Do you want to learn about the lung histology?
In this article I am going to discuss on normal lung histology of animal. I will also discuss on trachea histology with diagram.
You will get little information on pneumocytes from lung histology diagram. After reading this article you will able to learn histology of lung alveoli. You will able to differentiate different types of bronchi from bronchiole of lung. You may also learn about the respiratory membrane at the end of this article.
I have a special gift for you – histology of lung ppf at the end of the article.
If you have interest to learn lung histology slide labeled continue this article. Okay, let’s learn lung histology slide together.
Lung histology identification
I would like to enlist the structures that you should identify under the microscope –
#1. Primary bronchi
#2. Secondary bronchi
#3. Tertiary bronchi
#4. Primary bronchiole
#5. Terminal bronchiole
#6. Respiratory bronchiole
#7. Alveolar duct
#8. Alveolar sac
#9. Alveoli or alveolus
#10. Type I pneumocytes
#11. Type II pneumocytes
#12. Pulmonary or alveolar macrophage
#13. External covering of lung
Lung is composed of external covering of serous membrane of visceral pleura. You will find mesothelium lining on connective tissue layer in lung serous membrane.
There is a sub serous areolar tissue in lung histology.
Do you know about the bronchial tree of lung?
There bronchial tree includes the followings structures –
#1. Primary bronchus (extrapulmonary bronchi)
#2. Intrapulmonary bronchi (secondary and tertiary bronchi)
#3. Primary bronchiole
#4. Terminal bronchiole
#5. Respiratory bronchiole
#6. Alveolar duct (two to eleven ducts)
You will find the following changes in a lung histology slide –
#1. The lining epithelium gradually decrease in thickness as it is traced distally
#2. The gland and goblet cells gradually decrease and disappears completely
#3. Cartilaginous support decrease while the number of elastic fibers increase
Lung histology slide
The lung contains loose fibroelastic connective tissue called stroma. You will find loose connective tissue septa that separate the lung lobes and lobules.
There is very little intralobular connective tissue occurs in lung tissue. Large blood vessels are found in the lung tissue.
The most available space of lung tissue filled with clumps of alveoli. These alveoli are most associated with alveolar sac or part of wall of alveolar duct.
In the lung histology slide, you will find different types of bronchi and bronchiole. Let’s learn the histology of bronchus from lung together.
There are three types of bronchi in lung and they are –
#1. Extrapulmonary bronchi (primary bronchi)
#2. Intrapulmonary bronchi (secondary and tertiary bronchi)
I would like to discuss the details histological features of these bronchi.
Extrapulmonary bronchi histology of lung
The histology of extrapulmonary bronchi is similar with trachea histology. Do you want to describe bronchi histology? Then you should know the general organizational pattern of a tubular organs.
In the histology of extrapulmonary bronchi you will find the following layers –
#1. Mucosa layer
#2. Lamina propria layer
#3. Submucosa layer
#4. Muscularis layer
#5. Adventitia layer
In the mucosa layer of primary bronchi you will find the respiratory epithelium. Respiratory epithelium contains the following types of cells –
#1. Pseudostratified ciliated columnar epithelium (tall and densely packed cells)
#2. Goblet cells (mucous secretory cells)
#3. Basal cell (round cell)
#4. Brush cell (columnar cells)
#5. Small granule cells
Thin layer of loose fibro-elastic connective tissue present in lamina propria of bronchi. In submucosa of primary bronchi, you will find moderate dense fibro-elastic connective tissue.
In the muscularis layer of primary bronchi you will find the following structures –
#1. Presence of c shaped irregular hyaline cartilage which is open dorsally. The free end of hyaline cartilage os bridged by smooth muscle
#2. Presence of dense connective tissue
#3. The smooth muscle layer run spirally in criss cross bundle.
In adventitia of primary bronchi you will find the loose connective tissue.
Intrapulmonary bronchi histology of lung
All the histological features are almost similar with the histology of extrapulmonary bronchi. You will find exceptional features in the muscular layer. In muscularis layer of intrapulmonary bronchi you will find the following exceptional features –
#1. Presence of isolated, irregular plate of hyaline cartilage (shown on lung histology slide)
#2. Smooth muscle occurs less complete circular arrangement between cartilage plate and lamina propria
#3. Presence of dense connective tissue between the adjacent cartilaginous plates
Histology of bronchiole from lung
There are three types of bronchioles in lung and they are –
#1. Primary or larger bronchiole
#2. Terminal bronchiole
#3. Respiratory bronchiole
Do you want to learn histology of these bronchioles? I am going to provide the basic histology of different types of bronchioles.
Do want to describe the histology of bronchiole? You should also know about the general organizational pattern of tubular organ. You will find the same layers as you found in bronchi –
#1. Mucosa layers
#2. Submucosa layer
#3. Muscularis layer and
#4. Adventitia layer
The epithelium of bronchiole varies according to the size of air passageway. In primary bronchiole you will find pseudostratified ciliated columnar epithelium. You may also find few scattered goblet cells. In primary bronchiole.
At terminal bronchiole you will find the ciliated simple columnar epithelium. You will find the ciliated, non-ciliated simple low columnar epithelium in respiratory bronchiole. Sometime you may find cuboidal epithelium with patches of simple squamous epithelium.
In lamina propria of bronchioles there are loose fibro-elastic connective tissues. There may present solitary lymphoid tissue in laminar propria of bronchiole.
# There are loose fibro-elastic connective tissues in the submucosa of bronchioles.
# There are some exceptional features in the muscularis layer of different bronchioles. In primary and terminal bronchioles you will find spirally arranged smooth muscle.
But in respiratory bronchioles you will find scatter of smooth muscle. Sometime the smooth muscular layer is absent in the respiratory bronchioles.
In adventitia, there is very sparse loose fibro-elastic connective tissue in bronchioles.
Histology of lung alveoli
Alveoli are sac like structure of respiratory bronchioles, alveolar duct and alveolar sac. These alveoli are responsible for spongy structure of lung. They are separated by interalveolar septa that contain one or more alveolar pore.
The intraalveolar septa are the partition of two adjacent alveoli. They consists of two thin squamous epithelium layer.
Mucosa layer of alveoli
Alveolar duct and alveolar sac lined by the patches of simple cuboidal epithelium. But alveolus is lined by simple squamous epithelium. These simple epithelium of alveoli contain the three major cells –
#1. Type I pnemocytes
#2. Type II pnemocytes
#3. Pulmonary or alveolar macrophage (dust cell)
Type I pnemocytes
#1. These are the thin small squamous cells
#2. Most gass exchanges occurs through Type I pneumocytes
#3. Covers almost all surface of the alveolar surface
Type II pnemocytes
#1. These are great or giant alveolar cell
#2. Rough cuboidal and bear microvilli on free surface
#3. It contains fomay vacuolated cytoplasm due to presence of lamellate bodies
#4. Produce pulmonary surfactant
Pulmonary or alveolar macrophage (dust cell)
#1. Derived from monocytes and part of mononuclear phagocytic system
#2. Found interior of interalveolar septum or often seen in alveolar surface
#3. Remove inhaled dust and other particle trapped in pulmonary surfactant
There is thin loose fibro-elastic connective tissue in the lamina propria of alveoli. Sometimes you may find scattered fibroblast and very fine collagen fibers in propria. There are numerous capillaries warraped around the alveolus.
The submucosa and muscularis mucosa are absent in most area of alveoli. Few scattered smooth muscle fiber may occurs around some of the alveolar duct.
Histology of lung pdf
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Blood air barrier
Air in alveoli is separated from capillary blood by three components. These are referred to collectively as blood air barrier.
#1. Surface lining and cytoplasm of alveolar cell
#2. Fused basal lamina of closely apposed alveolar cell and endothelium cells of capillary
#3. Cytoplasm of endothelium cells of continuous capillary within the interalveolar septum
Do you want to know the function of blood air barrier?
#1. Permit diffusion of gases between alveolar air space and blood
Membrane of all terminal portion of lung collectively known as respiratory membrane
The structures of respiratory membrane are –
#1. Surfactant layer – a layer of fluid lining pulmonary blood and containing the surfactant
#2. A layer of alveolar epithelium
#3. An epithelium basement membrane
#4. A very thin interstitial space between the alveolar epithelium and capillary membrane
#5. A capillary basement membrane
#6. Capillary endothelium membrane
Function of respiratory membrane
# Gaseous exchange between alveolar air and pulmonary blodd occurs through respiratory membrane
You may also learn histology of following organs from anatomylearner.com –
#2. Best guide to learn liver histology in details
Do you want to learn the details anatomy of lung from different animals? You may find details anatomy of lung here in this blog.
Hope you got a better idea about lung histology. Please watch the video carefully and learn from lung histology diagram.
You may practice again and perform lung histology slide diagram. Please let me inform if you need histology of lung pdf.
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