What is a Thumb?

The thumb is known to be the outermost finger of the 5 fingers of the hand. It is capable of unique and amazing motions that make it completely different from the other fingers of a human hand. Here, you will be learning what is a thumb, the structure of thumb, and several other features of the thumb. The human hand is a complex structure and the thumb is one of its parts. So, gathering all the important information about this structure will help in understanding the anatomy of the human body.


Thumb Anatomy

We all are familiar with the fact that a human hand commonly consists of 5 fingers. The thumb or the pollex is the first one of the fingers that are present in the human hand. There is a wide and unique range of qualities in the human thumb that the other fingers don’t really have. Not only is the thumb able to bend the knuckle, but the thumb tip is capable of easily reaching the other fingertips as well. Hence, this particular motion range allows people to have a very unique ability to grasp and hold different items. We are going to learn much more about the parts of the thumb below.


How is the Human Thumb Similar and Different from Other Fingers

There are a few qualities that the thumb shares with the other 4 fingers of a human hand. Here we are going to mention some of these similarities so that the students can have a better understanding of the topic in the easiest way.

  • There is a particular skeleton consisting of phalanges in the thumb and there are hinge-type joints as well. This is one similarity that thumbs tend to have with other fingers. These hinge joints help in providing flexion toward the hand’s palm.

  • The thumb has a particular dorsal surface, just like the other fingers. There are hair and a single nail present in this certain type of dorsal surface. Also, there is a hairless aspect along with the fingerprint ridges.

While there are so many similarities between the thumb and the other fingers of a human hand, there are certain differences as well. These differences set the thumb apart from other fingers and provide unique abilities to the hand.

  • The thumb is always in an opposite direction to the other 4 fingers of the hand.

  • There are 2 phalanges present in the thumb while the other fingers have three phalanges.

  • The breadth of the thumb is greater in the hand’s distal phalanx than the width in the hand’s proximal phalanx.

  • The thumb has an attachment to the mobile metacarpus and hence produces the opposability trait that is seen in the human hand.

So, the structure of the thumb clearly states that while there are certain similarities between the fingers and the thumb, there are certain differences as well.


Thumb Anatomy: Learn about the Parts of the Thumb

The human thumb basically consists of a metacarpal that has a connection to the trapezium which is the carpal bone that is located in the wrist. The first metacarpal is properly connected to the proximal phalanx. Hence, there is a connection between the distal phalanx of the thumb and that is known as the tip of the thumb. Unlike the other fingers, there is no intermediate phalanx bone present. The oxygenated blood is provided to the thumb via princeps pollicis arteries. Apart from that, there are some other details that will be useful information for the thumb facts.


When it comes to the thumb’s skeleton, there is the metacarpal bone and that is articulated in the carpus right at the carpometacarpal joint. The latter portion of the bone is articulated along with the distal phalanx and that happens at the interphalangeal joint. There are 2 different sesamoid bones present as well and these are located in the metacarpophalangeal joint.


Due to the opposability factor of the thumb, it is able to provide a wide range of different motions that allow humans to act in certain ways. For example, when it comes to holding or grasping certain items, the thumb really has a very important role to play. It is also able to rotate, flex, and pinch various items. So, these are the different functions that make the thumb one of the most important parts of the human hand.

FAQs (Frequently Asked Questions)

1. What is a Thumb?

Ans: A thumb is known to be the one digit on the human hand that is different from all the other fingers of the hand. One of the most important things to know about the thumb is that it is not generally referred to as a particular finger. This is because there are certain differences in the structure and the anatomy of the thumb which sets it apart from all the other fingers that are present in the hand of a human being. For example, while all the other fingers contain three phalanges in their structure, the thumb only consists of two. Also, the thumb is placed in an opposite direction than all the other fingers of the hand.

2. What is the Function of a Thumb?

Ans: There are many different functions that the thumb has when it comes to the structure and the formation of it in the human hand. The presence of the thumb allows the humans an ability to grasp the items in their hands without any trouble. This is due to the fact that the thumb is able to reach all the fingertips of the hands. This ability can be credited to the opposability of the thumb. It means that the thumb is situated completely opposite to the other fingers. Not to mention that the thumb is also able to rotate and bend without any difficulty. There are other functions such as pinching and flexing.