Human Respiratory System Lesson: Parts and Functions

Lesson Overview

• What Is Human Respiratory System?
• What Are the Features of the Respiratory System?
• What Does Human Respiratory System Look Like?
• What Are the Parts of the Respiratory System?
• The Different Parts of the Respiratory Tract
• What Are the Functions of the Respiratory System?
• Conclusion

What Is Human Respiratory System?

The respiratory system is a network of organs and tissues that help us breathe and provide oxygen to our cells while removing carbon dioxide. It includes:

• The nose and nasal cavity filter, warm, and moisten incoming air.
• The pharynx acts as a pathway for air.
• The larynx routes air and contains the vocal cords.
• The trachea connects to the bronchi.
• The bronchi and bronchioles distribute air to the lungs.
• The lungs are where gas exchange with blood vessels occurs in the alveoli.
  
  The diaphragm, a key muscle at the top of the abdomen, helps the lungs expand and contract, ensuring efficient air movement. Gas exchange with the bloodstream is vital for maintaining balance and health, making sure cells get oxygen and carbon dioxide is removed.

What Are the Features of the Respiratory System?

The human respiratory system is essential for sustaining life by facilitating gas exchange, supporting cellular respiration, and maintaining overall homeostasis. Key features of the respiratory system include

1. Energy Generation
   • Cellular Respiration: Energy in the human body is generated through the breakdown of glucose molecules within all living cells. This process, known as cellular respiration, is fundamental for the production of energy.
   • Role of Oxygen: Oxygen inhaled through the respiratory system is crucial for this energy generation process. It is transported to various cells throughout the body, where it participates in the oxidative breakdown of glucose molecules.
2. Gas Exchange
   • Oxygen Inhalation: The respiratory system ensures the intake of oxygen from the environment. This oxygen is then transported via the bloodstream to cells all over the body where it is used in metabolic processes.
   • Carbon Dioxide Exhalation: As a byproduct of glucose metabolism, carbon dioxide is produced and must be expelled from the body. The respiratory system efficiently removes this waste product through exhalation.
3. ATP Production
   • Energy Currency of the Cell: The glucose molecules are broken down in the presence of oxygen and release energy, which is stored in the form of ATP (adenosine triphosphate). ATP is the primary energy carrier in cells, used for various biological processes.
4. Homeostasis Maintenance
   • pH Balance: By regulating the levels of carbon dioxide in the blood, the respiratory system helps maintain the body's acid-base balance, ensuring that the pH of the blood remains within a narrow, healthy range of 7.35 to 7.45.
   • Temperature Regulation: Through the process of breathing, the respiratory system also plays a role in maintaining body temperature by expelling heat generated during metabolic reactions.
5. Protection and Defense
   • Filtration of Air: The respiratory system filters out harmful particles and pathogens from the air we breathe, protecting the body from infections and diseases.
   • Mucociliary Clearance: The mucous lining of the respiratory tract traps foreign particles, which are then moved out of the respiratory passages by cilia, small hair-like structures.

Take This Quiz:

Respiratory System Quiz: Questions With Answers

What Does Human Respiratory System Look Like?

Fig: Labeled Diagram of the Human Respiratory System

What Are the Parts of the Respiratory System?

The human respiratory system is a complex network of organs and tissues that facilitate breathing and gas exchange. Each part plays a crucial role in ensuring the efficient movement of air and the exchange of gases essential for life.

Here is a detailed look at the main parts of the respiratory system:

1. Nostrils (Nares):
   • Structure: The nostrils, or nares, are the external openings of the nose that serve as the entry points for air into the respiratory system. These openings are lined with coarse hairs and mucus membranes.
   • Function: Nostrils serve as the primary entry point for air into the respiratory system. They are lined with coarse hairs that filter out large particles and prevent them from entering the nasal passages.
2. Nasal Cavity:
   • Structure: The nasal cavity is a large, air-filled space located above and behind the nose in the middle of the face. It is divided into two cavities by the nasal septum and lined with mucous membranes and tiny hairs (cilia).
   • Function: It filters, warms, and humidifies the air we breathe. The nasal cavity is lined with mucous membranes and tiny hairs (cilia) that trap dust, microbes, and other particles. It also contains olfactory receptors responsible for the sense of smell.
3. Soft Palate:
   • Structure: The soft palate is a flexible, muscular part of the mouth's roof located towards the back, made of muscle fibers covered by mucous membranes.
   • Function: It separates the nasopharynx from the oropharynx and moves during swallowing to close off the nasal passages, preventing food and liquid from entering the nasal cavity.
4. Hard Palate:
   • Structure:  The hard palate forms the bony front part of the roof of the mouth, made of the maxillary and palatine bones. It is covered by a mucous membrane.
   • Function: It forms a barrier between the oral and nasal cavities, providing structural support and allowing for the separation of the respiratory and digestive tracts. This structure allows us to eat and breathe at the same time. 
5. Oral Cavity (mouth):
   • Structure: The oral cavity includes the lips, tongue, teeth, and salivary glands. The lips form the entrance, while the tongue aids in tasting and manipulating food. Teeth serve to chew and break down food, aided by the salivary glands that produce saliva to further breakdown. 
   • Function: It serves as an alternative entry and exit point for air. The oral cavity is also involved in speech, digestion, and taste.
6. Larynx (Voice Box):
   • Structure:  Located at the top of the trachea, the larynx is made up of cartilage, muscles, and ligaments, and houses the vocal cords. Key cartilage structures include the thyroid, cricoid, and arytenoid cartilages.
   • Function: The larynx is responsible for sound production, as the vocal cords vibrate to produce sound when air passes through them. The larynx muscles and a flap called the epiglottis work together to block the entrance to the larynx and prevent food and liquids from entering the trachea. 
7. Trachea (Windpipe):
   • Structure:The trachea is a cartilaginous tube approximately 10-12 cm long, extending from the larynx to the bronchi. It is lined with cilia and mucus and reinforced with C-shaped cartilaginous rings.
   • Function: The trachea provides a clear airway for air to enter and exit the lungs. It is lined with cilia (small hairs that continually move back and forth) and mucus to trap and expel foreign particles and pathogens. The tracheal cartilage rings maintain its open structure.
8. Carina of Trachea:
   • Structure: A ridge at the base of the trachea where it divides into the right and left main bronchi. It is an important anatomical landmark.
   • Function: The carina is a sensitive area that triggers the cough reflex when it detects foreign particles or irritants, which protects the lungs.
9. Right Main Bronchus:
   • Structure: The bronchus that branches off from the trachea into the right lung. It is shorter, wider, and more vertical than the left bronchus.
   • Function: It conducts air into the right lung and further divides into smaller bronchi and bronchioles, distributing air throughout the lung.
10. Right Lung:
    • Structure:  The right lung is divided into three lobes: upper, middle, and lower. It is larger and heavier than the left lung and contains millions of alveoli.
    • Function: The right lung houses millions of alveoli, where oxygen is exchanged for carbon dioxide. It is responsible for a significant portion of the body's gas exchange.
11. Pharynx:
    • Pharyngeal Tonsil:
      • Structure: The pharyngeal tonsil, also known as the adenoid, is a mass of lymphatic tissue located in the nasopharynx, the upper part of the pharynx.
      • Function: It helps protect the body against infections by trapping and destroying pathogens that enter through the nose and mouth.
    • Nasopharynx:
      • Structure: The nasopharynx is the upper part of the pharynx connected to the nasal cavity. It is lined with respiratory epithelium, tissue which includes ciliated cells and mucus-secreting goblet cells.
      • Function: It serves as a passageway for air during breathing, helping to filter, warm, and humidify the air before it moves to the lower respiratory tract.
    • Oropharynx:
      • Structure: The oropharynx is the middle part of the pharynx located behind the oral cavity. It is lined with stratified squamous epithelium, which is well-suited to withstand the mechanical stress of swallowing.
      • Function: It serves as a passageway for both air and food, directing air to the lungs and food to the esophagus. It also plays a role in speech and maintaining the airway during breathing.
12. Tongue:
    • Structure: A muscular organ in the mouth composed of skeletal muscles and covered in mucous membrane, with taste buds on the surface.
    • Function: The tongue is involved in taste, speech, and the manipulation of food for chewing and swallowing. It also helps to maintain an open airway during breathing.
13. Epiglottis:
    • Structure: It is a leaf-shaped flap of cartilage located at the entrance of the larynx, attached to the thyroid cartilage.
    • Function: During swallowing, the epiglottis closes over the trachea to prevent food and liquids from entering the airway, directing them instead into the esophagus.
14. Left Main Bronchus:
    • Structure: It is the bronchus that branches off from the trachea into the left lung. It is longer, narrower, and more horizontal than the right bronchus.
    • Function: It conducts air into the left lung and further divides into smaller bronchi and bronchioles, distributing air throughout the lung.
15. Bronchi:
    • Structure: They are the main passageways into the lungs, branching into progressively smaller tubes called bronchioles. They are reinforced with cartilage and lined with mucous membranes and cilia.
    • Function: The bronchi distribute air evenly throughout the lungs. The bronchioles end in clusters of alveoli, where gas exchange occurs.
16. Left Lung:
    • Structure: The left lung is divided into two lobes: upper and lower. It is smaller than the right lung to accommodate the heart and contains millions of alveoli.
    • Function: The left lung, like the right lung, houses millions of alveoli and is responsible for gas exchange, supplying oxygen to the bloodstream and removing carbon dioxide.
17. Diaphragm:
    • Structure:  It is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, composed of skeletal muscle fibers and a central tendon.
    • Function: The diaphragm is the primary muscle responsible for breathing. During inhalation, it contracts and moves downward, increasing the volume of the thoracic cavity and reducing the pressure inside the lungs, causing air to flow in. During exhalation, it relaxes and moves upward, decreasing the volume of the thoracic cavity and increasing the pressure inside the lungs, forcing air out. The diaphragm also assists in functions such as coughing, sneezing, and playing wind instruments by generating the necessary changes in thoracic pressure.

Take This Quiz

Respiratory System Anatomy: MCQ Quiz!

The Different Parts of the Respiratory Tract

The respiratory tract is the pathway through which air travels as it moves into and out of the lungs. It can be divided into two main sections: the upper respiratory tract and the lower respiratory tract. Each section comprises specific structures that play crucial roles in ensuring that air is properly channeled, filtered, and conditioned for efficient gas exchange in the lungs.

Upper Respiratory Tract

The upper respiratory tract includes the following components:

1. Nose:
   • Structure: The external part of the respiratory system with nostrils (nares) serving as the entry points for air.
     
   • Function: The nose filters large particles from the air using coarse hairs. It also warms and humidifies the air before it passes into the nasal cavity, making it more suitable for the delicate tissues of the respiratory tract.
     
2. Nasal Cavity:
   • Structure: A large, air-filled space above and behind the nose, lined with mucous membranes and tiny hairs (cilia).
     
   • Function: The nasal cavity continues to filter, warm, and humidify the air. It also traps dust, microbes, and other particles with mucus and cilia. Additionally, it houses olfactory receptors that are responsible for the sense of smell.
     
3. Sinuses:
   • Structure: Air-filled spaces within the bones of the skull, including the frontal, maxillary, ethmoid, and sphenoid sinuses.
     
   • Function: The sinuses help lighten the weight of the skull, produce mucus that moistens the nasal cavity, and contribute to the resonance of the voice.
     
4. Pharynx (Throat):
   • Structure: A muscular tube that extends from the nasal cavity to the larynx and esophagus, divided into three parts: nasopharynx, oropharynx, and laryngopharynx.
     
   • Function: The pharynx serves as a passageway for air from the nasal cavity to the larynx and for food from the oral cavity to the esophagus. It also plays a role in speech and immune defense (with the presence of the pharyngeal tonsil).
     
5. Larynx (Voice Box):
   • Structure: Located at the top of the trachea, the larynx is made of cartilage, muscles, and ligaments, containing the vocal cords.
     
   • Function: The larynx produces sound by vibrating the vocal cords as air passes through them. It also acts as a protective mechanism, closing off the trachea during swallowing to prevent food and liquids from entering the lower respiratory tract.

Lower Respiratory Tract

The lower respiratory tract includes the following components:

1. Trachea (Windpipe):
   • Structure: A cartilaginous tube approximately 10-12 cm long, extending from the larynx to the bronchi. It is lined with ciliated epithelium and mucus-producing cells.
     
   • Function: The trachea provides a clear passageway for air to travel to and from the lungs. It also filters out dust and pathogens, with cilia moving mucus and trapped particles upward toward the pharynx for expulsion.
     
2. Bronchi:
   • Structure: The trachea divides into the right and left main bronchi, each entering a lung. These bronchi further branch into smaller secondary and tertiary bronchi.
     
   • Function: The bronchi conduct air into the lungs and distribute it evenly throughout the lung tissues. They also continue the process of filtering and humidifying the air.
     
3. Bronchioles:
   • Structure: Smaller branches of the bronchi, with diameters less than 1 mm, leading to the alveolar ducts and alveoli.
     
   • Function: The bronchioles ensure that air reaches the alveoli, the tiny air sacs where gas exchange occurs. They play a role in regulating airflow resistance and air distribution within the lungs.
     
4. Lungs:
   • Structure: The primary organs of the respiratory system, the lungs are divided into lobes (three in the right lung and two in the left lung). They contain millions of alveoli surrounded by capillaries.
     
   • Function: Gas exchange occurs in the lunges. Oxygen from inhaled air diffuses through the walls of the alveoli into the capillaries, while carbon dioxide from the blood diffuses into the alveoli to be exhaled. The lungs also help maintain the body's acid-base balance and filter small blood clots from the bloodstream.

Take This Quiz:

Respiratory System Multiple Choice Questions And Answers

Summary of Roles

Each part of the respiratory tract plays a specific role in ensuring that air is properly channeled, filtered, and prepared for gas exchange in the lungs:

• The upper respiratory tract (nose, nasal cavity, sinuses, pharynx, and larynx) filters, warms, humidifies air, and produces sound.
  
• The lower respiratory tract (trachea, bronchi, bronchioles, and lungs) conducts air to the alveoli for gas exchange, filters the air, and regulates airflow.

What Are the Functions of the Respiratory System?

The respiratory system performs several vital functions essential for maintaining life and overall health. Here are the detailed functions of the respiratory system:

1. Gas Exchange

• Primary Function: The main role of the respiratory system is to facilitate the exchange of gases between the body and the environment.
  
• Oxygen Uptake: During inhalation, oxygen from the air enters the alveoli in the lungs. Oxygen then diffuses across the thin walls of the alveoli into the surrounding capillaries and binds to hemoglobin molecules in red blood cells. This oxygen-rich blood is then transported to tissues and organs throughout the body where it is used for cellular respiration.
  
• Carbon Dioxide Removal: Carbon dioxide, a waste product of cellular respiration, diffuses from the tissues into the bloodstream. It is transported back to the lungs, where it diffuses into the alveoli and is expelled from the body during exhalation. This exchange of gases is critical for maintaining the body's internal environment and supporting cellular functions.

2. Protection

• Filtering Mechanism: The respiratory system acts as a defense mechanism against harmful substances in the air. The nasal cavity, trachea, and bronchi are lined with mucous membranes and cilia that trap and remove dust, pollutants, and pathogens.
  
• Mucociliary Clearance: The mucus produced by the respiratory tract traps particles, and the cilia move this mucus upwards towards the pharynx, where it can be swallowed or expelled. This process helps keep the airways clear of debris and reduces the risk of infections.
  
• Immune Defense: The pharyngeal tonsils and other lymphoid tissues in the respiratory system contain immune cells that can detect and respond to pathogens, providing an additional layer of protection.

3. Regulation

• Acid-Base Balance: The respiratory system helps maintain the body's acid-base balance by regulating the levels of carbon dioxide in the blood. Carbon dioxide is converted to carbonic acid in the blood, which can influence the pH level of the blood and cause respiratory and kidney issues.
  
• Respiratory Rate and Depth: The rate and depth of breathing can be adjusted to manage the concentration of carbon dioxide and adjust the pH of the blood. Increased breathing rate (hyperventilation) expels more carbon dioxide, reducing acidity, while decreased breathing rate (hypoventilation) retains carbon dioxide, increasing acidity.
  
• Buffering Systems: The lungs work in conjunction with the kidneys and other buffering systems to stabilize blood pH within a narrow range (7.35-7.45), which is crucial for normal cellular functions.

4. Sound Production

• Vocal Cords: Located in the larynx, the vocal cords are essential for producing sound. When air passes through the vocal cords during exhalation, they vibrate and produce sound waves.
  
• Speech and Communication: The tension and length of the vocal cords can be adjusted to produce different pitches and volumes. The coordinated movement of the lips, tongue, and other structures further modulates these sounds to form speech.
  
• Protection During Swallowing: The larynx also protects the lower airways during swallowing by closing the vocal cords and preventing food or liquids from entering the trachea, thus avoiding aspiration.

5. Olfaction

• Sense of Smell: The nasal cavity contains specialized olfactory receptors responsible for detecting odor molecules. These receptors are located in the olfactory epithelium, a small area in the upper part of the nasal cavity.
  
• Olfactory Nerves: When odor molecules bind to these receptors, they generate nerve impulses that travel along the olfactory nerves to the olfactory bulb in the brain. The brain then interprets these signals as specific smells.
  
• Role in Taste: Olfaction is closely linked to the sense of taste, enhancing the perception of flavors and aiding in the enjoyment and detection of food and beverages.

The respiratory system's multifaceted functions highlight its critical role in sustaining life, protecting the body, regulating internal conditions, enabling communication, and enhancing sensory experiences. Understanding these functions underscores the importance of maintaining respiratory health for overall well-being.

Take This Quiz:

Respiratory System Assessment Quiz

Conclusion

This respiratory system course has explored its amazing machinery, from the air filters of your nose to the gas exchange powerhouses in your lungs. You've learned how this intricate network keeps you alive with every breath, fuels your body, and even helps you speak and smell the world around you. But this knowledge is just the beginning!  Remember, taking care of your respiratory system is vital for a healthy and vibrant life. So breathe deep, breathe easy, and keep exploring the fascinating world within!