Organs of the Respiratory System

- The respiratory system is crucial for the exchange of gases between the body and the environment.

- It consists of various organs and structures that work together to facilitate breathing and gas exchange.

- Key components include the nose, pharynx, larynx, trachea, bronchi, lungs, and diaphragm.

1. Nose and Nasal Cavity

Functions: 

  - Acts as the primary entrance for air into the respiratory system.

  - Filters out dust, pollen, and other particles from the air.

  - Warms and humidifies the air to body temperature and moisture levels.

  - Contains olfactory receptors for the sense of smell.

Anatomy: 

  - External nose: Composed of bone and cartilage, covered by skin.

  - Nasal cavity: Hollow space behind the nose lined with mucous membranes and cilia.

  - Nasal conchae: Bony projections that increase the surface area of the nasal cavity, aiding in air filtration and humidification.

  - Nasal septum: Divides the nasal cavity into left and right sides.

2. Pharynx (Throat)

Location:  Located behind the nasal cavity and mouth, extending to the larynx and esophagus.

Functions: 

  - Serves as a common pathway for both air and food.

  - Participates in swallowing reflexes.

  - Contains tonsils, which are part of the body's immune system.

Sections of the Pharynx: 

  1. Nasopharynx: Located behind the nasal cavity, serves only as an air passageway.

  2. Oropharynx: Located behind the mouth, serves as a passage for air, food, and drink.

  3. Laryngopharynx: Lowest part of the pharynx, connects to both the esophagus and larynx.

3. Larynx (Voice Box)

Location:  Located between the pharynx and trachea, at the level of the Adam's apple (thyroid cartilage).

Functions: 

  - Provides a passageway for air between the pharynx and trachea.

  - Contains the vocal cords, which vibrate to produce sound during speech and singing.

  - Acts as a protective mechanism during swallowing, closing off the airway to prevent food and drink from entering the lungs.

Cartilages of the Larynx: 

  - Thyroid cartilage: Forms the Adam's apple, protects the vocal cords.

  - Epiglottis: Leaf-shaped cartilage that covers the opening of the larynx during swallowing, directing food and drink into the esophagus.

4. Trachea (Windpipe)

Location:  Extends from the larynx to the bronchi, located anterior to the esophagus.

Structure: 

  - Composed of C-shaped rings of hyaline cartilage, which provide support and prevent collapse of the trachea during inhalation.

  - Lined with mucous membranes and cilia, which trap and remove particles from the air.

  - Divides into the left and right primary bronchi at the level of the fifth thoracic vertebra.

5. Bronchi and Bronchioles

Bronchi: 

  - Primary bronchi: Branch off from the trachea into the left and right lungs.

  - Secondary bronchi: Enter each lobe of the lungs.

  - Tertiary bronchi: Further divide within each lobe into smaller bronchioles.

Bronchioles: 

  - Smaller airways that lack cartilage support.

  - Branch extensively within the lungs and eventually lead to the alveoli.

  - Smooth muscle in bronchioles regulates airway diameter, influencing airflow.

6. Lungs

Location:  Paired organs located in the thoracic cavity, on either side of the heart.

Structure: 

  - Each lung is enclosed by a double-layered pleural membrane, consisting of the visceral and parietal pleura.

  - Divided into lobes: Right lung has three lobes (superior, middle, inferior), while the left lung has two lobes (superior, inferior) to accommodate the heart.

  - Bronchial tree branches within the lungs, culminating in terminal bronchioles and alveolar ducts.

7. Alveoli

Structure: 

  - Tiny air sacs clustered at the end of bronchioles.

  - Surrounded by a network of pulmonary capillaries.

  - Thin-walled with a rich blood supply, facilitating efficient gas exchange between air and blood.

  - Covered by surfactant, a substance that reduces surface tension and prevents alveolar collapse.

8. Diaphragm

Location:  Dome-shaped muscle separating the thoracic and abdominal cavities.

Function:  Main muscle of respiration, responsible for changes in thoracic volume during breathing.

Mechanism of Action:  Contracts during inhalation, flattening and increasing the volume of the thoracic cavity. Relaxes during exhalation, returning to its dome-shaped position.