Human Digestive System

1. Food and Its Functions

Food provides nutrients for body growth and regeneration. Food Also helps your body fluids stay in balance. The main fuction of food is to provide energy to conduct activities, such as walking, exercising, reading, and even sleeping.

The nutrients you consume will be broken down into subtances which later can be absorbed by the boyd. There are six major classes of nutrients that are needed. Those nutrients are carbohydrates, fat, protein, vitamins, minerals, and water. Lacking one of those nutrients will cause defiency.

1. Carbohydrates

Are a source of energy. Excess carbohydrate will be stored im the liver and muscle. Source for carbohydrates, for example, rice, corn, sweet potatoes, potatoes and cassavas. One gram of carbohydrate provides 4 calories of energy or 17 kJ(kilojoules).

In the digestion procces, carbohydrates are broken down into simple saccarhides or monosacarhides, such as, glucose, fructose, and galactose. If we consume more carbohydrates more than our body needs, the excess will be converted to glycogen or fat. Lack of carbohydrates will cause the body to be thin and weak. If this condition continues, it will cause a lack of energy, anxiety, and reduced body immunity.

1. Protein

The main fuction of protein is for the formation of body ‘s structures, cell regeneration, and coordination of biological processes in the body. One gram of protein provides 17 kJ of energy. Protein are acquired from both plants and animals. Protein that are acquired from animals are called animal proteins; meat, fish, eggs and cheese. Protein that are acquired  from plant usually from cereal, are called vegetable proteins; soybeans, peanuts, and green beans.

In the digestive systems, proteins are broken down into pepton with the help of the pepsin enzyme in the stomach, and the trypsin enzyme in the intestine . In the intestine, pepton will be broken down into amino acids with the help of the erepsin enzyme. Th the body will then absorbs these amino acids. Lack of protein can cause kwashiorkor disease in children and hunger edema in adults.

1. Fat

Functions: as a source of energy. One gram of fat provides 9 kilocalories or about 38 kJ. Fat is acquired from both plats and animals.

• Animal fat:  meat, butter, milk, eggs, and cod fish oils.
• Vegetable fat: coconuts, candlenuts, peanuts and avocado

In the digestion process,fat is broken down into fatty acids and glycerol with the help of enzymes.

Other functions:

1. As a food store, and it is stored under the skin
2. Protects vital organs, exmaples, eyes kidneys and heart.
3. Fat is stored under  the skin, as an insulator and prevents the loss pf body heat.
4. Help to dissolve vitamins A,D, E and K so that they can be easily absorbed.

1. Vitamin 

Vitamins are needed only in a small amounts, but lack of one of the vitamins can cause avitaminosis. In the human body, vitamins act as coenzymes (biocatalysts), substances that help accelerate chemical reactions in the body.

Vitamins are classified into fat-soluble and water-sluble (based on solubilty):

1. Fat-soluble vitamins: vitamins A, D, E, and K.
2. Water-soluble vitamins: B and C. These vitamins cannot be stored in the body, which means that the body will only use as much as it needs and excretes the rest.

• Vitamin A

Found naturaly in liver, cod fish, oil, animal fat, and yellow colored vegetables carrot and tomatoes. Yellow-colored vitamin contain carotene. Vitamin A is needed to strengthen the body immunity against aliments,and to keep the eyesand ephitelium in good condition. Vitamin A deficiency can cause  dry skin, night-blindness, etc.

• Vitamin B

• B1, B2, B6, B12.

• Vitamin B1 can be found in the outer layers of rice grains, green beans, vegetables, liver, milk, and meat

• Helps the body oxidize the food to acquire energy. Vitamin B1 deficiency can cause beriberi and neurodegeneration.

• Vitamin B2 is very important in cellular respiration, keeping the corneas and nervous system in good condition, and improving the transfer of stimulus (light) to the eyes nerves.

• Deficiency of Vitamin B2 may cause cataracts, keratomalacia,etc.
• Sources of Vitamin B2 are liver, eggs, milk, and yeast.

• Vitamin B6 is found in eggs, meat, potatoes,and cabbage. It helps the body ro process proteins and is important in celullar respiration.

• Deficiency of Vitamin B6 may cause anemia and pellagra.

• Vitamin B12 helps blood cell regeneration and is found in meat, milk, and yeast.

• Deficiency will cause pernicious anaemia.

• Vitamin C

Is important in the synthesis of collagen, the maintenence of epithelium, preventing nose and esophagus infections and accelerating the development of hemoglobin.

• Deficiency can cause bleeding due to fril blood vessels. Can also cause scuvy, which leads to spongy gums, loss of teeth and slow wound healing.
• Vitamin C is found in fresh vegetables and fruits; limes, papayas, tomatoes, and bananas.

• Vitamin D

Skin contains provitamin D, which will be synthesized into Vitamin D when the skin is exposed to sunlight (ultraviolet).

• Lack of vitamin can disrupt the bone development in children. A childhood disease characterized by impeded growth and deformity of leg bones is called rickets.
• Sources: butter, milk, egg, cod fish oil.

• Vitamin E

Plays an important role in the reproductive system.

• Deficiency can cause infertility
• Found in cereal, vegetables, eggs, butter, and milk.

• Vitamin K

Is vital for blood clotting .e. the forming of prothrombin in the liver.

• Deficiency cause the inability of blood to clot.
• Sources: vegetables, cereals, and liver.

1. Dietary Minerals

Needed only in small amounts. Each minerals has certain fuctions in the body.

• Calcium (Ca)

Forming bones and teeth

• Iron (Fe)

Forms hemoglobin component of red blood vessels to circulate oxygen troughout the body.

• Iodine (I)

Required in forming the thuroxine hormone produced in throid glands.

• Phosporus (P)

With calcium needed for bone development.

• Potassium (K)

Affects heart contraction and helps to contain waters in cells

• Sodium(Na)
• Affect the function of the heart and muscles, helps in sending neural impulses, and together with chloride, keeps the body fluids in balance.
• Fluorine (F)

Acquired from seafood, tea, plain, etc. helps the formation pf enamel.

• Chlorine(Cl)

Found in table salt (NaCl). It helps to manage body fluid and cellular osmosis.

1. Water 

The main component of protoplasm. The human body contains 60% water. In the body, water has the role of:

• Dissolving nutrients and accelerating chemical reactions
• Carrying metabolic waste.
• Carrying other bodily substances.
• Forming body fluids.
• Regulating body heat.

Acquired from drinking water/fruits, vegetables,etc. Lack of water consumption may result in dehydration.

1. Digestive Systems

1. Mouth

The teeth, tongue,cand salivary glands exist in the oral cavity. Teeth tear, scrape, and chew food so that it is easy to swallow. Tis process called mechanical digestion.

1. Classification of teeth

1. Incisors Scrape the food
2. Canines tear the food.
3. Premolars and molars chew food

1. Parts of the tooth

1. Crownthe part above the gum
2. Neck of the root inside the gum
3. Rootplanted  to the jawbone and covered by cementum

1. Esophagus

Food from the mouth will enter the esophagus through the pharynx. Pharyx is the intersection between esophagus and trachea. The Esophaus is a narrow muscular tube about 25 cm long. The wall of the esophagus containd glands that that secrete mucin to wet the esophagus. The wall is composed of longitudinal muscles that can contract in sequence to squeeze and push the food into the stomach. This muscles called peristaltic contraction.

1. Stomach

Located in the upper left part of abdomen. Divided into three parts: cardia, fundus, and pylorus. The stomach secretes gastric acids and enzymes (pepsin and rennin)

1. Pepsin: breaks down protein into peptone
2. Rennin emulsifies protein in milk
3. Gastric acids provides an optimum pH for the reaction of the enzyme pepsin and kills many microorganisms in the food.

From stomach, food passes to the small instestine.

1. Small Intestine

Small Intestine is the longest part of the digestive tract, about 5 meter long, and posesses many blood and lympathic vessels.

The small instestine divided into # parts: duodenum, jejunum, and ileum.

Duodenum ducts from the pancreas and gallbladder enter the duodenum. Food is broken down and chemically converted by enzymes produced in pancreas:

1. Trypsin breaks down protein into amino acids
2. Amylase breaks down carbohydrates into monosacharides
3. Lipase breaks down fat into fatty acid and glycerol.

The duodenum is also received bile produced in the gallbladder.

Jejunum from the duodenum. Food is brought into the jejunum. In this section, food is being prosessed for the last time before it is finally absorbed.

1. Carbohydrates are broken down into dissacharides and monosacharides
2. Protein into amino acids
3. Fat into fatty acids and glycerol.

Vitamins and mineral are not processesd. Instead, they are directly absorbed.

Ileumthe last section in small intestineand this is where the food absorption occurs. The interior wall of small intestine is arranged in concentric folds called villi.

• Villi, greatly increases the surface area for food absorption. Inside the villi is blood vessels and lymph vessels. Blood capillaries absorb  and transport nutrients throughout the body. Lymph vessels transport fatty acids and glycerol into the portal vein under the pelvis.

1. Large intestine

Function to control the amount of water in the waste materials that will be remove through the anus.

• If the amount of the water is too high, the large intestine will absorb it. If the amount of water is too low, the large intestine will add water to the waste materials. Inside the large intestine are coliform bacteria: Escherichia coli help decompose waste. The waste, along with gasses is called feces. Fecal materials is stored in the large intestine for about 12-14 hours before finally being removed through the anus.

1. Disorders in the Digestive system

May occur if there are infection caused by microorganisms. Microorganisms can enter the digestive systems by:

1. Through raw food, example, Salmonella and Clotridium botulinum. Salmonella can be found in chicken, eggs and meat, but can be killed by heating them at the high temperature. But, Clotridium botulinum cannot be destroyed even at a high temperature.
2. Through contaminated food, examples, Staphylococus and Entamoeba
3. Through dirty surface of eating utensils and dirty hands.

Will cause dissorders such as:

1. Poisoning caused by Salmonella infections known as salmonellis. The symptoms are diarrhoe, headache, vomiting, and fever within 12-36 hours after the consumption of contaminated food.
2. Poisoning caused by the toxin produced by Staphylococcus. The sympton are nausea, vomiting, and diarrhea within 3 hours after the consumption of the contaminated food.
3. Poisoning caused by the toxin produced by Clostridium Botulinum found in canned food. The symptons are weakness, headache, and constipation within 24-36 hours after the consumption of the contaminated food. The symptoms are central nervous system disorder, hoarse voice, trouble eyesight, paralysed throat muscles, and the inability to speak.
4. Amoebic dysentery or intestinal amebiasis is an infection caused by the protozoan Entamoeba Hystolytica. The symptoms are nausea, abdominal pain, uncontrollable intestinal muscle contraction, and irregular episodes of diarrhea. Chronic illness is marked by blood in fecal matter, high fever, and fast pulse.

In addition to the diseases caused by microorganisms, there are also other disorders and diseases such as:

1. Appendictis (inflammation of Appendix). May cause inflammation of the diaphragm membrane
2. Constipation(the delayed passage of waste).will cause irregular defecation and headache
3. Paroritis or mumps, is a feverish cold, soon followed by swelling and stiffening in the region of the parotid salivary glands in front of the ear. Medication  vitamin C supplement and consult a doctor.
4. Xerostamia is a disease thet infects the oral cavity.