Musculoskeletal/Skin/CT- Anatomy and Physiology Flashcards
What is an ‘unhappy triad’?
commonly occurs due to lateral force applied to a planted leg and consists of damage to the ACL, MCL, and medial meniscus (attached to the MCL)
What is this?
A baker cyst, a popliteal fluid collection commonly relayed to chronic joint disease
What are the ‘rotator cuff’ muscles?
SiTS
Supraspinatus
Infraspinatus
teres minor
Subscapularis
What innervates the supraspinatus and infrapspinatus?
suprascapular n.
What does the supraspinatus do?
abducts the arm initially (before the action of the deltoid); assessed by empty can test
What does the infraspinatus do?
laterally rotate the arm (pitching injury)
What innervates teres minor?
the axillary n.
What does the teres minor do?
adduct and laterally rotate the arm
What innervates the subscapularis?
upper and lower subscapular nn.
What does the subscapularis do?
medially rotate and adduct
What is the major cause of medial epicondylitis? Lateral?
medial: golfing (aka golfer’s elbow)
lateral: tennis
What are the wrist bones?
from thumb to pinky first row: scaphoid, lunate, triquertrum, pisiform
from thumb to pinky second row: trapzeium, trapezoid, capitate, hamate
What is the most commonly fractured wrist bone and the most prone to avascuar necrosis owing to retrograde blood supply?
scaphoid
Dislocation of the ____ may cause acute carpal tunnel syndrome
lunate
A fall on an outstretch hand that dmaages the hook of the hamate cause cause _____ injury
ulnar nerve
What is carpal tunnel syndrome?
compression of the median nerve commonly seen in pregnancy, rheumatoid arthritis, and hypothyroidism
What is Guyon canal syndrome?
compression of the ulnar nerve at the wrist or hand classically seen in cyclists
What are some common causes of axillary n. (C5-C6) damage?
fractured surgical neck of the humerus, anterior dislocation of the humerus
How would a C5-C6 lesion present?
- atropied deltoid
- loss of arm abduction at sholder at 15+ degrees
loss of sensation over deltoid muscle and lateral muscle
What is a common cause of musculocutaneous (C5-C7) lesions?
upper trunk compression
How would a musculocutaneous lesion present?
loss of forearm flexion and supination
loss of lateral forearm sensation
What are some common causes of radial (C5-T1) lesions?
-midshaft fracture of the humerus
compression of the axilla, e.g. due to crutches or sleeping with an arm over a chair (aka Saturday night palsy)
How would a radial branch lesion present?
wrist drop: loss of elbow, wrist, and finger extension
decreased grip strength loss of sensation over posterior forearm/arm and dorsal hand
What are some causes of median branch lesion (C5-T1)?
supracondylar fracture of the humerus (proximal)
carpal tunnel syndrome and/or wrist laceration (distal)
How would a median n. lesion present?
- ape hand and popes blessing
- loss of wrist flexion, flexion of lateral fingersm thumb opposition, and lumbricals of the 2nd and 3rd digits
- loss of sensation over the thenar eminence and dorsal and palmar aspects of lateral 3.5 fingers
- positive Tinel sign
What are the major causes of ulnar (C8-T1) n. lesions?
fracture of the medial epicondyle of the humerus
fractured hook of hamate
How does an ulner n. lesion present?
ulnar claw on digital extension
radial deviation of wrist upon flexion
loss of wrist flexion, flexial of medial fingers, abduction and adduction of fingers (interossei)
loss of sensation over medial 1.5 fingers including hypothenar eminence
How would lesion of the recurrent branch of the median n. present?
ape hand with loss of thnar muscle group including opposition, abduction, and flexion of the thumb but without loss of sensation
What brachial roots contribute to the Long thoracic n.?
C5-C7
What are the parts of the brachial plexus?
Roots
Trunks
Divisions
Cords
Branches
What roots contribute to the upper trunk? middle? lower?
Upper- C5-C6
Middle- C7
Lower- C8-T1
Erb’s palsy results from lesion of what?
the upper trunk (C5-C6)
How does Erb’s palsy present?
adduction (deltoid and supraspinatus lost)
medial rotation (lateral rotation impaired due to loss of infraspinatus)
arm extended and pronated (loss of biceps brachii)
Claw hand (aka Klumpke palsy) is caused by lesion to what?
lower TRUNK (C8-T1)
Wrist drop is commonly due to lesion of the _____
posterior cord (which the axillary and radial nn. arise from)
What are some common causes of Klumpke palsy (claw hand)?
infants- pulling the arm during delivery
adults- trauma (e.g. grabbing a tree branch when falling)
What trunks contribute to the lateral cord? posterior? medial?
lateral: upper and middle (C5-C7)
posterior: all (C5-T1)
medial: lower only (C8-T1)
What cords contribute to the musculocutanous n.? median n? ulnar n?
MSCutaneous: lateral only (C5-C7)
Median: lateral and medial (C5-T1)
Ulnar: medial only (C8-T1)
What cords contribute to the axillary and radial nn.?
posterior only
What muscles are deficient in Klumpke palsy?
intrinsic hand muscles: lumbricals, interossei, thenar, and hypothenar
What causes thoracic outlet syndrome?
compression of the lower trunk of the BP and subclavian vessels commonly due to an additional cervical rib or pancoast tumor
How does TOS present?
There are three main types: neurogenic, venous, and arterial.
The neurogenic type is the most common and presents with pain, weakness, and occasionally loss of muscle at the base of the thumb.
The venous type results in swelling, pain, and possibly a bluish coloration of the arm.
The arterial type results in pain, coldness, and paleness of the arm
TOS affects mainly the upper limbs, with signs and symptoms manifesting in the shoulders, neck, arms and hands. Pain can be present on an intermittent or permanent basis. It can be sharp/stabbing, burning, or aching. TOS can involve only part of the hand (as in the pinky and adjacent half of the ring finger), all of the hand, or the inner aspect of the forearm and upper arm. Pain can also be in the side of the neck, the pectoral area below the clavicle, the armpit/axillary area, and the upper back (i.e., the trapezius and rhomboid area). Discoloration of the hands, one hand colder than the other hand, weakness of the hand and arm muscles, and tingling are commonly present.
TOS is often the underlying cause of refractory upper limb conditions like frozen shoulder and carpal tunnel syndrome that frequently defy standard treatment protocols. TOS can be related to Forward head posture.
A painful, swollen and blue arm, particularly when occurring after strenuous physical activity, could be the first sign of a subclavian vein compression related with an unknown TOS and complicated by thrombosis (blood clots), the so-called Paget–Schroetter syndrome or effort-induced thrombosis.
TOS can be related to cerebrovascular arterial insufficiency when affecting the subclavian artery. It also can affect the vertebral artery, in which case it could produce vision disturbances, including transient blindness, and embolic cerebral infarction.
TOS can also lead to eye problems and vision loss as a circumstance of vertebral artery compression. Although very rare, if compression of the brain stem is also involved in an individual presentation of TOS, transient blindness may occur while the head is held in certain positions.[8] If left untreated, TOS can lead to neurological deficits as a result of the hypoperfusion and hypometabolism of certain areas of the brain and cerebellum
What muscle is impacted by a lesion of the LTN?
serratus anterior
What is the function of the lumbricals?
flexion of the MCP, and extension of the DIP/PIP joints
Clawing is most commonly sseen with distal lesions of the _____ or ______ nn.
median or ulnar (remaining extrinsic flexors of the digits exaggerate the loss of the lumbricals)
defects are less pronounced in proximal lesions
Ulnar claw (below) which is marked by this appearance at rest or when trying to extend the fingers is caused by lesion of what?
DISTAL ulnar n. lesion
Pope’s blessing, which looks similar to an ulnar claw, and occurring when a pt. tries to make a fist is caused by what?
a proximal median n. lesion
A median claw (below), seen when a pt. tries to extend their fingers or at rest is caused by what?
distal median n. lesion
An “OK gesture” which appears the same as a median claw and occurring when a pt. tries to make a fist is caused by what?
a proximal ulnar nerve lesion
Note that atophy of the thenar eminence can be seen in median n. lesions, while atrophy of the hypothenar eminence is more commonly seen in ulnar n. lesions
What do the dorsal interossei do? Palmar?
Dorsal abduct (DAB)
Palmar adduct (PAD)
What do lumbricals do?
flex at the MCP, extend at the PIP and DIP
Obturator n. lesion (L2-L4) is common when?
following pelvic surgery
How does obturator n. lesion present?
decreased thigh sensation (medial) and adduction
Femoral n. lesion (L2-L4) is common when?
pelvic fracture
How does femoral n. lesion present?
decreased thigh flexion and leg extension
Common peroneal (L4-S2) n. lesion is common when?
trauma or compression of the lateral aspect of the leg, or fibular neck fracture
How does common peroneal n. lesion present?
foot drop- inverted and plantarflexed at rest
loss of eversion and dorsiflexion
“steppage gait”
loss of sensation on foot dorsum
What are some common causes of tibial (L4-S3) n. lesion?
knee trauma,
Baker cyst (proximal lesion)
tarsal tunnel syndrome
How does a tibial (L4-S3) n. lesion present?
Inability to curl toes and loss of sensation on the sole of the foot. In proximal lesions, the foot will be everted at rest with loss of inversion and plantarflexion
What are some common causes of superior gluteal (L4-S1) n. lesion?
iatrogenic injury during intramusclar injection in _**Upper medial gluteal region**_
How does superior gluteal n. lesion present?
Trendelenburg sign/gait- pelvis tilts because weigh-bearing leg canot maintain alignment of pelvis through hip abduction. Lesion is contralateral to the side of the hip that drops
Gluteus medius and minimus lost
What is a common cause of inferior gluteal n. (L5-S2) n. lesion?
posterior hip dislocation
How does an inferior gluteal n. lesion present?
difficulty climbing stairs, rising from seated position
Loss of hip extension (inferior nerve- maximus lost)
The sciatic n. (L4-S3) innervates the posterior thigh and splits to form what?
common peroneal and tibial nn.
Which way do intervertebral discs generally herniate and why?
posterolaterally due to the thin posterioe longitudinal ligamant and thicker anterior longitudinal ligmant along the midline of the vertebral bodies
Weaknes of knee extension and decreased patellar reflexes suggest herniation of what disc?
L3-L4
Weakness of dorsiflexion and difficult in heel-walking suggest herniation of what disc?
L4-L5
Weakness and plantarflexion, difficult in toe-walking, and decreased achilles reflex suggest herniation of what disc?
L5-S1
Injury to the axilla is likely to injur what n./a. pair?
long thoracic n. and a.
What n./a. pair run near the surgical neck of the humerus?
the axillary n. and posterior circumflex a.
What n./a. pair run near the midshaft of the humerus?
radial n. and deep brachial a.
What n./a. pair run near the distal humerus/cubital fossa of the humerus?
median n. and brachial a.
What n./a. pair run near the popliteal fossa of the humerus?
tibial n. and popliteal a.
What n./a. pair run posterior to the medial malleolus of the humerus?
tibial n. and posterior tibial a.
What are the steps of striated muscle contraction?
- action potential depolarization due to Ca2+ influx causing neurotransmitter release and binding to the postsynaptic motor end plate.
2) Depolarization travels the muscle cell and down the T-tubule causing depolarization of voltage-sensitive dihydropyridine receptors, and then ryanodine receptors, causing Ca2+ influx from the SR
3) Ca2+ binds to Troponin C, causing tropomyosin to move out of the myosin-binding groove on actin filaments
4) Myosin releases bound ADp and inorganic PO43-, and binds actin causing a power stroke
What parts of the sarcomere shorten during muscle contraction?
H and I bands and Z distance
A band remains the same
What causes detachment of myosin head from actin?
binding of ATP to myosin
Describe Type I muscle fibers
slow twitch, red fibers resulting from increased mitochondria and myoglobin concentration (increased oxidative phosphorylation) to produce sustained contraction
1 slow red ox
Describe Type II muscle fibers
fast twitch, white fibers resulting from decreased mitochondria and myoglobin conc (incrased anaerobic glycolysis)
Weight training= hypertrophy of ___ twitch fibers
fast
How does smooth muscle contraction occur?
action potential causes membrane depolarization causing Ca2+ influx through L-type voltage gated Ca2+ channels. Ca2_ binds to camodulin to activate MLCK which phosphorylates myosin to cause contraction
How does NO cause relaxation of smooth muscle?
it increased cGMP from GTP (via guanylate cyclase) which activates myosin-light-chain-phosphatase (MLCP) to dephosphorylate myosin so that is doesnt interact with actin
Describe endochrondral ossification
bones of axial and appendicular skleton and base of skull undergo this. Carilaginous model of bone is first made by chrondrocytes. Osteoclasts and osteoblasts later replace with woven bone and then remodel to lamellar bone.
Describe membranous ossification
bone of calvarium and facial bones- woven bone formed directly without cartilage. Later remodeled to lamellar bone
What do osteoblasts differentiate from?
mesenchyma stem cells in periosteum
PTH hormone review
at low, intermittent levels, exerts anabolic effects on osteoblasts, but catabolic effects in hyperPTHism
How does estrogen affect bone?
it inhibits apoptosid in bone-forming osteoblasts and induces apoptoside in osteoclasts (aka bone-building)
