14. (a) (i) What is meant by the term digestion? (ii) Why is digestion necessary in humans? (iii) What name is given to the removal of undigested wastes from the human body? (b) The diagram shows a longitudinal section (L.S.) of a villus from the human digestive system - Leaving Cert Biology - Question 14 - 2021

Digestion is necessary in humans to convert food into nutrients that can be absorbed and utilized by the body for energy, growth, and repair. It ensures that essential vitamins, minerals, proteins, carbohydrates, and fats are available for physiological functions.

The process of removing undigested wastes from the human body is referred to as 'Egestion'.

Villi are most abundant in the small intestine, particularly in the ileum or jejunum.

The main function of villi is to increase the surface area for the absorption of nutrients in the human digestive system.

The part labelled X is the 'Lacteal', and its role is to absorb digested fats (such as fatty acids) from the intestine.

The blood vessel that carries digested nutrients away from the digestive system is the 'Hepatic portal vein'.

Digested nutrients are first transported to the 'Liver' in the body.

One function of the liver, other than the storage of nutrients, is the detoxification of harmful substances or the breakdown of old red blood cells.

The process of moving food along the digestive system is called 'Peristalsis'. This involves rhythmic contractions of smooth muscles in the digestive tract that propel food along the esophagus, stomach, and intestines.