Histology of the respiratory system 1 Flashcards
What is the function of the respiratory system?
To provide O2 and to remove CO2 from the blood
Name the two divisions of the respiratory system.
- Conducting airways
- Respiratory airways
What is the function of the conducting airways? (4)
warming, humidifying, cleaning and delivering air
What is the function of the respiratory airways?
gas exchange
List the elements of the conducting airways (7)
Nasal cavity
Nasopharynx
Oropharynx
Larynx
Trachea
Bronchi
Bronchioles (regular and terminal)
List the elements of the respiratory airways (4)
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
What are the 4 basic tissues that make up (almost) every organ?
Epithelial tissue
Connective tissue
Muscular tissue
Nervous tissue
The conducting airways possess structures that ensure…
uninterrupted supply of air (bone, cartilage, smooth muscle and connective tissue which provide rigidity, flexibility and extensibility)
What structures in the conducting airways help remove foreign particles?
Serous glands
Mucous glands
Ciliated cells
Which structures allow breathing (form a ventilation mechanism)?
Thoracic cavity
Intercostal muscles
Diaphragm
Elastic properties of the lungs
Is the pressure between the parietal and visceral pleura
a) positive
b) negative
b) negative
Trachea is composed of 16-20 rings of…
hyaline cartilage (attached by dense fibroelastic connective tissue)
Name the first layer of the tracheal wall adjacent to the lumen and its two subcomponents
Mucosa:
1. pseudostratified columnar ciliated epithelium (respiratory epithelium)
2. lamina propria
Describe in detail the two layers of the mucosa in the trachea.
Pseudostratified columnar ciliated epithelium
* Columnar ciliated cells
* Goblet cells
Lamina propria
* Loose connective tissue
* Rich in elastic fibers
* Rich network of blood vessels (help bring nutrients to the trachea and warm the air, esp. in the winter)
After the mucosa, the next layer of the wall of the trachea is…
Name its 4 components
Submucosa
- Denser irregular connective tissue
* rich in elastic fibres - Hyaline cartilage
* 16-20 C-rings of hyaline cartilage embedded in submucosa
* fibroelastic connective tissue between the C-rings - Smooth muscle cells
- Serous and mucous glands
* these glands open into the lumen of the trachea
Cartilage is mainly composed of…
collagen fibers and cells called chondrocytes (secrete ECM, including collagen)
Cartilage and smooth muscle of the conducting airways are considered a part of the…
submucosa
What is the 3rd and outermost layer of the wall of the trachea?
Adventitia: dense irregular layer of CT
Connects the trachea to adjacent organs in the mediastinum.
Specify the type of epithelium that makes up the mucosa of the trachea
Pseudostratified columnar ciliated epithelium with goblet cells
Do not confuse cilia with microvilli! Describe each of the cellular projections.
Cilia:
* Hair-like projections found on the surface of certain epithelial cells
* Move in a coordinated, wave-like manner to move fluid, mucus and particles
* Composed of microtubules
Microvilli:
* Tiny, finger like projections on the surface of certain cells
* Primarily designed to increased the surface area for absorption
* Composed of actin filaments
What is the name of the smooth muscle in the trachea?
Trachealis muscle
Name all the cell types found in pseudostratified columnar ciliated epithelium (respiratory epithelium) (6)
- Columnar ciliated epithelial cells
- Goblet cells
- Brush cells
- Basal cells
- Small granule cells
- Serous cells
The most abundant cell type in the respiratory epithelium (pseudostratified columnar ciliated epithelium) are..
ciliated columnar cells
How many cilia does each columnar ciliated cell have on its luminal aspect?
~300 cilia
What is the second most abundant cell type in the respiratory epithelium? Describe its characteristics
Goblet cells
Apical cytoplasm (near lumen) contains mucous vesicles filled with glycoproteins (these are mucous cells).
Function of the goblet cells
Production of sticky mucous (to which foreign particles bind). They do so by releasing the glycoproteins from the mucous vesicles found in their apical cytoplasm.
What is the difference in staining between ciliated columnar cells and goblet cells in the respiratory epithelium?
Columnar ciliated cells are well stained, whereas goblet cells are poorly stained (appear paler).
Brush cells have … on their surface. Explain how this suggests their function in the respiratory epithelium.
Unlike columnar ciliated cells, brush cells have MICROVILLI on their surface. Microvilli are absorptive projections. This leads us to believe that brush cells play a chemosensory role in the airways (absorb particles that bind chemoreceptors).
What is the only way brush cells in the respiratory epithelium can be identified?
Electron microscopy
Give the name and function of small granule-containing cells in the lower part of the respiratory epithelium. What system do they belong to? Describe these cells
Small granule cells
* Part of the diffuse neuroendocrine system (DNES)
* Part of the argentaffin cell family
* Granules can absorb silver
* Granules contain hormones and peptides that cells release towards the lamina propria
* Secrete serotonin
The DNES produces…(2)
serotonin and epinephrine
What is the name of the short cells in the respiratory epithelium? Describe them.
Basal cells
* Short cells that rest on the basement membrane
* They are the stem cells of the respiratory epithelium (produce ciliated cell, small granule cells, goblet cells, etc.)
Smoking cigarettes can cause…
squamous metaplasia of the respiratory epithelium.
The columnar ciliated cells are replaced by tougher, flat squamous cells that can better withstand the chronic irritation. These cells do not have cilia, so the ability to clear mucus and debris is lost.
What is an axoneme?
It is the central structure of cilia, surrounded by plasma membrane.
What is the average length and diameter of cilia?
Cilia are around 5-10 um long and 0.2 um in diameter.
The axoneme is composed of…
9 pairs of microtubules surrounding a tenth, central pair.
How many basal bodies are there for each cilia?
1
What are basal bodies?
A structure similar to a centriole, lying immediately beneath the epithelial cell membrane. It is the origin of microtubules that make up the axoneme of cilia.
Describe the microtubule doublets of the axoneme.
Each doublet is made up of 1 complete microtubule (13 protofilaments) and 1 incomplete microtubule (10 protofilaments). 3 protofilaments are shared between the doublet.
Is the central microtubule pair complete or incomplete?
The central microtubule pair are made up of two complete microtubules (two singlets).
The 9 microtubule doublets of the axoneme are connected to each other by…
dynein arms
What is the role of radial spokes in the axoneme of cilia?
Radial spokes connect the 9 microtubule doublets to the central microtubule pair. They interact with dynein arms to generate ciliary movement.
Unlike the axoneme, the basal body is composed of … instead of doublets
microtubule triplets
Name two diseases resulting from mutations in the ciliary axoneme.
- Primary ciliary dyskinesia (PCD)
- Radial spoke protein 2 (RSP) mutations
Describe primary ciliary dyskinesia (PCD)
Caused by a mutation resulting in a lack of dynein arms, which renders cilia and sperm immotile or dysmotile
What are consequences of primary ciliary dyskinesia?
Impaired mucus clearing (bronchiectasis)
Chronic sinusitis
Male infertility
Name and describe a subset of primary ciliary dyskinesia (PCD)
Kartagener’s Syndrome
* Cilia are abnormal in movement
* Condition causes difficulty in clearing of mucus from the respiratory tract
* The defining characteristic of this condition is situs inversus
What is situs inversus? What disease is it seen in?
Situs inversus is a reversal of abdominal and thoracic organs. It is a defining characteristic of Kartagener’s syndrome.
Describe radial spoke protein mutations
Like PCD, radial spoke mutations result in immotile cilia and sperm.
Goblet cells produce a mucous made up of…
glycoproteins