Which muscles does the musculocutaneous nerve supply, and what is its sensory continuation?

It supplies coracobrachialis, biceps brachii and most of brachialis; the lateral part of brachialis may also receive radial-nerve fibers. Coracobrachialis acts at the shoulder, while biceps and brachialis flex the elbow. The nerve continues as the lateral cutaneous nerve of the forearm, supplying lateral forearm skin.

What can injury to the common fibular nerve at the fibular neck impair?

It can weaken ankle dorsiflexion and foot eversion, causing foot drop and a compensatory high-stepping gait. Sensory change can affect the anterolateral leg and dorsum of the foot. The exact motor and sensory deficits depend on the lesion’s extent and branches involved.

What is the main motor role of the obturator nerve, and what important adductor-magnus exception exists?

The obturator nerve (L2–L4) supplies most thigh adductors, including adductor longus, adductor brevis, the adductor part of adductor magnus and gracilis; it also supplies obturator externus. Its main compartment role is thigh adduction. The hamstring part of adductor magnus is supplied by the tibial division of the sciatic nerve.

Which hand muscles are recalled by LOAF, and how do median-nerve branches supply the hand?

LOAF means lateral two lumbricals, opponens pollicis, abductor pollicis brevis and usually the superficial head of flexor pollicis brevis. The recurrent motor branch supplies thenar muscles; palmar digital branches supply lumbricals 1–2. Median sensation includes the palmar lateral 3½ digits and their dorsal fingertips; its palmar cutaneous branch supplies the lateral palm. Flexor pollicis brevis innervation varies.

What part of the brachial plexus is typically affected in Erb palsy, and what weakness pattern can follow?

An upper-plexus injury involving C5–C6 can weaken shoulder abduction and external rotation, elbow flexion and forearm supination. The arm may rest adducted and internally rotated, with the elbow extended and forearm pronated. The pattern varies with the extent of injury; complete paralysis is not required.

Which capsular ligaments and labra help stabilize the shoulder and hip?

At the shoulder, the superior, middle and inferior glenohumeral ligaments and coracohumeral ligament reinforce the capsule; the glenoid labrum deepens the socket. At the hip, iliofemoral, pubofemoral and ischiofemoral ligaments reinforce the capsule, and the acetabular labrum deepens the socket. Labra are fibrocartilage, not ligaments; muscles also provide dynamic stability.

Where do the knee’s cruciate ligaments attach, and which tibial translations do they primarily resist?

The ACL runs from the anterior intercondylar tibia to the medial surface of the lateral femoral condyle; it primarily resists anterior tibial translation relative to the femur. The PCL runs from the posterior intercondylar tibia to the lateral surface of the medial femoral condyle; it primarily resists posterior tibial translation.

Which ligaments form the ankle’s lateral complex, and which is commonly injured in a plantarflexion-inversion sprain?

The anterior talofibular, calcaneofibular and posterior talofibular ligaments form the lateral complex. The anterior talofibular ligament is the most frequently injured in typical inversion sprains, especially with the ankle plantarflexed; more extensive injuries can involve the others.

What distinguishes the atlas and axis, and which upper-cervical joints mainly permit nodding and rotation?

The atlas (C1) has anterior and posterior arches and lateral masses, but no body or spinous process. The axis (C2) has the dens. The atlanto-occipital joints mainly permit nodding; the atlantoaxial joints permit much of the head’s side-to-side rotation.

What is the usual organization of the brachial plexus from proximal to distal?

Ventral rami C5–T1 form roots, then three trunks, six divisions and three cords. The five major terminal nerves are musculocutaneous, axillary, radial, median and ulnar. The plexus also gives off other branches; these five are not its entire output.

How does the axillary nerve relate to the proximal humerus, and what can injury there impair?

It passes through the quadrangular space with the posterior circumflex humeral artery and winds around the surgical neck. Fracture or shoulder dislocation can injure it, weakening the deltoid and arm abduction and reducing sensation over the lateral shoulder. Findings depend on injury severity.

Which muscles and nerves contribute to raising the arm overhead in abduction?

Supraspinatus (suprascapular nerve, C5–C6) and deltoid (axillary nerve, C5–C6) abduct the arm. Serratus anterior (long thoracic nerve, C5–C7) and trapezius (motor supply from cranial nerve XI) upwardly rotate the scapula. Their actions overlap; they do not work in exclusive 0–15°, 15–90° and 90–180° phases.

What is the classical “unhappy triad” of the knee, and why is it not a universal injury pattern?

The classical triad is injury to the anterior cruciate ligament, medial collateral ligament and medial meniscus. Actual combined knee injuries vary: the lateral meniscus or additional structures may be injured instead of, or alongside, those in the classical description.

What does the long thoracic nerve supply, and how can its injury affect the scapula?

The long thoracic nerve usually arises from C5–C7 and supplies serratus anterior. Injury can impair scapular protraction and upward rotation, producing medial scapular winging that may become clearer during a wall push. Scapular winging also has other causes.

In anatomical position, what are the carpal bones from the thumb side to the little-finger side in each row?

Proximal row: scaphoid, lunate, triquetrum, pisiform. Distal row: trapezium, trapezoid, capitate, hamate. The pisiform lies on the anterior surface of the triquetrum rather than simply beside it.

Which posterior-leg muscles does the tibial nerve supply, and which tendon reflex does it mediate?

It supplies gastrocnemius, soleus and plantaris in the superficial posterior compartment, and popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus in the deep compartment. It mediates the Achilles tendon reflex, involving S1–S2, predominantly S1.

Why can a scaphoid waist fracture threaten the proximal pole’s blood supply?

Much of the scaphoid’s arterial supply enters distally from radial-artery branches and travels proximally within the bone. A waist fracture can interrupt this supply to the proximal fragment, increasing the risks of avascular necrosis and nonunion. These complications are possible, not inevitable.

Which four muscles form the rotator cuff, and what are their main actions at the shoulder?

Supraspinatus assists arm abduction; infraspinatus and teres minor externally rotate the arm; subscapularis internally rotates it. All four help stabilize the humeral head in the glenoid. Supraspinatus is important early in abduction, but its contribution is not confined to the first 15°.

What are the two divisions of the skeleton, and what are their conventional adult bone counts?

The typical adult count is 206: 80 axial bones and 126 appendicular bones. The axial skeleton includes the skull, auditory ossicles, hyoid, vertebral column, ribs and sternum. The appendicular skeleton comprises the limb bones and their pectoral and pelvic girdles. Individual bone counts can vary.

What is Klumpke palsy, and when can Horner syndrome accompany it?

It is a lower-brachial-plexus injury, typically involving C8–T1, that can weaken intrinsic hand muscles and grip and produce clawing. Horner syndrome can occur when a proximal injury also disrupts T1 sympathetic pathways. It is not a necessary consequence of every lower-trunk lesion.

Which intrinsic hand muscles does the ulnar nerve supply, and what clawing can a distal lesion cause?

It supplies the interossei, hypothenar muscles, lumbricals 3–4, adductor pollicis and palmaris brevis. The deep head of flexor pollicis brevis is commonly ulnar-innervated, with variation. A distal lesion can cause ring- and little-finger clawing: metacarpophalangeal hyperextension with interphalangeal flexion. Clawing is not inevitable in every injury.

What does the radial nerve supply, and what can a lesion at the humeral radial groove cause?

It supplies the posterior arm and forearm muscles, including extensors and the elbow flexor brachioradialis. A radial-groove lesion can weaken wrist and finger extension, producing wrist drop; elbow extension is usually spared. Sensory change may affect the dorsoradial hand. The pattern depends on the branches and extent of injury.

Which tendons border the anatomical snuffbox, which bones form its floor, and which artery crosses it?

The lateral border is formed by abductor pollicis longus and extensor pollicis brevis tendons; the medial border by the extensor pollicis longus tendon. Scaphoid and trapezium form the bony floor. The radial artery crosses that floor; it is not itself a floor-forming bone.

How do the knee’s medial and lateral menisci differ in shape, attachment and mobility?

The medial meniscus is C-shaped, attaches to the deep medial collateral ligament and is relatively less mobile. The lateral meniscus is more nearly circular, lacks a direct attachment to the lateral collateral ligament and is more mobile. Injury patterns depend on the mechanism and other knee damage.

What are the four leg compartments, and which major nerve and artery run in the anterior compartment?

The compartments are anterior, lateral, superficial posterior and deep posterior. The anterior compartment contains the deep fibular nerve and anterior tibial artery. Acute compartment syndrome can damage these structures, but absence of weakness or numbness does not exclude it; neurological deficits may be late findings.

What does the inferior gluteal nerve supply, and what tasks can its injury make difficult?

It supplies gluteus maximus, important for powerful hip extension. Injury can cause weakness when rising from a chair or climbing stairs. The functional loss depends on the degree of injury and compensation by other muscles.

What are the sciatic nerve’s roots and terminal divisions, and is the division level fixed?

The sciatic nerve usually receives L4–S3 fibers and divides into tibial and common fibular (peroneal) nerves. Division often occurs near the upper end of the popliteal fossa, but it can occur higher in the thigh or pelvis. The level varies between individuals.

What are the six synovial-joint types, with one anatomical example of each?

Plane: intercarpal. Hinge: humeroulnar. Pivot: proximal radioulnar. Condyloid (ellipsoid): radiocarpal. Saddle: first carpometacarpal joint of the thumb. Ball-and-socket: glenohumeral joint. These are types within the synovial category, not the broader division into fibrous, cartilaginous and synovial joints.

How do the four normal spinal curves relate to the five vertebral regions and their usual segment counts?

Cervical and lumbar curves are secondary lordoses; thoracic and sacrococcygeal curves are primary kyphoses. The usual regional counts are 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and about 4 coccygeal segments. Coccygeal number and fusion vary. About 33 segments do not mean 33 separate adult bones.

What muscles does the femoral nerve supply, and which tendon reflex does it mediate?

The femoral nerve (L2–L4) supplies much of the anterior thigh, including quadriceps and sartorius, as well as iliacus. It mediates the patellar tendon reflex, involving L2–L4, particularly L4. This is a selected muscle list, not every femoral-nerve branch.

What does the superior gluteal nerve supply, and what does a Trendelenburg sign suggest?

It supplies gluteus medius, gluteus minimus and tensor fasciae latae. Dropping of the unsupported side of the pelvis during single-leg stance suggests dysfunction of the hip-abductor mechanism on the supporting side. Superior-gluteal nerve injury is one possible cause, not the only one.

What are the main parts of an intervertebral disc, and which root can a posterolateral lumbar herniation compress?

A disc has an outer annulus fibrosus and inner nucleus pulposus. A typical posterolateral lumbar herniation can compress the traversing nerve root: for example, an L4–L5 disc can affect L5. A foraminal or far-lateral herniation can affect the exiting root instead, such as L4 at L4–L5.

Musculoskeletal Anatomy: Limb Nerves, Bones & Major Joints

32 musculoskeletal-anatomy review cards on limb plexuses and peripheral nerves, major joints, spinal and appendicular bones, muscular compartments, and classic nerve- and joint-injury patterns. Assumes basic anatomical terminology.

Level: basic
Languages: en → en
Cards: 32
Markdown: Musculoskeletal Anatomy: Limb Nerves, Bones & Major Joints (.md)

Flashcards (32)

#	Front (Term / Question)	Back (Definition / Answer)
1	Which muscles does the musculocutaneous nerve supply, and what is its sensory continuation?	It supplies coracobrachialis, biceps brachii and most of brachialis; the lateral part of brachialis may also receive radial-nerve fibers. Coracobrachialis acts at the shoulder, while biceps and brachialis flex the elbow. The nerve continues as the lateral cutaneous nerve of the forearm, supplying lateral forearm skin.
2	What can injury to the common fibular nerve at the fibular neck impair?	It can weaken ankle dorsiflexion and foot eversion, causing foot drop and a compensatory high-stepping gait. Sensory change can affect the anterolateral leg and dorsum of the foot. The exact motor and sensory deficits depend on the lesion’s extent and branches involved.
3	What is the main motor role of the obturator nerve, and what important adductor-magnus exception exists?	The obturator nerve (L2–L4) supplies most thigh adductors, including adductor longus, adductor brevis, the adductor part of adductor magnus and gracilis; it also supplies obturator externus. Its main compartment role is thigh adduction. The hamstring part of adductor magnus is supplied by the tibial division of the sciatic nerve.
4	Which hand muscles are recalled by LOAF, and how do median-nerve branches supply the hand?	LOAF means lateral two lumbricals, opponens pollicis, abductor pollicis brevis and usually the superficial head of flexor pollicis brevis. The recurrent motor branch supplies thenar muscles; palmar digital branches supply lumbricals 1–2. Median sensation includes the palmar lateral 3½ digits and their dorsal fingertips; its palmar cutaneous branch supplies the lateral palm. Flexor pollicis brevis innervation varies.
5	What part of the brachial plexus is typically affected in Erb palsy, and what weakness pattern can follow?	An upper-plexus injury involving C5–C6 can weaken shoulder abduction and external rotation, elbow flexion and forearm supination. The arm may rest adducted and internally rotated, with the elbow extended and forearm pronated. The pattern varies with the extent of injury; complete paralysis is not required.
6	Which capsular ligaments and labra help stabilize the shoulder and hip?	At the shoulder, the superior, middle and inferior glenohumeral ligaments and coracohumeral ligament reinforce the capsule; the glenoid labrum deepens the socket. At the hip, iliofemoral, pubofemoral and ischiofemoral ligaments reinforce the capsule, and the acetabular labrum deepens the socket. Labra are fibrocartilage, not ligaments; muscles also provide dynamic stability.
7	Where do the knee’s cruciate ligaments attach, and which tibial translations do they primarily resist?	The ACL runs from the anterior intercondylar tibia to the medial surface of the lateral femoral condyle; it primarily resists anterior tibial translation relative to the femur. The PCL runs from the posterior intercondylar tibia to the lateral surface of the medial femoral condyle; it primarily resists posterior tibial translation.
8	Which ligaments form the ankle’s lateral complex, and which is commonly injured in a plantarflexion-inversion sprain?	The anterior talofibular, calcaneofibular and posterior talofibular ligaments form the lateral complex. The anterior talofibular ligament is the most frequently injured in typical inversion sprains, especially with the ankle plantarflexed; more extensive injuries can involve the others.
9	What distinguishes the atlas and axis, and which upper-cervical joints mainly permit nodding and rotation?	The atlas (C1) has anterior and posterior arches and lateral masses, but no body or spinous process. The axis (C2) has the dens. The atlanto-occipital joints mainly permit nodding; the atlantoaxial joints permit much of the head’s side-to-side rotation.
10	What is the usual organization of the brachial plexus from proximal to distal?	Ventral rami C5–T1 form roots, then three trunks, six divisions and three cords. The five major terminal nerves are musculocutaneous, axillary, radial, median and ulnar. The plexus also gives off other branches; these five are not its entire output.
11	How does the axillary nerve relate to the proximal humerus, and what can injury there impair?	It passes through the quadrangular space with the posterior circumflex humeral artery and winds around the surgical neck. Fracture or shoulder dislocation can injure it, weakening the deltoid and arm abduction and reducing sensation over the lateral shoulder. Findings depend on injury severity.
12	Which muscles and nerves contribute to raising the arm overhead in abduction?	Supraspinatus (suprascapular nerve, C5–C6) and deltoid (axillary nerve, C5–C6) abduct the arm. Serratus anterior (long thoracic nerve, C5–C7) and trapezius (motor supply from cranial nerve XI) upwardly rotate the scapula. Their actions overlap; they do not work in exclusive 0–15°, 15–90° and 90–180° phases.
13	What is the classical “unhappy triad” of the knee, and why is it not a universal injury pattern?	The classical triad is injury to the anterior cruciate ligament, medial collateral ligament and medial meniscus. Actual combined knee injuries vary: the lateral meniscus or additional structures may be injured instead of, or alongside, those in the classical description.
14	What does the long thoracic nerve supply, and how can its injury affect the scapula?	The long thoracic nerve usually arises from C5–C7 and supplies serratus anterior. Injury can impair scapular protraction and upward rotation, producing medial scapular winging that may become clearer during a wall push. Scapular winging also has other causes.
15	In anatomical position, what are the carpal bones from the thumb side to the little-finger side in each row?	Proximal row: scaphoid, lunate, triquetrum, pisiform. Distal row: trapezium, trapezoid, capitate, hamate. The pisiform lies on the anterior surface of the triquetrum rather than simply beside it.
16	Which posterior-leg muscles does the tibial nerve supply, and which tendon reflex does it mediate?	It supplies gastrocnemius, soleus and plantaris in the superficial posterior compartment, and popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus in the deep compartment. It mediates the Achilles tendon reflex, involving S1–S2, predominantly S1.
17	Why can a scaphoid waist fracture threaten the proximal pole’s blood supply?	Much of the scaphoid’s arterial supply enters distally from radial-artery branches and travels proximally within the bone. A waist fracture can interrupt this supply to the proximal fragment, increasing the risks of avascular necrosis and nonunion. These complications are possible, not inevitable.
18	Which four muscles form the rotator cuff, and what are their main actions at the shoulder?	Supraspinatus assists arm abduction; infraspinatus and teres minor externally rotate the arm; subscapularis internally rotates it. All four help stabilize the humeral head in the glenoid. Supraspinatus is important early in abduction, but its contribution is not confined to the first 15°.
19	What are the two divisions of the skeleton, and what are their conventional adult bone counts?	The typical adult count is 206: 80 axial bones and 126 appendicular bones. The axial skeleton includes the skull, auditory ossicles, hyoid, vertebral column, ribs and sternum. The appendicular skeleton comprises the limb bones and their pectoral and pelvic girdles. Individual bone counts can vary.
20	What is Klumpke palsy, and when can Horner syndrome accompany it?	It is a lower-brachial-plexus injury, typically involving C8–T1, that can weaken intrinsic hand muscles and grip and produce clawing. Horner syndrome can occur when a proximal injury also disrupts T1 sympathetic pathways. It is not a necessary consequence of every lower-trunk lesion.
21	Which intrinsic hand muscles does the ulnar nerve supply, and what clawing can a distal lesion cause?	It supplies the interossei, hypothenar muscles, lumbricals 3–4, adductor pollicis and palmaris brevis. The deep head of flexor pollicis brevis is commonly ulnar-innervated, with variation. A distal lesion can cause ring- and little-finger clawing: metacarpophalangeal hyperextension with interphalangeal flexion. Clawing is not inevitable in every injury.
22	What does the radial nerve supply, and what can a lesion at the humeral radial groove cause?	It supplies the posterior arm and forearm muscles, including extensors and the elbow flexor brachioradialis. A radial-groove lesion can weaken wrist and finger extension, producing wrist drop; elbow extension is usually spared. Sensory change may affect the dorsoradial hand. The pattern depends on the branches and extent of injury.
23	Which tendons border the anatomical snuffbox, which bones form its floor, and which artery crosses it?	The lateral border is formed by abductor pollicis longus and extensor pollicis brevis tendons; the medial border by the extensor pollicis longus tendon. Scaphoid and trapezium form the bony floor. The radial artery crosses that floor; it is not itself a floor-forming bone.
24	How do the knee’s medial and lateral menisci differ in shape, attachment and mobility?	The medial meniscus is C-shaped, attaches to the deep medial collateral ligament and is relatively less mobile. The lateral meniscus is more nearly circular, lacks a direct attachment to the lateral collateral ligament and is more mobile. Injury patterns depend on the mechanism and other knee damage.
25	What are the four leg compartments, and which major nerve and artery run in the anterior compartment?	The compartments are anterior, lateral, superficial posterior and deep posterior. The anterior compartment contains the deep fibular nerve and anterior tibial artery. Acute compartment syndrome can damage these structures, but absence of weakness or numbness does not exclude it; neurological deficits may be late findings.
26	What does the inferior gluteal nerve supply, and what tasks can its injury make difficult?	It supplies gluteus maximus, important for powerful hip extension. Injury can cause weakness when rising from a chair or climbing stairs. The functional loss depends on the degree of injury and compensation by other muscles.
27	What are the sciatic nerve’s roots and terminal divisions, and is the division level fixed?	The sciatic nerve usually receives L4–S3 fibers and divides into tibial and common fibular (peroneal) nerves. Division often occurs near the upper end of the popliteal fossa, but it can occur higher in the thigh or pelvis. The level varies between individuals.
28	What are the six synovial-joint types, with one anatomical example of each?	Plane: intercarpal. Hinge: humeroulnar. Pivot: proximal radioulnar. Condyloid (ellipsoid): radiocarpal. Saddle: first carpometacarpal joint of the thumb. Ball-and-socket: glenohumeral joint. These are types within the synovial category, not the broader division into fibrous, cartilaginous and synovial joints.
29	How do the four normal spinal curves relate to the five vertebral regions and their usual segment counts?	Cervical and lumbar curves are secondary lordoses; thoracic and sacrococcygeal curves are primary kyphoses. The usual regional counts are 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and about 4 coccygeal segments. Coccygeal number and fusion vary. About 33 segments do not mean 33 separate adult bones.
30	What muscles does the femoral nerve supply, and which tendon reflex does it mediate?	The femoral nerve (L2–L4) supplies much of the anterior thigh, including quadriceps and sartorius, as well as iliacus. It mediates the patellar tendon reflex, involving L2–L4, particularly L4. This is a selected muscle list, not every femoral-nerve branch.
31	What does the superior gluteal nerve supply, and what does a Trendelenburg sign suggest?	It supplies gluteus medius, gluteus minimus and tensor fasciae latae. Dropping of the unsupported side of the pelvis during single-leg stance suggests dysfunction of the hip-abductor mechanism on the supporting side. Superior-gluteal nerve injury is one possible cause, not the only one.
32	What are the main parts of an intervertebral disc, and which root can a posterolateral lumbar herniation compress?	A disc has an outer annulus fibrosus and inner nucleus pulposus. A typical posterolateral lumbar herniation can compress the traversing nerve root: for example, an L4–L5 disc can affect L5. A foraminal or far-lateral herniation can affect the exiting root instead, such as L4 at L4–L5.