Anatomy of Alveoli Diagram Labeling

Alveoli

• The alveolus is the site of gas exchange, where CO2 is diffused out and O2 is diffused into the blood.
• Type I alveolar cells are simple squamous epithelial cells that form the site of gas exchange.
• Type II alveolar cells are cuboidal epithelial cells that secrete surfactant, which reduces surface tension.
• Alveolar macrophages remove dust and debris from the alveoli.
• Fibroblasts produce reticular and elastic fibers that provide structural support to the alveoli.

Pleura and Pleural Cavity

• The pleura is a double-layered membrane that surrounds the lungs and lines the thoracic cavity.
• The visceral pleura is the inner layer that adheres to the lungs, while the parietal pleura is the outer layer that lines the thoracic cavity.
• The pleural cavity is the space between the visceral and parietal pleura, which contains a small amount of fluid that reduces friction between the two layers.

Gross Anatomy of the Lungs

• The lungs are cone-shaped organs located in the thoracic cavity.
• The apex is the top of the lung, while the base is the bottom.
• The superior, middle, and inferior lobes are separated by the oblique and horizontal fissures.
• The cardiac notch is a indentation on the surface of the left lung that accommodates the heart.

Lung Blood Supply

• The lungs receive blood from two sets of arteries: pulmonary arteries and bronchial arteries.
• Pulmonary arteries carry deoxygenated blood from the right heart to the lungs for oxygenation.
• Bronchial arteries branch from the aorta and deliver oxygenated blood to the lungs, primarily perfusing the muscular walls of the bronchi and bronchioles.

Respiration

• Pulmonary ventilation is the movement of air between the atmosphere and the alveoli, consisting of inhalation and exhalation.
• External respiration is the exchange of gases between the alveoli and the pulmonary capillaries.
• Internal respiration is the exchange of gases between the systemic capillaries and the tissues.

Ventilation-Perfusion Coupling

• Blood flow to each area of the lungs matches the extent of airflow to the alveoli in that area.
• In response to hypoxia, vasoconstriction diverts pulmonary blood from poorly ventilated areas to well-ventilated regions.

Volume-Pressure Relationship

• The pressure of a gas in a closed container is inversely proportional to the volume of the container (Boyle's Law).

CO2 Transport

• CO2 is transported in the blood in three forms: dissolved in the plasma, converted into carbonic acid, and attached to hemoglobin (Hb).

O2 Transport

• O2 is transported in the blood attached to hemoglobin (Hb) and dissolved in the plasma.
• The most important factor that determines how much O2 binds to hemoglobin is the partial pressure of oxygen (PO2).

Control of Respiration

• The medulla oblongata, carotid body, and aortic bodies are responsible for controlling respiration.
• The respiratory center in the brain stem responds to changes in PO2 and PCO2 to maintain homeostasis.

Trachea and Bronchial Tree

• The trachea is a semi-rigid pipe made of cartilaginous rings that divides into the right and left primary bronchi.
• The bronchial tree is composed of 4 layers: mucous-secreting epithelium, submucosa, hyaline cartilage, and adventitia.

Pulmonary Lobule

• The pulmonary lobule is a functional unit of the lung that contains a lymphatic vessel, arteriole, venule, and terminal bronchiole.
• Respiratory bronchioles give way to alveolar ducts, which are lined with simple squamous epithelium.

Respiratory System

• The respiratory system is divided into upper and lower respiratory tracts.
• The respiratory system has two functional zones: the conducting zone, which brings air to the site of external respiration, and the respiratory zone, which is the site of gas exchange.