epiphyseal growth plate
d) Elbow joint
c) Epiphyseal growth plate
Synchrondroses are temporary cartilaginous joints (hyaline cartilage) that ossify with growth
Pubic symphysis = Symphysis (secondary)
Elbow = uniaxial synovial
Intervertebral disc = secondary symphysis
During skeletal muscle relaxation, calcium is actively pumped back into ________ via SERCA; tropomyosin recovers actin sites stopping contraction
a) cytoplasm
b) sarcoplasmic reticulum
b) sarcoplasmic reticulum
contains ryanodine receptors (RyRS)
What action is lost with damage to the long thoracic nerve?
a) shoulder extension
b) elbow flexion
c) thumb opposition
d) scapular protraction
d) scapular protraction
The serratus anterior, innervated by the long thoracic nerve, protracts the scapula; damage causes winged scapula
the medial collateral ligament prevents ___ stress, whereas the lateral collateral ligament prevents ____ stress
a) varus, valgus
b) valgus, varus
b) valgus, varus
Valgus = leg abduction
Varus = leg adduction
Which ligament of the shoulder prevents downward displacement of the humerus due to gravity?
a) glenohumeral ligament
b) coracohumeral ligament
c) transverse humeral ligament
d) coracoacromial ligament
b) coracohumeral ligament
RANKL stimulates osteoclast activity and bone resorption, but is secreted by osteoblasts. What is first secreted by osteoclasts to resorb bone?
a) H+
b) Collagenases
c) all of the above
c) all of the above
Which of the following types of muscle are non-striated?
a) cardiac
b) skeletal
c) smooth
c) smooth
like cardiac, they are uninucleated and involuntary control
Which two hypertension drugs reduce the influx of Calcium, slowing heart rate?
a) beta blockers
b) nitroglycerin
c) calcium channel blockers
d) a&c
d) a&c
Which movement is lost in foot drop?
a) plantarflexion
b) inversion
c) dorsiflexion
d) toe flexion
c) dorsiflexion
foot drop is caused by common peroneal nerve injury, affecting dorsiflexors like tibialis anterior
Which meniscus is C-shaped, firmly attached to MCL and less mobile and more injury prone?
a) medial meniscus
b) lateral meniscus
a) medial meniscus
lateral is more mobile, loosely attached to fibula, assists knee rotation
Which of the following is not a muscle of mastication (muscles of jaw closing)
a) temporalis
b) masseter
c) medial pterygoid
d) lateral pterygoid
d) lateral pterygoid
lateral pterygoid is more for jaw protrusion (moving forward)
Which hormone, produced by chief cells, can rapidly increase serum calcium and thus increase bone resorption if it's excessive?
a) PTH
b) ADH
c) Estrogen
a) PTH
Parathyroid hormone in high amounts can have a catabolic effect on bone, leading to bone resorption and osteitis fibrosa cystica (bone pain, fractures, cortical bone thinning)
Compact (cortical) bone is dense, strong and weight bearing. Its Haversian canals contain blood vessels and nerves. What is the name of the structure that connects the Haversian canals for vascular communication?
a) lacunae
b) lamellae
c) volkmann's canals
c) volkmann's canals
During cardiac muscle relaxation, what structure pumps Calcium out of the cell?
a) SERCA pump
b) Na/Ca exchanger
b) Na/Ca exchanger
SERCA pump goes first to pump Ca back into SR
a) common peroneal nerve
b) superior gluteal nerve
c) sciatic nerve
d) saphenous nerve
b) superior gluteal nerve
superior gluteal nerve injury weakens the gluteus medius and minimus, leading to a contralateral pelvic drop
Which hip joint ligament prevents excessive abduction?
a) iliofemoral (ligament of bigelow)
b) pubofemoral
c) ischiofemoral
b) pubofemoral
the others prevent overextension, iliofemoral is strongest
Which TMJ ligament is part of the joint capsule, and resists posterior dislocation of the mandible?
a) Lateral ligament (intrinsic)
b) Stylomandibular ligament
c) Sphenomandibular ligament
a) Lateral ligament (intrinsic)