Human Digestive System: Functions, Anatomy, and Diseases
Digestive System Physiology
Gastrointestinal Tract Function
The gastrointestinal tract, a 10-12 meter tube with associated glands, digests food, transforming complex molecules into simple, usable substances for the body.
The Digestive Process
Digestion starts in the mouth where food mixes with saliva, is crushed by chewing, and formed into a bolus for swallowing.
Stomach Functions
The stomach, a muscular bag, secretes gastric juice, mixing food into chyme. This semi-fluid mass then passes to the duodenum. The stomach also acts as a temporary reservoir and has some antibacterial action.
Importance of the Stomach
The stomach is essential, though its removal causes digestive issues, it doesn’t primarily affect overall health.
Chyme Transformation
Chyme passes the pylorus into the duodenum, where secretions from the pancreas, small intestine, and liver further digest and absorb it.
Small Intestine
Chyme progresses through the 5-meter-long small intestine. In the duodenum, it receives intestinal, bile, and pancreatic juices containing enzymes to break down food.
Large Intestine
The large intestine, just over five feet long, follows. The ileocecal valve controls the flow from the small intestine and prevents reflux.
Large Intestine Function
The large intestine’s main functions are feces formation, transport, and disposal. It also absorbs water, especially in the cecum and ascending colon.
Feces Formation
Fecal matter remains in the colon until defecation.
Structure of the Digestive Tract
Muscle Layers
The digestive tract’s muscle layer may have longitudinal or both longitudinal and circular muscles.
Mucosal Structures
Mucosal crypts and villi may be present; the submucosa can have permanent or functional folds.
Wall Thickness
Wall thickness varies by location; the surface can be smooth or not.
Epithelium
The epithelium can be stratified squamous, columnar, or simple with microvilli. Mucous glands may be in the mucosa or submucosa. Villi are mucosal projections.
Anatomical Description: Esophagus
The esophagus is a muscular tube (40 cm) from the pharynx to the stomach’s cardia.
It passes through the neck, chest, and diaphragm. It’s usually a virtual cavity, opening when a bolus passes.
The 25 cm esophagus has two muscle layers for peristalsis, waves that move food to the stomach.
Anatomical Description: Stomach
The stomach stores food and its shape varies with fullness, typically J-shaped.
It includes the fundus, body, antrum, and pylorus.
The lesser curvature and greater curvature define its edges.
The cardia is the esophageal junction, and the pylorus joins the small intestine.
It’s about 25 cm long and 12 cm wide.
It transforms the bolus chemically with digestive juices.
Parietal cells secrete hydrochloric acid (HCl) and intrinsic factor. Chief cells secrete pepsinogen, activated by HCl.
Gastric secretion is regulated by the nervous and endocrine systems (gastrin, cholecystokinin (CCK), secretin, and gastric inhibitory peptide (GIP)).
Stomach Digestion
Proteins (mainly by pepsin).
Lipids.
NO Carbohydrate digestion.
Elimination of bacteria by HCl.
Small Intestine
Starts at the duodenum and ends at the ileocecal valve (6-7 meters long).
Its diameter decreases from start to end.
The duodenum is 25-30 cm long; the rest is the jejunum and ileum.
The duodenum joins the jejunum 30 cm from the pylorus.
The jejunum-ileum has relatively fixed ends.
Its size decreases towards the large intestine; the jejunum-ileum boundary is indistinct.
Villi increase surface area for absorption. The small intestine, especially the duodenum, receives bile and pancreatic juice.
Digestion of proteins, lipids, nucleic acids, and carbohydrates occurs mainly in the duodenum.
Large Intestine
Starts at the ileocecal valve with the cecum and ends at the rectum.
It’s 120-160 cm long, narrowing to 3 cm at the rectosigmoid junction from 6-7 cm at the cecum.
The ascending colon is 15 cm, the transverse colon is 50 cm, and the descending colon is 10 cm.
Followed by the sigmoid colon, rectum, and anus.
The rectum is the terminal part.
Attached Glands: Pancreas
A mixed gland near the duodenum, secreting hormones (like insulin) and pancreatic juice for digestion.
Attached Glands: Liver
The largest internal organ (1500 grams), with four lobes.
Bile ducts excrete bile into the duodenum.
Performs vital functions: plasma protein synthesis, detoxification, vitamin and glycogen storage.
Removes harmful substances from the blood.
The hepatic duct joins the cystic duct from the gallbladder to form the common bile duct.
Liver Physiology
Bile production for digestion.
Carbohydrate metabolism:
Gluconeogenesis: glucose formation.
Glycogenolysis: glycogen breakdown.
Glycogenogenesis: glycogen synthesis.
Insulin and hormone elimination.
Lipid metabolism:
Cholesterol synthesis.
Triglyceride production.
Protein synthesis (albumin, lipoproteins).
Clotting factor synthesis.
Blood detoxification:
Neutralizes toxins, drugs, and hemoglobin.
Storage:
Glycogen (150 g).
Vitamin B12, iron, copper.
Red blood cell production in early fetus.
Gallbladder
A reservoir (50-60 cc bile) on the biliary tract.
Oval or pear-shaped (8-10 cm).
Liver Anatomical Location
Attached Glands: Spleen
Part of the circulatory system but aids digestion by filtering blood.
Size varies with blood content.
Digestive System Diseases
(including cancer), usually result from external factors such as diet and infection, which we can deduce that most of the times in which it occurs is a product anomaly of our own carelessness and poor hygiene and rigorous diet. Having these data, we can say that diseases are not random and are preventable.
Diseases of the digestive
Gastritis is characterized by inflammation of the stomach lining, caused by irritants in foods or constant stress.
Symptoms of the disease would be abdominal pain, severe pangs.
Other factors that promote gastritis are viral infections, bacterial infections, malnutrition, constant intake of drugs and alcohol.
Diseases of the digestive
Gastric ulcer and gastroduodenal: ulcers are wounds that occur in the stomach lining, and often in the duodenum, following an increase in gastric secretions stimulated by nervous tension, alcohol, stress, large meals or spicy.
Liver Disease:
Hepatitis A
Hepatitis B
Hepatitis C
Liver Cirrhosis
Autoimmune diseases: cholangitis, primary biliary cirrhosis, and so on.
congenital
hepatocarcinoma
Diseases of the digestive
Colitis: Inflammation of the intestine.
Material frequent bowel movements usually liquid. This is due to abnormally rapid passage of stool through the large intestine, without enough time to absorb the water.
The causes can be bacterial pathogens, chemicals, nerve disorders, irritation in the bowel wall caused by undigested food. Prolonged diarrhea can result in dehydration.
Diseases of the digestive
Pancreatitis:
It is a serious inflammatory disease, non-bacterial results from pancreatic autodigestion by the enzymes secreted by the body itself.
Diseases of the digestive
Cholecystitis:
Inflammation of the gallbladder wall. Should in most cases (95%) in the presence of stones inside the body, which eventually occlude the cystic duct, which empties into the common bile duct.
Diseases of the digestive
Appendicitis: Inflammation of the appendix. Its main symptoms are pain in the right side of the abdomen (below the line joining the umbilicus to the hip), accompanied by vomiting, constipation or sometimes diarrhea, sometimes diarrhea
Diseases of the digestive
Peritonitis: Inflammation of the peritoneum (lining of the abdominal cavity) by the action of pathogenic bacteria from a ruptured appendix or stomach perforation.
Diseases of the digestive
Constipation or constipated: delay defecation.
The cause of this delay may be pathological, such as tumors or inflammation of the intestinal wall.
Their most common origins, today, are stress, improper diet, and especially the lack of fiber in the diet and a sedentary lifestyle and intake of medications such as antidepressants and others.
Diseases of the digestive
Food poisoning:
Contaminated food:
Golden staphylococcus
E. Coli
Diseases of the digestive
The main cause of liver cirrhosis in alcohol.
Causes damage to liver tissue causing progressive decline in liver function.
Diseases of the digestive
Irritable bowel syndrome (spastic colon) is characterized by symptoms such as diarrhea, constipation and abdominal pain. It is associated with states of stress and anxiety.
Stomach cancer is the result of several causes, among which we can have an infection with Helicobacter pylori, but is preventable with proper food handling and all products that could be ingested.
Why is digestion important?
When we eat foods like bread, meat and vegetables, they are not in a way that the body can use for nourishment.
Food and beverages we consume must be transformed into smaller molecules of nutrients before being absorbed into the blood and carried to cells throughout the body.
Digestion is the process by which food and drink are broken down into their smallest parts so the body can use for energy and to build and nourish cells.
How food is digested?
Digestion involves the mixing of food, its passage through the digestive tract and the chemical breakdown of large molecules into smaller molecules. It begins in the mouth when you chew and eat, and ends in the small intestine.
Food Poisoning
Poisoning is caused by ingestion or inhalation of toxic substances. Accidental or deliberate poisoning due to consumption of drugs are the most common. Other pollutants are: industrial, household, gardening, drugs, carbon monoxide.
The severity of poisoning depends on the product’s toxicity, mode of introduction of the ingested dose and the age of the victim.
Is essential to detect signs of life-threatening: Check the state of consciousness, breathing and pulse.
Food Poisoning
In adults, poisonings are due to the association of several drugs.
In children the main cause is an overdose of a single product.
The drugs most frequently implicated in cases of poisoning are: benzodiazepines, analgesics, antidepressants, barbiturates, and drugs active against heart disease.
According to the drug and the dose ingested, can cause alterations of consciousness, severe cardio-respiratory problems, seizures and liver and kidney damage. You have to call the poison control center or emergency room.
Poisoning by cleaning products.
Children are often the main victims, poisonings occur when using food grade container with toxic products.
All are potentially toxic household products. In general, are irritating to the digestive tract, producing abdominal pain and sometimes diarrhea.
However, in some cases constitute a serious threat: the caustic (drain cleaners, descaling, paint removers, bleach), can cause burns of the mouth and digestive tract.
They are also dangerous industrial products for domestic use (turpentine, thinner, ammonia), which cause severe digestive disorders, cardiopulmonary and neurological.
Whatever the nature of the product and the amount ingested, call poison control center or emergency room. Should not cause vomiting never the victim or make him drink water, this would have the effect of increasing the path of swallowed product or make sparkling, with a risk of suffocation.
Poisoning gardening products. Affecting mainly children. Herbicides are the most toxic, followed by insecticides, fungicides (against fungi) and rodenticides (rodent). If swallowed, call poison control center or emergency room.
Irritable bowel syndrome (spastic colon) is characterized by symptoms such as diarrhea, constipation and abdominal pain. It is associated with states of stress and anxiety.
Stomach cancer is the result of several causes, among which we can have an infection with Helicobacter pylori, but is preventable with proper food handling and all products that could be ingested.
Why is digestion important?
When we eat foods like bread, meat and vegetables, they are not in a way that the body can use for nourishment.
Food and beverages we consume must be transformed into smaller molecules of nutrients before being absorbed into the blood and carried to cells throughout the body.
Digestion is the process by which food and drink are broken down into their smallest parts so the body can use for energy and to build and nourish cells.
How food is digested?
Digestion involves the mixing of food, its passage through the digestive tract and the chemical breakdown of large molecules into smaller molecules. It begins in the mouth when you chew and eat, and ends in the small intestine.
Food Poisoning
Poisoning is caused by ingestion or inhalation of toxic substances. Accidental or deliberate poisoning due to consumption of drugs are the most common. Other pollutants are: industrial, household, gardening, drugs, carbon monoxide.
The severity of poisoning depends on the product’s toxicity, mode of introduction of the ingested dose and the age of the victim.
Is essential to detect signs of life-threatening: Check the state of consciousness, breathing and pulse.
Food Poisoning
In adults, poisonings are due to the association of several drugs.
In children the main cause is an overdose of a single product.
The drugs most frequently implicated in cases of poisoning are: benzodiazepines, analgesics, antidepressants, barbiturates, and drugs active against heart disease.
According to the drug and the dose ingested, can cause alterations of consciousness, severe cardio-respiratory problems, seizures and liver and kidney damage. You have to call the poison control center or emergency room.
Poisoning by cleaning products.
Children are often the main victims, poisonings occur when using food grade container with toxic products.
All are potentially toxic household products. In general, are irritating to the digestive tract, producing abdominal pain and sometimes diarrhea.
However, in some cases constitute a serious threat: the caustic (drain cleaners, descaling, paint removers, bleach), can cause burns of the mouth and digestive tract.
They are also dangerous industrial products for domestic use (turpentine, thinner, ammonia), which cause severe digestive disorders, cardiopulmonary and neurological.
Whatever the nature of the product and the amount ingested, call poison control center or emergency room. Should not cause vomiting never the victim or make him drink water, this would have the effect of increasing the path of swallowed product or make sparkling, with a risk of suffocation.
Poisoning gardening products. Affecting mainly children. Herbicides are the most toxic, followed by insecticides, fungicides (against fungi) and rodenticides (rodent). If swallowed, call poison control center or emergency room.
Symptoms of poisoning:
Abdominal Pain
Bluish lips
Chest pain
Confusion
Cough
Diarrhea
Difficulty respitaroria
Dizziness
Double vision
Sleepiness
Fever
Headache
Heart palpitations
Irritability
Perity of appetite
Bladder control loss
Nausea and vomiting
Entumecimeinto or tingling
Rashes
Unconsciousness
Weakness
Bad breath, unusual.
Weakness
Symptoms of poisoning:
Abdominal Pain
Bluish lips
Chest pain
Confusion
Cough
Diarrhea
Difficulty respitaroria
Dizziness
Double vision
Sleepiness
Fever
Headache
Heart palpitations
Irritability
Perity of appetite
Bladder control loss
Nausea and vomiting
Entumecimeinto or tingling
Rashes
Unconsciousness
Weakness
Bad breath, unusual.
Weakness