General Functions of Balanced Dosha:

सर्वशरीरचरास्तु वातपित्तश्लेष्माणः सर्वस्मिञ्छरीरे कुपिताकुपिताः शुभाशुभानि कुर्वन्ति- प्रकृतिभूताः शुभान्युपचयबलवर्णप्रसादादीनि, अशुभानि पुनर्विकृतिमापन्ना विकारसञ्ज्ञकानि||९||
uraḥ śiro grīvā parvāṇyāmāśayo medaśca śleṣmasthānāni, tatrāpyuro viśeṣesarvaśarīracarāstu vātaPittaśleṣmāṇaḥ sarvasmiñcharīre kupitākupitāḥ śubhāśubhāni kurvanti- prakṛtibhūtāḥ śubhānyupacayabalavarṇaprasādādīni, aśubhāni punarvikṛtimāpannā vikārasañjñakāni||9||

The normal (physiology) Dosha, in balanced condition, result in good health, Upachaya (body nourishment)
Bal – improvement of strength and immunity
Varna Prasad – improvement of skin health and complexion and in imbalanced state, cause illness.

Characteristics of Dosha

Vata

The major function of Vata in the body is mobility. The sites of Vata are the ones with mobility as a defining factor. Excretion is one of the important functions of Vata apart from the limb movement. Also the major diseases are the ones which blocks the mobility (constipation) or excess movement (joint pain).

Physiological sites of Dosha in the body:
Place of Vata Dosha – 
बस्तिः पुरीषाधानं कटिः सक्थिनी पादावस्थीनि पक्वाशयश्च वातस्थानानि, तत्रापि पक्वाशयो विशेषेण वातस्थानं;
bastiḥ purīṣādhānaṃ kaṭiḥ sakthinī pādāvasthīni pakvāśayaśca vātasthānāni, tatrāpi pakvāśayo viśeṣeṇa vātasthānaṃ;
Basti – Urinary bladder
Pureeshaadhaana – rectum,
Sakthi – waist,
Padau – thighs, legs,
Asthi – bones and
Pakvashaya – colon are the sites of Vata
Pakvashaya (colon) is the most important site.

Pitta

The abode of Pitta is the sites of major biochemical reactions or transformations like the intestine, liver, pancreas etc. Pitta is basically related to conversions in the state or quality of matter. The sites of Pitta have a distinctive characteristic of high density of secretory glands. The secretions from these glands are sharp (acidic/basic) unlike the secretions of the Kapha, which are mainly protective in nature (mucus, ear wax etc.). These sites are also of very low mobility.

Place of Pitta Dosha –
स्वेदो रसो लसीका रुधिरमामाशयश्च पित्तस्थानानि, तत्राप्यामाशयो विशेषेण पित्तस्थानम्;
svedo raso lasīkā rudhiramāmāśayaśca Pittasthānāni, tatrāpyāmāśayo viśeṣeṇa Pittasthānam;
The important sites of location of these three Dosha are as below:
Svedo – Sweat,
Rasa – Rasa Dhatu – end product of food digestion, contains all nutrients
Lasika – Lymph,
Rudhira – blood,
Amashaya – small intestine (site of food under digestion after stomach)
Small intestine (lower part of Amashaya) is the most important site of Pitta Dosha.

Kapha

Let us consider the region around the clavicle or the neck collar as the example of Kapha region.

In this region, the only part with big movement ability is neck. This region is more about stability, protective coatings and shock absorbers, because it harbours the most important organs i.e. the brain, sense organs, spinal cord, lungs etc.. Higher amount of protective liquid resides as cerebrospinal fluid, fluids in eye balls, and nose secretions as compared to rest of the body. No high mobility like the limbs and no major chemical reactions like the stomach occur in this part. Because of such arrangements, stability is achieved, also this part remain cooler than rest of the body which enables better functioning of brain and other sense organs. Consequently the major diseases that can happen are due to blocking/ choking of Kapha channels (excess Kapha) like glaucoma, hydrocephaly, sinusitis or dryness(Kapha deficiency) like meningitis(Pitta excess),headache, dementia(Vata excess). As kapha decreases , other dosha increase , to maintain the energy balance.

Place of Kapha Dosha –
उरः शिरो ग्रीवा पर्वाण्यामाशयो मेदश्च श्लेष्मस्थानानि, तत्राप्युरो विशेषेण श्लेष्मस्थानम्||८||
uraḥ śiro grīvā parvāṇyāmāśayo medaśca śleṣmasthānāni, tatrāpyuro viśeṣeṇa śleṣmasthānam||8||
Ura – Chest,
Shira – head,
Greeva – neck,
Parva – joint,
Amashaya – stomach (upper part of Amashaya) and
Meda – Adipose tissue
Chest is the most important site of Kapha Dosha.