Tridosha

vāyu: pittaṃ kaphaśceti trayo doṣā: samāsata: ||
vikṛtā’vikṛtā dehaṃ ghnanti te varttayanti ca |
Vayu – Vata, Pitta and kapha are the three Doshas of the body. Perfect balance of three Doshas leads to health, imbalance in Tridosha leads to diseases.
How Thridosha are spread in body and in a day?

te vyāpino’pi hṛnnābhyoradhomadhyordhva saṃśrayā: ||
vayo’horātribhuktānāṃ te’ntamadhyādigā: kramāt |

The Tridosha are present all over the body, but their presence is especially seen in particular parts. If you divide the body into three parts, the top part upto chest is dominated by Kapha
Dosha, between chest and umbilicus is dominated by Pitta, below umbilicus part is dominated by vata.
Similarly, in a person’s life, day and in night (separately), the first part is dominated by Kapha,
second part is dominated by Pitta and third part is dominated by Vata. While eating and during
digestion, the first, second and third part are dominated by Kapha, Pitta and Vata respectively.

Types of digestive tracts / nature of bowels

koṣṭha: krūro mṛdurmadhyo madhya: syāttai: samairapi |

There are three types of digestive tracts (Koshta):
1. Kroora Koshta – wherein the person will take long time for digestion. The bowel 
evacuation will be irregular. It is influenced by Vata.
2. Mrudu Koshta – Sensitive stomach, has a very short digestion period. Even
administration of milk will cause bowel evacuation.
3. Madhya Koshta – Proper digestive tract, bowel evacuation at appropriate times. It is influenced by Tridosha balance.