Do you know how do we get energy from our food? In this lesson we will learn about what is nutrition, ingestion and how does the food moves through the human digestive system till the oesophagus.
What is nutrition?
Nutrition is the process by which organisms obtain food and get energy for growth, repair and maintenance of the body.
In a human body, nutrition consists of the following processes:
Ingestion
Digestion
Absorption
Assimilation
Ingestion:
Ingestion or feeding is the intake of food from the mouth into the body.
Now, how does the food moves through the digestive system?
The Human Digestive System:
The human digestive system consist of the gut or the alimentary canal and the organs associated with it. The gut is nine meters long tube, that extends from the mouth to the anus, which much of it's length coiled in the the abdomen or abdominal cavity.
Mouth and the Buccal Cavity:
Food enters our body through the mouth which leads to the buccal cavity. In the mouth there are:
Teeth: the role of teeth in digestion is already discussed. Click here.
Salivary Glands: these secrete saliva into the mouth. Saliva flows into the buccal cavity via the salivary duct.
Tongue: it helps to mix the food with the saliva and rolls down the food into the oesophagus through the pharynx.
The Pharynx:
The pharynx is the part of the gut which connects the buccal cavity to the oesophagus and the larynx (voice-box). Both food and air first pass through the pharynx and then the food goes into the oesophagus and air passes into the trachea.
The epiglottis is a flap like structure just above the larynx which prevents food from going into the trachea. During swallowing, the larynx moves upwards and epiglottis moves downwards, hence covering the trachea (windpipe).
The Oesophagus:
The oesophagus is a narrow and muscular tube, it passes through the thorax (chest) and the diaphragm to join the stomach. The wall of the oesophagus contains two layers of muscles. These muscles are present along the whole gut from the oesophagus to the rectum. The two layers of muscles are:
Longitudinal Muscles: These are on the outer side of the muscles.
Circular Muscles: These are on the inner side of the muscles.
Both muscles are antagonist muscles, that is when one muscle contracts the other relaxes. These contractions move the food along the gut via peristalsis.
Peristalsis are the rhythmic, wave-like muscular contractions in the wall of the alimentary canal.
Peristalsis allows the food to be mixed with the digestive juices and to move along the gut. When the circular muscles constricts and the longitudinal muscles relaxes, the wall of the gut becomes narrower and longer (constricts). This pushes the food forward. When the longitudinal muscles constricts, the wall of the gut becomes wider and shorter (dilates).
The rest organs will be discussed in the next lesson.
*All pictures are taken from google*
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