Human Digestion, Circulation, and Nutrition
Diet and Nutrition
Diet varies according to individuals, regions, days, and seasons of the year. A balanced diet allows the individual, according to their age and situation, to maintain good health. To create a balanced diet, we must take into account:
- A diet needs to provide the necessary calories and essential nutrients.
- Calories should come from carbohydrates, fats, and proteins.
- Animal proteins should not exceed 40% of the total protein intake.
- Intake of vegetable fats and bluefish should be more significant than cholesterol and animal fats.
- The amount of plant fiber must be sufficient to facilitate intestinal movement.
The Digestive System
The main layers that make up the digestive system are:
- Inner mucosa: Secretes digestive juices and mucus that protects the surface.
- Muscle layer: It has involuntary twitch fibers arranged in a circular and longitudinal direction, producing peristaltic movements.
Numerous nerves are interspersed between these layers.
Digestive Process
During digestion, there are two types of processes:
- Mechanical or physical: During which the molecules do not transform.
- Chemical: Enzymes are produced by the digestive juices, which break down molecules into simpler ones.
Absorption of Nutrients
Enzymes containing the digestive juices convert food into a solution of simple molecules.
Blood Composition
Blood is a red liquid that circulates through the blood vessels. It is formed by plasma and blood cells. Blood cells are formed in the bone marrow and include:
- Red blood cells (erythrocytes): Contain hemoglobin.
- White blood cells (leukocytes): Defend us from microbes and infectious agents. The most important are neutrophils, monocytes, and lymphocytes.
- Platelets (thrombocytes): Fragments of cytoplasm that intervene in the coagulation or solidification of blood.
Blood Vessels
Blood vessels form a network of channels that distributes blood throughout the body. There are three types:
- Arteries: Carry blood from the heart to all organs.
- Veins: Carry blood from the organs to the heart.
- Capillaries: Facilitate the exchange of substances between blood and cells.
The Heart
The heart is an organ located in the thoracic cavity, wrapped by a membrane called the pericardium. Its walls are formed by the heart muscle or myocardium. It is divided into two halves. Each half has two chambers: an atrium and a ventricle. The mitral and tricuspid valves allow the passage of blood from the atria to the ventricles and prevent backflow.
Blood Circulation
There are two main circulatory pathways:
Pulmonary Circulation
Takes place between the heart and lungs. It begins with the contraction of the right ventricle, which sends deoxygenated blood through the pulmonary artery. The artery divides into two branches, which penetrate the lungs and branch to form capillaries, through which gas exchange occurs. Oxygenated blood returns through the pulmonary veins to the left atrium, which is relaxed.
Systemic Circulation
Takes place between the heart and the rest of the body. It begins with the contraction of the left ventricle, which sends oxygenated blood through the aorta artery. The blood is distributed through the arteries and arterioles to the various organs, where exchange occurs in the capillaries.