A Short Story of Thermoregulation – Part 2

In my last blog, I touched on the hypothalamus being the epicentre for temperature control, a thermostat of sorts for the human body. I briefly covered fever and virus, and in light of COVID-19, we must be more aware of how our bodies respond to its environment, and why. This is especially important when we use tools like thermography, so we can understand what we are looking at and what we are measuring. We can also understand better the benefits thermography brings and its limitations.

Skin for the performance and medical thermography application is one of the most critical anatomies to understand. Did you know that the skin is an organ and is the largest organ in the body! Incredible right. Did you know that it varies in thickness between 1.5 and 4mm or more in different anatomical regions and represents 7% of total body weight? The skin consists of tissues that work together to perform specific functions. Skin in my mind is an extraordinary architectural wonder.

When we are using thermography on humans, we measure the surface temperature of the skin or body region. The skin’s temperature at the superficial layer is dictated by what is going on within the body and is also affected by environment heterogeneity and changes. It is vital to understand these physiologies and their relationship to each other to prevent false negatives in your thermography assessments, recordings and data.

Not only does the skin protect us by providing cushioning (I will discuss this in the next blog), it insulates the deeper body organs. The epidermis layer (outer layer) is waterproof and prevents unnecessary water loss; this layer also produces pigment to protect us from the harmful effects of Ultraviolet (UV) radiation, although the epidermal cells use UV radiation to synthesise vitamin D.

NOTE: your vitamin D level is one that should be optimised to support your immune system, especially against viruses like COVID-19. It helps your body produce over 200 antimicrobial peptides that help fight all sorts of infections.

Body temperature regulation is helped along by the skin’s rich capillary networks and sweat glands which regulate the loss of heat from the body and helps to control body temperature. The skin is a sort of excretory system where salt, urea and water are lost through sweating. When the body is too hot, loss of heat is increased by sweating and by the dilation of capillaries. When the body is too cold the sweat glands are inactive, the capillaries contract and a layer of air is trapped over the epidermis by the erected hairs. NOTE: Sweat glands: exocrine glands lie in the dermis layer and discharge secretion through a duct which opens up onto the skin’s surface.

Other factors that increase the secretion of sweat include pain, nausea, nervousness, and drugs. The environment can play a considerable part in temperature loss or gain through heat loss by forced convection or conduction from radiation.

NOTE: Forced convection is a process causing progressive heat loss from the skin in a windy environment. It can be seen clearly in an infrared camera, and the subject should be only scanned in draft-free environments and out of sunlight

Sensory receptors are sense organs found in the skin; these are associated with nerve endings and which carry information throughout the body towards the brain and spinal cord. They directly communicate with the hypothalamus in the brain to control the bodies temperature.

NOTE: The hypothalamus also controls water balance, thirst, hunger, eating and sexual function. It is also closely connected to the emotional activity, sleep and is the centre for the integration of hormonal and autonomic nervous activity).



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