Pharynx, lower resp, larynx trachea, and bronchial tree

Definition: The pharynx is commonly referred to as the throat.
Regions of the Pharynx:
- Nasopharynx:
  - Located at the back of the nasal cavity.
  - Function: Exclusive passageway for air; not for food (can lead to discomfort if food passes through).
  - Lining: Pseudostratified ciliated columnar epithelium, designed to reduce abrasion and facilitate mucus coating.
  - Soft Palate: Moves upwards when swallowing to prevent food from entering this region.
  - Eustachian Tube Connection: Balances middle ear pressure (similar sensations felt during air travel when swallowing).
  - Pharyngeal Tonsils: Part of the lymphatic system with an immune function to filter breathed-in particles.
- Oropharynx:
  - Extends from the soft palate to the hyoid bone (located above the voice box).
  - Function: Serves as a passageway for both food and air.
  - Lining: Non-keratinized stratified squamous epithelium to withstand abrasion from food particles.
  - Location of Tonsils: Contains palatine and lingual tonsils, which are part of the immune system.
- Laryngopharynx:
  - Extends from the hyoid bone down to the esophagus.
  - Function: Passageway for food along with air, sharing the same lining as the oropharynx.

Definition: Comprises structures from the larynx down to the terminal bronchioles, functioning in conducting air and gas exchange.
Conducting Pathway: Includes the trachea and extends to bronchi.
Gas Exchange Structures: Respiratory bronchioles, alveolar ducts, and alveoli are involved in actual gas exchange.

Location: Positioned between the laryngopharynx and the trachea; serves as a critical air passage.
Functionality:
- Prevents food and non-air materials from entering the respiratory system through the epiglottis, which covers the larynx during swallowing.
- Houses vocal cords, where sound is produced by the air passing over them.
- Facilitates bodily functions such as the Valsalva maneuver (increasing abdominal pressure) during defecation and childbirth, as well as coughing and sneezing reflexes.
Anatomical Features:
- Cartilage: Nine pieces of cartilage, held together by muscles and ligaments (labeled in previous videos).
- Laryngeal Prominence: Often referred to as the Adam's apple; more pronounced in males due to a sharper angle.
Vocal Folds:
- True Vocal Cords: Responsible for sound production; extend between thyroid and arytenoid cartilages.
- False Vocal Cords (Vestibular Folds): Provide stability but do not produce sound.
Muscle Regulation:
- Extrinsic muscles stabilize the larynx during swallowing.
- Intrinsic muscles modulate sound production and stability.

Description: A cartilaginous tube running from the pharynx to the lungs (larynx to main bronchi).
Structure: C-shaped cartilaginous rings prevent collapse. The esophagus is located behind it, allowing for flexibility during swallowing.
Lining:
- Mucosal Layer: Lined with pseudostratified ciliated columnar epithelium and goblet cells to secrete mucus.
- Submucosa: Contains connective tissues, nerves, blood vessels for immune support.
- Tracheal Cartilage: Provides structural integrity.
- Adventitia: Outermost layer made of elastic connective tissue.
Functionality: Mucus traps irritants and cilia propel it upward towards the mouth for expulsion or swallowing.
Bronchial Tree:
- The trachea bifurcates into right and left main bronchi at the level of the sternal angle.
- Right Bronchus: Shorter, wider, and more vertically oriented, more likely to trap inhaled objects.
Divergence of Bronchi:
- Divides into secondary (lobar) and tertiary (segmental) bronchi, leading to more branchings.
- Terminal bronchioles, marking the end of the conducting zone, lead into the respiratory bronchioles where gas exchange begins.
Bronchodilation/Bronchoconstriction:
- Bronchodilation increases airflow (widens airways);
- Bronchoconstriction decreases airflow (narrows airways).
Carina: A structure at the bifurcation of the trachea with sensory receptors that detect irritants, prompting cough reflexes.