HISTOLOGY OF TRACHEA AND LUNG

Dr.ushakannan,Asst.professor.

RESPIRATORY SYSTEM Conducting Part-

responsible for passage of air and conditioning of the inspired air. Examples:nasal cavities,pharynx, trachea, bronchi and their intrapulmonary continuations.

Respiratory Part-involved with the exchange of oxygen and carbondioxide between blood and inspires air.Includes the lungs

Trachea

Left and Right lobar bronchus Lungs.

Lobar Bronchi. . Lobes(Right 3 and Left 2.).

Segmental bronchi Broncho-pulmonary segments(10+10)

Bronchioles Terminal bronchioles. Respiratory Bronchioles. Alveolar ducts Alveolar sacs

Alveoli.

RESPIRATORY SYSTEM HISTOLOGY

Trachea Bronchus -Primary bronchus -Secondary bronchus -Tertiary bronchus Bronchiole Lung

Trachea

Mucosa -Epithelium -Lamina propria Sub mucosa Cartilage &muscle

layer Adventitia

RESPIRATORY EPITHELIUM

Trachea Mucosa Epithelium -Pseudo stratified ciliated

columnar/ Respiratory epithelium

Cells-Ciliated columnar cells - Goblet cells -Brush cells - Basal cells -Granule (kulchitsky)

cellsSecretory cells -Clara

cells( bronchiolar cells) surfactant.

Lamina propria - Elastic fibre, Lymphocyte, Mast cells, Blood vessels

Trachea Sub mucosa- Loose connective tissue Tracheal glands-Mixed

(serous &mucus) glands Blood vessels and ducts Cartilage &smooth muscle

layer- ”C” Shaped hyaline cartilage

having perichondrium and chondrocytes

Ends of cartilage connected by smooth muscles

Adventitia-fibro elastic tissue

TRACHEA (T.S. LOW POWER)

CELLS SEEN IN THE RESPIRATORY PASSAGES Goblet cells Non-ciliated serous cells Basal cells Cells of Clara Brush cells Argyrophil Cells similar to diffuse

endocrine cells of gut Lymphocytes

HISTOLOGY OF LUNG

BRONCHUS Principal bronchus -same as trachea Secondary /Lobar bronchus -Irregular hyaline cartilage -Pseudo stratified ciliated

columnar Tertiary /Segmental

bronchus -Columnar epithelium -Patches of cartilage

Segmental or tertiary bronchus: The number of Goblet cells reduced.

(epithelium) The number of Glands reduced.

(submucosa) The cartilage is present in the irregular

plates.

BRONCHIOLE Terminal bronchiole -Columnar epithelium -No cartilage

- smooth muscle + -Clara cells (dome shaped)

present

-Cuboidal epithelium -No mucous gland Respiratory bronchiole

RESPIRATORY BRONCHIOLE

Cuboidal epithelium.

No mucus gland.

Lined by simple ciliated or columnar epithelium.

Smooth muscles form ring underneath the epithelium in between two adjacent alveoli.

Alveolar duct-Alveolar sac. Alveolar duct lined by simple squamous

epithelium. Increase the surface area of gaseous

exchange. Surrounded by network of capillaries.

Inter alveolar septum- Is the wall present in between the two

adjacent alveoli. Consists of epithelial cells of each alveolus on

both sides. Connective tissues contain

capillaries,collagen,elastic fibres,fibroblasts and macrophages(dust cells).

Alveoli are thin walled outpouchings , lined by a single layer of cells.

Two types: Pneumocyte 1 and2 cells. Also called pneumocyte or alveolar cells.

Type 1 Pneumocyte are squamous cells ,adjacent cells are joined together by tight junctions.

Function: Gaseous exchange. Type 11 Pneumocytes: Cuboidal cells,scattered among type 1 cells. Secrete Pulmonary surfactant which lowers the surface

tension and prevents alveoli from collapsig. Alveolar macrophages or Dust cells – Remove debris.

Bronchus and Bronchiole

DIFFERENCES BETWEEN BRONCHI AND BRONCHIOLES

Bronchus Glands are present. Presence of cartilage. Goblet cells are

present. Spiraliy arranged

smooth muscle layer. Mucosa folded lined

by ciliated pseudostratified columnar cells.

Bronchioles No glands No cartilage No goblet cells Thick smooth muscle

layer Mucosa highly folded

lined by simple columnar or cuboidal cells with Presence of Clara cells

Many elastic fibres

Trachea (T.S. Low Power)