Histology Guide | Respiratory
The respiratory portion consists of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli. It is hard to investigate the organisation of these structures in. The trachea, bronchi and bronchioles form the tracheobronchial tree - a system of Epithelial Injury: Relationship to Granulocyte Emigration in the Lung Quiz. Question 1 / 3. The trachea is a continuation of what upper. This lung anatomy and physiology quiz will test your knowledge on the The right & left bronchus along with the pulmonary artery & vein enter into the lungs at .
Urinary system introduction Video transcript So here's a little person, and I've drawn their face, and you can see in blue at the bottom I've drawn their voice box, and I'm going to show you exactly what happens when you draw a little molecule like this of oxygen and to follow it along it's journey.
So it's going to be breathed in either through the nose or through the mouth. And you know it's going to kind of end up in the same place or so we think, right? We said that basically kind of the back of the throat is where it's going to end up, and this is my nose kind of going in the back of the throat, and the mouth kind of empties into the same spot.
But already, there are going to be some differences. So for example, you have in your nose, these little yellow nose hairs, and the first question, of course, people think of with nose hairs is what the heck is their purpose?
What do they do? And nose hairs are part of our filter system, so we have this great filter system and there's nose hair, and their job is to make sure that all of the kind of large particles of dirt and dust are kind of picked up.
So they're good for getting all the large particles out of the air so it's cleaned up. Then you also have this green slime, right? And so of course, if you compared nose air or the air that you breathe in through your nose to air that you breathe in through your mouth, the mouth air will be, of course a little dirtier, because they didn't have that nice filter system. And kind of thinking along the same route, if you think about picking your nose, that would be basically kind of cleaning the filter, right?
So that's kind of a new way maybe of thinking about that habit. So air is going to end up going to the back of the throat. So air is going to kind of go in this way, and a little molecule of oxygen is going to kind of end up at the back of the throat. And another kind of interesting difference is that already, that oxygen molecule and the air around it is going to be slightly different in other ways.
It's going to be cleaner if it went through the nose, but either way, nose or mouth, it's going to be warmer and also more moist. So that's another change. In comparison, on the outside, the air is a little colder and drier.
So these are some key differences in terms of what's happening to the air. These are two major differences, right? So now the air or little molecule of oxygen has got a choice. It can either go kind of down one of two paths. One, I'm going to draw is going to be into the larynx.
The bronchial tree
This is our larynx right here. And we also call our larynx our voice box, so you might remember that was the name I had mentioned previously, voice box, or larynx, is kind of the more medical word, I guess.
And sitting over the larynx is the epiglottis. And the epiglottis is basically like a lid kind of protecting the larynx from making sure that food and water don't go into it. Now, there's another tube I just alluded to, and it's sitting right here, and this purple tube, is our esophagus So the esophagus is basically, it's fantastic for things like food and water.
You want food and water to go down the esophagus because it's going to lead to the stomach. So you want food and water to go that way, but you don't want food and water to go into the larynx. And so you want to make sure that the epiglottis, that lid, is working really well. And if you're swallowing food and water, this epiglottis will literally just kind of close up and protect your larynx.
But in this case, that's not happening. We're not actually food and water, we're a little molecule of oxygen, so let's follow that molecule a little bit further down.
Let's see what happens to it. I'm going to drag up the canvas a little bit. Let's make a little bit of space, and I want to just stop it right there because I want to show you that the air molecule, the oxygen molecule has already kind of made an interesting crossroads. It's actually kind of broken an important boundary, and that's this boundary right here. And on the top of this boundary, I've included the larynx and of course, all the other stuff we just talked about-- the mouth and the nose-- and this is considered our upper respiratory tract.
So anything above this dashed line is our upper respiratory tract, and then, of course, you can then guess that anything below the line must then be our lower respiratory tract.
So this is an important boundary because people will talk about the upper and lower tract, and I want to make sure you know what is on which side. So on the top of it, is the larynx and everything above that, and below it is the trachea.
Respiratory System | histology
Let me label that here. The trachea is right here, the wind pipe or the trachea, and everything below that, which, of course, mainly includes things like the lungs, but as we'll see a few other structures that we're going to name. So I'm going to keep moving down, but now you know that important boundary exists.
So now let me just make a little bit more space you can see the entire lungs. You can see the molecule is going to go through the trachea, and actually, I have my left lung incompletely drawn. Let me just finish it off right there. So we have our right and left lung, right? These are the two lungs, and our air is going to just kind of slowly pass down-- our molecule of oxygen is going to pass down, and it's going to go either into the right lung or the left lung.
These cartilage "bracelets" are open on the posterior wall of the trachea adjacent to the esophagus.Difference Between Bronchi and Bronchioles
A bundle of smooth muscle fibers bridges the gap between the two ends of the cartilage. Intrapulmonary air conduits extend from the intralobar bronchi to the terminal bronchioles.
When the bronchi enter the lung, the C-shaped cartilages that characterize the trachea and primary bronchi are replaced by irregular plates or cartilage that completely surround the cylindrical muscular airway tube. Cartilage disappears in the terminal bronchioles, which have narrowed to a diameter of 1 millimeter. The terminal bronchioles initially have a ciliated columnar epithelium that soon transitions to a low cuboidal epithelium. Mucous and seromucous glands and diffuse lymphatic tissue are associated with smaller bronchi but are not found distal to the region where there is a loss of cartilage plates.
Respiratory Airways The respiratory airways extend from the respiratory bronchioles to the alveoli. The respiratory bronchioles have a diameter of 0. The epithelium here remains low cuboidal. Each respiratory bronchiole branches into between 2 and 11 alveolar ducts that still contain smooth muscle fibers in their walls. Along these walls, the alveolar ducts give rise to single alveoli and to numerous alveolar sacs, which are associated with 2 to 4 alveoli.
The space at the entrance from the alveolar duct to an alveolar sac is referred to as the atrium. Alveoli can be studied most easily in preparations of expanded lung, especially in those areas in which erythrocytes have been retained in the capillaries.
- The Tracheobronchial Tree
- Chapter 25: Multiple Choice Questions
- Respiratory System
Alveoli have a distinct cup shape separated by loop- or crescent-shaped walls known as interalveolar septa. The interalveolar septa contain myriad capillaries. The interface between the capillary lumen and the alveolar epithelium is known as the air-blood barrier. The barrier consists of the endothelium of the capillary, the epithelium of the alveolus, and their shared basement membrane.
The surface epithelium of the alveoli contains two developmentally related but functionally distinct cells, known as pneumocytes. Type I pneumocytes are attenuated vesicle-studded cells that line the alveolar walls near the capillaries.
Only their flattened nuclei can be recognized with certainty by light microscopy. Type II pneumocytes are cuboidal and occur singly or in small clusters between type I cells.
Club Clara cells are also thought to participate in the synthesis of surfactant. Type II cells serve as precursors to type I cells. Where there are no capillaries, the alveolar septum contains fibroblasts, collagen, elastic fibers, smooth muscle cells, and macrophages known as dust cells. Also notable are alveolar pores, which equalize air pressure between the alveoli. Circulatory System of the Lung Branches of the pulmonary artery accompany the bronchi to the level of the respiratory bronchioles.
From there they branch into an extensive network of capillaries suspended within the alveolar walls. Venules arising from these capillaries join in the intersegmental connective tissue and later empty into the pulmonary veins.