Introduction to Respiratory System

Introduction to Respiratory System

• The body's cells require energy for chemical activities, maintaining homeostasis.
• Most energy is derived from chemical reactions requiring oxygen.
• Carbon dioxide is the main waste product.
• External respiration: gas exchange between atmosphere and blood.
• Internal respiration: gas exchange between blood and body cells.

Subtopics and Learning Outcomes

• Subtopics: Anatomy of upper respiratory tract, Anatomy of lower respiratory tract.
• Learning outcomes:
  • List the composition of upper and lower respiratory systems.
  • Discuss the anatomy of the nasal cavity, sinuses, pharynx, nasopharynx, oropharynx, laryngopharynx and larynx.
  • Describe the structure of the trachea.
  • Describe the anatomy of bronchi and bronchioles.
  • Describe the anatomy and types of alveoli.
  • Describe the anatomy of the lungs.

Nose and Nasal Cavity

• Divided into external and internal portions.
• External nose: visible portion, supported by bone and hyaline cartilage, covered by muscle and skin, lined by mucous membrane.
• Frontal bone, nasal bones, and maxillae form the bony framework.
• External nares (nostrils) are openings on the undersurface of the external nose.
• Nasal cavity is the internal space.
• Bony framework: frontal bone, nasal bones, maxilla.
• Cartilaginous framework: lateral nasal cartilages, septal nasal cartilage, alar cartilage.
• Air is warmed, filtered, moistened, and olfaction occurs within the nasal cavity.
• The nasal cavity is divided into two passages by the septum.
• Posterior bony part of the septum is formed by the perpendicular plate of the ethmoid bone and the vomer.
• Anteriorly, the septum consists of hyaline cartilage.
• Nasal vestibule is the anterior part of the nasal cavity, lined by skin and containing coarse hairs that filter large dust particles.
• Superior, middle, and inferior nasal conchae extend out from each lateral wall of the nasal cavity.
• Mucous membrane lines the nasal cavity and its shelves.

Paranasal Sinuses

• Cavities in facial and cranial bones containing air.
• Lined with mucous membrane, continuous with the nasal cavity's mucous membrane.
• Function in speech and lighten the skull.
• Nasolacrimal ducts drain tears from the eyes into the nasal cavity.

Respiratory Functions of the Nose

• Warming: due to immense vascularity of the mucosa.
• Filtering and cleaning of air: hairs in anterior nares trap larger particles; smaller particles settle and adhere to mucous.
• Mucus protects underlying epithelium from irritation and prevents drying.
• Cilia beat synchronously, wafts the mucous towards the throat.

Olfactory Function of the Nose

• The nose is the organ of smell.
• Nerve endings detect smell, located in the roof of the nose, in the cribriform plate of the ethmoid bone and superior conchae.
• Stimulated by chemical substances from odoruous materials.
• The resultant nerves transmit the sense of smell.

Pharynx (Throat)

• Funnel-shaped tube (13cm long).
• Starts at internal nares and extends to the cricoid cartilage (lowest cartilage of the larynx).
• Passageway for air and food.
• Resonating chamber for speech sound.
• Houses tonsils (play a role in immunological reactions).
• Divided into three anatomical regions: nasopharynx, oropharynx and laryngopharynx.

Nasopharynx

• Superior part of the pharynx.
• Lies posterior to the nasal cavity, extends to the soft palate.
• Contains internal nares, auditory tubes (eustachian tubes), and an opening to the oropharynx.

Oropharynx

• Intermediate part of the pharynx.
• Lies posterior to the oral cavity.
• Extends from the soft palate to the level of the hyoid bone.
• Opening from the mouth (fauces) is present.
• Function as respiratory, digestive, and serves as a passageway for air, food, and drink.
• Lined with nonkeratinized stratified squamous epithelium.
• Contains palatine and lingual tonsils.

Laryngopharynx

• Inferior part of the pharynx.
• Begins at the level of the hyoid bone.
• Opens into both the esophagus (posteriorly) and larynx (anteriorly).
• Function as both respiratory and digestive pathways.
• Lined with nonkeratinized stratified squamous epithelium.

Larynx (Voice Box)

• Extends from the root of the tongue and hyoid bone to the trachea.
• Located in front of the laryngopharynx at the level of the 3rd, 4th, 5th, and 6th cervical vertebrae.
• Composed of nine irregularly shaped cartilages (three singular, three paired).
• Larger in males.
• Adam's apple (prominence) is part of the thyroid cartilage.

Trachea (Windpipe)

• 16-20 C-shaped rings of hyaline cartilage.
• Stacked one above another, connected by dense connective tissue.
• Open part of each cartilage ring faces posteriorly toward the esophagus (and is spanned by a fibromuscular membrane).
• Semirigid support prevents inward collapse/obstruction during inhalation.
• Trachealis muscle allows for diameter adjustments.

Bronchi and Bronchioles

• Bronchi: same tissue as trachea, lined with ciliated columnar epithelium.
• Bronchi progressively subdivide into bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts and alveoli.

Bronchi

• Right primary bronchus is more vertical, shorter, and wider than left bronchus.
• More likely to be obstructed by inhaled foreign bodies.
• Left primary bronchus more horizontal.

Bronchioles

• Contain club cells, columnar non-ciliated cells interspersed among epithelial cells.
• Club cells help in protection, produce surfactant, and function as stem cell reserves.

Respiratory Bronchioles and Alveoli

• Lobules: end of respiratory tract distal to terminal bronchioles (consist of respiratory bronchioles, alveolar ducts, and alveoli).
• Gas exchange occurs in these structures.
• Alveoli are surrounded by a network of capillaries.
• The exchange of gases takes place across alveolar and capillary membranes.

Alveoli

• Numerous alveoli and alveolar sacs around the circumference of alveolar ducts.
• Cup-shaped out-pouchings, lined by simple squamous epithelium, supported by a thin elastic basement membrane.
• Alveolar sac contains two or more alveoli sharing a common opening.
• Walls of alveoli are composed of two types of alveolar epithelial cells. (Type I and Type II)

Alveoli Types

• Type I alveolar cells: squamous epithelium, main sites of gaseous exchange, continuous lining.
• Type II alveolar cells: secrete alveolar fluid—keeps surface moist, lowers surface tension, and reduces the tendency for alveoli to collapse.

Lungs

• Two lungs, one on each side of the midline in the thoracic cavity.
• Separated by the heart and mediastinum.
• Cone-shaped with apex, base, costal surface, and medial surface.
• Apex: Rounded, into the root of the neck (above the clavicle).
• Base: Concave, semilunar shape.
• Left lung is slightly smaller than the right.
• Each lung has a cardiac notch in the medial surface of the left lung. The left lung contains a cardiac notch for the heart.

Pleural Membrane

• Double-layered serous membrane enclosing each lung.
• Parietal pleura: superficial layer, lines the thoracic cavity wall.
• Visceral pleura: deep layer, covers the lungs themselves.

Hilum and Mediastinum

• Structures forming the root of the lung enter and leave at the hilum (primary bronchus, pulmonary arteries, pulmonary veins, bronchial arteries, veins, lymphatic and nerve supply).
• Mediastinum: area between the lungs.
• Contains the heart, great vessels, trachea, right and left bronchi, esophagus, lymph nodes, lymph vessels and nerves.

Lungs: Lobes

• Right lung: three lobes (superior, middle, inferior).
• Left lung: two lobes (superior, inferior).
• Heart positioning results in the left lung being smaller than the right.
• These lobes are separated by fissures.

Summary

• The respiratory system is a complex network for gas exchange between the body and the environment.
• Its various structures (nose, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, and lungs), work in coordination to warm, moisten, filter air, produce sound, protect the lower respiratory tract, regulate air flow.

Explore the anatomy and function of the respiratory system in this quiz. Learn about the various components involved in gas exchange and how oxygen is essential for energy production in the body. Test your knowledge on the upper and lower respiratory tract structures and their roles in respiration.