Dr. Sama ul Haque

Dr. Safaa

Histology of Respiratory Tract

Objectives

Differentiate between the olfactory and nasal mucosa.

Discuss the microscopic structure of larynx.

Describe the microscopic structure of trachea and lungs.

Differentiate between the terminal and respiratory

bronchioles.

Explain alveolar cells.

Respiratory System

This consists of the lungs and the air passages that lead to and form the lungs.

The air passages branch as they enter the lungs to finally form alveoli.

This system has 3 functions: 1.Air conduction;

2.Air filtration; 3.Gas exchange (respiration).

Air passages consist of: A conducting portion A respiratory portionConducting portion1.Nasal cavities;

2.Nasopharynx and oropharynx; 3.Larynx; 4.Trachea; 5.Paired primary bronchi.

Bronchi within the lungs branch extensively to form bronchioles. The terminal bronchioles form the last part of the conducting system.

The respiratory portion is the part of the tract where gaseous exchange takes place and includes: 1.Respiratory bronchioles; 2.Alveolar ducts; 3.Alveolar sacs; 4.Alveoli.

Respiratory Epithelium

The typical respiratory epithelium consists of

5 cell types:

1.Ciliated cells;

2.Goblet cells;

3.Brush cells (have short

blunt microvilli);

4.Small granule cells (contain secretory granules);

5.Basal cells (stem cells).

Nasal Cavity

Keratinized stratified squamous epithelium

Non Keratinized stratified squamous

epithelium

Pseudostratified ciliated columnar

epithelium with goblet cells

Olfactory Epithelium

Nasal Cavity

Nasal Cavity formed of:

1.Vestibule.

2.Respiratory

segment.

3.Olfactory segment

Vestibule:

Keratinized stratified squamous

epithelium

Non Keratinized stratified squamous

Contains vibrissae (fine hair), sebaceous

glands and sweat glands

Nasal CavityRespiratory segment

- Respiratory Epithelium

- Lamina Propria

Olfactory segment

- Olfactory Epithelium:

i. Olfactory cells (bipolar neurons)

ii. Basal cells

iii. Supportive cells

- Lamina Propria

Nasal Cavity

Lamina Propria

Mucous GlandsSerous GlandsVenous SinusesMucoperiosteum or Mucoperichondrium

Secretions of nasal mucosa- Bactericides - Lysozymes

Olfactory Epithelium

Nasopharynx

MucosaRespiratory EpitheliumStratified Squamous Epithelium

Lamina PropriaElastic TissueMucus Gland

Larynx

MucosaFalse vocal cords: Pseudostratified ciliated

columnar epithelium True vocal cords: Non Keratinized stratified

squamous epitheliumIntrinsic MusclesCartilages

- Larger Laryngeal Cartilages (Hyaline)

Larynx

Epiglottis

MucosaAnteriorly (Lingual mucosa):

Non Keratinized stratified squamous epithelium

Posteriorly: (Laryngeal mucosa):Pseudostratified ciliated columnar epithelium

Elastic Cartilage

Epiglottis

Trachea Mucosa

Pseudostratified ciliated columnar epithelium Lamina propia

Sub mucosa Connective Tissue Seromucous bronchial Glands

Hyaline Cartilage

Adventitia

Trachea

Trachea

Lung

BronchiMucosa;

Pseudostratified ciliated columnar epithelium Lamina propia

Muscularis; Submucosa;

Connective Tissue Seromucous Glands

Cartilage layer; Adventitia. Connective Tissue

At 1 mm diameter, the cartilage plates disappear and it becomes a bronchiole.

Respiratory Bronchioles

Alveolar Ducts

And

Alveoli

Intrapulmonary Bronchus

Terminal Bronchiole

Respiratory Bronchiole

Simple cuboidal epithelium

Alveolar CellsAlveolar Epithelial Cells (Type I Pneumocyte)Type II PneumocyteInteralveolar Pores Alveolar Macrophages (dust cells)Alveolar Surfactant

Alveolar walls & Alveolar cells

Alveolar walls & Alveolar cells

Respiratory Membrane It is the area where gas exchange occurs. It is formed of:

Alveolar Epithelium.

Fused basement membranes of the alveolar epithelium and the capillary endothelium.

Capillary Endothelium.

Thank you