On the navel circle (comes) the knowledge of the constitution of the body.

Verse 3.30

नाणबचिे कामव्यहऻानभ ू ॥३० ् ॥

nabhichakre kayavyoohajnanam

On the navel circle (comes) the knowledge of the constitution of the body.

Verse 3.31

कण्ठकूऩ ऺे णत्पऩासाणनव ु णत्त् ॥३१ ृ ॥

kanthakoope kshutpipasanivrittih

On the hollow of the throat (comes) cessation of hunger.

By samyama on the navel area or nabhi cakra, also called manipuraka chakra, a yogi can gain perfect knowledge of the constitution of the human body.

He knows the activities of his each and every cell and therefore becomes a master of his own body.

According to yoga texts, the navel is known as kandasthana (kanda = egg or bulb; sthana = region). 

The root of all the nerves is in the navel. From the navel, 72,000 root nerves (in hath a yoga terminology, nadis) branch out.

Each root nerve is connected with another 72,000 nerves.

These 72,000 multiplied by another 72,000 branch off into various directions, supplying energy to the entire system.

By samyama on the pit of the throat, the yogi overcomes hunger and thirst.

By samyama on the pit of the throat (khechari mudra) , a yogi can arrest pangs of hunger and thirst and conquer them.

Kantha kapa stands for the vishuddhi chakra of later yoga texts, which is said to be situated in the region of the pit of the throat.

 PATANJALI YOGA SUTRAS