Unit 2 - Respiratory System Functional Anatomy

Dr. Swartz A&P 2 Lecture

Respiratory General Features Pt. 1

1. Olfactory pits (placodes) form the nasal cavity and fuse with the pharynx

2. Stomodeum forms and fuses with the pharynx (throat)

3. Pharyngeal slits develop into pharynx

4. Foregut develops via ENDODERM and bud (laryngotracheal) from goregut to form trachea/bronchi/lungs

Respiratory General Features Pt. 2

Contains 4 layers

1. Mucosa

   • Made of lamina propria and epithelium

   • Lamina propria = loose connective tissue

   • Respiratory epithelium (ciliated)

   • Simple squamous epithelium

   • Epithelia can transition from one type to another → metaplasia

2. Submucosa

   • Lots of glands (goblet cells)

   • Connective tissues → cartilage, collagen, and elastin

3. Muscularis

   • Skeletal muscle, smooth muscle

4. Adentita

Respiratory General Features Pt. 3

Divided into UPPER & LOWER respiratory systems

1. Upper

   • Nose/nasal cavity

   • Paranasal sinuses

   • Pharynx

   1. Lower (Divided further into conducting & respiratory zone)

      • Larynx → Conducting

      • Trachea → Conducting

      • Bronchi → Conducting

      • Bronchioles → Conducting

      • Respiratory bronchioles → Respiratory

      • Alveoli ducts, sacs,, and individual alveoli → Respiratory

Respiratory General Features Pt. 4

Blood perfusion (transport) is performed by the right and left sides of the heart

1. Pulmonary circulation from the right side

   • Most of the blood, low O2, high CO2

2. Bronchial circulation from left side

   • high O2, low CO2

   • feeds bronchi just like how vasorum “feed” large vessel walls

3. Exchanges O2 and CO2

   • External respiration → exchange of gases between liquid (blood) to gas (air)

     • O2 out of air into blood; CO2 out of blood into air

   • Internal respiration → exchange of gases (in liquid phase) between blood and tissues

     • O2 out of blood into tissues

     • CO2 out of tissues into blood

Respiratory General Features Pt. 5

1. Site of olfaction

   • Mostly occurs in the nasal cavity using specialized mucosa

2. Major site of phonation

   • Larynx

   • Pharynx

   • Oral cavity/tongue

3. Cleans, Moistens, and Warms inspired air

   • Sticky to the surface and hair for cleaning

   • Secretions to moisten the air

   • Turbulent air flow and relatively high surface area for heat exchange

4. Site of virus and microbial infections

   • NOT STERILE ENVIRONMENT

   • Most cold viruses have evolved to enter epithelial cells of the respiratory mucosa

   • COVID-19 uses angiotensin converting enzyme for infection

Describe the location, structure, and function of each of the following: nose, paranasal sinuses, and pharynx

• Nose/Nasal Cavity:

  • Location: Anterior part of the face; part of the upper respiratory system.

  • Structure:

    • External nose: cartilage + maxillary bone (frontal process).

    • Nasal cavity: lined by respiratory epithelium (pseudostratified ciliated with goblet cells).

    • Separated by septum (vomer + ethmoid).

    • Has conchae (turbinates) for airflow turbulence.

  • Function:

    • Conducts air into the respiratory system.

    • Filters, warms, and moistens inspired air.

    • Houses olfactory receptors (olfaction).

    • Acts as a resonance chamber for voice (phonation).

• Paranasal Sinuses:

  • Location: Surrounding the nasal cavity; found in frontal, ethmoid, sphenoid, and maxillary bones.

  • Structure:

    • Bony air-filled chambers lined with respiratory epithelium

    • Connected to the nasal cavity via drainage canals

  • Function:

    • Lighten the skull

    • Contribute to voice resonance

    • Condition air (warm/moist)

    • Mucous drainage (can get blocked → sinusitis)

• Pharynx:

  • Location: Posterior to nasal and oral cavities; connects to the larynx and esophagus.

  • Structure:

    • Muscular tube lined with mucosa (respiratory epithelium and stratified squamous).

    • Divided into 3 regions:

    • Nasopharynx: behind nasal cavity.

    • Oropharynx: behind oral cavity.

    • Laryngopharynx: leads to larynx and esophagus.

  • Function:

    • Passageway for air and food

    • Swallowing (directs food into the esophagus, air into the larynx)

    • Resonance for speech

    • Contains tonsils (immune function)

List and describe several protective mechanisms of the respiratory system

Muco-ciliary Escalator: Sticky mucous traps particles; cilia move it to oropharynx for removal.

Nasal Hairs and Secretions: Vibrissae and mucous trap particles; lysozymes and defensins kill microbes. Goblet cells secrete defensins.

Nasal conchae: create turbulent air to trap particles

Ciliated Epithelium: Moves debris-laden mucous away from lungs.

Macrophages: Dyson cells in alveoli remove particulates.

Olfactory Mucosa: Detects irritants.

Immune Tissue: Tonsils and lymphoid tissue in pharynx help fight infection

Conducting vs. Respiratory Zone Structures

1. Conducting Zone:
   Nose, pharynx, larynx, trachea, bronchi, bronchioles; no gas exchange; conditions air.
   

2. Respiratory Zone: Respiratory bronchioles, alveolar ducts, alveoli; site of gas exchange.

Larynx, Trachea, and Bronchi: Functional Anatomy

• Larynx: Organ of phonation; contains vocal cords and cartilages (thyroid, cricoid).

• Trachea: Connects larynx to bronchi; has C-shaped hyaline cartilage rings.

• Bronchi: Branch from trachea; primary, secondary, tertiary branches; lined with respiratory epithelium, cartilage, and smooth muscle.

Respiratory Membrane: Structure and Function

• Very thin barrier of type I pneumocytes, capillary endothelial cells, and fused basal laminae.

  • Type 1 pneumocytes: thin and main cell involved in gas exchange

• Allows efficient diffusion of O₂ and CO₂.

Descending Respiratory Passageway to Alveoli

• Nose → Nasal cavity

• Pharynx

• Larynx

• Trachea

• Primary → Secondary → Tertiary bronchi

• Bronchioles

• Terminal bronchioles

• Respiratory bronchioles

• Alveolar ducts → Alveolar sacs → Alveoli

Gross Structure of Lungs and Pleurae

• Right lung: 3 lobes; Left lung: 2 lobes + cardiac notch.

• Lobes → segments → lobules.

• Covered by visceral pleura; thoracic wall lined by parietal pleura with serous fluid in between.

Importance of Intrapleural Partial Vacuum

• Intrapleural pressure is always negative (Pip < Ppul).

• Prevents lung collapse by maintaining linkage between lung and thoracic wall (transpulmonary pressure).

Boyle’s Law and Ventilation

• Boyle’s Law: P1V1 = P2V2.

• Increased thoracic volume → decreased pressure → air flows in (inhalation).

• Decreased volume → increased pressure → air flows out (exhalation).