Lecture on Nasal Cavity and Pharynx Anatomy

Witch Reference: Elizabeth Montgomery's iconic nose crinkling as a metaphorical introduction to the flexibility of the human nose.

External Nose Structure:
- Figure 22.3 illustrates the external nose:
- Picture and idealized colorized representation show osseous and cartilaginous structures.
Nasal Cavity:
  - Located posterior to the external nose.
  - Air enters via nares (nostrils).
  - Divided by the midline septum:
    - Anteriorly by septal cartilages.
    - Posteriorly by vomer and ethmoid bones.
  - Continuous with posterior nasal apertures (coanae).

Coanae Identification: Reference Figure 22.4 to locate three coanae:
  - Superior coanae
  - Middle coanae
  - Inferior coanae
Nasal Structures:
  - Roof: Formed by the perpendicular plate of the ethmoid bone and sphenoid bones.
  - Floor: Composed of two parts:
    - Anterior: Hard palate (palatine and maxillary bones).
    - Posterior: Soft palate (unsupported by osseous structures).

Location: Superior to each nostril.
Histology:
  - Lined with skin containing:
    - Sebaceous glands.
    - Sweat glands.
    - Hair follicles (vibrissae).
Function of Vibrissae:
- Filter coarse particles from inspired air, especially in dusty environments.

Types:
  - Olfactory Mucosa: Contains smell receptors.
  - Respiratory Mucosa: Pseudostratified ciliated columnar epithelium:
    - Scattered goblet cells.
    - Serum-mucous nasal glands secrete:
      - Watery fluid containing lysozyme (an antibacterial enzyme).
      - Defensins (natural antibiotics).
  - Functionality:
    - Traps dust, bacteria, and debris.
    - Lysozymes destroy bacteria chemically.
    - Defensins combat microbes invasively.
  - High water content (around 1 liter/day) humidifies air.
  - Vascularization explains profuse bleeding when injured (e.g., nose trauma).

Common Cause:
  - Kids putting fingers up their noses.
    - Alternative pressing objects like marbles and small toys.
  - Not allergies or physical impact as initially guessed.

Function of Conchae:
- Increase mucosal surface area for exposed air.
- Enhance air turbulence, allowing heavy particles to contact mucosal surfaces.
Air Trapping:
  - Particles larger than 6 microns are trapped by mucus.
  - Benefits include humidifying and warming inspired air.
    - Important in cold environments (e.g., Minnesota winters).

Functions:
  - Help warm and moisten inhaled air.
  - Lighten the skull (empty spaces reduce weight).
  - Provide resonance for the voice.
Sinus Locations:
- Frontal, sphenoid, ethmoid, and maxillary bones (paired).

Definition: Commonly known as the throat.
Subdivision: Comprised of:
  - Nasopharynx
  - Oropharynx
  - Laryngopharynx
Connections: Links nasal cavity and mouth to larynx and esophagus (extends to cervical vertebra #6).

Nasopharynx:
- Located posterior to the nasal cavity, continuous with nasal cavity through coanae.
- Passage Characteristics: Air only; contains a soft appendage (uvula) that prevents food/liquid from entering nasopharynx during swallowing.
Epithelial Structure: Lined with pseudostratified ciliated columnar epithelium.
Pharyngeal Tonsils:
- Also known as adenoids; help trap bacteria.
- Surgical removal of tonsils is less common today based on understanding of their immune function.
Pharyngotympanic Tube:
- Also called Eustachian tube; connects nasopharynx with the middle ear.
- Infection can cause pain and is identifiable by symptomatic vocalizations in infants and differing symptoms in adults.
Oropharynx:
- Positioned posterior to the oral cavity, continuous with oral cavity through the isthmus of Fauci's.