DIGESTIVE SYSTEM

DIGESTIVE SYSTEM

Digestion

Process by which foods are transformed into simpler substances (nutrients) so they can be absorbed and used by our cells.

• Mecanical processes: responsable for shredding and reducing the size of the food. It is carried out in the mouth by chewing and in the stomach by moving its walls
• Chemical processes: performed by digestive enzymes found in digestive juices. When these enzymes mix with food, chemical reactions occur that break down the substances found in food and transform them into simpler components.

CONTINUE

Parts

Functions

– Digest the food and transform it into nutrients– Absorb the nutrients– Excrete the remains of food that we do not absorb

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The Mouth Cavity in whitch tooth and the tongue are found. It is the first part of the digestive system. Digestion begins with ingestion (putting food into the mouth). Here two types of digestion take place:–Mechanical processes: Chewing.–Chemical processes: Salivation. Inside it we can find the teeth and the tongue •Theeth are the structures responsable for grinding and crushing. They are very hard and formed by calcium and fluorine compounds. Humans have two sets of teeth:–Baby teeth or milk teeth: 20 pieces. –Permanent or adult theeth: 32 teeth, 16 on each jaw •The tongue: Organ made up of muscle tissue. Functions: – Participates in speech– Taste organ thanks to the taste buds– Mix the crushed food with the saliva to form the food bolus– Helps with swallowing

Salivary glands Saliva: watery liquid released by the salivary glands, which are located under the tongye and on the sides of the mouthFunctions:– It starts the digestion of starch molecules, which are present in many foods and transforms the into simple sugars, thanks to a digestive enzyme named amylase–Defensive function: It destroys some bacteria by using an enzyme named lysozyme.–It eases the bolus into the pharynx and oesophagus. Saliva contains mucin, a mucous substances that lubricates and mixes with food. As a result, foods go through the pharynx and oesophagus easily without causing damage.

Stomach •Muscular, hollow organ in the gastrointestinal tract.•Secretes several substances that are collectively called gastric juices, made up mainly of hydrochloric acid and pepsin, which mainly digest proteins•It is separated from the small intestine by a valve called the pylorus.The bolus enters the stomach and suffers digestion, mixing with gastric acids and transforming into chyme: –Mechanical digestion: Food is churned by the stomach through muscular contractions of the wall.–Chemical digestion: The gastric juice is a mixture of water, proteases (protein-digesting enzymes such as pepsin) and hydrocloric acid, which kills or inhibits bacteria and provides the acidic pH of 2 for the enzymes to work

Oesophagus •Muscular tube that empties into the stomach.•It is separated from the stomach by a valve called the cardia.

Gallbladder •Small pear-shaped hollow organ located under the liver where bile secreted by the liver is stored and concentrated before it is released into the small intestine•Bile: fluid that aids the digestion and absorption of lipids and fat-soluble substances in the small intestineThrough the bile, excess cholesterol and waste products of hemoglobin metabolism, such as bilirubin, are excreted, as well as some drugs.

Liver •The liver is a major organ which performs many essential biological functions:–It synthesizes plasma proteins that are involved in blood coagulation and in the transport of substances.–It produces the bile–stores glucose as glycogen–Regulates the level of fats circulating in the blood–It intervenes in the metabolism of toxic substances, transforming them so they can be eliminated (alcohol, drugs…)–Removes old erythrocytes from the bloodstream, generating substances such as bilirubin that are eliminated in the bile

Pancreas •Organ of the digestive system and endocrine system of vertebrates.• As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum, which which break down carbohydrates, proteins, and fats.• As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones like insulin and glucagon

Large intestine •End part of the digestive tract, about 1,5 m long, divided into three sections:–Cecum–Colon–Rectum• Absorption of most water and minerals takes place in the large intestine.• In the colon is where symbiotic bacteria of the intestinal flora develop. Certain vitamins, such as B12 and K, are produced here.• Faeces are compacted and stored in the rectum and are expelled to the outside through the anus by a mechanism called defecation.

Small intestine •Tube around 6-7 m long divided into three sections:–Duodenum–Jejunum–Ileum•The inner layer of the small intestine is covered in creases, known as villi, which are full of microscopic blood capillaries that collect nutrients obtanied after digestion. To increase the surface area, the plasmatic membrane that forms villi has extra creases known as microvilli.•Pancreatic juice and bile are secreted in the duodenum and mixed whith chyme forming the chyle.•Nutrient absorption takes place in the jejunum and ileum.

Pharinx • Short tube that communicates with the nostrils, the middle ear, the larynx, and the esophagus.• The epiglottis is a valve that closes when swallowing, preventing food from passing into the larynx and obstructing the airways

Anus The anus is the final opening of the digestive tract. It is a sphincter (valve) that has the function of controlling the process of expelling feces to the outside.

Mouth

Salivary glands

Liver

Gallblader

Oesophagus

Stomach

Pancreas

Small intestine

Appendix

Rectum

Anus

Large intestine