the five elements in tai chi chuan

The Five Elements are a fundamental concept which impacts on many areas of life. In time one can develop an intuitive understanding of the interaction of the elements. There are many explanations of the Five Elements applied to martial arts, and I've yet to see one that explains the directions (forward, back,up-down etc.) in a way I can integrate with my knowledge of TCM (Traditional Chinese Medicine). So here (I trust) is a simple interpretation on I hope to improve as my understanding deepens.

Water
Just like a great river, water has enormous power combined with tremendous softness. Water prevails without doing, just by being itself. 'Water' houses the will. The emotion associated with this element is Courage & conversely Fear if this element is weak, The bones are the related tissue. Weakness in this element can cause lower back pain and sore knees. Controls reception of qi, memory and concentration. Energy flows up the water channels and the legs and back (Bladder, Kidney) from your root in the earth at the bubbling spring point (K-1). People may lose control of the bladder in times of great fear as the qi suddenly descends.
Sense organ - the ears

Wood
Like bamboo 'Wood' has flexibility. It controls judgement & strategy. This element houses the ethereal soul which gives direction in life. The emotion of 'Wood' is Anger. In people with long term Anger you may see two vertical furrows between the eyebrows. 'Wood' controls the sinews (ligaments and tendons) and ensures the free flow of qi.
Sense organ - the eyes

Fire
Our Shen (mind or consciousness) is housed by 'Fire' which also governs the blood and blood vessels. 'Fire' is linked with sensitivity, relationship to oneself and toward others. The triple heater channel or meridian of the 'Fire' element distributes original qi (chi that you are born with) and its energy radiates in all directions. The sense organ of the 'Fire' element is the tongue.

Earth
Very central parts of the body such as the waist fall under the influence of this pivotal element. Its functions include transforming. It houses another aspect of the mind - the yi (focus and intellect), Imbalances here can lead to or be caused by worry which knots the qi. 'Earth' controls the raising and descending of qi, sinking & connection with the earth. It also 'dominates' the muscles and the limbs providing nourishment to the body.
Sense organ - the mouth

Metal (air)
Element which governs the exterior - defence, boundaries, skin, taking in and letting go. It governs qi and controls breathing. 'Metal' houses the 'po' (animal nature). I suspect that 'Opening' and 'Closing' in the form are part of the 'Metal' element.
Sense organ - the nose