Questions and Answers
Which bone is located in the medial position of the proximal row?
What mnemonic word is associated with the Trapezium?
Which of the following bones is found in the distal row?
What is the lateral bone of the proximal row?
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Which mnemonic component corresponds to the Capitate?
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What percentage of the scaphoid's blood supply is provided by the dorsal branch?
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Which of the following bones is not directly involved in the fracture of the scaphoid?
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As the fracture location moves toward the proximal pole of the scaphoid, what happens to the union rate?
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What is the approximate union rate if the fracture occurs in a range of 5.90-5.80?
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Which artery supplies the volar branch of the scaphoid?
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Which muscles form the anterior boundary of the anatomical snuffbox?
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What is located on the floor of the anatomical snuffbox?
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Which muscle is located posterior to the anatomical snuffbox?
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What is the anatomical term used to describe the space on the radial side of the thumb during its full extension?
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Which of the following correctly describes the boundaries of the anatomical snuffbox?
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Which structure is located superficially within the anatomical snuffbox?
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What is the anatomical term for the fibrous band that holds the tendons of the extensor muscles in place at the wrist?
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Which of the following muscles forms part of the floor of the anatomical snuffbox?
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What is the primary artery providing access to arterial blood within the anatomical snuffbox?
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Which of the following veins originates in the region of the anatomical snuffbox?
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Which structure forms the roof of the carpal tunnel?
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Which bone is located laterally in the proximal row of the carpal tunnel?
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Which two bones are located medially in the carpal tunnel?
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Which nerve is located within the carpal tunnel?
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What is located posteriorly in the carpal tunnel?
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Which structure is a tendon found within the carpal tunnel?
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Which nerve is primarily associated with the carpal tunnel?
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What forms the roof of the carpal tunnel?
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Which of the following tendons is NOT found within the carpal tunnel?
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What is contained within the ulnar and radial bursae in the carpal tunnel?
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What is a primary symptom of Ulnar Canal Syndrome?
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Which muscle group is likely weakened in a patient with Ulnar Canal Syndrome?
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Which condition is also known as Cyclist's Palsy?
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What anatomical structure is primarily affected in Ulnar Canal Syndrome?
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Which finger region experiences sensation loss due to Ulnar Canal Syndrome?
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Which nerve is primarily associated with Guyon's Canal?
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What structure is found within the carpal tunnel?
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Which artery accompanies the ulnar nerve in Guyon's Canal?
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Which structure primarily traverses the carpal tunnel?
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What is a key distinguishing feature of Guyon's Canal compared to the carpal tunnel?
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What is the primary function of the extrinsic muscles?
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Which muscle originates in the hand and is involved in precision gripping?
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Which of the following is NOT classified as an intrinsic muscle of the hand?
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The intrinsic muscles are primarily responsible for which type of gripping?
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Which of the following muscles is included in the intrinsic muscles of the hand?
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Which compartment of the hand is primarily involved in the movement of the little finger?
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What is the function of the adductor pollicis muscle?
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Which anatomical structure extends from the lateral border of the palmar aponeurosis to the 3rd metacarpal?
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Which muscle is NOT considered part of the intrinsic muscles of the hand?
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What space is located beneath the palmar aponeurosis and between the central and hypothenar compartments?
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Which component primarily provides support to the central compartment of the hand?
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What is the primary function of the palmaris brevis muscle?
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Which nerve innervates the palmaris brevis muscle?
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The palmaris brevis muscle is classified as what type of muscle?
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Which area does the palmaris brevis muscle overlie?
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What is the anatomical position of the palmaris brevis muscle in relation to the hand?
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Which muscle is responsible for the abduction of the little finger?
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Which nerve innervates the thenar muscles?
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What is the primary responsibility of the opponens digiti minimi muscle?
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Which muscle has both a superficial and deep head?
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Which of the following muscles is NOT part of the hypothenar group?
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What is one of the main functions of the adductor pollicis muscle?
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Which of the following statements about the adductor pollicis muscle is true?
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What are the two heads of the adductor pollicis muscle?
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Which nerve is responsible for the innervation of the adductor pollicis muscle?
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Which anatomical direction is indicated by the term 'palmar view' in relation to the adductor pollicis?
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Which muscle is primarily responsible for the abduction of the thumb?
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What is the primary function of the adductor pollicis muscle?
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Which muscles contribute to the flexion of the thumb?
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Which action of the thumb is performed by the opponens pollicis muscle?
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Which of the following muscles is NOT involved in the extension of the thumb?
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What is the primary origin point for the lumbrical muscles?
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Which nerve innervates the first and second lumbrical muscles?
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What is the shape of the lumbrical muscles?
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Where do the lumbricals insert in the hand?
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Which of the following correctly describes the innervation of the fourth lumbrical muscle?
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What is the primary function of the lumbrical muscles in the hand?
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Which nerves innervate the lumbrical muscles in the hand?
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What is the shape of the lumbrical muscles?
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Where do the lumbrical muscles originate?
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What is the insertion point of the lumbrical muscles?
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What is the primary structure that the dorsal expansion hood encapsulates?
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Which component is NOT associated with the formation of the dorsal expansion hood?
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What is the primary function of the dorsal expansion hood?
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The dorsal expansion hood is formed primarily by which type of connective tissue?
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In which anatomical region is the dorsal expansion hood located?
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What is the primary function of the dorsal expansion hood?
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Which of the following is NOT formed by components of the dorsal expansion hood?
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Which anatomical structure does the dorsal expansion hood primarily cover?
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Which muscles are indicated in the image as being associated with the dorsal expansion hood?
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What shape best describes the structure of the dorsal expansion hood?
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What is the primary action of the palmar interossei muscles?
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Which muscles are responsible for spreading the fingers apart?
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What is the innervation nerve for both the palmar and dorsal interossei muscles?
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How many dorsal interossei muscles are present in the hand?
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Which of the following correctly describes the palmar interossei muscles?
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What is the primary function of the Palmar Interossei?
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What is the prevalence percentage of the Pollical interossei muscle?
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Where do the Palmar Interossei insert into?
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Which view is specifically mentioned in relation to the Palmar Interossei?
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What type of muscular function is primarily associated with the Palmar Interossei?
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What is the primary function of the dorsal interossei muscles?
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Where do the dorsal interossei muscles insert?
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Which artery is associated with the dorsal interossei muscles?
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What distinguishes lumbricales from interossei muscles?
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In relation to finger movements, what role do the interossei play?
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What is the origin of the lumbrical muscles?
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Which interossei are characterized by a unipennate structure?
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How many dorsal interossei are present in the human hand?
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Which nerve innervates all lumbricals of the hand?
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What distinguishes the origin of palmar interossei from dorsal interossei?
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Which artery is primarily associated with the main supply to the hand?
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What are the two terminal branches of the Brachial Artery in the cubital fossa?
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Which artery branches off the Ulnar Artery?
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Which arteries contribute to the vascular supply in the palm of the hand?
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Which artery branches from the Common Interosseous Artery?
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What type of arteries are the palmar, carpal, and dorsal carpal arteries?
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What is the primary function of the anastomosis between the ulnar artery and the radial artery?
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Which artery completes the superficial palmar arch formed by the ulnar artery?
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How many common palmar digital arteries branch from the superficial palmar arch?
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What structure lies deep to the palmar aponeurosis?
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Which of the following arteries is NOT a branch of the superficial palmar arch?
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Which artery passes through the anatomical snuff box to supply the dorsum of the hand?
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What is one of the branches of the radial artery mentioned in the content?
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Which structure does the radial artery pierce as it travels towards the palmar surface?
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What completes the arterial pathway provided by the radial artery on the palmar surface?
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How many palmar metacarpal arteries are branches of the radial artery?
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Study Notes
Carpal Bones Overview
- The human wrist comprises eight carpal bones categorized into two rows: proximal and distal.
Proximal Row of Carpal Bones
- Scaphoid: Located laterally, plays a crucial role in wrist movement and is the most commonly fractured carpal bone.
- Lunate: Central bone in the proximal row, important for wrist stability and articulation with the radius.
- Triquetrum: Positioned next to the lunate, articulates with the pisiform and helps in wrist flexibility.
- Pisiform: Medially located and is a sesamoid bone within the flexor carpi ulnaris tendon, providing increased leverage.
Distal Row of Carpal Bones
- Trapezium: Located laterally in the distal row, articulates with the first metacarpal, significant for thumb movement.
- Trapezoid: Found centrally, supports the index finger, and is the smallest bone in the distal row.
- Capitate: The largest carpal bone, centrally placed in the wrist, articulates with the second and third metacarpals, providing stability.
- Hamate: Medially situated, notable for its hook-like projection, and articulates with the fourth and fifth metacarpals.
Mnemonic for Carpal Bones
- Mnemonic Phrase: "Town To Comes Hamlet Shouting Loudly aT Polonius" serves as a memory aid to recall the carpal bones in sequence.
- Corresponding mnemonic for each bone helps in associating the name with its position and location.
Key Facts
- The proximal row contains four bones, while the distal row also contains four bones.
- The arrangement of bones is crucial for grasping and maneuvering objects in daily activities.
Arterial Supply of Scaphoid Bone
- Blood supply to the scaphoid bone is unidirectional, primarily impacting fracture healing.
- Dorsal branch accounts for 70-80% of the blood supply, originating from the radial artery.
- Volar branch contributes 20-30% of the blood supply, also from the radial artery, supplemented by the palmar carpal branch.
- A fracture near the proximal pole can lead to avascular necrosis of the distal fragment due to inadequate blood supply.
Fracture and Union Rates
- The scaphoid fractures can affect surrounding carpal bones, including the radius, ulna, triquetrum, lunate, pisiform, hook of hamate, capitate, and trapezium.
- Union rates for scaphoid fractures decrease significantly with proximity to the proximal pole:
- Rates: 100% at higher ranges, dropping to 57% as distances decrease.
- Critical ranges include 6.81-6.71 (100%), 6.64-6.6 (90%), 6.51-6.40 (84%), and 5.50-5.39 (27%).
- Understanding the location of a fracture is essential in predicting the risk of non-union or complications.
Anatomical Snuffbox
- Visible on the radial side of the hand when the thumb is fully extended.
- Acts as a cavity located at the base of the thumb.
Boundaries
- Posterior Boundary: Defined by the extensor pollicis longus muscle, which is responsible for extending the thumb.
-
Anterior Boundaries: Composed of two muscles:
- Extensor pollicis brevis: Assists in thumb extension.
- Abductor pollicis longus: Responsible for abducting the thumb.
- Floor: Formed by the scaphoid bone, one of the carpal bones in the wrist.
Anatomical Snuffbox Overview
- The anatomical snuffbox is a triangular depression on the dorsum of the hand, primarily formed by tendons of the surrounding muscles.
- It serves as an important landmark for anatomical and clinical assessments of the wrist.
Contents of the Snuffbox
- Radial Artery: Provides access to arterial blood and is palpable in this region.
- Superficial Branch of Radial Nerve: Crosses the snuffbox superficially, supplying sensory innervation to the skin.
- Cephalic Vein: Originates in this area, important for venous drainage of the hand.
Anatomical Features
- Extensor Retinaculum: A fibrous band that holds the extensor tendons in place, stabilizing the structures as the wrist moves.
- Extensor Pollicis Longus: A muscle that extends the thumb, and its tendon contributes to the boundaries of the snuffbox.
- Radial Nerve, Superficial Branch: This branch innervates the skin over the snuffbox, playing a role in sensory feedback.
- Extensor Pollicis Brevis: Another muscle involved in thumb extension, located beside the longus in the snuffbox.
- Abductor Pollicis Longus: Muscles that abduct the thumb, forming part of the snuffbox boundaries.
- Anterior View: Important for understanding the spatial relationships of structures within the snuffbox from a frontal perspective.
Carpal Tunnel Boundaries
- Roof (Anterior): Formed by the flexor retinaculum, also known as the transverse carpal ligament, providing structural support and limiting the space within the tunnel.
-
Medial Boundaries:
- Pisiform bone serves as the proximal boundary.
- Hook of hamate acts as the distal boundary, forming the medial wall of the carpal tunnel.
-
Lateral Boundaries:
- Proximal boundary defined by the scaphoid bone.
- Trapezium bone marks the distal lateral boundary, contributing to the tunnel's lateral wall.
-
Posterior Boundaries:
- Formed by the triquetrium and lunate bones in the proximal row of carpal bones.
- Distal row includes capitate and trapezoid bones, completing the posterior outline of the tunnel.
Key Structures within the Carpal Tunnel
- Hamate, Capitate, Trapezium: These carpal bones are crucial structural components providing stability and articulation within the wrist.
- Flexor Retinaculum: A fibrous band across the wrist, creating the carpal tunnel and anchoring tendons.
-
Tendons:
- Flexor digitorum superficialis and profundus tendons facilitate finger flexion.
- Palmaris longus tendon can vary among individuals but contributes to wrist flexion.
- Flexor carpi radialis tendon aids in wrist movement.
- Flexor pollicis longus tendon is essential for thumb movement.
-
Nerves:
- Median nerve is essential for motor and sensory function of the hand located within the tunnel.
- Ulnar nerve also traverses the area but primarily runs outside the tunnel, influencing hand movements.
-
Arteries:
- Ulnar artery and radial artery supply blood to the hand and wrist, contributing to vascular integrity and function.
Carpal Tunnel Anatomy
- Contains tendons and nerves that facilitate hand and finger movement.
- Flexor Pollicis Longus: A tendon responsible for thumb flexion.
- Flexor Digitorum Superficialis: Helps flex the middle joints of the fingers.
- Flexor Digitorum Profundus: Allows flexion of the distal joints of the fingers.
- Flexor Carpi Radialis: A separate tendon that aids in wrist flexion and abduction.
Nerves and Blood Supply
- Median Nerve: Main nerve passing through the carpal tunnel, crucial for thumb and finger sensations.
- Ulnar and Radial Bursae: Provide lubrication and reduce friction among the tendons.
Key Structures in Cross-Section
- Cross-section of the carpal tunnel reveals:
- Flexor digitorum superficialis and profundus tendons.
- Flexor carpi radialis and flexor pollicis longus tendons.
- Ulnar Artery and Nerve: Important for hand function.
- Scaphoid Bone: A critical carpal bone located within the tunnel.
Ligaments and Vascular Components
- Flexor Retinaculum (Transverse Carpal Ligament): Forms the roof of the carpal tunnel, supporting the structures within.
- Superficial Palmar Artery and Vein: Vascular structures that supply blood to the palm, indicated in the cross-section image.
Ulnar Canal Syndrome
- Occurs due to entrapment of the ulnar nerve in the ulnar canal, a narrow passageway located at the elbow.
- Results in loss of sensation specifically affecting the medial 1 1/2 fingers: the ring finger and half of the little finger.
- Characterized by weakness in intrinsic muscles of the hand, impacting fine motor skills and grip strength.
Cyclist's Palsy
- A condition often related to prolonged pressure on the ulnar nerve while gripping bicycle handlebars.
- Commonly manifests as numbness and tingling in the same distribution as ulnar canal syndrome.
- May lead to similar motor deficits due to compression of the nerve in different positions or activities.
Extrinsic Muscles
- Origin from the forearm, primarily contributing to hand movement.
- Function is predominantly forceful gripping, enabling strong holds.
- Major muscle groups include:
- Flexors: Responsible for bending the wrist and fingers.
- Extensors: Responsible for straightening the wrist and fingers.
Intrinsic Muscles
- Originate within the hand, allowing for delicate and precise movements.
- Key function is precision gripping, essential for tasks requiring fine motor skills.
- Major muscles include:
- Palmaris brevis: Enhances grip by supporting skin on the palm.
- Thenar muscles: Control thumb movements; assist in opposition, flexion, and abduction.
- Hypothenar muscles: Control movements of the little finger.
- Adductor pollicis: Facilitates the adduction of the thumb.
- Interossei: Allows for abduction and adduction of the fingers.
- Lumbricals: Aid in flexing the fingers at the metacarpophalangeal joints while extending at the interphalangeal joints.
Carpal Bones
- Carpal bones are organized into two rows: proximal and distal.
-
Proximal row:
- Scaphoid (lateral), Lunate, Triquetrum, Pisiform (medial)
-
Distal row:
- Trapezium (lateral), Trapezoid, Capitate, Hamate (medial)
Mnemonic for Carpal Bones
- Mnemonic aids in memorization: "Town To Comes Hamlet Shouting Loudly aT Polonius."
Scaphoid Bone
- Blood supply is unidirectional; primarily from the radial artery.
- The proximal pole of the scaphoid is particularly vulnerable to avascular necrosis if fractured.
-
Blood supply distribution:
- Dorsal branch: 70-80%
- Volar branch: 20-30%
Scaphoid Fracture
- Fractures can also affect surrounding bones: Radius, Ulna, Triquetrum, Lunate, Pisiform, Capitate, and Hamate.
Union Rate of Scaphoid Fractures
- Union rates decrease as proximity to the proximal pole increases.
- Highest union rate: 100% (6.81-6.71)
- Lowest union rate: 27% (5.90-5.80).
Anatomical Snuffbox
- Located on the radial side of the hand, visible during thumb extension.
-
Boundaries:
- Posterior: Extensor pollicis longus
- Anterior: Extensor pollicis brevis & Abductor pollicis longus
- Floor: Scaphoid
Contents of the Anatomical Snuffbox
- Radial artery, superficial branch of the radial nerve, and cephalic vein.
Carpal Tunnel: Boundaries
- Roof: Flexor retinaculum (transverse carpal ligament)
- Medial: Pisiform and Hook of hamate
- Lateral: Scaphoid and Trapezium
- Posterior: Triquetrum, Lunate, Capitate, and Trapezoid
Carpal Tunnel: Contents
- Contains tendons: Flexor pollicis longus, Flexor digitorum superficialis, and Flexor digitorum profundus.
- Also includes Median nerve, Ulnar and radial bursae.
Ulnar Canal Syndrome
- Caused by ulnar nerve entrapment in Guyon's canal leading to sensory loss in the medial 1.5 fingers and weakness in hand muscles.
Cyclist's Palsy
- Another condition related to ulnar nerve compression, commonly seen in cyclists.
Comparison: Ulnar Canal vs. Carpal Tunnel
- Guyon's Canal (Ulnar Tunnel): Contains ulnar nerve and artery.
- Carpal Tunnel: Contains median nerve and flexor tendons.
Muscles of the Hand
-
Extrinsic muscles:
- Origin from the forearm, primarily responsible for forceful gripping (e.g., flexors and extensors).
-
Intrinsic muscles:
- Origin located within the hand, allowing for precision gripping (includes Palmaris brevis, Thenar and Hypothenar muscles, Adductor pollicis, Interossei, and Lumbricals).
Intrinsic Muscle Compartments of the Hand
- Hypothenar compartment controls movements of the little finger and consists of muscles such as abductor digiti minimi.
- Thenar compartment facilitates thumb movement, containing muscles like the opponens pollicis and abductor pollicis brevis.
- Central compartment includes flexor tendons and lumbricals, essential for grasping and hand dexterity.
- Adductor compartment primarily responsible for adducting the thumb, featuring the adductor pollicis muscle.
- Interosseous compartment contains interossei muscles that aid in finger abduction and adduction.
Anatomical Structures
- Palmar aponeurosis serves as a protective and supportive fascia for the underlying muscles and tendons of the palm.
- Midpalmar space situated between the central and hypothenar compartments, important for hand mobility.
- Medial fibrous septum extends from the palmar aponeurosis to the 5th metacarpal aiding in muscle compartmentalization.
- Hypothenar fascia encapsulates the hypothenar muscles, providing stability and support.
- Dorsal fascia (aponeurosis) overlays the dorsal hand and connects to the palmar fascia.
- Thenar space is a potential space between thenar and central compartments facilitating movement.
- Lateral fibrous septum originates from the lateral border of the palmar aponeurosis and extends to the 3rd metacarpal, separating the thenar and central compartments.
Functional Importance
- Understanding the intrinsic muscle compartments and their anatomical structures is crucial for grasping the complex movements and functionality of the hand.
- These intrinsic muscles are vital for fine motor tasks and coordination in everyday activities.
Muscles of the Hand
-
Palmaris Brevis:
- Located superficially in the hand
- Positioned subcutaneously, as it lies above deeper structures
- Overlaps with hypothenar muscles, which are responsible for the movement of the little finger
- Function: Enhances grip by deepening the palm's cup shape, facilitating a better hold
- Innervated by the ulnar nerve, a key nerve that controls various muscles in the hand and wrist
Hypothenar Muscles
- Located in the palm, responsible for movements of the little finger (digiti minimi).
- Abductor digiti minimi: Responsible for abduction of the little finger; innervated by the ulnar nerve.
- Flexor digiti minimi brevis: Flexes the little finger; also innervated by the ulnar nerve.
- Opponens digiti minimi: Allows opposition of the little finger to the thumb; innervated by the ulnar nerve.
Thenar Muscles
- Responsible for movement of the thumb (pollicis).
- Abductor pollicis brevis: Facilitates abduction of the thumb; innervated by the median nerve.
-
Flexor pollicis brevis:
- Superficial head: Flexes the thumb; innervated by the median nerve.
- Deep head: Flexes the thumb; innervated by the ulnar nerve.
- Opponens pollicis: Enables opposition of the thumb; innervated by the median nerve.
Additional Information
- The hypothenar muscles are typically represented in green on anatomical diagrams.
- The thenar muscles are typically represented in blue on anatomical diagrams.
- Nerve connections: Ulnar nerve primarily innervates hypothenar muscles, while the median nerve innervates most thenar muscles.
Adductor Pollicis Muscle
- Positioned beneath the thenar muscles of the hand.
- Comprised of two distinct heads: the oblique head and the transverse head.
- Functions as a major adductor, facilitating movement of the thumb towards the palm.
- Innervated by the ulnar nerve, crucial for its motor function.
- Anatomical diagrams often highlight its position and structure in the hand's palmar view.
Actions of the Thumb
Abduction
- Involves moving the thumb away from the palm.
- Muscles responsible include the abductor pollicis longus and abductor pollicis brevis.
Adduction
- The action of bringing the thumb back towards the palm.
- Key muscles are the adductor pollicis and palmar interossei, which assist in stabilizing and controlling thumb movement.
Extension
- This action straightens the thumb away from the hand.
- Primary muscles include extensor pollicis brevis and extensor pollicis longus, along with abductor pollicis longus which also aids in the extension.
Flexion
- Involves bending the thumb towards the palm.
- Key muscles are flexor pollicis brevis, flexor pollicis longus, and the adductor pollicis, which help in gripping actions.
Opposition
- A unique movement enabling the thumb to touch the other fingers.
- Involves muscles like opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis, crucial for grasping and pinching.
Reposition
- The movement of returning the thumb from opposition back to the neutral position.
- Utilizes actions and muscles that may not have been listed, focusing on returning the thumb to its anatomical position.
Lumbricals of the Hand
- Lumbricals arise from the tendons of the flexor digitorium profundus muscle, which flexes the fingers.
- These muscles insert on the radial (dorsal) side of the extensor expansion, located distally to where interosseous muscles insert.
- Lumbricals are characterized by a fusiform shape, which is spindle-like and allows for efficient contraction.
Innervation
- The first and second lumbricals are innervated by the median nerve, enabling thumb and index finger movements.
- The third and fourth lumbricals receive innervation from the ulnar nerve, influencing the ring and little finger actions.
Lumbricals of the Hand
- Originates from the tendons of the flexor digitorum profundus muscle.
- Inserts on the radial (dorsal) side of the extensor expansion, positioned distal to the interosseous muscle insertions.
- Exhibits a fusiform shape, tapering at both ends.
Innervation of Lumbricals
- Lumbricals 1 and 2 are innervated by the median nerve.
- Lumbricals 3 and 4 are innervated by the ulnar nerve.
Dorsal Expansion Hood
- Composed of specialized connective tissue that enhances finger movement.
- Created by the flattening of extensor tendons, specifically Extensor Digitorum (ED) and Extensor Pollicis Longus (EPL).
- Shaped like a triangle, it envelops the back and sides of the metacarpal and proximal phalanx of the fingers.
- Functionally crucial as it secures the extensor tendon, preventing displacement during finger extension.
Dorsal Expansion Hood
- A specialized connective tissue structure associated with finger movement.
- Composed of flattened extensor tendons, specifically extensor digitorum (ED) and extensor pollicis longus (EPL).
- Takes on a triangular shape that envelops the dorsal aspect of the metacarpal and proximal phalanx.
- Primary function is to stabilize and hold the extensor tendons in place during hand movements.
Labeled Anatomical Structures
- Tendon of Extensor Digitorum: Key tendon responsible for extending the fingers.
- Dorsal Digital Expansion: Also known as the dorsal expansion hood; facilitates coordinated extension of the toes or fingers.
- Lumbrical Muscles: Intrinsic muscles that assist in flexing the metacarpophalangeal joints while extending the interphalangeal joints.
- Interosseous Muscles: Located between the metacarpals, these muscles play a crucial role in finger movement, aiding in both abduction and adduction.
Visual Reference
- A dorsal view image helps clarify the anatomical arrangement of tendons and muscles associated with finger extension.
Interossei Muscles
- Comprised of two groups: palmar interossei and dorsal interossei.
- Innervated by the ulnar nerve.
Palmar Interossei Muscles
- Total of three muscles, characterized as unipennate.
- Function: Adduction of the fingers (PAD – Palmar ADduction).
- Located on the palm side of the hand.
Dorsal Interossei Muscles
- Total of four muscles, characterized as bipennate.
- Function: Abduction of the fingers (DAB – Dorsal ABduction).
- Located on the dorsal (back) side of the hand.
Anatomical Illustrations
- Illustrations depict the anatomical position and structure of palmar and dorsal interossei muscles.
- Both images are labeled with relevant anatomical terms for better understanding.
Dorsal Interossei
- Function: Assists in abduction of fingers, often remembered by the acronym "DAB" (Dorsal Abduction).
- Insertion: Attaches to the dorsal hood of the fingers, which is essential for extending the fingers while preventing flexion at the metacarpophalangeal joints.
- Base of Metacarpal: Each muscle arises from adjacent metacarpals, allowing for effective finger movement.
- First Dorsal Interosseous: This muscle is the largest and most prominent of the interossei, primarily responsible for abducting the index finger.
- Vascular Supply: Primarily supplied by the radial artery, which provides blood flow essential for muscle function.
Lumbricales vs Interossei
- Lumbrical muscles flex the metacarpophalangeal joints while extending the interphalangeal joints, contributing to the finger's dexterity.
- Interossei muscles include the dorsal interossei (abduct fingers) and plantar interossei (adduct fingers).
- Each group has distinct functions and anatomical positioning influencing the grip and manipulation of objects.
Carpal Bones
- Carpal bones arranged in two rows: proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate).
- Mnemonic: Town To Comes Hamlet Shouting Loudly aT Polonius.
- Scaphoid has limited blood supply primarily from the dorsal branch (70-80% via radial artery) and a smaller volar branch (20-30%).
- Union rates for scaphoid fractures decrease significantly as distance from the proximal pole increases.
Anatomical Snuffbox
- Located on the radial side of the wrist during thumb extension.
- Boundaries include extensor pollicis longus (posterior), extensors pollicis brevis & abductor pollicis longus (anterior), and the scaphoid (floor).
- Contains radial artery, superficial branch of the radial nerve, and origin of the cephalic vein.
Carpal Tunnel
- The carpal tunnel is formed by the flexor retinaculum, with boundaries including the median nerve and multiple tendons (flexor pollicis longus, flexor digitorum superficialis, profundus, and radialis).
- Structures inside the carpal tunnel: flexor tendons, median nerve, ulnar and radial bursae.
Ulnar Canal Syndrome
- Causes include entrapment of the ulnar nerve in Guyon's canal leading to sensory loss in the medial 1½ fingers and weakness in hand's intrinsic muscles.
Muscles of the Hand
- Extrinsic muscles originate in the forearm, responsible for forceful gripping (e.g., flexors and extensors).
- Intrinsic muscles originate in the hand, facilitating precise gripping (e.g., thenar, hypothenar muscles, and interossei).
Hypothenar and Thenar Muscles
- Hypothenar muscles (innervated by ulnar nerve): abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.
- Thenar muscles (innervated by median nerve): abductor pollicis brevis, flexor pollicis brevis (both heads), and opponens pollicis.
Adductor Pollicis
- Located deep to the thenar muscles, possesses oblique and transverse heads for thumb adduction.
- Innervated by the ulnar nerve.
Thumb Actions
- Abduction by abductor pollicis longus/brevis.
- Adduction by adductor pollicis and palmar interossei.
- Extension by extensor pollicis longus/brevis.
- Flexion by flexor pollicis longus/brevis.
- Opposition by opponens pollicis and abductor pollicis brevis.
Lumbricals and Interossei Muscles
- Lumbricals: innervated by median nerve (1 & 2) and ulnar nerve (3 & 4), originating from flexor digitorum profundus tendons.
- Interossei: palmar interossei (adduction, innervated by ulnar nerve) and dorsal interossei (abduction, innervated by ulnar nerve).
Dorsal Expansion Hood
- Connective tissue structure that holds the extensor tendon in place.
- Formation includes extensor digitorum and extensor pollicis longus tendons, covering the back and sides of the metacarpal proximal phalanx.
Summary of Key Muscles
- Palmaris Brevis: Enhances grip, innervated by ulnar nerve.
- Adductor Pollicis: Powerful thumb adductor, innervated by ulnar nerve.
- Interossei: Crucial for finger movement, specifically for adduction and abduction.
Overall, the carpal bones, muscle groups, innervation pathways, and anatomical features combine to create a complex system that allows for precise hand movements and grip functions.
Lumbricales
- Originate from the flexor digitorum profundus (FDP) tendons.
- Insert into the dorsal expansion of the extensor mechanism, distal to the interossei insertion.
- Fusiform shape, allowing for optimal contraction.
- Innervated by the median nerve for lumbricals 1 & 2 and the ulnar nerve for lumbricals 3 & 4.
Dorsal Interossei
- Composed of four muscles, each with a double head originating from the adjacent sides of two metacarpals.
- Insert into the extensor expansion and the base of the proximal phalanges, facilitating finger abduction and assistance in flexion at the metacarpophalangeal joints.
- Possess a bipennate structure, which enhances force generation.
- Innervated by the ulnar nerve.
Palmar Interossei
- Comprised of three muscles, each originating from the palmar surfaces of the respective metacarpals.
- Insert similarly to the dorsal interossei, in the extensor expansion and the base of the proximal phalanges, predominantly facilitating finger adduction.
- Characterized by a unipennate design, maximizing efficiency during contraction.
- Also innervated by the ulnar nerve.
Brachial Artery
- Brachial artery divides at the cubital fossa into two primary arteries.
- Radial Artery serves as the main blood supply to the hand.
- Ulnar Artery acts as the main arterial supply for the forearm.
- Ulnar artery branches into the Common Interosseous Artery, which further splits into:
- Anterior Interosseous Artery supplies the front compartment of the forearm.
- Posterior Interosseous Artery supplies the back compartment of the forearm.
- At the wrist, several arteries contribute to blood supply:
- Palmar arteries
- Carpal arteries
- Dorsal carpal arteries
- Within the palm, blood supply is organized into:
- Superficial Palmar Arterial Arch
- Deep Palmar Arterial Arch
Superficial Arterial Supply of the Hand
- The hand's blood supply is primarily through anastomosis between the ulnar artery and the radial artery.
- Ulnar artery runs deep to the palmar aponeurosis, contributing significantly to the hand's arterial network.
- The superficial palmar branch of the radial artery completes the anastomosis with the ulnar artery.
Branches of Superficial Supply
- Three common palmar digital arteries arise from this arterial arrangement, facilitating blood flow to the digits.
- Proper palmar digital arteries branch off from the common palmar digital arteries, supplying individual fingers with oxygenated blood.
Deep Arterial Supply of the Hand
- Radial artery traverses the anatomical snuff box, providing blood supply to the dorsum of the hand.
- The radial artery pierces the first dorsal interossei muscle, enabling access to deeper structures.
- It travels between the two heads of the adductor pollicis muscle to reach the palmar surface.
- Blood supply to the deep palmar area is complemented by the deep palmar branch from the ulnar artery.
Key Branches of the Radial Artery
- Supplies three palmar metacarpal arteries, which contribute to the circulation in the metacarpal region.
- The princeps pollicis artery is a significant branch that supplies the thumb.
- The radial indicis artery branches off to provide blood to the index finger.
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Description
This quiz covers the eight carpal bones in the human wrist, divided into proximal and distal rows. Learn about the specific roles and characteristics of each bone, including their significance in wrist movement and stability. Test your knowledge on this essential aspect of human anatomy.
