22.9 The Bronchi and Subdivisions

Air passages undergo how many orders of branches?

23 branches

Branching referred too-

bronchial tree

from tips of bronchial tree

-conducting zone structures give rise to respiratory zone structures

Conducting Zone

Each meain bronchus enter what ? into 1 lung

hilum

Conducting zone

Each main bronchus then branches into ?

Lobar (secondary) bronchi

Conducting zone

Each lobar bronchus branches into ?

Segmental ( Tertiary ) bronchi

Bronchioles -

less than 1 mm in diameter

Terminal bronchioles

smallest of all branches

-less than 0.5 mm in diameter

In conducting zone, from bronchi to bronchioles, changes occur: 

-support structures change

-epithelium type changes

-amount of smooth muscle increases

When support structures change from bronchi to bronchioles -

• Cartilage rings become irregular plates

• In bronchioles, elastic fibers replace cartilage altogether

when epithelium type change from bronchi to bronchioles -

• Pseudostratified columnar gives way to cuboidal

• Cilia and goblet cells become more sparse

When the mount of smooth muscle increases when bronchi to bronchioles -

• Allows bronchioles to provide substantial resistance to air passage

Repiratory zone begins where

terminal bronchioles feed into respiratory bronchioles, which lead into alveolar ducts and finally into alveolar sacs (saccules)

Alveolar sacs contain clusters of

alveoli

Respiratory membrane in bronchi -

• Blood air barrier that consists of alveolar and capillary walls along with their fused basement membranes

• -very thin

Alveolar walls consist of:

• • Single layer of squamous epithelium (type I alveolar cells)

  • Scattered cuboidal type II alveolar cells secrete surfactant and antimicrobial proteins

• Alveolar pores connect adjacent alveoli which does-

• Equalize air pressure throughout lung

  • Provide alternate routes in case of blockages 

Alveolar macrophages

keep alveolar surfaces sterile