Our shastras look at reality from multiple perspectives. This creation, especially the living system, can be looked at through the trishareeras or through the lens of the Panchakoshas or through the lens of antah karana and bahya karana.
The Panchakosha include Annamaya, Pranamaya, Manomaya, Vijnanamaya and Anandamaya. They are not typically layers but encase the atman and represent different dimensions of the system. Just as in a light bulb, the bulb is the physical dimension and the electricity is the energy dimension, similarly the panchakosha represent various dimensions. The Panchakosha are best understood in the human system as it is easy to relate through personal experience.
The Tattva bodha defines Pranayamaya Kosha as
प्राणाद्याः पञ्चवायवः वागादीन्द्रियपञ्चकं प्राणमयः कोशः ।
The panchapranas together with the five karmendriya constitute the Pranayamaya kosha.
Prana, Apana, Samana, Vyana and Udana constitute the panchaprana. Speech, grasping, locomotion, excretion and reproduction constitute the karmendriya.
The Prana vayu operates in the chest region and controls respiration. The Apana vayu functions in the lower abdominal region and takes care of excretion. The Samana vayu operates in the abdominal and stomach regions and controls digestion, the Vyana vayu is spread throughout the body and takes care of circulation and Udana vayu is upward moving, operating in the throat and head region thereby controlling speech and brain functions including memory.
The Prashna Upanishad highlights the importance of Prana and how it holds and supports the body.
तान्वरिष्ठः प्राण उवाच । मा मोहमापद्यथाऽहमेवैतत्पञ्चधात्मानं प्रविभज्यैतद्बाणमवष्टभ्य विधारयामीति तेऽश्रद्दधाना बभूवुः ॥ ३ ॥
tānvariṣṭhaḥ prāṇa uvāca | mā mohamāpadyathā’hamevaitatpañcadhātmānaṃ pravibhajyaitadbāṇamavaṣṭabhya vidhārayāmīti te’śraddadhānā babhūvuḥ || 3 ||
Prana, the greatest, said to them, ‘Do not cherish this foolish vanity. I alone, having divided myself five-fold, hold this body together and support it.’ They did not believe.
सो’भिमानादूर्ध्वमुत्क्रामत इव तस्मिन्नुत्क्रामत्यथेतरे सर्व एवोत्क्रामन्ते तस्मिँश्च प्रतिष्ठमाने सर्व एव प्रतिष्ठन्ते । तद्यथा मक्शिका मधुकरराजानमुत्क्रामन्तं सर्व एवोत्क्रमन्ते तस्मिँश्च प्रत्ष्ठमाने सर्व एव प्रतिष्टन्त एवं वाङ्मनष्चक्शुः श्रोत्रं च ते प्रीताः प्राणं स्तुन्वन्ति ॥ 4 ॥
so’bhimānādūrdhvamutkrāmata iva tasminnutkrāmatyathetare sarva evotkrāmante tasmim̐śca pratiṣṭhamāne sarva eva pratiṣṭhante | tadyathā makśikā madhukararājānamutkrāmantaṃ sarva evotkramante tasmim̐śca pratṣṭhamāne sarva eva pratiṣṭanta evaṃ vāṅmanaṣcakśuḥ śrotraṃ ca te prītāḥ prāṇaṃ stunvanti || 4 ||
He from indignation seemed to ascend from the body, and when he ascended, all the others immediately ascended too; and when he was quiet they were quiet too, just as bees fly up when their king flies up and settle down when he settles down; so, mind, speech, eye, ear and the rest being pleased, praise Prana.
The body is composed of various organs and systems that constitute the annamaya kosha and the vital forces that help these organs function is the Pranayamaya kosha, much like the electricity that helps the bulb to light up.
Just as the blood flows through arteries and veins, the Prana flows through dedicated channels called Nadis. The Hata Yoga Pradipika talks of 72,000 Nadis. The primary ones that we often hear of are Ida, Pingala and Sushumna.
The Yoga Yajnavalkya Samhita (YYS) goes into great detail describing Prana, the location of nadis and the functions they perform. The human body is of 96 angulas and Yogic achievement is looked at maintaining the Prana within oneself without dissipating. The YYS talks of 14 primary Nadis Ida, Pingala, Susuhmna, Sarasavati, Varuni, Pushpa, Hastijihva, Yashasvini, Visvodara, Kuhu and Shankini, Payasvini, Alambusha and Gandhari.
The Susuhmna Nadi is located at the center and the Ida and Pingala are located in the left and right sides respectively. The YYS further highlights the location of the pancha vayu in Chapter 4. Between the nose and mouth, center of the heart, center of the navel and in the big toe is situated the prana vayu. In the anus, thighs, knees and lower parts is located the apana vayu. In the middle of the ear and eyes and in the sides of neck, ankles, nose, throat and posterior region is located the vyana vayu. Udana is present in joints, legs and hands enabling movement. The samana pervades the body distributing the energy derived from food. Inhalation, exhalation and coughing are the functions of Prana, Excretion of faeces, urine is the function of Apana. Taking and giving are the functions of Vyana. Raising the body is the function of Udana. Providing nutrition is the function of Samana. Functions like belching, blinking etc are also controlled by various pranas. The YYS describes Nadi Shodhana practice in great detail for the proper functioning of the nadis and circulation of prana.
So we see that the Pranamaya kosha is the critical dimension of the system that provides energy for everything to function properly.