8/3/2019 Histology of The

1/24

Histology of the

Respiratory System

8/3/2019 Histology of The

2/24

8/3/2019 Histology of The

3/24

The respiratory system provides for gasexchange between the environment andthe blood. It is subdivided into two parts.The Conducting portion is a continuum of

air passageways that conduct air from theenvironment into respiratory spaces andback out. The respiratory portion consists

of many interconnected air-filled spaceswith very thin linings which allow rapid gasexchange.

8/3/2019 Histology of The

4/24

Microanatomy of theRespiratory System

8/3/2019 Histology of The

5/24

Microanatomy of the Respiratory System

A. Nose

B. Pharynx

C. Larynx

D. Trachea and Primary Bronchi

E. Lungs

8/3/2019 Histology of The

6/24

NOSE The anterior region of the nasal cavity is lined with stratified

squamous epithelium, while the posterior region is made upof the olfactory epithelium with modified bipolar neuronsand the pseudostratified ciliated columnar epithelium with

Goblet cells, basal cells, brush cells (columnar cells withmicrovilli) and dense core granule cells (argyrophilic cells).

The Muscularis Externa region in the nasal cavity isoccupied by cartilage of the nose and the skeletal elements

of skull The Lamina Propria is primarily loose Fibrous Elastic

Connective Tissue with numerous blood vessels

8/3/2019 Histology of The

7/24

OlfactoryCell

SupportingCell

BasalCell

8/3/2019 Histology of The

8/24

8/3/2019 Histology of The

9/24

PHARYNX Most areas are covered by Pseudostratified ciliated

epithelium with Goblet cells, while Stratified SquamousEpithelium covers regions of wear and tear. Theseare areas that contact food during swallowing.

The lamina propria consists primarily of loose tomoderately dense Fibrous Elastic Connective Tissuewith many elastic fibers

8/3/2019 Histology of The

10/24

8/3/2019 Histology of The

11/24

LARYNX

Pseudostratified ciliated epithelium w/Goblet cells

Stratified squamous epithelium linesregions such as vocal cords, epiglottisand the upper part of larynx.

8/3/2019 Histology of The

12/24

8/3/2019 Histology of The

13/24

8/3/2019 Histology of The

14/24

TRACHEA AND PRIMARY BRONCHI

The epithelium lining the trachea and bronchi is very similar to thepseudostratified ciliated columnar respiratory epitheliumdescribed for the nasal cavity.

In the lower trachea,Clara cells appear in lower trachea andnumerous in Bronchi. Clara cells have a smooth apical surface

which protrudes as a dome. A Submucosa is visible, containing tubuloacinar glands.

The muscularis externa in the trachea and bronchi containsTracheal rings (hyaline cartilage enclosed by a perichondrium ofdense regular collagenous connective tissue) and Trachealis

muscles (smooth muscle tissue that connects the ends of eachtracheal ring).

The Lamina Propria consists of a thin layer of loose FibrousElastic Connective Tissue

8/3/2019 Histology of The

15/24

8/3/2019 Histology of The

16/24

8/3/2019 Histology of The

17/24

LUNGS Each lung is covered by a serosa(visceral pleura)

It is composed of the following:

Intrapulmonary Bronchi

Bronchioles

Alveoli, Alveolar Ducts, Alveolar Sacs

8/3/2019 Histology of The

18/24

INTRAPULMONARY

BRONCHI The epithelium is apsudeostratified ciliated columnarepithelium with goblet cells, brush cells, clara cells and smallgranule cells.

TheLamina propria is loose Fibrous Elastic ConnectiveTissue , containing solitary lymphoid nodeles.

The Submucosa is loose to moderately dense Fibrous ElasticConnective Tissue

The muscularis externacontains hyaline cartilage plates A sparse tunica adventitia is loose Fibrous Elastic

Connective Tissue

8/3/2019 Histology of The

19/24

BRONCHIOLES The epithelium varies according to the size of the air

passageway. Pseudostratified ciliated columnar epitheliumwith a few scattered goblet cells occurs in larger bronchioles.Ciliated simple columnar epithelium occurs in terminalbronchioles. Ciliated and non ciliated simple low columnar or

cuboidal epithelium with patches of simple squamousepithelium occurs in respiratory bronchioles. Non ciliatedclara cells become more numerous in terminal bronchiolesand increased in number.

The lamina propria of loose Fibrous Elastic ConnectiveTissue may contain lymphoid nodules.

The Muscularis externa of smooth muscle spirals aroundbronchioles and terminal bronchioles.

8/3/2019 Histology of The

20/24

ALVEOLI, ALVEOLAR DUCTS,ALVEOLAR SACS

Patched simple cuboidal epithelium occur in the walls of alveolar ducts andalveolar sacts while alveoliare lined by simple squamous epithelium containing:

Type I pneumocytes (small alveolar cells) squamous cells across which most gasexchange occurs

Type II pneumocytes(giant alveolar cells) rounded cells that secrete

surfactant.

Pulmonary or alveolar macrophages irregularly-shapged monocyte-derivedcells which remove foreign materials from alveoli and small air passageways.

The Lamina propriais very thin loose Fibrous Elastic Connective Tissuecontaining scattered fibroblasts and very fine collagenous fibers.

The submucossa and muscularis externa layers are absent in most areasaround alveoli but a few scattered smooth muscle fibers occur around somealveolar ducts.

8/3/2019 Histology of The

21/24

8/3/2019 Histology of The

22/24

8/3/2019 Histology of The

23/24

Histological Criteria for ClassifyingIntrapulmonary Structures

8/3/2019 Histology of The

24/24

Bronchi large lumen, pseudostratified columnar, hyalinecartilage plates in the wall

Bronchioles smaller lumen, pseudostratified columnar tosimple cuboidal epithelium, One or more layers of smoothmuscle in the wall, no cartilage in the wall

Respiratory bronchioles some simple squamous lining

epithelium, luminal surface lined by simple cuboidal or columnarepithelium

Alveolar ducts and sacs simple cuboidal lining epithelium,luminal surface is lined by simple squamous epithelium

Alveoli lined by simple squamous epithelium with occasionalrounded cells.