1. Lungs: Mammals have two lungs, located in the thoracic cavity on either side of the heart. The lungs are highly vascularized, meaning they contain a dense network of blood vessels that facilitate the exchange of gases between the air and the bloodstream.
2. Diaphragm: The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity. It plays a crucial role in breathing by contracting and relaxing to generate changes in lung volume.
3. Airways: The airway system consists of the nasal passages, pharynx, larynx (voice box), trachea (windpipe), and bronchi, which branch into smaller bronchioles leading to the lungs. These airways act as conduits for air to flow into and out of the lungs during respiration.
4. Alveoli: The alveoli are tiny, sac-like structures within the lungs where gas exchange occurs. The walls of the alveoli are extremely thin, allowing for the efficient diffusion of oxygen from the inhaled air into the blood, while carbon dioxide is expelled from the blood back into the lungs.
5. Bronchial Tree: The trachea divides into two primary bronchi, which further branch into smaller bronchi and eventually into bronchioles. These form the bronchial tree, which ensures the distribution of air to all regions of the lungs.
6. Pleura: The lungs are encased in a double-layered serous membrane called the pleura. The pleura helps reduce friction during lung movement and creates an airtight space within the thoracic cavity, allowing the lungs to expand and contract efficiently.
7. Respiratory Muscles: In addition to the diaphragm, other muscles, including the intercostal muscles and abdominal muscles, assist in altering the volume of the thoracic cavity during inhalation and exhalation.
8. Respiratory Control: The rate and depth of breathing are regulated by the respiratory center located in the brain, specifically in the medulla oblongata and the pons. The respiratory center responds to changes in blood gas levels, particularly carbon dioxide levels, to maintain optimal gas exchange.
9. Pulmonary Circulation: Deoxygenated blood from the right ventricle of the heart is pumped into the pulmonary arteries and sent to the lungs. Within the lungs, the blood vessels in the capillary beds of the alveoli facilitate the exchange of oxygen and carbon dioxide, leading to the oxygenation of the blood.
10. Systemic Circulation: The oxygen-rich blood from the lungs is returned to the heart via the pulmonary veins and then pumped by the left ventricle to the rest of the body through the systemic circulation, supplying oxygen to various tissues and organs.
The mammalian respiratory system efficiently extracts oxygen from the inhaled air and removes carbon dioxide, a waste product of cellular metabolism, thereby maintaining proper oxygen levels in the body and supporting cellular respiration.