it is voluntary and involuntary too and it is same process as urination,when the waste nitrogenous material enters the rectum due the filling of rectum an impulse is created which travels to brain to hypothalamus and we get the urge to defecation

Egestion is an involuntary process.

Egestion, also known as elimination, is the process by which undigested waste materials are removed from the body. It involves the elimination of indigestible substances, such as fiber, through the rectum and anus. Egestion is an essential part of the digestive system, as it ensures the removal of waste products that cannot be utilized by the body.

1. Involuntary Nature of Egestion:
Egestion is primarily an involuntary process, meaning that it occurs without conscious control. The muscles involved in egestion, such as the smooth muscles of the intestines and the sphincter muscles of the rectum and anus, are controlled by the autonomic nervous system. This means that egestion is regulated by the body's internal mechanisms and does not require conscious effort or decision-making.

2. The Role of the Autonomic Nervous System:
The autonomic nervous system is responsible for controlling various bodily functions, including digestion and elimination. It consists of two main divisions: the sympathetic nervous system and the parasympathetic nervous system. The parasympathetic division is primarily responsible for regulating digestion and the elimination process.

3. The Process of Egestion:
During digestion, food is broken down and nutrients are absorbed by the body. However, some components of the food, such as dietary fiber, cannot be digested by the enzymes in our digestive system. These undigested materials pass through the small intestine and enter the large intestine, where water absorption takes place. As the waste materials move through the large intestine, they gradually solidify into feces.

4. Defecation Reflex:
Once the feces reach the rectum, stretch receptors in the walls of the rectum send signals to the spinal cord, triggering the defecation reflex. This reflex causes the smooth muscles of the rectum and anus to contract, while the sphincter muscles relax. The coordinated muscle contractions propel the feces out of the body through the anus, resulting in egestion.

Conclusion:
In conclusion, egestion is an involuntary process that involves the elimination of undigested waste materials from the body. It is regulated by the autonomic nervous system and occurs through the defecation reflex. The involuntary nature of egestion ensures that waste products are efficiently removed from the body without requiring conscious control.