Res system

They are located in the head, neck, and thoracic cavity.

Where are the organs of the respiratory system located?

The system also includes the blood vessels of the pulmonary circuit, rib cage, and respiratory muscles.

What structures are included in the respiratory system besides the lungs and respiratory tract?

• Nose and nasal cavity

• Pharynx

• Larynx

• Trachea

• Bronchial tree

List the main components of the respiratory tract.

It is divided into the upper respiratory tract and the lower respiratory tract.

How is the respiratory system divided anatomically?

The upper respiratory tract includes passageways from the nasal cavity to the larynx.

What structures are included in the upper respiratory tract?

• The conducting zone transports air (no gas exchange).

• The respiratory zone is where gas exchange occurs (in the alveoli).

What is the difference between the conducting zone and the respiratory zone?

Respiration—it provides body cells with oxygen and removes carbon dioxide.

What is the primary function of the respiratory system?

It provides a mechanism for speech and sound production by moving air through the vocal cords.

How does the respiratory system contribute to speech?

They assist with the flow of venous blood and lymph in both the thoracic and abdominopelvic cavities.

How do pressure changes in the thoracic cavity help other body systems?

It regulates carbon dioxide levels, which helps control pH in extracellular fluid through buffer systems.

How does the respiratory system help maintain acid-base balance?

They warm, humidify, and filter inhaled air, contain olfactory receptors, and enhance voice resonance.

What are the main functions of the nose and nasal cavity?

They create turbulent airflow, which helps trap debris and improve filtration.

How do the nasal conchae help with air processing?

Air is moistened by mucous membranes lining the nasal cavity.

How is inhaled air moistened in the nasal cavity?

Sinuses help warm, filter, and humidify air.

What is the function of the sinuses in the respiratory system?

• Nasopharynx → Oropharynx → Laryngopharynx

• Inspired air enters the pharynx after the nasal cavity in this order.

What are the three anatomical segments of the pharynx, and in what order does inspired air pass through them?

• Pseudostratified ciliated columnar epithelium

• Suitable because it warms, humidifies, and filters inspired air; cilia help move debris out of the airway.

Which type of epithelium lines the nasopharynx, and why is this type suitable for its function?

• The oropharynx handles both air and food, so it experiences more mechanical stress.

• Stratified squamous epithelium provides better protection against abrasion.

Why is the oropharynx lined with nonkeratinized stratified squamous epithelium instead of the ciliated columnar epithelium seen in the nasopharynx?

• Anteriorly: Opens into the larynx (voice box) → airway

• Posteriorly: Opens into the esophagus → digestive tract

What openings does the laryngopharynx have anteriorly and posteriorly, and what does each connect to?

• The oropharynx and laryngopharynx are shared pathways for air and food.

• Air passes to the larynx and trachea, while food passes to the esophagus.

• This dual function requires protective epithelium to prevent damage.

Explain how the pharynx serves as a common pathway for both the respiratory and digestive systems, and indicate which segments are involved.

• Protects the airway by keeping food and liquids out of the lower respiratory tract.

• Houses the vocal cords, enabling sound production.

What are the two main functions of the larynx in the respiratory system?

• Nine cartilages total:

  • Three unpaired (thyroid, cricoid, epiglottis)

  • Six paired (arytenoid, corniculate, cuneiform)

• These cartilages provide a flexible framework for the larynx.

How many cartilages make up the larynx, and how are they categorized?

• Muscles connecting the larynx to the neck

• Intrinsic laryngeal muscles within the larynx itself

Besides cartilage, what structures support the larynx?

• Begins in the inferior neck

• Extends to the mediastinum, leading into the lower respiratory tract

Where does the trachea begin and end?

• Hyaline cartilage forms U-shaped rings on the anterior and lateral surfaces

• Function: Keeps the trachea open while allowing flexibility for changes in diameter during breathing

What type of cartilage covers the trachea, what shape does it form, and what is its function?

• posterior surface: Covered with elastic connective tissue and smooth muscle

  • Allows the esophagus to expand during swallowing

• Last tracheal ring: Called the carina

What covers the posterior surface of the trachea, and why is it important? What is the last tracheal ring called?

Air enters the left or right primary bronchi, each leading into a lung.

Where does inhaled air go after passing through the trachea, and what are these structures called?

A series of progressively smaller branching tubes within the lungs that ultimately end in the alveoli, where gas exchange occurs.

What is the bronchial tree?

• Lobar (secondary) bronchi

• Segmental (tertiary) bronchi

• Each lung has about 10 segmental bronchi.

What are the next two levels of bronchi after the primary bronchi?

• Changes from pseudostratified ciliated columnar epithelium (larger bronchi)

• To simple columnar epithelium (smaller bronchi)

How does the epithelial lining change as the bronchi get smaller?

• Smooth muscle increases

• Hyaline cartilage decreases

How do smooth muscle and hyaline cartilage change as the bronchial tree branches become smaller?

They are histologically similar, with pseudostratified ciliated columnar epithelium and supporting cartilage structures.

How are the primary bronchi similar to the trachea?

• As airway structure changes (epithelium type, cartilage, smooth muscle), its function also changes.

• Larger bronchi focus on air conduction, filtering, and support, while smaller bronchioles specialize in controlling airflow by changing diameter.

What does “structure change leads to function change” mean in the bronchial tree?

• From mucosal (pseudostratified ciliated columnar) epithelium in larger bronchi

• To simpler columnar and then cuboidal epithelium in smaller airways

How does the epithelium change as the bronchial tree gets smaller?

Increased smooth muscle allows bronchioles to constrict or dilate, helping regulate airflow to different parts of the lungs.

Why does smooth muscle increase as the bronchi get smaller?

• Smaller airways need to be more flexible, not rigid

• This flexibility allows diameter changes to control airflow

wy does hyaline cartilage decrease as the airways get smaller?

• Simple cuboidal epithelium with few cilia

• Thick smooth muscle layer

• No hyaline cartilage

What are the key structural features of bronchioles?

• At the terminal bronchioles

• Beyond this point, structures are involved in gas exchange rather than just air conduction

Where does the conducting zone of the respiratory tract end?

Terminal bronchioles branch into two or more respiratory bronchioles.

What do terminal bronchioles branch into?

About 65,000 terminal bronchioles.

Approximately how many terminal bronchioles are present in the lungs?

It begins at the respiratory bronchioles, where alveoli start budding from the walls.

Where does the respiratory zone of the respiratory system begin?

Respiratory bronchioles have alveoli attached to their walls, allowing gas exchange to begin

What structural feature distinguishes respiratory bronchioles from terminal bronchioles?

• They branch into alveolar ducts

• These ducts also have alveoli attached along their walls

What do respiratory bronchioles branch into, and what is unique about these structures?

• Alveolar sacs are the end structures of alveolar ducts

• They are grapelike clusters of alveoli, maximizing surface area for gas exchange

What are alveolar sacs, and how are they structured?

Alveoli are the final destination for inspired air and are the main site of gas exchange (oxygen and carbon dioxide).

What is the primary function of the alveoli?

• Type I alveolar cells

• Type II alveolar cells

• Alveolar macrophages

What are the three main cell types found in the alveoli?

• Thin squamous cells that make up about 90% of the alveolar wall

• Their thinness allows for rapid diffusion of gases across membranes

What is the structure and function of Type I alveolar cells?

• They produce surfactant

• Surfactant reduces surface tension, preventing alveoli from collapsing and making breathing easier

What do Type II alveolar cells do, and why is this important?

They remove debris, dust, and pathogens from the alveoli, helping keep lungs clean

What is the role of alveolar macrophages?

• Thin walls (Type I cells) → allow fast gas diffusion

• Surfactant (Type II cells) → prevents collapse

• Macrophages → keep surface clean for efficient gas exchange

How does the structure of alveoli support their function in gas exchange?

The lungs are separated by the heart and mediastinum.

What structures separate the right and left lungs?

• Base: Rests on the diaphragm

• Apex: Extends just below the clavicle

Where are the base and apex of each lung located?

• The hilum is a triangular depression on the medial surface of the lung

• It allows passage of:

  • Primary bronchi

  • Blood vessels

  • Lymphatic vessels

  • Nerves

What is the hilum of the lung and what passes through it?

• Right lung: 3 lobes (superior, middle, inferior)

• Left lung: 2 lobes (superior, inferior)

How many lobes does each lung have?

• Each lung is located within a pleural cavity.

Where is each lung located?

• The pleurae are two layers of serous membrane surrounding each lung

• They help reduce friction and allow smooth movement during breathing

What are the pleurae and what is their general function?

• Nares (nostrils) – entry of inspired air

• Nasal cavity – warms, humidifies, and filters air

• Nasopharynx – posterior to nasal cavity; continues filtering air

• Oropharynx – posterior to oral cavity; shared with digestive pathway

• Laryngopharynx – common passage for air and food; opens to larynx

• Larynx – voice box; protects airway, houses vocal cords

• Trachea – windpipe; supported by hyaline cartilage rings

• Primary bronchi – right or left bronchus enters respective lung

• Secondary (lobar) bronchi – branch to each lung lobe

• Tertiary (segmental) bronchi – branch to lung segments

• Multiple branches of smaller bronchi – progressively smaller tubes

• Bronchioles – small airways; smooth muscle increases, cartilage decreases

• Terminal bronchioles – last part of conducting zone

• Respiratory bronchioles – start of respiratory zone; alveoli budding

• Alveolar ducts – ducts with alveoli along their walls

• Alveolar sacs – grapelike clusters of alveoli

• Alveoli – site for gas exchange

pathway of air (17)