Respiratory System Overview

Respiratory System

• Respiratory system is a network of organs that supports gas exchange for breathing.
• Gas exchange occurs between lungs and atmosphere, lungs and blood, and blood and tissues.
• The system is regulated by respiratory centers.

Respiratory Tract

• Trachea is supported by C-shaped cartilage to avoid obstruction of the airway when head and neck move.

Epithelial Lining

• The nasal vestibule is lined by stratified squamous epithelium.
• The upper respiratory tract is lined by pseudostratified columnar epithelium.
• The narrower bronchioles are lined by cuboidal epithelium.
• Alveoli are composed of type I and type II alveolar cells.

Nose and Nasal Cavity

• The nasal cavity is lined with ciliated columnar epithelium to remove contaminated mucus.
• Goblet cells secrete mucus with lysozyme and defensins.
• Rhinitis is a condition with a runny nose, sneezing, and nasal stuffiness, caused by allergy or non-allergy triggers.

Sinuses

• Sinusitis is a condition caused by swollen or inflamed lining and excess mucus due to infection.

Pharynx

• Pharynx, also known as throat, is a funnel-shaped tube of skeletal muscle connecting to the nasal cavity and mouth, and larynx and esophagus.
• The pharynx is lined with ciliated pseudostratified columnar epithelium.
• The pharynx is divided into nasopharynx, oropharynx, and laryngopharynx.

Larynx

• Larynx connects to the hyoid bone and opens into laryngopharynx.
• It's a continuous structure with the trachea.
• Vocal folds vibrate to produce sound, and are longer and thicker in males during puberty.

Tonsils

• Tonsils are masses of lymphatic tissue located in the pharynx.
• They filter airborne pathogens.

Trachea

• Trachea is composed of 3 layers: inner, middle, and outer.
• The inner layer is lined with ciliated columnar epithelium and mucus-secreting goblet cells.
• The middle layer is composed of C-shaped cartilage and smooth muscle.
• The outer layer is fibrous and elastic tissue enclosing the cartilage.

Functions of the Trachea

• Cartilage supports the trachea and prevents obstruction of the airway.
• Ciliated cells push mucus upwards towards larynx where it's either swallowed or coughed up.
• Cough reflex is stimulated by irritation in the region, sending impulse to the respiratory center, causing coughing.
• Trachea warms, humidifies, and filters air.

Autonomic Innervation of the Airway Tract

• Smooth muscle in the trachea is innervated by neurons from the autonomic nervous system.
• Sympathetic nerves (fight-or-flight) stimulate B2-adrenergic receptors and dilate airways.
• Parasympathetic nerves (rest-and-digest) stimulate muscarinic receptors and decrease airway diameter.

Bronchus

• Bronchi (singular bronchus) connect to the trachea.
• Bronchi walls contain less goblet cells than trachea.
• Amount of smooth muscle increases in the bronchi.

Chronic Bronchitis

• Chronic bronchitis is caused by increased thickness of mucus gland layer of bronchus, airway inflammation, and productive cough.

Bronchioles

• Bronchioles are smaller airways branching off from the bronchi.
• They are mostly composed of smooth muscle and lack cartilage.
• Bronchioles have a diameter of 1 mm or less.
• The smooth muscle layer is sensitive to various chemical and physical stimuli.

This quiz covers the various aspects of the respiratory system, including gas exchange, respiratory tract structures, and the epithelial lining of the airways. Learn about the functions of the nasal cavity, sinuses, and conditions affecting respiration. Test your knowledge on key concepts of the respiratory system.