Hand Muscles│Anatomy Tips, Tricks and Mnemonics

Summary

This video takes a deep dive into the anatomy of hand muscles, breaking them down into three main areas: the thenar eminence (under the thumb), the hypothenar eminence (under the pinky), and the central hand muscles. Using mnemonic devices like the 'triforce' and 'half loaf' to simplify complex muscle names, the script also covers the lumbricals, interossai, and the mysterious palmaris brevis. It explains muscle functions, innervations, and a quirky visual of a 'lumbrical grip.' The video concludes with helpful tips on nerve innervations, making it both educational and fun for learners.

Takeaways

• 🖐️ The hand muscles are divided into three main areas: thenar eminence (thumb side), hypothenar eminence (pinky side), and intermediate muscles around the metacarpals.
• 🎮 A helpful mnemonic for remembering the three areas is to imagine slapping a Triforce in the middle of your palm, representing the three muscle groups plus an extra muscle.
• 💪 Thenar and hypothenar eminences both contain three similar types of muscles: a flexor, an abductor, and an opponens muscle.
• 📝 Mnemonic for muscle groups: 'One for All' for thenar (opponens pollicis, flexor pollicis brevis, abductor pollicis brevis) and 'All for One' for hypothenar (abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi).
• 🔺 The adductor pollicis is a two-headed muscle in the middle of the hand, originating from the metacarpals and inserting on the proximal phalanx of the thumb.
• 🐛 Lumbricals originate from the tendons of flexor digitorum profundus, insert on the extensor hood, and flex the MCP joints while extending the PIP and DIP joints, forming a lumbrical grip.
• ✋ Interossei muscles are located between metacarpals and are divided into palmar (adduct fingers) and dorsal (abduct fingers), with the mnemonic 'PAD & DAB' for easy recall.
• 💡 The palmaris brevis is a small, superficial muscle not part of the main compartments, likely aiding in gripping and protecting the ulnar nerve.
• 🧠 Most hand muscles are innervated by the ulnar nerve, while the median nerve supplies four muscles: lateral two lumbricals, opponens pollicis, abductor pollicis brevis, and part of flexor pollicis brevis (mnemonic: 'Half Loaf').
• 🏆 Using mnemonics and visual associations (Triforce, worms, PAD & DAB, Half Loaf) greatly aids in memorizing the anatomy and functions of hand muscles for exams.
• 🔄 The lumbricals and interossei work together to create the lumbrical grip, demonstrating the coordinated function of intrinsic hand muscles.

Q & A

What are the three main areas of muscles in the hand?

The three main areas are the thenar eminence (under the thumb), the hypothenar eminence (under the pinky), and the muscles in the middle of the hand based around the metacarpals.

What mnemonic is used to remember the three areas and their muscles?

The 'Triforce' mnemonic is used: imagine slapping a Triforce in the middle of your palm to remember the three areas and the three muscles in each area.

What are the three types of muscles found in both the thenar and hypothenar eminences?

Each eminence contains a flexor (closer to fingers), an abductor (closer to the edge of the hand), and an opponens muscle (running underneath the other two).

How can the muscles of the thenar and hypothenar eminences be remembered using mnemonics?

For the thenar eminence, 'One for All' represents Opponens pollicis, Flexor pollicis brevis, and Abductor pollicis brevis. For the hypothenar eminence, 'All for One' represents Abductor digiti minimi, Flexor digiti minimi brevis, and Opponens digiti minimi.

What is unique about the lumbrical muscles in the hand?

The lumbricals originate from the tendons of the flexor digitorum profundus instead of from bones, and they insert on the extensor hoods. They flex the MCP joints while extending the PIP and DIP joints, creating the 'lumbrical grip.'

What mnemonic helps remember the function of the interossei muscles?

The mnemonic 'PAD and DAB' helps: Palmar interossei adduct fingers (PAD), Dorsal interossei abduct fingers (DAB).

What is the 'Triforce + 1' in the hand muscles?

The '+1' refers to the palmaris brevis, a small superficial muscle that does not fit into the main compartments. It helps with gripping and may protect the ulnar nerve.

Which nerve innervates most of the hand muscles?

The ulnar nerve innervates the majority of the hand muscles.

Which muscles are innervated by the median nerve and how can they be remembered?

The median nerve innervates four muscles: the lateral two lumbricals, opponens pollicis, abductor pollicis brevis, and half of flexor pollicis brevis. This can be remembered with the 'Half-Loaf' mnemonic.

How do the lumbricals contribute to hand movement?

The lumbricals flex the metacarpophalangeal (MCP) joints while simultaneously extending the proximal and distal interphalangeal joints (PIP and DIP), producing a unique 'sideways L-shaped' grip called the lumbrical grip.

Where do the interossei muscles originate and insert?

Interossei muscles originate between the metacarpals and insert on the extensor hoods and proximal phalanges of the digits.

What is the function of the palmaris brevis?

The palmaris brevis contracts to slightly move the skin over the hypothenar eminence, potentially aiding in grip and protecting the ulnar nerve, though its exact function is not fully known.