Logan Steele
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are nine muscles that close the hand, and they attach to the fingers, thumb, hand, wrist, carpal tunnel, forearm, and elbow. The muscles that close the hand include the opponens digiti minimi, opponens pollicis, flexor pollicis brevis, flexor digiti minimi, and flexor pollicis longus. These muscles work together to produce grip strength and allow us to grasp objects.
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What You'll Learn
Opponens digiti minimi
The opponens digiti minimi is an intrinsic muscle of the hand. It is a small, triangular muscle that extends between the hamate bone (carpal bone) and the fifth metacarpal bone. The opponens digiti minimi is part of the hypothenar muscle group, which also includes the abductor digiti minimi and flexor digiti minimi brevis muscles. The hypothenar muscle group is located on the ulnar side of the palm, between the wrist and the base of the fifth digit.
The opponens digiti minimi is responsible for flexion, lateral rotation, and opposition of the little finger. This muscle helps to deepen the hollow of the palm by acting on the fifth carpometacarpal joint. When the opponens digiti minimi contracts, it causes finger flexion and lateral rotation, which moves the little finger towards the thumb. This action allows us to cup our hands and is essential for grasping objects.
The opponens digiti minimi is closely related to two neurovascular structures. The deep palmar branch of the ulnar artery and the deep branch of the ulnar nerve divide the muscle into two lamellae, or bands. The ulnar nerve supplies the hypothenar muscles, including the opponens digiti minimi, and passes through the hook of the hamate and pisiform bone. The blood supply to the opponens digiti minimi is provided by the deep palmar branch of the ulnar artery and the deep palmar arch, which is the terminal branch of the radial artery.
The opponens digiti minimi is located deep to the flexor digiti minimi brevis and abductor digiti minimi muscles. Along its course, it blends with the surrounding hypothenar muscles, often fusing with them. The opponens digiti minimi is responsible for fine motor movements of the hand, such as gripping round or irregular objects like a ball. This muscle works in conjunction with the other muscles in the hypothenar group to facilitate precise movements and control of the little finger.
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Opponens pollicis
The opponens pollicis is a small, triangular, intrinsic muscle of the hand. It is one of three thenar muscles, along with the abductor pollicis and flexor pollicis brevis. The thenar muscles are located on the radial (lateral) aspect of the hand, forming an elevation called the thenar eminence.
The opponens pollicis originates from the flexor retinaculum and the tubercle of the trapezium bone. It then passes downward and laterally, inserting into the whole length of the metacarpal bone of the thumb on its radial side. The superficial head of the flexor pollicis brevis is often blended with the opponens pollicis.
The opponens pollicis is innervated by the recurrent (thenar) branch of the median nerve (root value C8 and T1). In around 20% of people, the muscle is innervated by the ulnar nerve. The muscle receives its blood supply from the superficial palmar branch of the radial artery.
The primary function of the opponens pollicis is to produce opposition of the thumb, allowing the tip of the thumb to touch the tips of the other fingers. This opposition is a complex movement involving flexion, adduction, and medial rotation at the first carpometacarpal joint, which is essential for precise hand movements such as grasping round objects or gripping a pencil.
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Flexor pollicis brevis
The flexor pollicis brevis is a short, broad intrinsic muscle of the hand. It is part of the thenar muscles, which control the thumb. The thenar muscle group is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. The flexor pollicis brevis is the most medial of the thenar muscles. It lies medial to the abductor pollicis brevis and opponens pollicis muscles, while it is lateral to the adductor pollicis muscle.
The flexor pollicis brevis is composed of superficial and deep heads. The superficial head is originated from the crest of the trapezium and flexor retinaculum, while the deep head is originated from the trapezoid and capitate bones, as well as the palmar ligaments of the distal row of carpals bones. The deep head can vary in size and sometimes may even be absent. The two heads of the flexor pollicis brevis usually differ in their innervation. The superficial head receives its nerve supply from the recurrent branch of the median nerve, while the deep head is innervated by the deep branch of the ulnar nerve, derived from spinal roots C8 and T1.
The flexor pollicis brevis receives its blood supply from the superficial palmar branches of the radial artery. The radial artery runs along the radius, closer to the thumb. The flexor pollicis brevis flexes the thumb at the metacarpophalangeal joint and also produces flexion and medial rotation of the first metacarpal bone at the carpometacarpal joint. This action aids in the opposition of the thumb, allowing us to grasp objects.
The flexor pollicis brevis can be activated by placing the palm facing up and the wrist in a neutral position. Bring the thumb to touch the base of the little finger and apply pressure for a few seconds before releasing it. The muscle can also be tested and palpated on the thenar eminence when the thumb is flexed against resistance.
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Flexor digiti minimi
The flexor digiti minimi brevis is a hypothenar muscle in the hand that flexes the little finger (also known as digit V) at the metacarpophalangeal joint. The muscle is situated on the ulnar (medial) aspect of the hand, where it forms an elevation above the base of the little finger, called the hypothenar eminence. The flexor digiti minimi brevis is one of three muscles in the hypothenar muscle group, the other two being the abductor digiti minimi and the opponens digiti minimi. These three muscles form the fleshy mass at the base of the little finger and are solely concerned with the movement of digit V.
The flexor digiti minimi brevis arises from the hamulus of the hamate bone and the palmar surface of the flexor retinaculum of the hand. It is inserted into the medial side of the base of the proximal phalanx of digit V. The muscle fibres run distally and medially, passing over the fifth metacarpophalangeal joint. The flexor digiti minimi brevis is located on the ulnar side of the palm, creating the hypothenar eminence with the abductor digiti minimi and opponens digiti minimi muscles.
The flexor digiti minimi brevis is innervated by the deep branch of the ulnar nerve, which arises from the spinal nerve levels C8-T1. The ulnar nerve has both superficial and deep branches, but it is the deep branch that innervates the flexor digiti minimi brevis. The muscle receives its blood supply from the deep palmar branch of the ulnar artery.
The main function of the flexor digiti minimi brevis is the flexion of the little finger at the metacarpophalangeal joint. This muscle also participates in the lateral rotation and opposition of the little finger. The hypothenar muscles, which include the flexor digiti minimi brevis, line the outer edges of the palm on the outside of the pinky finger and control the area of the hand that is opposite the thumb.
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Flexor pollicis longus
The flexor pollicis longus is a long muscle in the forearm and hand that flexes the thumb. It is one of the two long flexors located on the underside of the forearm, with the other being the flexor digitorum superficialis. It is also classified as an extrinsic muscle of the hand because it lies in the forearm but inserts in the hand.
The flexor pollicis longus is a deep flexor of the forearm, along with the flexor digitorum profundus and pronator quadratus. It originates from a broad area on the radius and adjacent structures, including the interosseous membrane and the lateral border of the coronoid process of the ulna. It crosses three joints and finally inserts onto the distal phalanx of the thumb. An occasionally present accessory long head of the flexor pollicis longus is called the 'Gantzer' muscle. This accessory head may also be referred to as the 'Gantzer's muscle'.
The main function of the flexor pollicis longus is flexion of the thumb at the interphalangeal joint, which is essential for gripping. It is the only muscle that flexes the interphalangeal joint of the thumb, making it vital for activities that require hand gripping. When the thumb is fixed, it also assists in flexing the wrist.
The flexor pollicis longus receives nervous supply from the anterior interosseous branch of the median nerve, derived from spinal roots C7 and C8. It receives dual blood supply, with its medial part supplied by the anterior interosseous artery (a branch of the ulnar artery) and its lateral part receiving blood from the radial artery.
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Frequently asked questions
There are 9 muscles that close the hand.
The 9 muscles that close the hand are: Opponens digiti minimi, Opponens pollicis, Flexor pollicis brevis, Flexor digiti minimi, Flexor pollicis longus, Palmaris brevis, Abductor digiti minimi, Flexor digiti minimi brevis, and Adductor pollicis.
The Opponens digiti minimi muscle originates on the transverse carpal ligament (the roof of the carpal tunnel) and inserts at the metacarpal of the pinky finger, allowing us to cup our hands.
The Opponens pollicis muscle is one of the three Thenar muscles located at the base of the thumb. It helps pull the thumb away from the fingers, allowing us to grasp objects.
The Flexor pollicis brevis muscle is one of the three Thenar muscles and it bends the thumb toward the small finger.
