Respiratory System Anatomy

• The respiratory system is a complex of organs and tissues, and it is responsible for the exchange of blood carbon dioxide (CO2) with air oxygen (O2).

Conducting Portion

• Consists of structures that conduct air to the sites of respiration, including the nasal cavities, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles

Respiratory Portion

• Consists of structures where gas exchange takes place
• This includes the respiratory bronchioles, alveolar ducts, alveolar sac, and alveoli

Nasal Cavities

• Contains two types of regions: olfactory and non-olfactory

Non-Olfactory Regions

• Has pseudostratified ciliated columnar epithelium with goblet cells
• Contains mucous glands and venous sinuses in the lamina propria
• Venous plexuses swell every 20-30 minutes, alternating air flow from side to side to prevent over-drying
• Arterial blood flow warms inspired air and Held open by surrounding cartilage or bone

Olfactory Regions

• Has particularly thick pseudostratified epithelium, and no goblet cells or mucus
• Contains olfactory cells (bipolar neurons) and Bowman’s glands that flush odorants from the epithelial surface

Pharynx

• Contains mucous glands and is lined by stratified squamous epithelium
• The epithelium is continuous with the proximal end of the larynx

Larynx

• Has ventricular folds that are lined by pseudostratified epithelium
• Ventricles and their folds give resonance to the voice
• Vocal cords are lined by stratified squamous epithelium
• Can stop foreign objects from reaching the lungs and Close to build up pressure when coughing is required

Trachea

• The wall trachea consists of three-layers:
  • Mucosa
  • Submucosa
  • Adventitia

Mucosa

• Lined by typical respiratory epithelium, and it is underlain by connective tissue of the lamina propria that contains seromucous glands.

Submucosa

• Contains C-shaped rings of hyaline cartilage, covered by perichondrium.

Adventitia

• Consists of connective tissue containing collagen

Bronchus

• Principal bronchus is the same as trachea

Secondary/Lobar Bronchus

• Has irregular hyaline cartilage and pseudo stratified ciliated columnar

Tertiary/Segmental Bronchus

• Consists of columnar epithelium and Patches of cartilage

Bronchiole

• Terminal bronchiole consists of columnar epithelium, smooth muscle, and Clara cells, but no cartilage
• Respiratory bronchiole composes of cuboidal epithelium and has no mucous glands

Bronchioles

• No glands
• No cartilage
• No goblet cells
• Thick smooth muscle layer
• Presence of Clara cells
• Many elastic fibres

Bronchus

• Smooth Muscle
• Cartilage

Terminal Bronchiole

• Columnar epithelium
• No cartilage
• Smooth muscle
• Clara cells present

Respiratory Bronchiole

• Cuboidal epithelium
• No mucous gland

Alveoli

• Saclike evaginations (about 200 m in diameter) of the respiratory bronchioles, alveolar ducts, and alveolar sacs
• Structurally, they resemble small pockets that are open on one side, similar to the honeycombs of a beehive
• Within these cuplike structures, O2 and CO2 are exchanged between the air and the blood
• The structure of alveolar walls is specialized to enhance diffusion between the external and internal environments

Interalveolar Septum

• The wall lies between two neighboring alveoli
• These septa are vascularized with the richest capillary network in the body

Blood-Air Barrier

• Surface lining and cytoplasm of the alveolar cells
• Fused basal laminae of the closely apposed alveolar cells and capillary endothelial cells
• Cytoplasm of the endothelial cells