Human Respiratory System Overview

Respiratory Tract

• The respiratory tract is responsible for gas exchange.
• It has two main functions: describing the gross and microscopic structure and explaining the link between structure and function.
• The tract includes conducting passages and gas exchange surfaces.

Human Respiratory System

• The human respiratory system includes the nasal cavity, nose, mouth, throat, epiglottis, esophagus, trachea, lungs, bronchi, bronchioles, and alveoli.
• The diagram displays the location of various parts of the system, including the right and left lungs, trachea, and diaphragm.

Pharynx

• The pharynx connects the nasal passages, mouth, and larynx to the trachea.
• It's subdivided into nasopharynx, oropharynx, and laryngopharynx, connecting to the nose, mouth, and larynx respectively.
• The nasopharynx sits above the soft palate.
• During swallowing, the soft palate separates the nasopharynx and oropharynx.

Larynx

• The larynx is connected to the trachea inferiorly and hyoid bone superiorly.
• It has protective and speech functions and involves the epiglottis, thyroid, arytenoid, and cricoid cartilages.
• The larynx opens to allow for breathing
• swallowing causes the vocal folds to close, and the epiglottis to cover the opening of the larynx.

Trachea

• The trachea is a tube extending from the larynx to the bronchi.
• Located near the level of the fourth or fifth thoracic vertebra.
• Has C-shaped rings supporting the trachea cartilage
• Completed posteriorly by the trachealis muscle.

Respiratory Tree

• The trachea divides into the right and left primary bronchi at the carina.
• The right bronchus is shorter and more vertical than the left.
• Foreign bodies often enter the right lung as a result of its structure.
• Primary bronchi divide into secondary (lobar) bronchi which further divide into tertiary (segmental) bronchi.
• Bronchioles are the final divisions of the airways branching into terminal bronchioles and these branch into respiratory bronchioles
• progressively smaller airways ending in bronchioles

Zones within Respiratory Tree

• The conducting zone involves airways proximal to respiratory bronchioles, assisting air movement.
• The respiratory zone involves airways distal to terminal bronchioles, involved in gas exchange.

Acinus

• The acinus is the part of the airway involved in gas exchange.
• It includes respiratory bronchioles leading to alveolar ducts.
• Alveolar ducts that open to two or three alveolar sacs which in turn lead to several alveoli.

Blood-air interface

• Alveoli are microscopic air sacs at the end of the respiratory tract.
• They are responsible for gas exchange between the air and the blood through a very thin membrane.
• The average surface area of the alveolar-capillary membrane is 50–100 m2, and its average thickness is 0.4 mm.

Alveolar macrophages

• Alveolar macrophages, also called dust cells, are abundant in the lungs.
• They clear up debris, including dust, mucus, and pathogens.
• They phagocytize bacteria, foreign particles, and cellular debris
• They clear out debris from the lungs and are involved in the mucociliary escalator.

Collateral Ventilation

• Interbronchiolar channels, Bronchiolar-alveolar, and alveolar pores of Kohn allow for ventilation to occur between parts of the lungs.

Bronchioles

• Bronchioles are the final divisions of the airways in the lungs, without cartilage, held open by radial traction.
• The bronchioles have smooth muscle, enabling adjustments to airway diameter.

Bronchi and Bronchiole Cross Section

• Diagram showing epithelium, lamina propria, cartilage, blood vessels, and goblet cells in both bronchi and bronchiole cross sections.

Respiratory Bronchioles

• These bronchioles are lined with ciliated cuboidal epithelium.
• Goblet cells are absent, but they have alveoli in the walls, indicating gaseous exchange occurs within their walls, meaning this is the beginning of gas exchange

Alveoli - Microscopic Structure

• Type I pneumocytes form the walls of the alveoli, forming the primary site for gas exchange in the body.
• Type II pneumocytes produce surfactant, reducing surface tension.
• Alveolar pores connect neighbouring alveoli.
• Capillaries surround the alveoli for gas exchange with the blood.

Alveoli

• Alveoli are blind-end sacs within the lungs.
• They are the primary site for gaseous exchange
• Alveolar sacs are the clusters of sacs and have a complex structure that allows for efficient oxygen and carbon dioxide exchange.
• The alveoli are lined with simple squamous epithelium and are surrounded by capillaries.

Explore the intricate structure and functions of the human respiratory system. This quiz covers the respiratory tract, including the nasal cavity, pharynx, larynx, and gas exchange mechanisms. Test your knowledge on the connection between respiratory anatomy and its vital functions.