Anatomy on Headstands

1. Headstand develops the masculine qualities of will power, sharpness of the brain and clarity of thought. Headstand tends to heat the body and stimulate the nervous system and tones the neck muscles
There are four major systems in the body that the practice of sirsasana positively influences: cardiovascular, lymphatic, nervous, and endocrine.
The circulatory system is comprised of the heart, lungs and the entire system of vessels that feed oxygen and collect carbon dioxide and other waste products from the cells. Arteries fan out in an intricate tributary system from the heart, which pumps freshly oxygenated blood from the lungs outward. Veins return blood to the heart and, unlike arteries, make up a low-pressure system that depends on muscular movement or gravity to move blood along. One-way valves at regular intervals prevent backwash and keep fluids moving towards the heart in a system known as venous return. Turning yourself upside down encourages venous return.
Inversions also ensure healthier and more effective lung tissue. When standing or sitting upright, gravity pulls our fluids earthward, and blood “perfuses” or saturates the lower lungs more thoroughly. The lower lung tissue is thus more compressed than the upper lungs. As a result, the air we inhale moves naturally into the open alveoli of the upper lungs. Unless we take a good, deep breath, we do not raise the ration of air to blood in the lower lungs. When we invert, blood perfuses the well-ventilated upper lobes of the lungs, thus ensuring more efficient oxygen-to-blood exchange and healthier lung tissue.
Inverting also gives the heart a break. The heart works persistently to ensure that freshly oxygenated blood makes its way up to the brain and its sensory organs. When inverting, the pressure differential across the body is reversed, and blood floods to the brain with little work from the heart.
The lymphatic system is responsible for waste removal, fluid balance, and immune system response. Lymph vessels arise among the capillary beds of the circulatory system, but comprise a separate system that transports stray proteins, waste materials, and extra fluids, filtering the fluid back through the lymph nodes and dumping what remains into the circulatory system at the subclavian veins, under the collarbones. The lymphatic system is analogous to a sewage system, an intricate, underground network tied to every house in town which keeps the citizens healthy.
Lymph, like the blood returning to your heart via the veins, is dependent upon muscular movement and gravity to facilitate its return. Because the lymphatic system is a closed pressure system and has one-way valves that keep lymph moving towards the heart, when one turns upside down, the entire lymphatic system is stimulated, thus strengthening your immune system. Viparita karani is a good example of this, as it is a mild inversion that one can enjoy with no stress on the body.

Pressing down through the upper arms and forearms relieves pressure on the neck. Activating the entire core, the sides of the torso, and tucking the tail further aligns the joints and stabilizes the posture, enabling it to be held for a longer period of time. Glutes, quads, hamstrings, every muscle is active. Flexing the feet, spreading the toes, reaching up through the heels, pressing up at the arches of the feet, and activating the inner calves and thighs as you continue to press downward with the upper arms can give this posture more lift.