Lecture 7: Respiratory Histology Flashcards
What two portions can our respiratory system be divided into?
- Conducting portion
- Respiratory portion
Describe the conducting portion of the respiratory sytem
The conduction portion of the respiratory system is includes our:
nasal cavity, paranasal sinuses, nasopharynx, trachea, [primary, secondary and tertiary bronchi], bronchioles and terminal bronchioles.
Role: It collects and warms the air and sends it to our respiratory portion.
Descibe the respiratory portion of the respiratory system.
The respiratory portion of our respiratory system includes:
Respiratory bronchioles, alveolar ducts and alveolar sacs.
Role: Gas exhange
Describe the respiratory epithelium
-Pseudostratified columnar ciliated epithelium with an extensive lamina propia (a rich vascular network)
Located in the airways of the respiratory system.
What are the cells of the respiratory epithelium? (3)
- Ciliated columar epithelial cells
- Goblet cells-> secrete granules to produce a mucous layer, which collects substances.
- Stem cells (non-ciliated basal cells)
What are goblet cells? Describe them.
Goblet cells are modified columnar epithelial cells.
Mucigen granules, located in the cytoplasm, are released via exocytosis and combine with water to form mucus.
The stem of the golblet cell has a basal nucleus and many organnels
The nasal cavities are divided by what?
Nasal septum
What are the three regions of the nasal cavity?
- Nasal vestibule
- Respiratory region
- Olfactory region
What is the function of the nasal cavity?
Adjusts temperature and humidity of inspired air.
The [turbinate bones] enhances this process by increasing the SA.
Nasal vestibule
Cell type?
Located?
- Keratinized stratified squamous epithelium
- Located just inside the nostril and is lined by skin.
Respiratory region
Cell type?
Location?
- Pseurostratified columnar ciliated epithelium
- Located posterior to the nasal vestibule.
- Inferior 2/3 of the nasal cavity and lined with respiratory muscosa
Olfactory region
Cell type?
Location?
Fx?
-Pseudostratified columnar ciliated epithelium
EXCEPT; it is way thicker than the respiratory epithelium and does NOT have goblet cells.
-Located at the apex (superior 1/3 portion of the nasal cavity) and lined with olfactory mucosa
- Has receptors for smell and has our olfactory glands, that has serous secretiosns that dissolve odorant molecules.
What are the cell types in the olfactory mucosa?
1. Olfactory receptor cells
2. Basal cells
3. Brush cells
4. Supporting/sustentacular cells
Describe olfactory receptor cells.
- Have one dendrite process
- Non-motile cilia with odorant receptors
- When a ligand binds to the receptors, it sends the signal to the [olfactory bulb]
What are basal cells?
Stem cells for olfactory receptors and supporting cells
What are brush cells?
Ciliated columnar epithelial cells
What are supporting/sustentacular cells?
Give mechanical and metabolic support to the olfactory receptor cells.
How are the cells of the olfactory epithelium arranged?
Superficial–> deep
- Supporting/sustentacular cells and the mucuous layer
- Olfactory neurons
- Basal cells (deep in the basement membrane).
Below the basal cells, in the basement membrane, is the lamina propria.
As we go from the conducting portion–> respiratory portion of the respiratory system, how does the respiratory epithelium change in size?
It becomes thinner.
As we go from the conducting portion–> respiratory portion of the respiratory system, how does the amount of goblet cells change?
Equal amounts until our main bronchus, then decreases, ending at our bronchioles.
Thus, trachea has more than main bronchus.
Main bronchus has more than lobar bronchus.
Lobar bronchus has more than the segmental
As we go from the conducting portion–> respiratory portion of the respiratory system, how does the amount of ciliated cells, glands and hyaline cartilage change?
Ciliated cells- Equal amount from trachea- segmental bronchus, then decreases, with them ending at the respiratory bronchioles.
Glands- Equal amounts from trachea- segmental bronchus, then decreases and end at the the segmental bronchus.
Hyaline cartilage- decreases and ends at the segmental bronchus.
As we go from the conducting portion–> respiratory portion of the respiratory system, how does the amount of smooth muscle and elastic fibers change?
Smooth muscle- equal amounts until the segmental bronchus, then decreases and ends at the alveaolar duct.
Elastic fibers- Equal amounts until the respiratory bronchioles, then decreases until alveoli.
What is the trachea?
- A short, flexible tube that transports air that extends from our larynx and then divides into our main/primary bronchi.
- Stacks of hyaline cartilaginous rings keep the lumen of the trachea open.
- Has 4 layers
4 layers of the trachea
From top–> bottom:
1. Mucosa
2. Submucosa
3. Cartilaginous layer
4. Adventitia
[MSCA]
- Mucosa layer of the trachea
- Pseudostratified columnar ciliated epithelium
- Elastic/fiber rich
- A bunch of goblet cells
- Has BALT (bronchial assx lymphatic tissue)
- Submucosa layer of the trachea
-Has slightly denser CT than the lamina propia
- Has a bunch of submucosal glands
- Cartilaginous layer of the trachea
-Has C-shaped rings made up of hyaline cartilage, which keep the lumen of the trachea open.
4. Adventitia layer of the trachea
- made up of CT that binds the trachea (trachealis muscle) to adjacent structures
- Few submucosal glands
Epithelia of the bronchi
- Pseudostratified columnar ciliated epithelium. however, the cells are shorter in height.
- Less goblet cells
- More elastic fibers in the lamina propria
Submucosa of the bronchi
- Loose areolar CT
- Few submucosal glands
- Has cartilage plates (HALLMARK OF BRONCHI)!
Mucularis in the bronchi
The muscles are continous in larger bronchi & loosely organized in the smaller bronchi.
Adventitia in the bronchi
Made up of moderately dense CT
Epithelia of the bronchioles
- Larger bronchioles have simple ciliated columnar epithelia
- Smaller bronchioles have simple cuboidal epithelia
- Few goblet cells
- Clara cells
- Increased elased fibers
Muscle of the bronchioles
Smooth muscle so that they can regulat bronchoconstriction/dilation
Which DO NOT have submucosa?
Bronchi/bronchioles
Bronchioles
Which do NOT have cartilaginous plates?
Bronchi/Bronchioles
BRONCHIOLES
Which has an airway that is <1mm in diameter?
BRONCHI/BRONCHIOLES
Bronchioles
Describe terminal bronchioles
Epithelium and muscle.
- Simple cuboidal epithelium with clara cells
- Has 1-2 layers of smooth muscle.
- Increase amount of elastic fibers
What are clara cells?
Clara cells secrete a lipoprotein that prevents luminal adhesion with airway collapse during expiration
Epithelia and muscles and the respiratory bronchioles
What do they branch into?
- Simple cuboidal with elastic fibers.
- Surrounds by smooth muscle
Branch into alveolar ducts--> alveolar sacs–> alveoli
What are alveolar ducts?
Ends in alveolar sacs
What are alveolar sacs
2+ clusters of alveoli
What are alveolar rings?
Smooth muscle, collagen and elastic fibers that form rings around the alveolar ducts.
What are alveoli?
- Alveoli are sacs lined with type I and type II pneumocytes and made up of simple squamous epithelium
- They are the sites of gas exhange and are surounded by capillaries.
What is the alveolar septum?
A wall of capillaries that are surrounded by elastin and collagen.
What are alveolar pores?
Alveolar pores are small opening that allow air to travel between the alveoli.
What unique cell is present in alveoli?
Alveolar macrophages (dust cells)
What are type 1 pneumocytes?
Line the entire surface of the alveoli, creating the surface for gas exchange.
They are closely assx with capillaries.
Type II Pneumocytes
Type II pneumocytes are rounder cells and more numerous in alveoli (60%), but only make up 5% of the SA.
-They secrete surfactant, which decreases SA in the alveoli to prevent them from collapsing.
The surfactant is stored in lamellar bodies, which are rich in phospholipids, neutral lipids and proteins.
What is asthma?
Asthma is chronic inflammatory dz that involves the airway. The bronchioles inflame and the smooth muscles constrict (bronchospasm), making it hard to breathe. Thus, air cannot go in and out of the alveoli.
- Walls get infiltrated with eosinophils, lymphocytes and mast cells.
- The bronchiole epithelium with thicken due to an increase in goblet cells and thickening of basement membrane and hyperplastic smooth muscle cells.
What is emphysema?
Emphysema is common in those who smoke or inhale particles.
In this condition, air spaces distal to the terminal bronchiole permenately enlarge.
Bronchioles narrow, blocking airflow.
Alveolar walls destruct.
As a result, area for gas exchange is lost.
What is pneumonia?
Pneumoia is an inflammation of the lung tissue.
The air spaces become filled with exudate that contains WBCs (mainly neutrophils), RBCs, and fibrin. The capillaries becomes enlarged because they are congested with RBCs.
During an exam, the lung looks red, form (due to lack of air spaces) and heavy (because of exudate).
Lungs are housed in the _____________
pleural cavities.
They are lined by a serious membrane; the parietal and visceral plura.
Parietal and visceral pleura
Parietal pleura lines the internal cavity
Visceral pleura lines the lungs (organs).
They are seperated from one another by the pleural cavity, which contains serous fluid.
Tell me about visceral pleura.
Covered in _____
- Covered in a flat MESOTHELIUM.
- Has underlying fibrous tissue, such as collagen and elastin.
- Goes into the lungs as fibrous septa and is continous with the parenchyma of the lungs.
Has a bunch of lymphatic vessels
