Lab 10 Respiratory System: 1) Index 2) Introduction 3) Things to Identify 4) Olfactory Epithelium 5)Larynx and Vocal Cords 6) Trachea 7) Lung 8) Practical

 

Lungs

 

# 154 - Lung with bronchioles, pseudostratified ciliated columnar epithelium, h-e

# 153 - Lung, human, h-e

# 219 - Lung

 

Your section of adult lung may contain bronchi (lined with pseudostratified to simple ciliated columnar epithelium; reinforced with cartilage plates; containing seromucous glands and ringed with smooth muscle)or bronchioles (lined with ciliated columnar to non-ciliated cuboidal epithelium; ringed with smooth muscle bands, but containing no cartilage or seromucous glands.)

A branch of the pulmonary artery accompanies each bronchus and each bronchiole as they pass into the lung. Pulmonary veins, however, are found at a greater distance from bronchi and bronchioles in the interalveolar septa..

The walls of the alveolar ducts have numerous thin outpocketings or alveoli (air sacs) lined with simple squamous epithelium. Alveolar spaces are separated from one another by incomplete septa. This septal pattern is unique for the lung. Study the alveoli. Try to identify septal cells, alveolar phagocytes containing dust and soot particles, pulmonary arteries or arterioles, veins or venules, alveolar capillaries, lymphatics and lymphoid tissue.

Two types of cells in the alveolar epithelium are type I pneumocytes (squamous epithelial cells) and type II (cuboidal cells that synthesize surfactant that is secreted onto the alveolar luminal surface to reduce surface tension). Note the dust cells or alveolar macrophages that phagocytose debris that enters the airsacs.

Lung structures to identify:

1. Largest or first order bronchi - lined by respiratory epithelium (pseudostratified ciliated columnar with goblet cells). Crescent-shaped masses of cartilage may still be seen occasionally bound together by connective tissue.

2. Muscular bronchiole - lined with ciliated pseudostratified columnar or ciliated columnar epithelium and circularly (spirally) disposed smooth muscle and connective tissue. Cartilage usually absent. Goblet cells fewer. Its lining may be in folds. Bronchioles are less than 1 mm in diameter.

3. Terminal bronchioles - lined with ciliated columnar epithelium but no goblet cells. Thinner walls; decreased diameter. Bands of smooth muscle. Non-ciliated Clara cells with rounded apices and prominent nuclei bulge into the lumen. Clara cells secrete a glycoaminoglycan surfactant which differs from that secreted by Type II pneumocytes. Terminal bronchioles give rise to 2 or more respiratory bronchioles.

4. Respiratory bronchioles - lined with ciliated simple cuboidal epithelium (in distal regions, non-ciliated) and supported with smooth muscle and elastic connective tissue; their walls are interrupted by delicate air pockets and outpocketings.

5. Alveolar ducts - the respiratory bronchioles open up into these large spaces. They are demarcated by knobs of muscle fibers at the ends of alveolar walls.

6. The round spaces with a variety of radiating projections form alveolar sacs and the compartments formed by the respective projections are called alveoli. These are lined with simple squamous epithelium and are reinforced with elastic fibers.

References: Gartner, pp. 247 - 250 DiFiore, p. 239, Fig. 15.8 p. 241, Fig. 15-9, 15.10, 15-11 Ross, pp. 542-547 (EM of lung tissue) pp. 552 - 553 (bronchus) pp. 554 - 557 (lung tissue) Wheater, pp. 226 -234, Figs. 12.9 - 12.20

 

This is the One of the Larger Structures you will find in the Lungs. This is a Bronchus, outlined by the Red dotted line. The yellow arrows are pointing to Plates of Hyaline Cartilage. The presence of these plates is the Key way to classify this tube as a Bronchus because in bronchi, the cartilage plates are still present. So if you see cartilage, it is a Bronchus.

Red dotted Line - Bronchus

Yellow arrow - Plates Of Cartilage

 

 

 

This is another shot of a Bronchus, (white dotted line). The reason why we can call this a Bronchus is the PRESENTS OF THE CARTILAGE PLATE (blue arrow). As soon as you see cartilage you know it is a Bronchus, no matter how much of the cartilage is present.

White dotted line - Bronchus

Blue arrow - Cartilage Plate

 

 

 

 

This is the next smallest structure you will find in the lungs, which is the Muscular Bronchiole (Blue dotted line). There are two reasons why we can safely classify this as a Muscular Bronchiole. First the fact that CARTILAGE IS ABSENT. The next is the presence of the band of Smooth Muscle (red arrow) running around the bronchiole.

Red arrow - Smooth Muscle Band

Blue dotted Line - Muscular Bronchiole

 

 

 

This is an image showing the next two smaller structures transitioning into each other that you will find in the Lungs which are Terminal Bronchiole (blue arrow) and Respiratory Bronchiole (Red arrow). There are some main differences between these two that will allow you to differentiate them. The most important is the composition of the walls of each. Can you see the fact the the walls of the Terminal Bronchiole are very continuos (green arrows) and the walls of the Respiratory Bronchiole have Gaps and discontinuous (Black arrows). That is the major way to differentiate the two from each other. Of note is the fact that here is the transition from Conducting airway, (terminal bronchiole) and Respiratory Airway (Respiratory Bronchiole).

Red arrow - Respiratory Bronchiole

Blue arrow - Terminal Bronchiole

Black arrow - Gaps in wall

Green arrow - Continuos Wall

 

 

 

 

 

This is another image showing the transition from Terminal Bronchiole (Red arrow) to Respiratory Bronchiole (Blue arrow). Again notice the differences in the composition of the walls. The Terminal Bronchiole is continuos and solid while the Respiratory Bronchiole is full of gaps.

 

Blue arrow - Respiratory Bronchiole

Red arrow - Terminal Bronchiole

 

 

 

 

 

This is an image showing the final two smallest structure you will find in the lungs. Starting off with what is called the Alveolar Duct, (green arrow) which connects the Respiratory Bronchiole to the Alveolar Sacs (blue arrows) which are the ends of the airways. If it looks like a sac, like the ones in the image do, than you can safely call it an alveolar sac, but if it look like it has several sacs along it, it is probably a Alveolar duct.

 

Green arrow - Alveolar Duct

Blue arrow - Alveolar Sac

Lungs (Bronchus)

Lungs (Bronchus)

Lungs (Muscular Bronchiole)

Terminal Bronchiole to Respiratory Bronchiole

Terminal Bronchiole to Respiratory Bronchiole

Alveolar Duct to Alveolar Sac