Lecture 8.7: Respiratory Histology Flashcards
What structure makes up 30% of the respiratory epithelium?
Ciliated columnar cells: Sweep up mucous.
Goblet cells: Secrete mucous
Basal stem cells: Renew epithelium
Note that there are also sensory brush cells.
What kind of epithelium lines the respiratory tract?
Pseudostratified epithelium.
What are the three layers of the trachea?
Mucosa: Lines the lumen, includes lamina propria between submucosa and mucosa.
Submucosa: Contains mucous glands, keeps trachea moist.
Adventitia: Contain cartilage and outer layer of connective tissue.
Do bronchioles have cartilage?
No. The intrapulmonary bronchi still have plates of cartilage though.
What happens at the cellular level as we proceed further through bronchioles?
We lose goblet cells and ciliated columnar cells, but gain clara cells.
Smooth muscle is still present -> Main attack area of asthma.
Note that ciliated cells extend further than goblet cells, so they can still sweep up the mucous that goblets produce.
What are clara cells?
They are columnar to cuboidal cells with short microvilli, secretes surfactant that destroys surface tension.
Granules contain glycoproteins and can neutralise toxins.
What is found in terminal bronchioles?
No goblet cells left, but clara cells and some cuboidal epithelium with some clara cells. Also contains 1 or 2 layers of smooth muscles enough for vasoactive stimulation.
Gives rise to respiratory bronchioles as soon as it hits an alveoli.
What is the epithelium of respiratory bronchioles? What can be found at the end of them.
Cuboidal to squamous. Alveoli.
Describe alveoli. What are they lined with? What structures lie between them?
Lined with simple squamous epithelium, wall contains many pulmonary capillaries and they connect to one another by pores to allow gas permeation.
Interalveolar septum separates alveoli, keeping them open as they contain reticular and elastin fibres.
What are type 1 pneumocytes?
They are pneumocytes important for gas exchange, and thus cover 95% of SA. Not as abundant as type 2 though.
Contain tight junctions to prevent ECF leakage.
What are type 2 pneumocytes?
More numerous than type 1 but only cover 5% of SA. They are cuboidal cells with short microvilli, and secrete surfactant.
They divide and give rise to both type 1 and 2 pneumocytes. They commonly reside in the septum.
Describe intraalveolar macrophages.
They live in alveoli, gobble up foreign particles. After death, they go into terminal bronchiole, and are swept away. Others penetrate type 1 pneumocytes into alveolar septum.
