The structure of the human digestive system & ingestion

Question 1

what are the three primary functions of ingested food

Answer 1

• Provision of energywhich is particularly important is the role of fats and carbohydrates.
• Growth and repairof damaged tissues, mainly done by proteins.
• Regulation of body processessuch as cellular respiration and excretion, require the ingestion of vitamins, mineral salts and water.

Question 2

what is found in the human digestive system

Answer 2

The digestive system consists of a long muscular tube, almost 9 meters long, and several accessory organs including the salivary glands, pancreas, liver and gall bladder.It is responsible for foodingestionanddigestion,absorptionandassimilationof digested products, and theeliminationof undigested waste materials.

Question 3

what is found in the The Alimentary Canal

Answer 3

Thealimentary canalconsists of the

• mouth
• pharynx
• oesophagus (say: ‘a-soff-a-guss’)
• stomach
• small intestine (duodenum, jejunum, ileum)
• large intestine (caecum, colon, rectum)
• anus.

Question 4

what is found in the Accessory Organs

Answer 4

Theaccessory Organsinclude

• salivary glands
• liver
• gallbladder
• pancreas.

Question 5

what are the 5 nutritional processes

Answer 5

The five nutritional processes include:ingestion,digestion,absorption,assimilation, andegestion.

Question 6

what is the process of Ingesting in food

Answer 6

Ingestionoccurs whenfood enters the mouth (ingestion)and digestion begins with the teeth mechanically breaking down the food into smaller pieces.

Chewing, scientifically known asmastication,has 2 important functions.

1. it makes the food easier to swallow.
2. it increases the surface area of the food for enzymes to work on.

Thismechanical digestionis aided by the 32 teeth that an adult human has, which are all perfectly adapted to perform their specific function.

In the mouth,chemical digestionalso begins. Thesalivary glandssecrete saliva which mixes with the chewed food. Saliva contains the enzymeamylasewhich is acarbohydraseand breaks down starch into sugar. Saliva also containsmucuswhich lubricates the food and helps it pass down the next section of the alimentary canal, the oesophagus, through the process of swallowing.

Swallowing food without saliva would feel a little like trying to eat porridge without adding any liquid to it.

Swallowing is a reflex reaction and happens without us thinking about it. Before swallowing the tongue makes afood bolus,a soft ball-like mass of food, and pushes it to the back of the mouth. As food is swallowed it passes over theepiglottiswhich covers the opening of the respiratory system and prevents food entering it. When one thinks about how many times a day we swallow, it is remarkable to think about how perfectly designed the body is, ensuring that we never ever have food or liquids ending up in our lungs and that the process of peristalsis gets food to our stomach.

Next, the food bolus enters thestomach.People often think that nutrients are absorbed in the stomach. The stomach is in fact one large muscle playing a crucial part in themechanical and chemical digestive process.

The stomach cells secretegastric juiceswhich mix with the food and continue with the chemical digestion process. These gastric juices contain aproteaseenzymecalledpepsin,which breaks downproteins into amino acids

The gastric juices secreted in the stomach also containhydrochloric acidwhich creates the optimalacidicenvironment for pepsin.

While optimal for pepsin, the acidic environment is verysuboptimal forpathogensand, as a result, the low pH level of approximately 2 kills off unwanted bacteria and viruses preventing them from moving further along the alimentary canal.

As part of the mechanical digestion process, the muscular walls of the stomach churn the food with all the digestive juices, converting it into a thick liquid calledchyme.

Chyme enters into the 6 meter longsmall intestine, via thepyloric sphincter.

The small intestine is divided into 3 sections – theduodenum, jejunumandileum.