Respiratory Microanatomy Flashcards
(32 cards)
What do the upper and lower airways consist of?
Upper: nasal cavity, pharynx, larynx
Lower: trachea, bronchi, bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
What do the conducting zone and respiratory zone consist?
Conducting: nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
Respiratory zone: respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
Where are [pseudostratified columnar ciliated epithelium, goblet cells, club cells, Type I pneumocytes, Type II pneumocytes and macrophages] found in the airway and their functions?
P/s col. cil. epithelium + goblet cells: most of CZ- nasal cavity, nasopharynx, trachea, bronchi(large). Cilia–> move mucus, Goblet –> secrete mucus
Club cells (cuboidal): bronchioles. secrete watery substance with antimicrobial properties
Type I, II pneumocytes and macrophages: respiratory zone. I–> squamous, thin air-blood barrier, II- secrete surfactant
Where are [cartilage, elastic fibres, collagen and smooth muscles] found in the airways and their functions?
Cartilage: trachea, bronchi. –> keep airways open
Elastic fibres + collagen: EVERYWHERE –> ventilation
Smooth muscles: trachea- alveolar ducts –> control airflow through bronchioles
What are the two layers of the mucociliary escalator?
Gel layer on top and sol layer below
What does the respiratory epithelium consist of?
Pseudostratified columnar ciliated epithelium + goblet cells
Describe the features of pulmonary arteries and veins (size, pressure, location).
Pulmonary arteries are large vessels to conduct entire CO, they are low pressure (too high damage the lung?) vessels that run with the airway [ 30-10mmHg]
Pulmonary veins carry oxygenated blood, they have very low pressure (pressure gradient for blood flow) with no more than 3 layers of sm muscles, also they are loners that run with CT septa. [10-0mmHg]
How many generations of dichromatous branching are there in the lungs?
23 generations
What are the pores of Kohn?
Pores found in alveoli that connect alveoli
What are the embryological origin of lung airways, parenchyma and pleura?
Airways- endoderm
Parenchyma and pleura- mesoderm
What are the 5 stages of lung development and their time periods?
Embryonic - 26 days- 7 weeks Pseudoglandular - 5-17 weeks canalicular - 16-26 weeks saccular - 24 weeks to after birth alveolar - late foetal to 21 years
What happens during embryonic stage?
The lung bud arises as a ventral outpouching of the foregut endoderm (from the primitive oesophagus). It grows downwards and undergoes three initial rounds of branching – producing the primordia of the two lungs (primary bronchi), the lung lobes (lobar bronchi) and the bronchopulmonary segments (segmental bronchi).
What happens during pseudoglandular stage?
The respiratory tree undergoes more generations of branching, with the formation of branches including more bronchi, bronchioles all the way down to the terminal bronchiole.
What happens during canalicular stage?
Each terminal bronchiole gives rise to two or more respiratory bronchioles. Each of these divides into 3-6 alveolar ducts, which are lined by cuboidal cells. These cells then start to become attenuated. This means they begin to flatten and become more squamous, as this is necessary for gas exchange. It is possible for some babies to survive at about 22-23 weeks if this attenuation is extensive enough.
What happens during saccular stage?
he alveolar ducts give rise to clusters of thin-walled terminal air sacs (primitive alveoli). The type I alveolar cells become intimately associated with blood (and lymph) capillaries. This means there is increasing contact between capillaries and alveoli. This connection is necessary for air to be able to move through into the capillaries and for exchange to occur. The type II alveolar cells also develop and begin to produce surfactant (but this is not at significant levels to reduce the work of breathing until around 32 weeks).
What happens during alveolar stage?
The number of terminal sacs increases. The alveoli mature through continued thinning of the squamous epithelial lining and establishment of more intimate contacts with the surrounding capillaries. So, development of the lungs continues after birth, with development occurring at the alveolar level. There are no new alveoli produced after about 3 years old, but the surface area may increase. There is secondary septation which occurs. This involves adding additional septa to the alveoli (increasing the number of walls) which greatly increases the surface area available for gas exchange. The alveoli also mature through continued thinning of the squamous epithelial lining and establishment of more intimate contacts with surrounding capillaries (through increased number of walls).
What are the breathing characteristics of neonatal respiratory distress syndrome?
- sucking in between the ribcage due very negative intrapleural pressure required to inflate the lungs.
- increased work of breathing (breathing faster and harder) due to stiff lungs
- rapid breathing due to thickened gas transfer tissue
- less surfactant causing collapse of airways and further contribute to sitffness of lungs
need intubation, ventilation and exogenous surfactant therapy
What is chronic lung disease of prematurity/ bronchopulmonary dysplasia and their symptoms?
Abnormal development of airways - must breath harder and faster. Alveoli appear different due to inflammation adn scarring.
Symptoms: persistent increased work of breathing- indrawing of tissue between ribs and increased resp rate
abnormal cxr
requiring oxygen ventilation until 36 weeks for those under 32
What are the autonomic control of pulmonary arterioles?
SNS- a-adrenoreceptors- vasoconstriction
PSNS- muscarinic- vasodilation
what are the 5 factors that regulate diffusion of gas across tissue?
- thickiness of tissue
- solubility of gas
- molecular weight of gas
- partial pressure across tissue
- area
What factors create the Bohr’s shift? and which direction is the Bohr’s shift
shift the oxygen dissociation curve to the right (for a given PO2, lower affinity of Hb for O2 so more O2 released)
increased CO2, [H+}, temperature, DPG
why do we need RBC rather than just Hb?
- decrease blood viscosity
- provide environment for DPG (helps unload O2)
- encapsulate and concentrate carbonic anhydrase (for CO2 transport)
- prevent Hb loss through filtration via kidney
- concave shape helps pass through tight spaces
What are the 4 ways CO2 are transported in blood?
- dissolved in solution
- exist as HCO3- (60% in plasma)
- combined to amine group (esp Hg)
- As H2CO3 and CO32-
What is the Haldene effect for CO2 dissociation curve?
The Haldene effect is about how the affinity for CO2 by venous blood is greater than arterial. THis is because at lungs, reduced affinity so CO2 release. At low PO2 (tissues), greater affinity for CO2 uptake. THis enhances unloading of CO2 from tissue to blood
