Title: Anatomy / 5 Respiratory system

Q: Airways: parts and subdivision
A: The airways are divided into 2 main sections:
- Upper airways: Nasal cavity, oral cavity, and pharynx;
- Lower airways: Larynx, trachea, and bronchi

Q: Airways: Epithelium
A: - Respiratory epithelium: Characterized by being ciliated (containing tiny hair-like structures).
- Location: Found lining the nasal cavity and the mucosa of the trachea.

Q: Airways: nasal cavity
A: - Structure: Composed of both cartilaginous and osseous (bony) parts.
- Nasal septum: Divides the cavity into two halves.
- Nasal concha (Turbinates): Bony projections that increase surface area.
- Regions: Includes the respiratory region (epithelium) and the olfactory region (for sense of smell).

Q: Airways: Paranasal
sinuses
A: Air-filled extensions of the nasal cavity located in the cranial bones.
frontal sinus: drains into the middle nasal meatus via the frontonasal duct;
maxillary sinus: drains into the middle nasal meatus through the semilunar hiatus;
sphenoidal sinus: drains into the sphenoethmoidal recess above the superior nasal concha;
ethmoidal sinus: drains into the middle/superior nasal meatus

Q: Airways: Pharynx (levels, waldeyers tonsillar rings)
A: A muscular tube (containing levators and constrictors) where respiratory and digestive pathways cross;
- 3 Levels: Nasopharynx (upper), Oropharynx (middle), and Laryngopharynx (lower);
- Waldeyers tonsillar ring: A circular arrangement of lymphoid tissue in the pharynx;
- Consists of:
  - tubal tonsil;
  - palatal tonsil;
  - lingual tonsil^^.

Q: Airways: Larynx (Function, Cartilage, Innervation)
A: Functions as the "voice box" and protects the lower airways.
Cartilages:
- thyroid cartilage: forms the Adam’s apple, protects vocal chords;
- cricoid cartilage: ring-shaped, below the thyroid cartilage – provides support;
- epiglottis: leaf-shaped, bends down to cover the laryngeal inlet during swallowing;
- arytenoid cartilages: pyramid-shaped, anchor the vocal chords – control tension and position;
- mucosa: respiratory epithelium;
Innervation: Primarily supplied by the recurrent laryngeal nerve (a branch of the vagal nerve/Cranial Nerve X).

Q: Airwasys: Trachea (Windpipe)
A: - tubular structure connecting the larynx with the bronchi;
- wall supported by C-shaped hyaline cartilage rings;
- starts at 6th/7th cervical vertebra – bifurcation at 4th thoracic vertebra;
- ~12 cm long

Q: Airways Bronchi
A: The sequence of the airway passages into the lungs:
1. 2 Main bronchi (Right and Left).
2. Lobar bronchi.
3. Segmental bronchi.
4. Bronchioles (Note: these contain no cartilage).
5. Terminal bronchioles.
6. Alveoles (Site of gas exchange).

Q: Lung: Difference
between Right and Left
A: - Right Lung: Consists of 3 lobes.
- Left Lung: Consists of 2 lobes.

Q: Lung: Fissures
A: These are the deep grooves that separate the lobes.
- Oblique fissure: Present in both the right and left lungs.
- Horizontal fissure: Present only in the right lung.

Q: Lung: segments
A: The lobes are further divided into functional units called segments.
- Right lung: 10 segments.
- Left lung: 9 (sometimes 10) segments.

Q: Lung: Lobules & Acini
A: - Lobule: A smaller subdivision of a segment; each contains approximately 12 acini.
- Acinus: The functional unit of the lung; each contains approximately 200 alveoli (the sites of gas exchange).

Q: Lung: Pneumocytes
A: Specialized cells found in the alveolar walls.
- Type 1 (95%): responsible for gas exchange.
- Type 2: Responsible for producing surfactant (a substance that prevents the alveoli from collapsing)

Q: breathing
mechanism: parts
A: - Serous cavity: space between the lungs and the chest wall;
- Pleura layers: parietal -, costal - & visceral -, pulmonal pleura;
- Serous fluid: Fluid within the pleural cavity that creates a capillary force, keeping the lung attached to the chest wall;
- Muscles: Intercostal muscles (internal and external located between the ribs);

Q: breathing
mechanism: Working
mechanism
A: Expansion: The lungs expand within the thorax due to the capillary force, which ensures the visceral pleura follows the movement of the chest wall;
Pneumothorax: A condition where air enters the pleural cavity, breaking the capillary force --> lung collapses

Q: breathing
mechanism: relevant
innervation
A: - Diaphragm: Controlled by the phrenic nerve;
- Larynx: The recurrent laryngeal nerve; is responsible for opening the "voice box" during breathing to allow airflow.