Mouth is an organ of digestion because it breaks down food mechanically by the action of the teeth and begins the digestion of starch through the enzyme amylase in the saliva. Uvula hanging in the back of the mouth prevents the food from entering the pharynx.

The main function of the esophagus is a tube that connects our mouth to the stomach. It is also known as the gullet. The trachea is closely by the movement upward which closes the passage with the help of epiglottis The esophagus seems to have only one important function in the bodyto carry food, liquids, and saliva from the mouth to the stomach. The stomach then acts as a container to start digestion and pump food and liquids into the intestines in a controlled process. Food can then be properly digested over time, and nutrients can be absorbed by the intestines.

Stomach: muscular j-shape sac like organ in which food is temporarily stored while further chemical and mechanical digestion takes place with lots of gastric glands in the inner lining. The stomach's main function is digestion by storing the food we eat, breaking down the food into a liquidly mixture called chyme. Mixing enzymes which is are chemicals that break down food. Slowly empties that liquidly mixture into the small intestine.

Small intestine: The small intestine is responsible for absorbing most of the nutrients found within your food. By the time ingested food reaches the small intestine, it has been mechanically broken down into a liquid. The small intestine is where most chemical digestion takes place; peptides (complex chains of protein molecules) are broken down into amino acids; lipids (fats) are broken down into fatty acids and glycerol; and carbohydrates are broken down into simple sugars like glucose.

Duodenum: U shape, shortest and widest, have circular folds that increase surface area. Also has a finger like projection called Villi. The duodenum continues the process of food breakdown. Its name stems from the Latin "duodenum digitorum", meaning twelve fingers or inches. It is roughly horse-shoe-shaped.Jejunum: similar to duodenum, 2.5m long, contains more folds and intestinal glands than duodenum to be break. Roughly 4-7 feet in length, the jejunum is where chemical breakdown of the food chyme is completed. Pancreatic enzymes, along with enzymes produced by the jejunum wall, finalize the food digestion process. The term jejunum stems from the Latin jejunus, meaning empty. Note: in some gastric bypass operations, part of the jejunum is also "bypassed" to reduce calorie intake.

Ileum: 3 m long, contains smaller and fewer villi and they absorb the remaining nutrients. Roughly 7-5 feet in length, the ileum is the final section of the small intestine, linked to the large intestine by the ileocecal valve. The main function of the ileum is to absorb nutrients. Bile is also absorbed here and returns to the liver through blood vessels in the intestinal walls.

The large intestine is the thick, lower end of the digestive system, containing the appendix, colon and rectum. Its principle function is to reabsorb water and maintains the fluid balance of the body. Certain vitamins are also taken in through the large intestinal wall.

The main function of the rectum is to act as a temporary storage site for fecal matter before it is eliminated from the body through the anal canal. As the food you eat passes through the digestive system, it is broken down and nutrients are absorbed in the stomach, small and large intestines. Fecal matter, which includes digestive juices, bacteria and fiber, continues to move into the lower portion of the large intestine -- the rectum. The rectum holds the feces until you push it out of the body, through the anal canal, by having a bowel movement.

Bile is a greenish-yellow fluid secreted by the liver that helps digest fat. It breaks the fat into fatty acids that can be utilized by the body and .It also acts as antioxidant, It removes bacteria and other toxins from liver which are transported outside the body along with the waste.Liver is the largest internal organ. In adult, it has a size of football with mass of 1.5 kg.The main functions of the liver is to process nutrients from food, make bile, remove toxins from the body and build proteins.Pancreas secretes about 1 L of pancreatic fluid into duodenum which contains numerous enzymes that chemically digest carbohydrates, lipids and proteins.

The main function of pharynx is to act as a common passage for both food and air. Thus the pharynx should channel food without choking. Pharynx plays a major role in the first phase of swallowing. As the food bolus is pushed by the tongue into the pharynx, it pushes the food down by muscular contraction down the esophagusThe function of larynx is between the glottis and the trachea air passes through. The larynx, or voice box, connects the pharynx to the trachea and consists of cartilage, ligaments, connective tissue, muscles, and the vocal cords. The cartilage provides a rigid structural framework for the larynx and trachea below, making sure that the airways is open at all time. Larynx is where sound is well produced. To make sound, the vocal cords move closer together so that the pressure from air expelled from the lungs causes cords to vibrate.

The function of trachea (or windpipe) is just a hollow tube that is anterior to your esophagus that allows air to pass from your mouth to your lungs. It functions by staying open and unobstructed with help from the epiglottis which is normally upright to allow air freely into the trachea and the "C" shaped cartilage that lines the trachea.One of the primary function of bronchi (singular bronchus) is to allow air to pass through it. As the trachea splits into two parts, the inhaled air then enters the bronchi. The bronchus enters each lung.The lungs are divided into regions called lobes. The right lung has tree lobes and the left lung has two, leaving space for in the thoracic cavity. Each lung surrounded by thin, flexible, doubled layered sac called pleural membrane. The outer layer of this membrane is attached to the inside of chest wall and in the inner layer covers the lung. The thin space between these two layers contains lubricating fluid that allows the layers to slide easily against each other during the movement of breathing. The function stores the body's oxygen supply and they are the pumps that push air around and out of the body.

The function of bronchioles are smaller airways that send the air on to the inside walls of the lungs where the alveoli allow the oxygen to be absorbed by the blood cells and oxygenate the blood for transfer throughout the body. Inside the lungs, bronchus subdivides many times to form a network of microscopic tubules called bronchiole.Alveoli (singular alveolus) grape like cluster of tiny sacs. Surrounding each alveolus is a network of the capillaries. The walls of the alveoli and the walls of capillaries are only one cell thick. It is across these very thin membranes that the respiratory and circulatory system interact, as the oxygen from the air diffuses into the blood and carbon dioxide from the blood diffuses into the lungs. Therefore the gas exchange occur.The gallbladder is a small storage organ located inferior and posterior to the liver. Though small in size, the gallbladder plays an important role in our digestion of food. The gallbladder holds bile produced in the liver until it is needed for digesting fatty foods in the duodenum of the small intestine.

The function of the veins is to carry deoxygenated blood from the tissues back to heart.Capillaries are the site where oxygen and other nutrients in the blood are actually delivered to the tissues of the body. Capillaries are so small that these substances actually pass right through them via a process known as diffusion.Aorta is an artery that carries blood directly from the heart to other arteries. The left atrium pumps blood into the left ventricle where all the blood going tissues leaves trough the largest vessel in the body.

The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the atrioventricular valveThe right atrium) is one of four chambers (two atria and two ventricles) in the human heart. It receives de-oxygenated blood from the superior and inferior vena cavae and the coronary sinus, and pumps it into the right ventricle through the tricuspid.The function of the pulmonary trunk is to transport blood to the lungs. The pulmonary trunk is sometimes referred to as the pulmonary artery or main pulmonary artery. It begins at the bottom right ventricle of the heart

Pulmonary vein blood vessels that carries blood from the lungs to the heart. It brings an oxygen rich blood flows from the lungs back to the heart through the left atrium.Pulmonary artery is a large vessels that carries blood from the heart to the lungs. The oxygen poor blood flows from the right atrium into the right ventricle then out to pulmonary trunk.

The function of Superior vena cava is collects oxygen-poor blood coming from the tissues in the head, chest and arms.

The function of Inferior vena cava is to collects oxygen-poor blood coming from the tissues elsewhere in the body.The right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary arteries.

It is the chamber that pumps blood to the rest of the body. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.

The function of caecum is one end to the large intestine with the appendix(help fighting infection)

The function of colon is the water and minerals absorbed and the intestinal bacteria help in further breakdowns and absorption of the minerals left over is called feces.

Anal canal has 1.5 m long and has a larger diameter than smaller intestine. The end of intestine contains sphincters that control the time of excretion.

Nasal passageway at the back of the nose, air is warmed, moistened and cleanse of dust and other small particles.The nasal cavity is divided into a right and left passageway. The tissue that covers the wall of your nasal cavity contains many blood vessels. Heat from the blood in the vessels helps warm the air as you breathe. Moisture is added to the air you breathe by special cells in the walls of the nasal cavity. The air is warmed and moistened before it reaches your lungs.

Glottis is an opening that can be closed by epiglottis which is normally upright allow air pass freely into trachea.Blood vessels is a system hallows tubes through which the blood moves There are different blood vessels with different functions: 1) Arteries- Carry blood away from the heart. All arteries carry oxygenated blood except for the pulmonary artery .2) Veins- Carry blood back to the blood. All veins carry deoxygenated blood except for the pulmonary vein.3) Blood Capillaries- Carry blood from an arteriole (small artery) to a venule(small vein).- In capillaries, the blood is slowed down, giving more time for the exchange of substances. They branch repeatedly and provide a large surface area for the exchange of substances between the blood and arteries.