The Sensory World of Hands

The human hand is an evolutionary marvel. The development of the human brain coupled with the freeing of hands from ambulatory responsibilities enabled our hands to be both key sensory receptor sites and the actor in a myriad of functions. Examples include complex manipulation, exploring and learning about ourselves, the world and new skills, as well as communication, regulation, connection and emotional well-being.

Hands as sensory receptors

Proprioception receptors are located throughout our muscles, joints, tendons and fascia. There are 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons and highly innervated palmar fascia, a tough fibrous tissue. Collectively, these send ongoing, copious sensory information to the central nervous system for processing.

Tactile: Our hands have both hairy and glabrous skin (palms) containing several different types of receptors. These are: Merkel’s disks, Meissner’s corpuscles, Ruffini’s corpuscles, Pacinian corpuscles, hair follicle receptors, C-tactile receptors, pain and thermoreceptors.

Hairy skin is a mobile sensory surface used to sense interaction with the surrounding environment. Hair follicles help to navigate the world to understand what we are rubbing up against. They also regulate temperature, manage sweat, and regulate our emotions through the release of hormones, serotonin, dopamine and oxytocin. As such our hairy skin can also be considered part of our interoceptive system.

The human hand is an evolutionary marvel. The development of the human brain coupled with the freeing of hands from ambulatory responsibilities enabled our hands to be both key sensory receptor sites and the actor in a myriad of functions. Examples include complex manipulation, exploring and learning about ourselves, the world and new skills, as well as communication, regulation, connection and emotional well-being.

Parent holding baby's feet

Hands as sensory receptors

Proprioception receptors are located throughout our muscles, joints, tendons and fascia. There are 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons and highly innervated palmar fascia, a tough fibrous tissue. Collectively, these send ongoing, copious sensory information to the central nervous system for processing.

Tactile: Our hands have both hairy and glabrous skin (palms) containing several different types of receptors. These are: Merkel’s disks, Meissner’s corpuscles, Ruffini’s corpuscles, Pacinian corpuscles, hair follicle receptors, C-tactile receptors, pain and thermoreceptors.

Hairy skin is a mobile sensory surface used to sense interaction with the surrounding environment. Hair follicles help to navigate the world to understand what we are rubbing up against. They also regulate temperature, manage sweat, and regulate our emotions through the release of hormones, serotonin, dopamine and oxytocin. As such our hairy skin can also be considered part of our interoceptive system.

labrous skin on the palm and fingers, is supported by its attachment to the palmar fascia and features creases and ridges (see hand development next month) that help to grip and manipulate objects. Tightly packed highly sensitive receptors are found throughout but especially in the pads of finger and thumb. These gather complex detailed sensory information about precise location, shape, size, texture and movement. Our palms support exploration and our interaction with the world around us.

Our haptic sense allows us to rapidly and accurately identify three-dimensional objects by combining the sensory capabilities of the glabrous skin and kinaesthetic inputs derived from active use of muscles, tendons and joints.

The skin, muscles and joints of the hand are innervated by as many as 14 different types of nerve fibre. The extensive tactile inputs and proprioception from the hands, particularly the fingertips and thumb, result in overrepresentation on the somatosensory homunculus.

Interoception (physiological and emotional homeostatic functions)

Sweat glands are widely distributed through the hairy skin supporting thermoregulation. They are also in the glabrous skin of the palms, between the ridges. Here they are not activated by heat but by physiological and emotional stressors e.g. increased respiration, pain or mental stress. This stress initiates a sympathetic autonomic response. Sweating on the palm is therefore considered emotional sweating. It is thought to prevent slippage while grasping or performing a delicate task, using the fingertips in demanding situations. Measuring sweat on the palms can be used to assess sympathetic function and responses.

Another function of the autonomic nervous system is when fingers go wrinkly or ‘prune’ after being in water for some time. This only happens to glabrous skin and is thought to increase traction to grip things in the water.

Touch plays a crucial role in maintaining our emotional regulation, helping to support a return to homeostasis after an emotional disturbance. This process requires a feedback loop where one person experiences discomfort, another person provides comforting touch, and the first person perceives the emotional touch as calming and comforting.

Vision plays a pivotal role in directing and guiding the hand in goal-orientated hand movements, for example pointing, reaching, grasping, object manipulation and tool use. Vision provides information about the target while proprioception provides information about hand position. This visuomotor integration requires continuous multimodal sensory feedback as well as predictive gaze for precise exploration, grasp and tool use.

Processing of signals for eye-hand coordination is not confined to a couple of areas within the brain. Such a crucial function has been assigned to many cortical and subcortical areas. It is thought that even within the posterior parietal cortex (an associative region that integrates visual information and input from the somatosensory cortex) motor commands for eye-hand coordination can be initiated, something that otherwise would only happen in the frontal cortex.

Taste & Smell

As we wean, our hands grip food and other objects with precision and bring to our mouth, stimulating our sense of taste and bring smells closer to our nose.

Vestibular

Hands support our early mobility skills through crawling, holding to pull to stand and beginning to walk. Our power grip enables us to hold on to swing our body, climb a tree, they are a means of navigating the world and enable active vestibular experiences.

Hearing

Our hands can be used to make sounds, clapping, tapping, clicking. Before the development of speech, humans use gestures to communicate, doing so meaningfully with our hands. Using hand gestures early in life is a good predictor for later development of a strong vocabulary.

To emphasise, hands are multisensory generators!

This is why supporting hand use is so important in development.

test blog post

Learn. Connect. Share. Love

Sign up today to receive your free copy of ‘Sensory Wellbeing’. Full of sensory strategies for self care when working in a stressful environment.

You’ll also get the latest sensory news, information and updates straight to your inbox every month.

en_GBEnglish (UK)