Muscle, bone, and fractures Flashcards

(42 cards)

1
Q

Define muscle proprioreceptors

A

specialized sensory receptors that relay info about muscle dynamics

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2
Q

Describe the neuronal pathway in muscle stretch receptors

A
  1. Increased length & speed of stretch
  2. Afferent pathway via dorsal root ganglion
  3. Activation of inhibitory interneuron and alpha motor neuron
  4. Simultaneous inhibition of antagonist muscle (prevents overstretching) & activation of agonist muscle (contraction)
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3
Q

Type of innervation of muscle stretch receptors + location

A

Type Ia and II sensory axons
Located in the body of muscle

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4
Q

What activates muscle stretch receptors

A

Increased muscle stretch
Responsible for deep tendon reflexes

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5
Q

Describe the nerve pathway for Golgi tendon organ

A
  1. Increased tension
  2. Afferent pathway via DRG
  3. Activation of inhibitory interneuron
  4. Inhibition of agonist muscle (reduced tension within muscle and tendon
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6
Q

Type of innervation of Golgi tendon organ + location

A

Type Ib sensory axons
Tendons

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7
Q

What activates Golgi tendon organ

A

Increased muscle tension

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8
Q

Location of endochondral ossification

A

Bones of axial & appendicular skeleton, base of skull

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9
Q

Describe the process of endochondral ossification

A
  1. Cartilagenous model of bone is made by chondrocytes
  2. Osteoblasts/clasts later replace woven bone and remodel to lamellar bone
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10
Q

When does woven bone occur in adults

A

After fractures and in Paget disease

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11
Q

In what disease is endochondral ossification defective

A

Achondroplasia

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12
Q

Where does membranous ossification occur

A

Bones of calvarium, facial bones, clavicle

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13
Q

Describe the process of membranous ossification

A

Woven bone formed directly wo cartilage, then remodeled to lamellar

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14
Q

Describe the function of osteoblasts

A

Builds bone by secreting collagen & catalyzing mineralization in alkaline environments via ALP

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15
Q

Differentiation of osteoblasts

A

From mesenchymal stem cells in periosteum

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16
Q

What factors regulate osteoblast activity

A

Bone ALP, osteocalcin, propeptides of type I collagen

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17
Q

Describe the function of osteoclasts

A

Dissolves bone by secreting protons and collagenases

18
Q

Differentiation of osteoclasts

A

Fusion of monocyte/macrophage lineage precursors

19
Q

How is osteoclast activity regulated

A

RANK receptors on osteoclasts are stimulated by RANKL (RANK ligand, expressed on osteoblasts)
OPG (osteoprotegerin, a RANKL decoy receptor) binds RANKL to prevent RANK-RANKL interaction = reduction in activity

20
Q

Describe the function of PTH in bone formation

A

At low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect)

21
Q

What are the chronic effects of high PTH levels

A

Primary hyperparathyroidism
cause catabolic effects (osteitis fibrosa cystica)

22
Q

Function of estrogen in bone formation

A

Inhibits apoptosis in osteoblasts and induces apoptosis in osteoclasts
Causes closure of epiphyseal plate during puberty

23
Q

What does estrogen deficiency cause to bones

A

(Surgical/postmenopausal)
Increases cycles of remodeling and bone resorption = risk of osteoporosis

24
Q

Describe medial epicondylitis

A

Golfer’s elbow
due to repetitive flexion or idiopathic = pain near medial epicondyle

25
Describe lateral epicondylitis
Tennis elbow Repetitive extension (backhand shots) or idiopathic = pain near lateral epicondyle
26
Who are found to commonly have clavicle fractures
Children and as birth trauma
27
Causes of clavicle fractures
fall on outstretched hand or by direct trauma to shoulder
28
Weakest point of clavicle
at the junction of middle and lateral thirds
29
Common location of clavicle fracture
middle third segment
30
Presentation of clavicle fracture
Presents as shoulder drop, shortened clavicle (lateral fragment is depressed due to arm weight and medially rotated by arm adductors [eg, pectoralis major])
31
Define Guyon canal syndrome and who are they seen in
Compression of ulnar nerve at wrist Classically seen in cyclists due to pressure from handlebars May also be seen with fracture/dislocation of the hook of hamate
32
Define carpal tunnel syndrome
Entrapment of median nerve in carpal tunnel (between transverse carpal ligament and carpal bones) = nerve compression causing paresthesia, pain, and numbness in distribution of median nerve
33
Clinical findings of carpal tunnel syndrome
Thenar eminence atrophies but sensation spared (bc palmar cutaneous branch enters hand external to carpal tunnel)
34
Tests for carpal tunnel syndrome
Tinel sign (percussion of wrist causes tingling) and Phalen maneuver (90° flexion of wrist causes tingling)
35
Associations of carpal tunnel syndrome
Pregnancy (due to edema), RA, hypothyroidism, diabetes, acromegaly, dialysis-related amyloidosis May be associated with repetitive use
36
Define metacarpal neck fracture, seen commonly in which metacarpal
Also called boxer’s fracture Common fracture caused by direct blow with a closed fist (eg, from punching a wall). Most commonly seen in the 5th metacarpal
37
Define iliopsoas abscess and pathology
Collection of pus in iliopsoas compartment May spread from blood (hematogenous) or from adjacent structures (eg, vertebral osteomyelitis, tuberculous spondylitis/Pott disease, pyelonephritis)
38
What is iliopsoas abscess associated with
Crohn disease, diabetes, and immunocompromised states
39
Microbiological cause of iliopsoas abscess
Staphylococcus aureus most commonly isolated, but may also occur 2° to tuberculosis
40
Clinical (physical) findings of iliopsoas abscess
flank pain and bulge, fever, inguinal mass Positive psoas sign (hip extension exacerbates lower abdominal pain)
41
Lab findings of iliopsoas abscess
Imaging (CT/MRI) will show focal hypodense lesion within the muscle plane
42
Tx of iliopsoas abscess
Antibiotics based on culture, CT-guided percutaneous drainage (PCD), or surgical drainage