Your TONGUE and pulse are just a couple of many microsystems used in Oriental Medicine to not only diagnose, but to also cross-verify a diagnosis.
The texture, shape, coating, and color of your tongue all indicate whether you have a healthy or pathogenic state in specific organs or meridians/channels of your body.
Fundamentally, when we take your PULSE we are looking at not only the Yin aspect/Blood-forming organs, but also the Yang aspect/Qi-forming organs. At the most basic level, your pulse may indicate deficient Qi, stress, pathogens, or pain. How your pulse corresponds to your physiology is below.
Now, for a very special gift to you, I offer you this great clinical image of a patient with severe Rheumatoid Arthritis. That thick sticky, white coating is Liver congestion (fatty liver in Biomedicine). The foamy quality is from hormonal exhaustion, typically Adrenal fatigue. The fuscia-red tone is typical of Thyroid levels being out of balance, often hyper-active and deficient at the same time, meaning too much thyroid hormone is actively in the blood stream from stress-response, but there is very little for supporting repair of the body. The swollen, fat shape and fissures/cracks are from excessive internal damp, or metabolic syndrome. So many more details here, but not necessary to state. You get the general idea.
Your tongue tells a lot. Be careful when sticking it out around any Acupuncturist. Additionally, if your practitioner is good at facial diagnosis, they'll also know if "you're full of shit". Uh-oh. No dirty secrets anymore.