The structure of the hand
The structure of the hands is both complex and delicate. As such, the hand is able to make a wide range of precise movements. These movements include gripping, pinching and lifting as well as finer movements needed for activities such as needlework, art or tying a shoe.
The basic structure of a hand consists of the wrist, palm and fingers. Each human hand contains approximately 29 bones, although some people have more than others. 29 joints connect these bones along with over 123 named ligaments.
There are three groups of bones in the hand. The carpus bones are found in the wrist. The metacarpus bones are found in the palm. The phalanges are the bones of the fingers.
Nerves and arteries
Our hands also contain 48 named nerves. These are made up of 21 muscular branches, 3 major nerves and 24 sensory branches. The three main nerves are the median, ulnar and radial nerves. These nerves work together in order to control the muscles in the hand and to receive signals from the hand’s millions of sensory receptors. It is the sensory receptors that detect pain, pressure, temperature, texture and touch.
There are 30 named arteries in each hand in addition to several smaller branches. These deliver blood into and out of the hand.
Muscles and movement
Although there are no muscles in the fingers, their movements are controlled by 34 different muscles. There are 17 intrinsic muscles in the palm of each hand. The extrinsic muscles make up the 18 muscles in our forearms. muscles. The muscles together control the tendons in our fingers.
Anatomical terms describe all bodily movements, including those of the hand. There are many terms used. Four common terms used in hand movements are;
- Flexion – such as the movement of clenching your fist or curling a finger.
- Extension – The movement of straightening the fingers.
- Abduction – The movement of spreading out your fingers from the middle finger.
- Adduction– The movement of bringing the fingers together again.
Thumb sucking commonly involves flexion of the four fingers and abduction of the thumb.
Left and right
In many ways our brain controls the movements of our hands like a puppet on strings. The brain sends messages to the muscles, which then control the tendons, which then move the fingers. As such, the brain operates like a puppeteer. The right side of the brain controls the left hand. The left side of the brain controls the right hand.
Most people have a preference for using one hand for completing complex tasks. We describe this as being right or left handed.
The majority of people, between 70 and 95 %, are right handed. Of those who are left handed, men are considered more likely than women to have a strongly dominant left hand.
Right handed children tend to suck their right thumb. Left handed children show a preference for sucking their left thumb.
A smaller percentage of people are either cross-dominant or ambidextrous. Cross dominant people change hand preference depending upon the task at hand. For example they might write with their left hand but play darts with their right hand. A cross-dominant child with a thumb sucking habit, might draw with their right hand but suck their left thumb.
In the case of ambidexterity, the person is able to use either hand with equal skill. Natural ambidexterity is extremely rare. It is possible to learn to be ambidextrous. However, a person would still show a marked increase in skill when using their naturally preferred hand. Ambidextrous children may have an equal passion for sucking either thumb.
When it comes to thumb sucking, children often prefer to suck one thumb over the other. However, cover their thumb of choice and they will usually switch to sucking the other one. This is why we sell our thumb guards in packs of two or three. With a twin pack there is the option of buying a guard for each thumb. Our triple packs allow parents to buy two guards for the preferred thumb and a single guard for the other thumb in case the child switches.