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OIA1004 RESPIRATORY SYSTEM I
Overview of the Respiratory System
Learning Outcomes
Identify the major structures of the respiratory system.
Describe the function of each major structure of the respiratory system.
Structure of the Respiratory System
The respiratory system is divided into two main parts: the upper respiratory system (nose to larynx) and the lower respiratory system (below larynx).
The upper respiratory system includes the nose, nasal cavity, pharynx, and larynx, while the lower respiratory system includes the trachea, bronchi, bronchioles, and lungs.
Each structure plays a specific role in the process of respiration, from filtering air to facilitating gas exchange.
Functions of the Respiratory System
Gas exchange: Oxygen is delivered to the body, and carbon dioxide is removed through exhalation.
Inhalation and exhalation are essential for maintaining oxygen levels in the blood.
The respiratory system conditions air by purifying, warming, and humidifying it before it reaches the lungs.
It helps regulate blood pH by controlling the levels of carbon dioxide in the blood, which can affect acidity.
The larynx and other structures contribute to sound production, allowing for speech and communication.
Detailed Anatomy of the Respiratory Structures
The Nose
The external nose consists of the root, apex, bridge, and external naris (nostrils).
The internal nasal cavity is divided by the nasal septum and is lined with mucous membranes that filter and humidify air.
Nasal conchae increase surface area and help trap water droplets, preventing dehydration.
Paranasal Sinuses
Paranasal sinuses are cavities in the frontal, sphenoid, ethmoid, and maxillary bones.
They lighten the skull, produce mucus, and serve as resonating chambers for sound.
Inflammation of these sinuses can lead to conditions such as rhinitis.
The Pharynx
The pharynx is divided into three regions: nasopharynx, oropharynx, and laryngopharynx, each serving different functions.
The nasopharynx is a respiratory pathway only, while the oropharynx and laryngopharynx serve both respiratory and digestive functions.
The pharynx houses tonsils, which play a role in the immune response.
The Larynx and Its Functions
Anatomy of the Larynx
The larynx connects the laryngopharynx to the trachea and is located at the level of C4-C6 vertebrae.
It consists of 9 cartilages, including the epiglottis, which prevents food from entering the trachea during swallowing.
The glottis is formed by the vocal folds and the rima glottidis, which are essential for sound production.
Functions of the Larynx
The larynx serves as a passageway for air and plays a crucial role in phonation (sound production).
The lining of the larynx varies: it is stratified squamous epithelium above the vocal folds and pseudostratified ciliated columnar epithelium below.
The epiglottis acts as a guardian of the airway, covering the laryngeal inlet during swallowing.
Larynx
Functions of the Larynx
The larynx serves as a patent airway, ensuring that air can flow freely to and from the lungs.
It acts as a switching mechanism to direct air towards the trachea and food towards the esophagus, preventing aspiration.
Houses the vocal folds, which are essential for voice production, allowing for sound modulation during speech.
Speech production involves the intermittent release of expired air while opening and closing the glottis, the space between the vocal cords.
Intrinsic laryngeal muscles adjust the tension of the vocal folds and the size of the glottis, influencing pitch and sound quality.
The pitch of sound is directly related to the tension in the vocal folds; increased tension results in higher pitch.
Anatomy of the Larynx
The larynx is composed of several cartilages, including the thyroid, cricoid, and arytenoid cartilages, which provide structure and support.
The vocal folds (true vocal cords) are located within the larynx and are responsible for sound production when air passes through them.
The epiglottis, a flap of cartilage, prevents food from entering the trachea during swallowing, ensuring that the airway remains clear.
The laryngeal cavity is lined with mucous membranes that help trap particles and pathogens, contributing to respiratory health.
The larynx is situated at the level of the fourth to sixth cervical vertebrae, connecting the pharynx to the trachea.
The intrinsic muscles of the larynx are innervated by the recurrent laryngeal nerve, a branch of the vagus nerve.
Voice Production Mechanism
Voice production begins with the airflow from the lungs, which is modulated by the opening and closing of the glottis.
The tension of the vocal folds is adjusted by intrinsic laryngeal muscles, affecting the pitch of the sound produced.
Loudness is determined by the pressure of air forced through the vocal cords; greater pressure results in a louder sound.
The resonance of sound is enhanced by the shape and size of the vocal tract, including the throat, mouth, and nasal passages.
The quality of voice can be affected by factors such as hydration, health of the vocal cords, and technique used in voice production.
Vocal training can help individuals learn to control their vocal folds and improve their speech and singing abilities.
Trachea and Bronchi
Structure of the Trachea
The trachea, or windpipe, extends from the larynx to the superior border of T5, where it bifurcates into the right and left primary bronchi.
The tracheal wall consists of four layers: mucosa, submucosa, hyaline cartilage, and adventitia, each serving specific functions.
The mucosa is lined with pseudostratified ciliated columnar epithelium, which helps trap and expel particles.
The C-shaped rings of hyaline cartilage provide structural support, preventing the trachea from collapsing during breathing.
The adventitia is a layer of areolar connective tissue that anchors the trachea to surrounding structures.
The trachea is highly sensitive to irritants, triggering a cough reflex to clear the airway.
Bronchial Tree Structure
The trachea divides into the right and left primary bronchi, with the right bronchus being shorter, wider, and more vertical than the left.
The carina is the internal ridge where the trachea bifurcates into the primary bronchi, and it is sensitive to irritants.
The primary bronchi contain incomplete rings of cartilage and are lined with pseudostratified ciliated columnar epithelium, similar to the trachea.
As the bronchi branch into smaller bronchioles, the epithelium transitions from ciliated columnar to nonciliated cuboidal epithelium.
Goblet cells within the bronchi produce mucus to trap particles, while cilia help move mucus towards the pharynx for removal.
Smooth muscle increases in the bronchioles, allowing for regulation of airway diameter, which can be affected during asthma attacks.
Changes in Bronchial Structure
The mucous membrane changes from pseudostratified ciliated columnar epithelium in the primary bronchi to ciliated simple columnar epithelium in smaller bronchi.
In terminal bronchioles, the epithelium becomes nonciliated simple cuboidal, reflecting a decrease in mucus production.
Plates of cartilage replace the C-shaped rings as the bronchi branch further, eventually disappearing in the distal bronchioles.
The increase in smooth muscle allows for bronchoconstriction and bronchodilation, controlled by the autonomic nervous system.
The sympathetic nervous system promotes relaxation of bronchiolar smooth muscle, while the parasympathetic system causes contraction, affecting airflow.
Understanding these changes is crucial for managing conditions like asthma, where airway constriction can lead to difficulty breathing.
Lung Anatomy
Gross Anatomy of the Lungs
The lungs are paired cone-shaped organs located in the thoracic cavity, separated by the mediastinum, which contains the heart.
Each lung is enclosed by a double-layered pleural membrane: the parietal pleura lines the thoracic cavity, and the visceral pleura covers the lungs.
The pleural cavity, the space between the pleurae, contains pleural fluid that reduces friction during breathing and maintains surface tension.
The apex of each lung is the narrow superior tip, while the base rests on the diaphragm, facilitating breathing movements.
The hilum is the region where blood vessels and nerves enter and exit the lungs, crucial for lung function and blood supply.
The left lung is approximately 10% smaller than the right lung due to the presence of the heart, which creates a cardiac notch.
Lobes and Fissures of the Lungs
The right lung consists of three lobes: superior, middle, and inferior, while the left lung has two lobes: superior and inferior.
Each lobe is separated by fissures: the oblique fissure and the horizontal fissure in the right lung.
Each lobe receives its own secondary (lobar) bronchus, which further branches into tertiary (segmental) bronchi.
The bronchopulmonary segment is a specific lung tissue segment supplied by a tertiary bronchus, allowing for localized treatment of lung diseases.
Lobules, the smallest functional units of the lung, are wrapped in elastic connective tissue and contain lymphatic vessels, arterioles, venules, and branches from terminal bronchioles.
Terminal bronchioles branch into respiratory bronchioles, which lead to alveolar ducts and ultimately to alveoli, the sites of gas exchange.
Alveoli and Gas Exchange
Alveoli are cup-shaped outpouchings lined with simple squamous epithelium, facilitating efficient gas exchange.
An alveolar sac consists of two or more alveoli sharing a common opening, increasing surface area for gas exchange.
Type I alveolar cells form the majority of the alveolar wall and are the primary site for gas exchange due to their thin structure.
Type II alveolar cells secrete alveolar fluid, which keeps the alveolar surface moist and contains surfactant to reduce surface tension and prevent collapse.
Alveolar macrophages (dust cells) play a crucial role in immune defense by removing fine dust particles and pathogens from the alveoli.
The respiratory membrane, composed of the alveolar wall, basement membranes, and capillary endothelium, is extremely thin (0.5 μm), allowing for rapid diffusion of gases.
Discussion questions1 of 6
What are the major structures of the respiratory system, and how do they contribute to its overall function?
Difficulty: Easy
How does the structure of the larynx facilitate its function in voice production?
Difficulty: Medium
Discuss the significance of the respiratory zone in the respiratory system.
Difficulty: Medium
In what ways do the conducting and respiratory zones differ in structure and function?
Difficulty: Hard
Analyze the role of the pleural membranes in lung function.
Difficulty: Medium
What adaptations do alveoli have that enhance their function in gas exchange?
Difficulty: Hard
Show example answer
1. The major structures of the respiratory system include the upper respiratory system (nose, nasal cavity, pharynx, larynx) and the lower respiratory system (trachea, bronchi, bronchioles, and lungs). Each structure plays a role in filtering, warming, and humidifying air, facilitating gas exchange, and producing sound.
2. The larynx, composed of cartilages and lined with mucous membranes, houses the vocal folds which vibrate to produce sound. The intrinsic laryngeal muscles adjust the tension of the vocal cords and the size of the glottis, influencing pitch and loudness during speech.
3. The respiratory zone, which includes structures like respiratory bronchioles and alveoli, is crucial for gas exchange as it is where oxygen enters the blood and carbon dioxide is removed. Its thin walls facilitate rapid diffusion, making it essential for efficient respiratory function.
4. The conducting zone consists of airways that filter, warm, and moisten air, including the nose, trachea, and bronchi, while the respiratory zone is where gas exchange occurs, comprising alveoli and respiratory bronchioles. Structurally, the conducting zone has a more complex arrangement of cartilage and epithelium, whereas the respiratory zone features thin-walled alveoli optimized for diffusion.
5. The pleural membranes, consisting of the parietal and visceral pleura, create a pleural cavity that reduces friction during lung expansion and contraction. The pleural fluid within this cavity also helps maintain surface tension, allowing the lungs to adhere to the thoracic wall and facilitating efficient breathing.
6. Alveoli are adapted for gas exchange through their thin walls made of simple squamous epithelium, which minimizes diffusion distance, and their large surface area, which maximizes contact with capillaries. Additionally, type II alveolar cells secrete surfactant, reducing surface tension and preventing alveolar collapse, further enhancing gas exchange efficiency.
