The Circulatory and Respiratory Systems: A Comprehensive Guide

The Circulatory System


The musculature of the walls of the heart relaxes, allowing blood from the arteries to flow into the ventricles.


Each heartbeat consists of several phenomena that constitute a cardiac cycle.

Atrial Systole

The atria contract and push blood into the ventricles.

Ventricular Systole

The ventricles contract, forcing blood out through the arteries and opening the pulmonary and aortic valves.

Varicose Veins

These are abnormal dilatations of veins that are visible to the naked eye. In varicose veins, blood flow back to the heart slows and becomes difficult due to low blood pressure. This creates a vicious cycle.

Heart Disease

Myocardial Infarction

This is the death of a part of the heart muscle due to lack of blood flow caused by obstruction of the arteries that supply the myocardium. The obstruction is typically caused by a blood clot or narrowing due to atheroma. The patient experiences severe pain and a squeezing sensation in the chest, pallor, sweating, and anxiety. If the affected area is large, death may occur.

Angina Pectoris

This refers to the lack of oxygen in the myocardium during exertion or exercise. It is caused by the presence of atherosclerotic plaques in the coronary arteries, which do not cause the death of myocardial cells.

Circulatory System Functions

The circulatory system is responsible for transporting and distributing nutrients and oxygen, collecting waste products, and defending the body. It regulates temperature and consists of blood, blood vessels (arteries, capillaries, and veins), and the heart.

Heart Valves

  • Tricuspid valve (right atrium to right ventricle)
  • Mitral valve (left atrium to left ventricle)

Blood Flow

  • Right atrium: Receives blood from the superior and inferior vena cava.
  • Left atrium: Receives blood from the four pulmonary veins.
  • Right ventricle: Pumps blood to the lungs through the pulmonary artery.
  • Left ventricle: Pumps blood to the rest of the body through the aorta.

The Lymphatic System

Lymph is a colorless liquid consisting of blood plasma and white blood cells. It is essentially part of the blood that escapes from the porous blood capillaries.

The Respiratory System

Gas Exchange

The exchange of gases between the atmospheric air and blood occurs in the alveoli. The total surface area of all alveoli in the lungs is enormous. The alveoli are surrounded by numerous blood capillaries that circulate blood. The wall separating the alveolar air and blood is very thin.

Pulmonary Respiration

This is the process by which the body takes in oxygen from the outside and releases carbon dioxide.

Cellular Respiration

This is a series of chemical reactions that provide the energy needed for cells. Carbon dioxide molecules are produced as waste products of these reactions.


The circulatory system delivers food molecules and oxygen to all body cells and collects carbon dioxide, water, and ammonia (or its derivatives), which are waste products of cellular respiration.

Pulmonary Circuit

Deoxygenated blood leaves the right ventricle through the pulmonary artery, which splits into two branches that go to the lungs. In the lungs, the blood is oxygenated and then travels through the pulmonary veins to the left atrium of the heart.

Systemic Circuit

Oxygenated blood is pumped from the left ventricle through the aorta, which branches out to reach every part of the body. As the blood circulates through the organs, it loses oxygen and returns to the right atrium of the heart through the vena cava.

Greater Circulation

Oxygenated blood from the lungs enters the left atrium through the pulmonary veins. It then passes through the mitral valve into the left ventricle and is pumped out through the aorta. From the aorta, the blood reaches every corner of the body through successive branches.

The Respiratory System


* nostrils are two cavities open to the outside and covered by mucosa cn nasal.Comunican pharynx through the choanae (posterior nares)
* The pharynx is a common conduit to the airway and the tube digestivo.Contiene the epiglottis, which is located above the larynx closes during swallowing entry to avoid choking.
* cn larynx communicates the impasse and has some folds (vocal cords) that vibrate and allow us to make sounds.
* tranquea is a set of elastic, reinforced by rings of cartilage.
* The bronchial tree consists of two bronchi, which enter the lungs and bronchioles branch into increasingly smaller diameter.
* lungs are located in the thoracic cavity, protected by the ribs and wrapped by two membranes, the pleura, between which there is a space separated reyeno of liquido.Estan abdomen by a domed cn muscle called the diaphragm.
the respiratory funcionam:
* The pulmonary ventilation is the circulation of air from outside the lungs and air viceversa.produce renewal of the lungs and is carried out by two movements, inhalation and exhalation, which are involuntary, although we have some control on them.
* The exchange of gases is a process that is carried out by the diffusion through thin membranes alveolos.El moisture is more concentrated oxygen in the air and tends aveolos higher CO2 concentration than the air in the alveoli , so it bulges outward ..