Respiratory Part 2

Primary bronchi

Arise after division of the trachea and then passes into the lungs

Right primary bronchus

Wider and runs more superior then trifurcates at hilum

More susceptible to aspiration of foreign bodies

Left primary bronchus

Passes inferolateraly to the arch of the aorta and anterior to esophagus

Bifurcates at the hilum

Lobar (secondary) bronchi

Intrapulmonary, two on the left and three on the right to each lobe of the lung

Segmental (tertiary) bronchi

Intrapulmonary, 10 on the right and 8-10 on the left

Pyramidal-shaped bronchopulmonary segments of the lung that are surgically resectable because each has its own pulmonary artery and are drained by veins that run through the adjacent interlobar CT

Primary Bronchi histo

C shaped cartilage and an incomplete layer of smooth muscle deep to mucosa

Lobar and segmental bronchi histo

Surrounded by alveoli

Conducting (primary) bronchiole characteristics

Cartilage, plates, and glands are absent in all bronchioles

disease conditions: muscles contraction, fluid, mucus collection

Conducting (primary) bronchiole histo

Terminal bronchioles characteristics

largely clara cells and simple cuboidal

goblet cells are absent

surrounded by lung tissue

Respiratory bronchioles characteristics

Transition zone is involved in both air conduction and gas exchange

contatins alternating thick and thin walls

Respiratory bronchioles histology

High amont of elastic and reticular fibers in CT

Thin wall: made of alveoli outpouchings

Thick walls: made of cuboidal cells, Clara cells, and smooth muscle

Alveolar ducts

Continuation of respiratory duct

Walls consist of alveoli

Alveolar ducts terminate at alveolar sacs

gas exchange

Alveolar sacs

Arise from alveolar ducts

Common space surrounded by clusters of alveoli

Alveoli are seperated by interalveolar septa that contain blood capillaries

Alveoli

site of gas exchange

surrounded by network of capillaries that bring blood close to gas exchange

300-600- millionalveoli in an adult

surrounded by visceral pleura

Type 1 pneumocyte

covers 95% of surface

squamous cell joined by tight junctions

facilitate air exchange-rapid diffusion

terminally differentiated

Type 2 pneumocyte

Cuboidal cells at septal junctions

stem cell for type 1 pneumocyte

secretes lipid and protein surfactant that decreases surface tension mixes with alveolar fluid that establishes a liquid air interface and excess is resorbed by type 2 cells

modulates immune response

Alveolar septum thin portion

most gas exchange occurs here

air-blood barrier

Type 1 pneumocyte, surfactant, capillary endothelium

Basal lmina fusion stabilizes alveolar and capillary interface

Air blood barrier

formed by cells and cel products across gas must diffuse between alveolar and capillary compartments

Alveolar septum thick portion

Location of both types of pneumocytes, fibroblasts, WBC

abdundant elastic and reticular fibers

Alveolar macrophages phagocytize particulate matter found in lumen

Alveolar pores

septal wall can be interrupted by small pores that connect adjacent alveoli

not visible histologically

equalize pressure and allow collateral air flow if alveoli is blocked