WHAT IS THE THENAR EMINENCE? MUSCLES AND FUNCTIONS - ANATOMY AND PHYSIOLOGY - 2025

The thenar eminence is a set of four muscles located at the base of the thumb of the human body. This muscle group is responsible for the fine movements of the thumb. The muscles that make up the palm of the hand are grouped into three zones or regions, namely: the thenar eminence, the hypothenar eminence, and the middle palmar region.

The configuration of the muscles of the hand and their particular characteristics make possible a wide variety of movements of grip, precision, power, manipulation and many others. This allows children to begin to acquire motor skills essential for daily life from an early age.

Even the thenar eminence is considered a skillful muscle rather than a strong muscle. The ability to pick up and move a pencil with a tripod grip (the traditional way we write), or button / unbutton a button are some of its more popular functions.

The great variety of actions that human beings are capable of carrying out with their hands has allowed them throughout history to develop admirable abilities, arts and skills that not only allow them to carry out their daily activities, but also expand their capacities in tasks very specific and that require to be studied to learn them correctly.

Parts, functions and importance of the thenar eminence

The thenar eminence is made up of the following muscles:

- Abductor pollicis brevis muscle

It is responsible for the abduction movement of the thumb. This movement consists of placing the thumb in a position almost perpendicular to the palm of the hand and the rest of the fingers and fully extended.

- Flexor brevis muscle of the thumb

The short flexor allows the flexion movement, which is characterized by being the position in which the thumb is in a position parallel to the palm of the hand and flexed, as indicated in the following figure:

- Opponent thumb muscle

It is the muscle that makes possible the position in which the thumb, fully extended and tries to touch the opposite end in the plane parallel to the palm of the hand, in the direction of the base of the index finger.

The opposing muscle helps to produce complex movements, which are very important because they allow the ball of the thumb to be brought towards the tips of the other fingers, in addition to making very precise movements with the hands.

In fact, the opposition of thumbs is a unique characteristic of human beings, thanks to which man was able to build tools.

In turn, the tools help to develop manual skills and consequently, trades and occupations that make a great contribution to people's progress are also developed.

- Thumb adductor muscle

This muscle is what allows the so-called "adduction" which consists of bringing the thumb towards the midline (imaginary) that divides the body into two symmetrical parts.

The adductor pollicis is the one that retracts the thumb into the palm of the hand when it is in an abduction position. It also intervenes in some of the phases of the opposition movement, in combination with the opponent muscle.

It is of vital importance when you want to maintain a press movement on an object.

Diseases related to the thenar eminence

There are certain pathologies that affect this muscle group. Some are hereditary in nature while others have their origin in diseases previously acquired by the patient.

Among them we can mention the following:

Carpal tunnel syndrome

They are characterized by irregularities in the structure of the thenar eminence and even, in some cases, its absence. It is detected at birth, when the newborn is given a neonatal examination.

Agranulocytosis

This condition is caused by the low presence of granulocytes in the body. Granulocytes are a type of white blood cell that is responsible for destroying germs; agranulocytosis can cause necrosis (degeneration of a tissue due to cell death) in the muscles of the thenar eminence.

Hepatic cirrhosis

It is a disease that affects the liver tissue. One of its consequences is palmar erythema, that is, reddening of the skin due to inflammation that occurs in the palm of the hands, affecting the thenar and hypothenar eminence.

Lane's disease

This is the palmar erythema described above but caused by hereditary causes. It is a skin type condition, that is, at the level of the skin.

Treatments

Conditions that directly affect the muscles of the thenar eminence are usually treated through surgery and occupational or physical therapy.

The functions of the hand depend to a large extent on the good condition of the thumb, so children born with some type of defect in their upper limbs should be evaluated from birth, since part of their motor development would be affected.

In many cases, it is possible to do surgical reconstructions of the thumb and an absolutely normal quality of life is achieved.

The thenar eminence is one of the smallest muscle groups in the human body but its anatomy and function have allowed man to develop multiple manual skills throughout evolutionary history.

The ability to make tools with their own hands marked a before and after in human history throughout the centuries, largely thanks to the opposable thumbs configuration, which makes it easier to manipulate and hold objects of different shapes. and sizes.

The proper development of these manual skills must be monitored and stimulated from the first years of children's life, so that they are able to carry out important activities both in school, domestic and professional environments.

References

1. Thompson, S. The Write Stuff: Developing Fine Motor Skills & Handwriting in Students. Sanford, Handy Lerning Seminars Inc.
2. Thumb agenesis. Recovered from: manopediatrica.com.ar
3. Agranulocytosis. Recovered from: medlineplus.gov
4. Carpal tunnel syndrome, occupational disease on the rise. Recovered from: revista.consumer.es
5. Trew, M., and Everett, T. (2006). Fundamentals of the Human Movement. Barcelona, ​​Masson.
6. Palastanga, N., et al. (2000). Human Anatomy and Movement. Structure and Functioning. Barcelona, ​​Editorial Paidotribo.
7. Llusa, M., et al. (2004). Manual and Photographic Atlas of the Anatomy of the Locomotor System. Madrid, Editorial Médica Panamericana.
8. Martí, N. and Jordá, E. (2010). Elsevier: Hereditary palmar erythema: Lane's disease. Recovered from: elsevier.es.