Question

Pick one of the two following prompts to address:

1. Imagine you are an oxygen molecule. What is your pathway into a human respiratory system and ultimately into the bloodstream?

2. What is the complete pathway for food through the alimentary canal beginning with the oral cavity?

Answer 1

:Digestive Process:

The digestive system plays an important role in the absorption of nutrients into the body. The food we ingest, it breaks down mechanically, chemically in mouth and stomach as well. Then it absorbs nutrients, fats, proteins and water in the intestines before eliminating the waste through the rectum.

The process of digestion involves six activities:

1. Ingestion
2. Propulsion
3. Mechanical/physical digestion
4. Chemical digestion
5. Absorption
6. and Defecation

Description:

Firstly, Ingestion refers to the entry of food into the alimentary canal through the mouth. Here, the food is chewed and mixed with saliva (which contain enzyme). chewing increases the surface area of the food and allows an fine sized bolus to be formed or produced. Secondly, Propulsion which refers to the movement of food through the digestive tract. this include both the voluntary and involuntary process of peristalsis(consists of sequential,alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food). Peristalsis is so powerful that foods and liquids we swallow enter our stomach, even if we are standing on our head. Thirdly, digestion involves both mechanical and chemical processes. Mechanical digestion includes mastication or chewing as well as tongue movement that help break food into smaller bits and mix food with saliva. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digest juices, creating an acidic "soup" called chyme. Fourthly, in chemical digestion, starting in the mouth, digestive secretions breakdown complex food molecules into their chemical building blocks (for instance, proteins into seperate amino acids). This process completed in the small intestine. Now, in absorption which takes place primarily within the small intestine. Food that has been broken down is of no value to the body unless it enters the blood stream and its nutrients are to work. Lastly, the final step in digestion is defecation, undigested material are removed from the body as feces