Respiratory tract Flashcards
What consists of the conducting zone?
Nasal passages, pharynx, larynx, trachea, bronchi and most of the bronchioles as far as the terminal bronchioles.
What is the purpose of the conducting zone?
Warm, moisten, filter and deliver inspired air to the gas-exchanging or respiratory zone of the lungs
What consists of the respiratory zone?
Respiratory bronchioles, alveolar ducts and definitive alveoli
What is the purpose of the respiratory zone?
Exchange of gases between the air and blood
How is the conducting portion of airways adapted for removal and delivery of air?
Opening of airways maintained by bone, cartilage, elastic and collagen fibres and smooth muscle (provides flexibility)
Lining of epithelial cells with glands, secretory and protective functions
How is respiratory portion of airways adapted to gas exchange?
Thin walled pouches and cellular membranes with rich capillary network
What is the conducting portion lined with?
Mucous membrane
What does mucous membrane consist of?
Respiratory epithelium (mainly pseudocolumnar epithelium) and lamina propria (connective tissue) below it
What does mucous membrane do?
Warm and humidify inspired air
Provide sense of smell via olfactory epithelium
Cover and protects (ciliary clearing mechanism and immunological defence)
What is found beneath the mucous membrane?
Submucosa and adventitia
What seperates submucosa and mucous layer?
Elastic layer
What sort of epithelium makes up respiratory airways?
Ciliated pseudostratified columnar epithelium
What do all 5 cell types of respiratory airways do?
Reach basement membrane
What are the five types of cells in respiratory epithelium?
Ciliated columnar cells Mucous goblet cells Small granule (K cells) Basal cells Brush cells
What do ciliated columnar cells do?
Cilia on apical surface beat up and out to shift mucous out of respiratory tract
What facilitates cilia beating in ciliated columnar cells?
Beneath cilia are small mitochondria golgi, RER
What makes up the structure of cilia?
Cytoskeleton, 9x2+2 microtubule core (axoneme) dyenin arms supply motor movements
What is the name of action that moves mucus towards pharynx from respiratory tract?
Mucocilary escalator
What do goblet cells make?
Mucus
What does mucus do?
Trap particulate matter and pollutants lining respiratory tract as far as bronchi
What defines viscosity of mucus?
Contributions from goblet glands (cellular glands) and seromucus glands
What are basal cells?
Stem cells of respiratory epithelium (diff into other cell types)
What are brush cells?
Narrow columnar cells, have afferent nerve endings so are sensory receptors
What are small granule cells aka K cells?
Neuroendocrine cells with small granules containing neuroendocrine hormones
What is the lamina propria?
Loose connective tissue supporting the respiratory epithelia
What does lamina propria contain (5 things)?
Mucous gland Serous gland MALT Rich blood supply Elastic fibres
What do serous glands do?
Watery secretions that dilute mucus and humidify inspired air.
Also contain lysozyme and protease inhibitors for defence against bacteria
What is MALT? Give an example.
Mucosa associarted lymphoid tissue e.g BALT in bronchi (diffuse aggregates of lymphoid tissue providing specific immunity involving lymphocyte, neutrophils etc.)
What does air blood barrier consist of?
Fused basal laminae of epithelial layer and capillary endothelial cells
Capillary endothelial cells and single layered type 1 alveolar epithelial cells
What sort of alveoli cells form the ABB?
Type 1, squamous alveolar cells
What seperates adjacent alveoli?
Interalveolar septum
What does interalveolar septum consist of?
2 squamous epithelial layers from 2 alvoeli sandwiching connective tissue matrix and dense capillary network, many lymphoid cells and macrophages
What are interalveolar pores of Kohn, why are the useful?
Openings in interalveolar septum allowing communicaiton between alveoli and movement of gases betweeen alveoli in local brochiolar obstruction
What structurally supports the alveoli?
Elastic fibres
What are type 1 pneumocytes/alvoeli cells for?
Make up 90% alveolar epithelium
Absorb surfactant promoting its turnover
Form occluding junctions with each other preventing seepage of extracellular fluid into alveolar lumen
Describe structure of type 1 alveoli cells (junctions, width)
Squamous epithelial cells
Wide cells
Form occluding junctions with each other
From what cells can type 1 cells develop?
Type 2 cells
Where are type 2 cells positioned?
Dispersed among the type 1 cells
Describe the structure of type 2 cells (shape, junctions)
Cuboidal
Form occluding junctions with type 1 cells
How are type 2 pneumocytes a stem cell population?
Can diff into type 1 or 2 cells if alveolar epithelium damaged
What do type 2 cells do?
Secrete surfactant
What does surfactant do?
Maintains alveolar stability and lower alveolar surface tension (prevent collapse of alveoli in exhalation)
Minimise work required to inflate lungs
What are alveolar macrophages known as? What are they derived from?
Dust cells
Derived from monocytes in the blood
What is a serous membrane?
Thin, double layered membrane that secretes serous fluid
What are the 2 layers of serous membrane?
Inner membrane covers organs, visceral membrane
Second layer lines body wall, parietal layer
Where are serous membrane found?
Lining pericardial cavity
Pleura
Peritoneum (surrounding some abdominal organs)
Why is serous fluid beneficial?
Reduces friction
Difference between where mucous and serous membranes found?
Serous: line internal cavities
Mucous: line cavities that connect to exterior
Describe development of the alveolar epithelial surface
Endodermally derived epithelium (from respiratory diverticulum) which differentiates into respiratory epithelium that lines the airways and specialized epithelium that lines the alveoli.
What layer of the embryo are lungs derived from?
Endoderm
When are the primitive alveoli formed?
Week 36
When do alveoli mature?
After birth
What is the function of the nasal cavity and paranasal sinus surface?
Warming and moistening air
What three types of epithelium make up the nasopharynx?
Respiratory epithelium (pseudostratified columnar)
Stratified squamous epithelium
Olfactory epithelium
What three cell types make up the olfactory epithelium?
Olfactory receptor neurons, primary sensory neurons for smell perception, bipolar neurons whose apical end forms olfactory vesicle, cilia have odor receptors.
Sustentacular cells (supporting cells).
Basal cells, small stem cells at base replace other cell types.
What are vibrissae and what is their role?
Nasal hairs that filter out particulate matter (defence)
Are there goblet cells in bronchioles?
No
What do goblet cells get replaced by in the bronchioles?
Clara (club) cells
What is the role of Clara cells?
Domed apical surface.
Function of the Club cells is to secrete proteins that reduce the stickiness of the mucus produced by larger diameter airways and to produce lysozyme and immunoglobulins.
What are acini?
Includes all components capable of facilitating gas exchange. It consists of respiratory bronchioles alveolar ducts and alveoli.
Between pneumocytes and pulmonary endothelial cells …
The basement membranes are fused
Which cell types other than pneumocytes are commonly found in the walls of alveoli?
Macrophages
