I. Organization of the Respiratory System The Respiratory System The respiratory system allows the circulation of air and the gas exchange between the body and the outside environment. It consists of the respiratory pathway and the two lungs. Respiratory pathway is the set of organs that carry air to the lungs: Nasal Cavity, nose, pharynx, larynx, trachea, bronchus, and bronchioles. In each lung, a bronchus penetrates and divides into smaller bronchioles. Each bronchioles ends up in a cluster alveoli (air sacs) surrounded by blood capillaries. Alveoli are characterized by extremely thin wall, huge total surface area, and rich vascularization. This increases the contact between air in lungs and blood. Hence, it favors gaseous and enrichment. That s why alveoli called the sites of gas exchange. II. Diffusion: The Permeability (easy to flow through) of the alveoli facilities gas exchange through a process called diffusion. Diffusion is the movement of particles from a medium of high concentration to a medium of low concentration, or from a medium of high pressure to a medium of low pressure. Diffusion of a gas in alveoli happens from medium of high pressure to medium of low pressure of gases. So, oxygen gas moves from alveoli to blood, while carbon dioxide gas moves from blood to the alveoli.
III. Respiratory Gas Exchange: By inhaling (taking in air) and exhaling (releasing air from body to outside): the body absorbs O 2 and release CO 2. Air entering the body (inhaled) is rich in O 2. (It has high pressure of O 2 ). Air leaving the body (exhaled) is rich in CO 2.
IV. Cellular respiration: **Cells consume O 2 and release CO 2. Cells take O 2 from blood and undergo cellular respiration, releasing CO 2. Blood entering an organ has high O 2 pressure and low CO 2 pressure, while blood leaving an organ has high CO 2 pressure and low O 2 pressure. Oxygen + Glucose Carbon dioxide +water+ energy. Carbon dioxide is considered as wastes, so cells get rid of it. While,water and energy are stored in the cells for various cellular activities. Blood entering the lungs from the body organs through capillaries is rich in CO 2 and poor in O 2. Blood leaving the lungs toward the body organs through capillaries is rich in O 2 and poor in CO 2. O 2 (inhaled) lungs cells and tissues of organs. CO 2 (from cells) lungs exhaled to the outside.
V. Blood Constituents: Through centrifugation, and after adding ammonium oxalate (anti-coagulatent), blood constituents are separated. It is composed of plasma (55%), erythrocytes (45%), and leukocytes (white blood cells) and platelets (less than 1%). Erythrocytes are red blood cells (RBC s ): - have no nuclei - disk shaped. - have hemoglobin Hemoglobin is a protein that gives blood the red colored pigmentation, and it is rich in iron. Hemoglobin is capable of binding O 2 and CO 2 in a quick and reversible manner. This makes it the pigment responsible of carrying and transporting gases in blood. ** Role of hemoglobin: Transports gases O 2 and CO 2 in the human body. VI. Transport of Respiratory Gases: O 2 and CO 2 are carried and transported by blood. A. Forms of O 2 transportation: a- Hemoglobin binds O 2 to form oxyhemoglobin (reversible reaction): Hemoglobin + Oxygen gas oxyhemoglobin (HbO 8 ). In lungs: Hemoglobin + Oxygen gas oxyhemoglobin (HbO 8 ). In cells: Oxyhemoglobin Hemoglobin + Oxygen gas. b- Small amount of oxygen gas is dissolved in plasma.
** Blood rich in Oxygen gas has a bright red color, while blood poor in oxygen gas has a dark red color. B. Forms of CO 2 transportation: a- Large amount of CO 2 is dissolved in plasma: in the form by carbonate and bicarbonate (H 2 CO 3 ). b- And a small amount binds to hemoglobin: Hemoglobin + CO 2 Carbohemoglobin In lungs: Carbohemoglobin Hemoglobin + CO 2 In cells: Hemoglobin + CO 2 Carbohemoglobin. Smoking: At the level of the pulmonary alveoli, hemoglobin (Hb) in red blood cells fixes oxygen gas (O2) forming an unstable product : oxyhemoglobin (HbO2). In the presence of carbon monoxide (CO) in the alveoli, hemoglobin fixes (CO) forming a stable product (HbCO). Hemoglobin + Carbon monoxide Carboxyhemoglobin (irreversible) CO : a harmful gas contained in the fume of tobacco. **Carbon monoxide fixed by hemoglobin reduces the transport of oxygen gas by this hemoglobin. Respiratory diseases: Asthma: A severe allergic reaction characterized by the constriction of bronchioles.
Anemia: Anemia is a disease characterized by a low red blood cells (RBC) count in the blood. Bronchitis:is marked by the excessive production of mucus in the tracheabronchial tract, it is the inflammation of the lining of the bronchioles. Emphysema: is a respiratory disease where some alveoli do not function due to the destruction of their walls (no or low diffusion of gases)..