Thenar eminence
Encyclopedia
The thenar eminence refers to the group of muscle
s on the palm of the human hand
at the base of the thumb
. The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex
.
Another muscle that controls movement of the thumb is adductor pollicis. It lies deeper and more distal to flexor pollicis brevis. Despite its name, its main action is mainly rotation and opposition. It is not in the thenar group of muscles, so is supplied by the ulnar nerve
.
. The Flexor pollicis brevis can be innervated by the median or ulnar nerve. The adductor pollicis is typically innervated by the ulnar nerve
. There are normal variations. In a Cannieu-Riche anastomasis, fibers from the deep palmar branch of the ulnar nerve innervate the opponens pollicis and/or abductor pollicis brevis. Regardless of their final innervation, the nerves that reach the thenar muscles arise from the C8 and T1 roots, pass through the lower trunk of the plexus, and then through the lateral cord of the plexus.
The ulnar nerve is exclusively responsible for the innervations of the hypothenar eminence
. Both nerves contribute to the innervations of the midpalmar group.
Flexor Pollicis Brevis (FPB) is typically an ulnar-innervated muscle. Due to a common interconnection between the Median and Ulnar nerves in the hand (Riche-Cannieu interconnection), the Median nerve may innervate the FPB in 35% of people. It is innervated by the Ulnar nerve in 50% of people and by both the Median and Ulnar nerves in 15%.
The muscles in this location are usually innervated by the recurrent branch of the median nerve
. They all control movement of the thumb.
The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve. The lateral two lumbrical muscles
are the other exception.
, "A OF A OF A" for, Abductor pollicis brevis, Opponens pollicis, Flexor pollicis brevis, Adductor pollicis (thenar muscles) and Opponens digiti minimi, Flexor digiti minimi, Abductor digiti minimi (hypothenar muscles).
A good way to remember what muscles are in the thenar eminence is "OAF"; oafs have big thenar eminences. 'O' = opponens, 'A' = abductor, 'F' = flexor. There is only one opponens. The other two muscles each have a long partner and thus are called "brevis."
Meat-LOAF: the "M" in the word "Meat" helps you remember that the LOAF muscles of the hand (2 Lateral Lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis) are innervated by the Median Nerve
ABOF the Law muscles. The law states muscles of the hand are supplied by ulnar nerve. However, ABOF the Law muscles are supplied by MEDIAN nerve. 'AB' = abductor, 'O' = Opponens, 'F' = Flexor, Law 'L' = Lateral Lumbricals (2).
MAINTAINER—Main(Median nerve) --Tainer(thenar muscles)
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s on the palm of the human hand
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
at the base of the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
. The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex
Palmomental reflex
The palmomental reflex is a primitive reflex consisting of a twitch of the chin muscle elicited by stroking a specific part of the palm. It is present in infancy and disappears as the brain matures during childhood but may reappear due to processes that disrupt the normal cortical inhibitory...
.
Muscles
The following three muscles are considered part of the thenar eminence:- Abductor pollicis brevis abducts the thumb. This muscle is the most proximal of the thenar group.
- Flexor pollicis brevis, which lies next to the abductor, will flex the thumb, curling it up in the palm.
- Opponens pollicis lies deep to abductor pollicis brevis. As its name suggests it opposes the thumb, bringing it against the fingers. This is a very important movement, as most of our dexterity comes from this action.
Another muscle that controls movement of the thumb is adductor pollicis. It lies deeper and more distal to flexor pollicis brevis. Despite its name, its main action is mainly rotation and opposition. It is not in the thenar group of muscles, so is supplied by the ulnar nerve
Ulnar nerve
In human anatomy, the ulnar nerve is a nerve which runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest unprotected nerve in the human body , so injury is common...
.
Innervation
The Opponens pollicis and Abductor pollicis brevis are normally innervated by the median nerveMedian nerve
The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....
. The Flexor pollicis brevis can be innervated by the median or ulnar nerve. The adductor pollicis is typically innervated by the ulnar nerve
Ulnar nerve
In human anatomy, the ulnar nerve is a nerve which runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest unprotected nerve in the human body , so injury is common...
. There are normal variations. In a Cannieu-Riche anastomasis, fibers from the deep palmar branch of the ulnar nerve innervate the opponens pollicis and/or abductor pollicis brevis. Regardless of their final innervation, the nerves that reach the thenar muscles arise from the C8 and T1 roots, pass through the lower trunk of the plexus, and then through the lateral cord of the plexus.
The ulnar nerve is exclusively responsible for the innervations of the hypothenar eminence
Hypothenar eminence
Hypothenar refers to a group of three muscles of the palm that control the motion of the little finger.The three muscles are:* Abductor digiti minimi* Flexor digiti minimi brevis* Opponens digiti minimi-Muscles:...
. Both nerves contribute to the innervations of the midpalmar group.
Flexor Pollicis Brevis (FPB) is typically an ulnar-innervated muscle. Due to a common interconnection between the Median and Ulnar nerves in the hand (Riche-Cannieu interconnection), the Median nerve may innervate the FPB in 35% of people. It is innervated by the Ulnar nerve in 50% of people and by both the Median and Ulnar nerves in 15%.
The muscles in this location are usually innervated by the recurrent branch of the median nerve
Recurrent branch of the median nerve
The recurrent branch of the median nerve is the branch of the median nerve which supplies the thenar muscles. It is also occasionally referred to as the thenar branch, or the thenar muscular branch, of the median nerve...
. They all control movement of the thumb.
The innervation of these muscles by the median nerve is unusual, as most of the intrinsic muscles on the palm of the hand are supplied by the ulnar nerve. The lateral two lumbrical muscles
Lumbricals of the hand
The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.-Structure:There are four of these small, worm-like muscles on each hand. These muscles are unusual in that they do not attach to bone...
are the other exception.
Mnemonics
The muscles of hand can be remembered using the mnemonicMnemonic
A mnemonic , or mnemonic device, is any learning technique that aids memory. To improve long term memory, mnemonic systems are used to make memorization easier. Commonly encountered mnemonics are often verbal, such as a very short poem or a special word used to help a person remember something,...
, "A OF A OF A" for, Abductor pollicis brevis, Opponens pollicis, Flexor pollicis brevis, Adductor pollicis (thenar muscles) and Opponens digiti minimi, Flexor digiti minimi, Abductor digiti minimi (hypothenar muscles).
A good way to remember what muscles are in the thenar eminence is "OAF"; oafs have big thenar eminences. 'O' = opponens, 'A' = abductor, 'F' = flexor. There is only one opponens. The other two muscles each have a long partner and thus are called "brevis."
Meat-LOAF: the "M" in the word "Meat" helps you remember that the LOAF muscles of the hand (2 Lateral Lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis) are innervated by the Median Nerve
ABOF the Law muscles. The law states muscles of the hand are supplied by ulnar nerve. However, ABOF the Law muscles are supplied by MEDIAN nerve. 'AB' = abductor, 'O' = Opponens, 'F' = Flexor, Law 'L' = Lateral Lumbricals (2).
MAINTAINER—Main(Median nerve) --Tainer(thenar muscles)