Nutrition in Animals
Animals also require nourishment in order to grow and provide energy to other metabolic processes of their body. Different animals eat the different type of food with a different mode of food intake. For example, honey bees suck nectar with their proboscis, snakes prey on insects and mongoose by attacking them with its poisonous venom present in the fangs, infant humans depend on their mother’s milk, birds find small worms, seeds to eat with their beaks etc. In this section, we will learn about the digestive system in humans.
The digestive system of humans:
The food that we swallow every day is passed through our digestive system. During this process, the nutrients are extracted from the food and utilized to produce and store energy. The remaining unused digested part is excreted out from our body.
Our digestive system consists of various compartments in the following order,
Alimentary canal: - i) buccal cavity, ii) food pipe or esophagus, iii) stomach, iv) small intestine, v) large intestine and vi) anus
Glands: - salivary glands, digestive juices produced by the stomach, liver, and pancreas
Mouth and buccal cavity:
The process of taking in the food is called as ingestion. The food that we take in through our mouth is first tested by the taste buds present on the tongue and then chewed with the set of teeth which includes canine, premolar, molar and incisor teeth. The food is chewed and grinded mechanically with our teeth and mixed with saliva produced by the salivary glands present in the buccal cavity. The saliva is responsible for breaking down the starch into simple sugars. The food is broken down and made into a paste-like form which passes down the food pipe or the esophagus.
The esophagus runs from neck along the chest to upper abdomen region. The esophagus is lined with muscle in its inner side which contracts and expands at regular intervals in order to push the food down to the stomach. This constant movement of the esophagus is called as peristalsis. As the food is pushed down, the opening of the stomach has a ring of muscle called sphincter. The sphincter is closed during rest but opens up as the food is being pushed down. The food now enters the stomach where it is processed further.
The stomach is thick walled, brown bag. The stomach contains various digestive enzymes to break down the complex substances present in the food into simple substances. As the food enters the stomach, the stomach produces digestive enzymes, hydrochloric acid and mucous. The mucus protects the inner lining of the stomach wall, while hydrochloric acid kills any bacteria present in the food. The food is then mixed with other digestive enzymes and churned into a mixture called as chyme by constant peristalsis. Only after the completion of digestion of food in the stomach, the stomach then opens up to the small intestine.
Thus, in this section, we learn how food is broken down from complex substances to simpler substances. In the next section, we will learn how the nutrients are extracted from the food in the small and large intestine.
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