Respiratory - Histology Flashcards
What are the four main layers of the respiratory system?
Mucosa
Submucosa
Cartilage/muscle layer
Adventitia
What is the trachea?
A wide flexible tube
What keeps the lumen of the trachea patent?
20 C-shaped tracheal cartilages, which are hyaline in nature
What fills the gap between the rings of cartilage in the trachea?
Trachealis muscle and fibroelastic tissue
What is the role of the respiratory mucosa and submucosa?
Warm and moisten the air, and to trap foreign particles in mucous.
What is the mucosa of the trachea made up of?
Epithelium: Ciliated pseudostratified columnar epithelium with goblet cells.
What is the role of the trachea’s adventitia?
Connects and supports trachea to surrounding tissue, eg. thyroid and oesophagus.
What does the trachea’s adventitia contain?
Nerves, vessels and adipose tissue.
What does the trachea branch into?
The trachea branches into two primary bronchi, which again branches into secondary and then tertiary bronchi.
What are the features of the intrapulmonary bronchi?
In the intrapulmonary bronchi, there is less cartilage, and it does not completely encircle the lumen.
What does the extrapulmonary bronchi resemble?
The extrapulmonary bronchi (e.g. primary bronchi) closely resemble the trachea histologically.
What layers make up the bronchi?
Contains layers of smooth muscle between the mucosa and submucosa
What is the diameter of the bronchioles?
1mm or less
What type of muscle increases in the bronchioles?
Smooth muscle
What cells are present in bronchioles and what do they do?
Clara cells are present: secretes surfactant
What do bronchioles lack?
No goblet cells (a few goblet cell may be found in the initial part)
Non-ciliated cells
No submucosal Glands
No Cartilage
What is the terminal bronchiole lined by?
Ciliated cuboidal epithelium with clara cells and give rise to respiratory bronchiole
What is the respiratory bronchiole lined by?
Low cuboidal epithelium.
What are alveolar ducts surrounded by?
Smooth muscle, elastin and collagen
What are alveolar sacs surrounded by?
Blood vessels/ pulmonary capillaries
What are alveoli surrounded by?
Blood vessels/ pulmonary capillaries.
Gaseous exchange between blood and air occurs.
What are the two cell types in the epithelium of the alveoli?
Type I and Type II pneumocytes
Describe Type I pneumocytes
Large flattened cells - (95% of the total alveolar area) which present a very thin diffusion barrier for gases.
Describe Type II pneumocytes
(making up 5% of the total alveolar area, but 60% of total cells).
These cells secrete ‘surfactant’ which decreases alveolar surface tension and stops alveoli collapsing when we breathe out.
