Respiratory system histology Flashcards
What are the two functional elements of the respiratory system?
1.Conducting system
2. Gaseous exchange mechanism
What are the functions of the cavities in the conducting system of the respiratory system?
They cleanse, warm and humidify/moisten air.
What are the functions of the 2 cell types of the respiratory epithelium that line the cavities?
One secretes mucous, which traps particles.
One has surface cilia, which moves the thin layer of mucous.
Why do the cavities have numerous blood vessels under the epithelium?
The blood vessels are responsible for warming the inspired air
What is the function of seromucous glands?
They secrete mucous and watery fluid which moisten the air
T/F: The epithelium in larger airways has a different function to the one in the upper respiratory tract.
F
In larger airways the epithelium has a similar structure and function as upper respiratory tract.
What is the difference in the cartilage found in the trachea and the one in smaller branches of the tracheobronchial tree?
The trachea has a C-shaped cartilages, while the smaller branches have irregular cartilage plates.
What is the function of the smooth muscle in the airways?
Smooth muscle contracts and relaxes to modify diameter of airways, and thus flow of air
T/F: Bronchioles have irregular cartilage plates
F
Bronchioles have no cartilage. Cartilage ends at tertiary bronchi
What are the main components that constitute the gaseous exchange mechanism?
Blind-ending sacs called alveoli, as well as pulmonary capillaries
What are the transitional parts between the conducting part gaseous exchange mechanism?
Respiratory bronchioles and alveolar ducts
Where do alveolar ducts terminate?
In alveolar sacs which open into the alveoli
The nasal cavities and paranasal sinuses are lined by______________.
Respiratory mucosa
What is the function of the respiratory mucosa?
Adjusts temperature and humidity of inspired air.
Traps small particles that have not been caught by hair in the nasal cavity.
How do the nasal conchae enhance the function of the respiratory mucosa?
They increase surface area for contact between air and respiratory mucosa
What type of epithelium does the nasal mucosa consist of?
Pseudostratified ciliated columnar epithelium with several goblet cells (termed respiratory epithelium)
Describe the basement membrane of the respiratory mucosa
It is unusually thick
What is lamina propria?
Lamina propria is a layer of connective tissue that forms part of the moist linings – mucosa, and supports the delicate mucosal epithelium.
It is rich in blood vessels, serous and mucous glands.
Mucous from these glands are propelled to the______________ by coordinated movement of the ____________.
Pharynx
Cilia
What is the termed used for the coordinated movement of cilia to propel mucous?
Muco-ciliary escalator
Describe the mucosa found in the nasopharynx
-Has pseudostratified ciliated columnar epithelium
-Lamina propria has some mucous and serous glands.
-Dominant feature: large masses of lymphoid tissue (protects entry portals for the resp. system and GIT)
What changes occur in the nasopharyngeal mucosa due to age and extensive smoking?
patches of squamous epithelium occur with age and extensive smoking.
What is the name of the protrusion of lymphoid tissue found in the nasopharynx? and what is it similar to?
nasopharyngeal tonsil or adenoid
It is similar to a lingual tonsil
Describe the epithelium found in false vocal cords
Pseudostratified ciliated columnar epithelium with seromucous glands
Describe the epithelium found in true vocal cords, and its significance.
Stratified squamous epithelium. This is more resistant to physical damage that may be caused vibration of the cords during phonation
What makes up the trachea?
-Fibroelastic tissue
-Cartilage
-Trachealis muscle (Posterior wall)
-Longitudinal muscle (part of the oesophagus)
What is the function of smooth muscle in the trachea?
-It contracts to reduce tracheal diameter
-Assists in raising intrathoracic pressure during coughing.
T/F
The respiratory epithelium in the inner layer of the trachea is different from the nasal epithelium
False. It is similar
Name the different cell types found in respiratory mucosa of the trachea
-Pseudostratified columnar cells with cilia
-Goblet cells
-Basal cells
-Serous cells similar to submucosal cells
(Present in different proportions in different parts of the trachea)
T/F
Ciliated columnar cells are plentiful in the lower trachea, goblet cells are more common in upper trachea
True
Describe the lamina propria of the trachea
Loose, highly vascular connective tissue which becomes condensed at its deeper aspect to form a band of fibroelastic tissue.
Describe lamina propria of the trachea
Loose submucosa
-Has several seromucinous glands (decrease in number in lower region of trachea).
-Submucosa merges with perichondrium of underlying hyaline cartilage or with dense fibroelastic cartilage between rings.
Describe the mucosa of the primary bronchus (6)
-Resp. Epithelium less tall, fewer goblet cells.
-Upper lamina propria has more elastin.
- A layer of smooth muscle separates lamina propria from the submucosa.
- Submucosa has fewer seromucinous glands
- Cartilage is flattened into interconnected discs rather than rings.
- Cilia sweeps mucous up the bronchus
How would you identify goblet cells in an electron microscope?
They are recognised by their bulbous surface outline & lack of cilia.
Fragile cilia are vulnerable to damage from what?
Inhaled toxic chemicals and bacterial/viral infections.
Describe the mucosa of tertiary bronchi (4)
-Epithelium is talk & columnar but there is little pseudostratification.
-Lamina propria: thin & elastic, completely encircled by smooth muscle in a spiral manner.
-Seromucinous glands are scarce in submucosa
-Cartilage is reduced to a few irregular plates
What structures are absent in bronchioles? (2)
-Cartilage
-Submucosal glands
In terminal and respiratory bronchioles, what cells replace goblet cells? Describe these cells and their function
Clara cells - they are tall columnar cells with apical secretory granules.
-These cells produce surfactant, act as stem cells and contain enzymes which can detoxify noxious substances
What do terminal bronchioles divide into?
They divide to form respiratory bronchioles which have a small number if single alveoli in their walls
What do respiratory bronchioles divide into?
They divide into alveolar ducts which end in alveolar sacs - which then open into several alveoli
T/F
Smooth muscle is absent in the wall of bronchioles
F
What structure is closely related to respiratory bronchioles?
A distended thin-walled pulmonary artery branch lies next to bronchiole
Describe alveolar ducts
-The walls of alveolar ducts can be seen as small aggregations of smooth muscle cells, collagen & elastin fibres - which form alveolar rings that surround the alveolar ducts.
-This smooth muscle regulates alveolar air movements.
What is the name of cells that line alveoli?
Describe these cells
They are lined by by flattened epithelial cells called pneumocytes (predominantly type I)
Type I pneumocytes are large squamous cells and cover most of the alveolar surface.
___________ occasionally have small openings called______________ which allow movement of air between adjacent alveoli.
Alveolar septa
Alveolar pores
How is the supporting meshwork for lung parenchyma formed?
Collagen and elastic fibres of the septum condense around openings of alveoli to form a supporting meshwork for lung parenchyma.
Describe type II pneumocytes
These cells are rounded in shape and occupy about 5% of the alveolar surface, but about 60% of the alveolar lining.
They secrete surfactant.
They can differentiate into type I pneumocytes if needed.
Explain squamous metaplasia
Tracheobronchial mucosa is exposed to several damaging agents – such as inhaled chemical toxins,
bacteria and viruses.
* Prolonged damage, or repeated damage, to respiratory epithelium leads to the death and replacement
by squamous epithelium – squamous metaplasia.
* Squamous metaplasia is one of the three contributions to Chronic obstructive pulmonary disease (COPD) along with bronchoconstriction and emphysema.
Which part of the respiratory tract is more prone to developing malignant tumours?
The bronchial tree is an important site for development of malignant tumours – bronchial
carcinoma.
This often originates in areas of squamous metaplasia in the bronchial mucosa in heavy smokers.
Explain emphysema
Anatomically defined as abnormal enlargement
of alveolar airspaces distal to terminal
bronchiole.
* Usually in smokers, associated with chronic
bronchitis.
* Involves loss of lung parenchyma
