The word chakra literally translates as wheel or disk and refers to a spinning sphere of bioenergetic activity emanating from the major nerve ganglia branching forward from the spinal column. Generally, six of these wheels are described, stacked in a column of energy that spans from the base of the spine to the middle of the forehead. And the seventh which is beyond the physical region. It is the six major chakras that correlate with basic states of consciousness.
Anja (along with Bindu, is also known as the third eye chakra) is linked to the pineal gland which may inform a model of its envisioning. The pineal gland is a light sensitive gland that produces the hormone melatonin which regulates sleep and waking up. Ajna is symbolised by a lotus with two petals, and corresponds to the colour white, indigo or deep blue. Ajna's key issues involve balancing the higher & lower selves and trusting inner guidance. Ajna's inner aspect relates to the access of intuition. Emotionally, Ajna deals with clarity on an intuitive level.
(Note: some opine that the pineal and pituitary glands should be exchanged in their relationship to the Crown and Brow chakras, based on the description in Arthur Avalon's book on Kundalini called Serpent Power or empirical research.)
Vishuddha (also Vishuddhi) may be understood as relating to communication and growth through expression. This chakra is paralleled to the thyroid, a gland that is also in the throat and which produces thyroid hormone, responsible for growth and maturation. Symbolised by a lotus with sixteen petals. Vishudda is characterized by the color light or pale blue, or turquoise. It governs such issues as self-expression and communication, as discussed above. Physically, Vishuddha governs communication, emotionally it governs independence, mentally it governs fluent thought, and spiritually, it governs a sense of security.
Anahata, or Anahata-puri, or padma-sundara is related to the thymus, located in the chest. The thymus is an element of the immune system as well as being part of the endocrine system. It is the site of maturation of the T cells responsible for fending off disease and may be adversely affected by stress. Anahata is symbolised by a lotus flower with twelve petals. (See also heartmind). Anahata is related to the colours green or pink. Key issues involving Anahata involve complex emotions, compassion, tenderness, unconditional love, equilibrium, rejection and well being. Physically Anahata governs circulation, emotionally it governs unconditional love for the self and others, mentally it governs passion, and spiritually it governs devotion.
Manipura or manipuraka is related to the metabolic and digestive systems. Manipura is believed to correspond to, Islets of Langerhans which are groups of cells in the pancreas, as well as the outer adrenal glands and the adrenal cortex. These play a valuable role in digestion, the conversion of food matter into energy for the body. Symbolised by a lotus with ten petals. The colour that corresponds to Manipura is yellow. Key issues governed by Manipura are issues of personal power, fear, anxiety, opinion-formation, introversion, and transition from simple or base emotions to complex. Physically, Manipura governs digestion, mentally it governs personal power, emotionally it governs expansiveness, and spiritually, all matters of growth.
Swadhisthana, Svadisthana or adhishthana is located in the sacram (hence the name) and is considered to correspond to the testes or the ovaries that produce the varioussex hormones involved in the repoductive cycle. Svadisthana is also considered to be related to, more generally, the genitourinary system and the adrenals. The Sacral Chakra is symbolized by a lotus with six petals, and corresponds to the colour orange. The key issues involving Svadisthana are relationships, violence, addictions, basic emotional needs, and pleasure. Physically, Svadisthana governs reproduction, mentally it governs creativity, emotionally it governs joy, and spiritually it governs enthusiasm.
Muladhara or root chakra is related to instinct, security, survival and also to basic human potentiality. This centre is located in the region between the genitals and the anus. Although no endocrine organ is placed here, it is said to relate to the gonads and the adrenal medulla, responsible for the fight and flight response when survival is under threat. There is a muscle located in this region that controls ejaculation in the sexual act of the human male. A parallel is charted between the sperm cell and the ovum where the genetic code lies coiled and the kundalini. Muladhara is symbolized by a lotus with four petals and the colour red. Key issues involve sexuality, lust and obsession. Physically, Muladhara governs sexuality, mentally it governs stability, emotionally it governs sensuality, and spiritually it governs a sense of security.