Introduction to Respiratory system + Oedema Flashcards
what do we mean by conducting zone vs gas exchange zone in the respiratory system
conducting zones (nose to bronchioles) form a path for conduction of the inhaled gases {aka air’s journey to respiratory zone}
respiratory zone (alveolar duct to alveoli) where the gas exchange takes place
immune defences of lung
1) 1st line: Non-specific barriers
a) Skin and mucous membranes b) Cilia
2) 2nd line: Non-specific (i.e. innate immune system) immune cells
a) Patrolling leukocytes – phagocytic WBCs –**primarily macrophages** b) In response to bacterial infection - neutrophils
3rd line: specific, acquired immunity=B and T cells + antibodies
defense against pathogens starts in the nose:
[______ _____ ______] in nasal passages spin air flow into vortex - dust particles and some airborne pathogens are thrown outwards into mucous – trapped and destroyed.
○ nasal epithelium covered in mucus. Air taken in nasally passes over mucous covered surfaces.
○ Turbinate bones (conchae) in nasal passages spin air flow into vortex - dust particles and some airborne pathogens are thrown outwards into mucous – trapped and destroyed.
○ Mucous contains antibodies + antibiotic peptides which can kill/ immobilise pathogens
Mucous continuously secreted by goblet cells which are interspersed w epithelial cells. Epithelial cells have cilia on their surface; cilia move back + forth and transmit mucous containing immobilised pathogens back into throat where swallowed and most pathogens killed by stomach acid
mucus is continuously secreted by goblet cells which is moved by cilia; what kind of epithelium covers the respiratory tract up until the bronchioles
respiratory tract epithelium: ciliated pseudostratified columnar epithelium until bronchioles
this system of mucus being moved by cilia is called the mucociliary elevator
what is cystic fibrosis
- Autosomal recessive genetic disorder
- Abnormal function of epithelial chloride channel - mutation in CFTR gene; Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) – key role in maintaining lungs epithelia
N.B. In CF mucous is abnormally thick (due to genetic mutation), and difficult for cilia to move. People with CF require regular physiotherapy to ‘cough up’ and remove thick mucous decrease infection with pathogens
why do alveolar ducts have no mucus lining?
as it would impede gas exchange
what is the relationship between pressure of a gas and the volume it occupies
Boyle’s Law
= inverse relationship between pressure of a gas and the volume it occupies
so the smaller the volume the higher the pressure
what is quiet inspiration
Quiet inspiration {breathing}, aka eupnea, is breathing at rest and does not require the cognitive thought of the individual.
describe lung mechanics of inspiration + expiration
quiet inspiration:
* Diaphragm contracts {inferiorly} and moves downward, external intercostal muscles contract, rib cage expands/chest pulled outwards
- Increases thoracic cavity volume
- As a result, intrapleural pressure becomes more negative (decreases further below atmospheric pressure)
- Increase in negative intrapleural pressure increases the transpulmonary pressure, causing lungs and alveoli) to expand
- As alveoli expand, alveolar pressure drops below atmospheric pressure.
*This pressure difference causes air to flow into lungs until alveolar pressure equals atmospheric pressure
quiet expiration: (passive)
*External intercostal muscles relax and the inward elastic recoil of lungs results in decrease in lung volume
- Alveolar volume decreases, thoracic cavity volume decrease
*(pressure increases inside lungs)
Causes alveolar pressure> atmospheric pressure and air leaves the lungs until pressures equalise and no more air movement; atmospheric pressure in lungs high again as smaller volume
- Intrapleural pressure remains negative relative to atmosphere, but less negative than at end inspiration
Thus still positive transpulmonary pressure – alveoli do not completely collapse despite increased pressure within lung from lung elastic recoil decreasing lung volume
define the following:
*tidal volume
*total lung capacity
*residual volume
*lung compliance
*lung elastic recoil/ aka elastance
define the following:
*intrapulmonary pressure
* intrapleural pressure
* transpulmonary pressure
Intrapulmonary pressure: pressure inside alveoli/lungs
Intrapleural (pleural) pressure: pressure in pleural space between visceral and parietal pleura
(Intrapulmonary pressure)- (intrapleural pressure)
=Transpulmonary pressure (always +ve; enables alveoli to expand and keeps the alveoli expanded so they don’t collapse (regardless of pressure)
what connects lungs to chest wall
connects lungs to chest wall: PLEURA
pleura is the reason when we expand our ribcage, expands our lungs; as remember no muscles or ligaments or tendons that attach lungs to ribcage just pleura. The chest wall is connected to lungs because of the pleural seal {surface tension cuz of intrapleural fluid}
► Pleura: Each of a pair of serous membranes lining thorax and enveloping lungs. ► Parietal pleura lines the inside of each hemi-thorax (the bony thoracic cage, diaphragm & mediastinal surfaces) ► Visceral pleura lines the outside of lung. ► Intrapleural space = space between visceral and parietal pleura, (potential space; between the 2 serous membranes) - contains about 15 ml fluid N.B. Fluid in pleural space
lungs have a natural [__] elastic recoil
chest wall has a natural [___] elastic recoil
these 2 opposing forces create a negative pressure in the intrapleural space= stopping the lungs from COLLAPSING
lungs have a natural inwardelastic recoil
chest wall has a natural outward elastic recoil
these 2 opposing forces create a negative pressure in the intrapleural space; -ve pressure due to elastic recoil of lung pulling visceral pleura inward and chest wall elastic recoil pulling parietal pressure outward
*intrapleural pressure negative throughout expiration + inspiration [becomes even more -ve up until end of inspiration] relative to atmosphere and intra-alveolar pressure keeps alveoli/lungs from fully collapsing with each expiration
what is the functional residual capacity (FRC) of lungs
FRC/ Functional residual capacity= volume air at resting expiratory level
resting expiratory level (REL)= state of equilibrium maintained by
–lung collapse inwards (lung elastic recoil)
-chest wall pulls outwards (chest elastic recoil)
these FORCES are equal and opposite so chest balances out= no movement of chest wall
n.b. if condition where recoil too strong then FRC will be lower, if lung elastic recoil is too weak the FRC will be larger BOTH ARE PATHOLOGICAL AND BAD NEWS
Each alveolus consists of three types of cell populations (listed below) can you explain their functions?
- **Type 1 pneumocytes** (70% internal surface of alveolus) These cells are thin and squamous, ideal for gas exchange. They share a basement membrane with pulmonary capillary endothelium, forming the air-blood barrier where gas exchange occurs. These pneumocytes joined one another and other alveolar cells by tight junctions, forming an impermeable barrier to limit the infiltration of fluid into the alveoli. - **Type 2 pneumocytes **(7% of the internal surface of each alveolus) These cells have a mean volume that's half that of type I pneumocyte with apical microvilli. Within their cytoplasm are characteristic lamellar bodies containing a surfactant, a substance secreted that decreases the surface tension of alveoli - **Alveolar macrophages** (mononuclear phagocytes that are residents in alveoli) They derive from blood monocytes. The cell membrane of these cells can utilize a network of microtubules to change shape during chemotaxis or phagocytosis.
Functions:
Type I pneumocytes :
* Facilitate gas exchange
* Maintain ion and fluid balance within the alveoli
* Communicate with type II pneumocytes to secrete surfactant in response to stretch
Type II pneumocytes:
* Produce + secrete pulmonary surfactant - surfactant is a vital substance that reduces surface tension, preventing alveoli from collapsing.
* Expression of immunomodulatory proteins that are necessary for host defense
* Transepithelial movement of water
* Regeneration of alveolar epithelium after injury
Alveolar macrophages:
* they collect inhaled particles from the environment e.g. coal, silica, asbestos, microbes i.e. viruses, bacteria, fungi.
* have a receptor named toll-like receptor, which binds to another receptor on surface of microbial cells, the pathogen-associated molecular receptor. This interaction facilitates the phagocytosis of the pathogen and the secretion of pro-inflammatory cytokines to enhance the local immune response.
* Within the alveolar macrophage, engulfed microbes become fused with their lysosome to destroy the pathogen
compliance is [____ ____] to elastic recoil/elastance
compliance is inversely proportional to elastance/elastic recoil
n.b. compliance is how much the lung can stretch. Elastance is ability of lungs to come back to their orginal shape after being distended
i.e.
-In tissues with high compliance (easier to stretch), elastic recoil is less
-In tissues with low compliance, elastic recoil (tendency to return to original size) is high
n.b. LUNG COMPLIANCE IS
=inversely related to connective tissue surrounding alveoli {elastic fibers including collagen and other matrix elements within the lung parenchyma}
=Inversely related to alveolar fluid surface tension
what is the function of surfactant in the lungs + where is it made
surfactant is secreted by type II pneumocytes in lungs
n.b. surface tension of fluid limits expansion of the alveoli; it decreases compliance making it more difficult for alveoli to expand… SURFACTANTcounters this; it decreases surface tension making lungs more compliant/making it easier for alveoli to expand
functions:
1) lowering surface tension at the air–liquid interface and thus preventing alveolar collapse at end-expiration,
2) interacting with and subsequent killing of pathogens or preventing their dissemination
3) modulating immune responses.
where is surfactant made?
(1) Surfactant is synthesized in the endoplasmic reticulum (ER) of alveolar pneumocyte type II cells, and transported to the Golgi
for further modification.
what is radial traction?
radial traction= ‘outward tugging traction’ the alveoli pull the bronchioles {which have no cartillage whereas bronchus has cartillage}. Bronchioles are therefore anchored by the alveoli and kept open by this ‘outward tugging’
The higher the elastic recoil of the lungs, the greater the radial traction will be. Radial traction helps to prevent airway collapse in expiration
Erythrocytes have a 120 day lifespan (roughly), the senescent RBCs are destroyed/ go through hemolysis in what part of the body?
Erythrocytes have a 120 day lifespan (roughly), the senescent RBCs are destroyed (hemolysis) in the spleen
n.b. RBCs do not have mitochondria. Instead they rely on anaerobic respiration which produces 2 ATPs which is enough to power the red blood cell.
where are platelets derived from and what glycoprotein hormone regulates/controls platelet production
Platelets small fragments are derived from the megakaryocyte unde the control of thrombopoietin
Thrombopoietin is a glycoprotein hormone produced by the liver and kidney which regulates the production of platelets. It stimulates the production and differentiation of megakaryocytes, the bone marrow cells that bud off large numbers of platelets
which granulocyte has heparin and histamine in its granule?
The granules of basophils hold both histamine and heparin
n.b. Heparin is an enzyme that prevents blood from clotting too quickly.
describe how a multipotent hematopoietic stem cell (hemocytoblast) differentiates into a mature erythrocyte
hematopoietic stem cell (hemocytoblast)-> common myeloid progenitor-> proerythroblast->basophilic erythroblast->polychromatic erythroblast->orthochromatic erythroblast-> reticulocyte (aka polychromatic erythrocyte) -> erythrocyte (mature RBC)
in bold is simplified progression to memorise
what is thalassaemia
Thalassaemia= group of inherited conditions that affect haemoglobin. People with thalassaemia produce either no or too little haemoglobin
Thalassemia is a genetic condition that damages your red blood cells, and anemia is a condition caused by a lack of healthy red blood cells. This means that it’s common for thalassemia to lead to anemia.
what nerve supplies the aorta + aortic body
The aortic body receives sensory innervation from the aortic nerve, which is a branch of the vagus nerve.
[_______] cover microvessels such as arterioles, venules and capillaries, while large-diameter vessels like arteries and veins are covered by vascular smooth muscle cells (VSMCs), the other type of mural cells
Pericytes cover microvessels such as arterioles, venules and capillaries, while large-diameter vessels like arteries and veins are covered by vascular smooth muscle cells (VSMCs), the other type of mural cells
