P L1 Flashcards
differences in what allows for the exchange of gases
Differences in partial pressure of O2 and CO2
What is external and internal resp? whr does it occur? what are the Partial P’s differences in each? how does it vary?
External –> occurs in the alveoli
Gas exchange occurs btwn the alveoli and pulm blood caps.
Higher O2 Partial P (PP) in the alveoli and lower CO2 PP in the alveoli compared to surrounding pulm caps.
Thus O2 diffuses out of alveoli into caps and CO2 diffuses out of caps into alveoli
Internal –> Occurs within cells and between cells and surrounding blood capillaries through the interstitial fluid surrounding the cells and caps.
Also occurs due to PP differences
PP differences here are opp to those in the alveoli
There’s a higher PP of O2 in the blood and lower PP of CO2. While the cells have a higher PP of CO2 and a lower PP of O2.
Thus O2 diffuses into the cells from the blood caps and CO2 diffuses out of the cells into the surrounding blood caps
What are the regulated variables that play a role in homeostasis?
- O2
- CO2
- pH
How are variables (O2, CO2 and pH) in homeostasis controlled?
They are often controlled by negative feedback loops
** (IMP) Controlling the rate and depth of breathing controls the levels of O2, CO2 and pH within tightly controlled limits
Describe some pathways that are a part of the respiratory control system
1) Most imp. one –> Resp center in the brainstem sends APs to elicit muscle contraction –> Causes an increase in the rate and depth of breathing –> Increases lung volume –> Signals lung stretch receptors –> -ve feedback: sends signals to resp center in brainstem for relaxation
2) Other sensory afferents:
They continuously sample blood/cerebrospinal fluid to check for levels of O2, CO2, pH etc.
3) Higher Brain centers:
Control through conscious control of breathing like during talking, eating (stop breathing when swallowing), stress (hyperventilate), pain, laughter, sleep/wake cycle (breathing slows down)
4) Chemoreceptors:
Increased CO2 or decreased O2 signals chemoreceptors to increase breathing
What system is the resp system usually coupled with?
Cardiovascular system
What are the 3 stages of respiration? Which nerves are active during them?
- inspiratory :: Phrenic and hypoglossal and intercostals
- Post inspiratory :: vagal nerves
- expiratory :: none (passive)
What are the respiratory muscles?
Inspiratory muscles:
– Diaphragm
– External intercostal musc (pulls chest wall up to inc lung vol.)
Inspiratory auxiliary muscles:
– Parasternal intercostals
Expiratory muscles (expiration is passive however, these muscles are used in forced expiration):
– Abdominal
– Internal intercostal
What are the inspiratory muscles? Which intercostal musc used?
Diaphragm
External intercostal musc.
What are the inspiratory auxillary muscles? Which intercostal musc used?
There are multiple inspiratory auxiliary muscles:
–> Parasternal intercostal muscles
- Genioglossus
- Geniohyoid
- Sternohyoid
- Scalene
- Sternocleidomastoids
What type of processes are expiration and inspiration generally?
Inspiration – active process – requires use of muscles
Expiration – usually passive process – involves relaxation of inspiratory musc to exhale the air
– but active expiration can also occur thru recruiting the expiratory muscles.
What are the expiratory muscles? Which intercostal musc used?
Abdominal muscles
Internal intercostal
How is muscle activity measured? What condition can it be important in detecting?
Using electromyography
Used to measure electrical activity within the musc
Used to measure activity of muscles during inspiration and expiration
Can be used to detect the condition called ALS (Amyotrophic Lateral Sclerosis)
– Its a progressive nerve disease and affects the brain and SC
– Disease where there’s loss of musc control due a decrease in the recruitment of musc by nerve cells
Which is the principle inspiratory muscle and what center in brain excites it? Which direction does it move in during inspiration?
The diaphragm
The central resp. patter generator
During inspiration the diaphragm contracts and moves downwards – causing an increase in the thoracic cavity
_______ is closely related to function
structure
Define how structure and function are related
Structure –> Structure is the way each component in inter-related
Function –> Function is the operation of each individual component as part of the structure
_____ is the way each component in inter-related
Structure
_____ is the operation of each individual component as part of the structure
Function
What are the types of tissue? Where are they found? What is their function? Give examples
Epithelium
– Line body surfaces and provide protection
– squamous, cuboidal, columnar (simple/stratified)
Connective tissue
– They provide tensile strength and elasticity
– EX: collagen (most abundant protein in body) and elastin (elastic recoil + stretching)
Muscle
– motile force thru contraction
– Skeletal musc, smooth muscle
Nervous tissue
– Receive stimuli from external and internal envrmts and analyse and integrate signals
What are the functions of the airways
PRIMARY::
It’s primary function is to match ventilation with perfusion and it does so by conducting gas thru the airways and allowing for gas exchange
–> Conducting Zone: Area which conducts air in and out of the site of gaseous exchange (Site associated with Mechanical respiration only - not cellular )
–> Respiratory Zone: The extensive area for gaseous exchange – provides O2 and removes CO2 and thus maintains blood pH levels
Thus its function is to match ventilation (air flow) with perfusion (blood flow)
SECONDARY:
- To maintain patency
- To humidify and warm air
- to clean particulates/fight infections (have prostaglandins and histamine (in all airways))
- Produce sounds
- site for olfactory sensation
Which primary function/zone of the lung is associated with mechanical respiration only
The conducting zone
What is the respiratory zone
What structures does it include?
Its the extensive site for the exchange of gases
Provides O2 and removes CO2
Maintains blood pH
Structures:
– Respiratory bronchioles
– Alveolar ducts
– Alveolar sacs
What is the conducting zone
It is involved in only mechanical resp.
It involves the movement of air in and out of the site of gas exchange
Structures:
– Trachea
– Bronchi [ Primary bronchus, Secondary bronchus (lobar), Tertiary bronchus (segmental)]
– Bronchioles
What are the main subdivisions of the respiratory tract?
UPPER RESP TRACT:
- Nose
- Pharynx
- Larynx
LOWER RESP TRACT:
- Trachea
- Bronchi
- Bronchioles
- Lungs
- Alveoli
What are the features of Respiratory mucosa? What type of epithelial cells does it have? What part of the nasal cavity does is not lined by resp. epithelium?
It forms the mucosal lining of the nasal cavity
- It is made of stratified columnar epithelial cells
- It has goblet cells
- It has mucus glands
- It has a rich blood supply to warm the air
The nasal cavity contains 2 types of mucosa:: Respiratory and olfactory mucosa.
The part of the nasal cavity near the roof is lined by the olfactory epithelium instead and contains olfactory receptors
[The transduction of olfactory information occurs in the olfactory epithelium, the sheet of neurons and supporting cells that lines approximately half of the nasal cavities. (The remaining surface is lined by respiratory epithelium, which lacks neurons and serves primarily as a protective surface.)]
What are the 2 types of mucosal linings found in the nasal cavity? What part of the nasal cavity are they found in?
Consists of Respiratory and olfactory mucosa.
Respiratory mucosa::
– Lines the entire nasal cavity with the exception of the roof
Olfactory mucosa::
Found near the roof of the cavity
Houses smell receptors
What is the function of Bowmans/ Olfactory glands?
- They release secretions thru ducts onto the epithelium lining the nasal cavity
- Secretion produces a fluid envrmt arnd the cilia
- This allows the cilia to clear the contaminated mucus posteriorly to allow access of new odoriferous substances
** Also produce a number of olfactory binding proteins
What receptors contribute to the diving reflex?
Receptors for cold and touch located in the face and nose
What is the diving reflex? What nerves are involved in the initial stimuli? What organ system is involved in the initial and secondary stimuli? What is the secondary stimuli?
What part of the brain do the signals get sent to?
INITIAL RESPONSE:
– Cold or wetness detected in the face by receptors
– Stimuli passes thru trigeminal nerve (main) and also glossopharyngeal n.
– Signals Respiratory center in medulla oblongata
– Which then signals resp. muscles
– Causes apnea (a stop in breathing)
– Prevents from breathing in water
SECONDARY RESPONSE
– A decrease in O2 conc. detected by arterial chemoreceptors
– Signals CVS center in medulla oblongata
– Causes a sympathetic and parasympathetic response
–> sympathetic: Vasoconstriction of peripheral BVs to direct blood to brain and heart
–> parasympathetic: Bradycardia to reduce energy consumption of heart
What cells line the nasopharynx and the oropharynx?
Nasopharynx:
- Pseudostratified ciliated columnar epithelium +goblet cells
Oropharynx:
- Stratified squamous epithelium (as its subject to abrasion)
why is snoring caused
Due to a partial obstruction of the airway
Which part of the respiratory tract is the most vulnerable to collapse in apnea?
The oropharynx
What is obstructive sleep apnea?
Apnea - a pause in breathing
- Requires arousal to reestablish airflow
- larynx particularly vulnerable due to lack of support to maintain its patency
- when we sleep - relaxation of our musc+body posture can lead to collapse of larynx
- often in obese ppl
How many lobes do the right and left lungs have?
Right - 3 lung lobes
Left - 2 lung lobes
What lines the outside of the lungs?
The visceral pleura
What forms the boundaries of the pleural cavity?
The visceral pleura and the parietal pleura
What is the blood supply of both the pleura lining the lungs?
Visceral pleura - Bronchial circ.
Parietal pleura - Intercostal arteries
What is pleuritis/pleurisy? Why is the diseased area vulnerable to this?
It is an infection of the pleural cavity by bacteria or other microorganisms
Vulnerable as it doesnt have any immune cells?
What is tidal volume?
A normal person, when breathing quietly without any active effort, takes in about 500 ml or half a liter of air - this is the tidal volume
Almost a third of this tidal volume or about 150 ml is trapped in this anatomic dead space, and the remaining 350 mL or so is used for gas exchange.
Anatomical and physiological dead space
Anatomical dead space:
– It is the air that we inhale that does not take part in gas exchange and is situated in the conducting zone
– Air in the nose, mouth, trachea, bronchi and bronchioles. (conducting zone)
– Cannot be altered (no matter what we do we cant use this air for gas exchange) - always remains at 150 ml/breath as it’s built in to the anatomy of the body
Physiological dead space:
– Vol of air in each breath that’s not involved in gas exchange
– Sometimes the alveoli are well ventilated but not well perfused (narrow blood caps) this leads to less gas exchange and more dead space air
– This value thus includes the unventilated and poorly perfused alveoli + anatomical dead space
– In a healthy individual this value is close to 150 ml/breath
– This value increases greatly in disease (due to inc. in unventilated/poorly perfused alveoli)
How many branches do the airways divide into each time? what is this type of division of airways called? What does this allow for?
They divide into 2 each time
Dichotomous airways
Large surface area at alveolar level
Large area for gas exchange
What type of cartilage are the c-shaped cartilage? are they flexible? What is their function?
They are hyaline cartilages
They provide flexible support
They maintain the patency of the trachea (hold the airway open)
What happens to the hyaline cartilage and smooth muscle as you move down the respiratory tract?
As you move down the resp. tract, The level of cartilage decreases and the amount of smooth muscle increases.
In the trachea – Large amnt of cartilage
small amt of smooth musc.
In the bronchioles – cartilage is mostly absent
large amt of smooth musc.
What is the name of the smooth muscle is present in the trachea and where is it located specifically?
Trachealis muscle
Joins the ends of the C-shaped cartilaginous rings (at the posterior side of the trachea)
What type of epithelium is present in the trachea?
Pseudostratified ciliated columnar epithelium
What are the different types of cells and fibres found in the tracheal epithelium?
- Goblet cells
- Brush cells
- Ciliated cells
- Serous cells
- Basal cells
– Elastin
What is present between the elastin layer and the pseudostratified squamous epithelium in tracheal epithelium?
A layer of loose lymphoid tissue
What is the function of diffuse neuro-endocrine cells in the resp system?
They secrete hormones that regulate muscle tone (serotonin and dopamine)
What is the function of the following cells in the tracheal epithelium:
- Goblet cells
- Basal cells
- Brush cells
- Ciliated cells
GOBLET CELLS (30%):
They secrete mucus
They slowly begin to disappear as you move down the resp. tract and are replaced by club cells
BASAL CELLS (30%):
They anchor the epithelium mainly
BRUSH CELLS (3%):
They have tiny microvilli on their apical membrane
On their basal side they make direct contact with the nerve fibre
They are thus believed to have a chemosensory role as they sense chemical composition of the airway and send info thru cholinergic response in order to modulate immune response and breathing.
CILIATED CELLS (30%):
They have cilia present on their apical membrane which performs the role of acting as a mucociliary escalator
What cell in the tracheal epithelium is connected to a nerve fibre on its basal side?
The brush cells
What cells in the tracheal epithelium secrete mucous?
Goblet cells
What is the mucociliary escalator? and its function?
– The epithelium is covered in a layer of high viscosity fluid within which the cilia exert a rhythmic beat directed outwards
– This process is known as the mucociliary escalator
– In larger airways the low viscosity fluid is coated with a layer of high viscosity fluid
– The mucociliary escalator functions to carry any intercepted particles in the mucous lining the membrane thru the rhythmic movement of the cilia down towards the pharynx where they are swallowed
How many times per minute does the mucociliary escalator beat? and how many cilia per epithelial cell
12-16 times per min
Approx 300 cilia per cell
Which lung is bigger? Which primary bronchus is shorter?
The right lung is bigger
The right primary bronchus is shorter than the Left primary bronchus
(Think abt it like the right lung is bigger so it’ll take up more space thus leaving less length available for the right bronchus)
How are the primary bronchi diff. form each other
Right primary bronchus is shorter, wider and more vertical
Where does the cartilage lose its c-shap?
in the secondary (lobar bronchi)
How many secondary/lobar bronchi are there in each lung?
Left:
2 lobar (as it has 2 lobes)
Right:
3 lobar (as it has 3 lobes)
What are the divisions of the bronchi? What is their relationship in terms of the SM and cartilage present?
Primary bronchi – R+L
– Right shorter, wider and more vertical than left
– C-shaped cartilage and SM present
Secondary/lobar bronchi;
– 3 on the right and 2 on the left
– cartilage plates (loses its c-shape) and SM present
Tertiary/segmental bronchi:
– Less cartilage and more SM present
What epithelium is present in the bronchi
pseudostratified ciliated columnar epithelium
What are the changes in epithelium as you move down the respiratory tract into the bronchioles?
- Less goblet cells and more club cells
- Decreased height of the epithelium
- Less cilia + pseudostratified ciliated columnar (in bronchi) –> simple columnar (in larger bronchioles) –> simple cuboidal (in smaller bronchioles)
- decrease in cartilage and increase in smooth muscle (bronchioles lack cartilage and glands )
What type of tissue surrounds the smooth muscle in brochioles?
Fibroelastic connective tissue
How do the epithelium cells in larger bronchioles differ from that in smaller ones?
Larger:
Simple columnar ciliated
some goblet cells
Smaller:
Simple cuboidal (some with cilia)
no goblet cells
What are the differentiating features of bronchioles?
- They have no cartilage or any glands
- They have less goblet cells
- They have smooth muscle surrounded by fibroelastic connective tissue
- They are made of simple columnar/cuboidal epithelium cells
- They have more club cells
- Terminal bronchioles have simple cuboidal epithelium (some ciliated) and have club cells with a domed apical surface
Where are club cells found? What is their general role? What is their structure? are they ciliated? What protein do they express? What are some other features?
- They are found in terminal bronchioles instead of goblet cells
- They have a secretory role (like goblet cells)
- They are non-ciliated dome shaped cells
- They express the SCG1A1 (Club cell 10) protein
- They have self renewal properties
What protein do club cells express that can help in their identification?
SCG1A1 (Club cell 10) protein
What do club cells replace and what type of cells are they? Where are they found?
They replace goblet cells in terminal bronchioles
Secretory cells
What are some of the possible roles of club cells?
- Produce a secretion that acts as a surfectant ( lowers surface tension and maintains airway patency)
- Secretion of SCG1A1 protein (club cell 10) –> This protein possesses anti-inflammatory properties relevant in allergic reactions, injury and infections.
- Anti-proteases that may protect against emphysema
– Oxidases that may protect against carcinogens and inhaled toxins
- May divide to replace other cells such as goblet or ciliated cells
- ACE2 production (Angiotensin converting enzyme)
How does the epithelium change in the respiratory zone?
Moves from simple cuboidal (resp. bronchioles) to simple squamous (alveoli) epithelium (not ciliated)
How is respiratory zone different in terms of the cells present?
– simple cuboidal to squamous epithelium (not ciliated)
– Few brush cells or small granule cells
– No goblet cells (they disappear before small bronchioles except in smokers)
Is having goblet cells in your respiratory bronchioles normal? Who migh thave them?
No. smokers
Characteristics of the respiratory zone that allow for gas exchange
- Has thin walls (simple squamous epithelium)
- Has a large SA (about 300 million alveoli)
- Rich blood supply (good perfusion thru pulmonary capillaries - Pulm A. and Pulm V. divide into caps which form a capillary network)
What does connective tissue surrounding the alveoli allow for
- It provides structural support
- It allows for movement of the lung as a whole unit
- There is an alveolar elastin network surrounding the alveoli
List the different cells found in the alveoli.
- Type I pneumocytes
- Type II pneumocytes
- Alveolar macrophages/ Type III pneumocytes
What type of cells are Type I pneumocytes and their role?
- They are simple squamous epithelial cells
- They are large flattened cells that thus allow for gas exchange
- They form 95% of the SA in the alveoli
- They have tight junctions
- Their cell wall is fused to capillary endothelium
- They are covered with a very small amt. of water to facilitate gas exchange
What type of cells are Type II pneumocytes and their role?
- They are dome shaped simple cuboidal cells
- Lamellar bodies in these cells produce and secrete surfactant
- Surfactant decreases surface tension and prevents the collapse of alveoli
- These cells are produced after 24 weeks of gestation period
—–» If these cells are not produced in unborn – surfactant is not secreted and can cause serious respiratory distress in newborns - They also produce ACE2
- They can also differentiate into Type I pneumocytes
What type of cells are Type III pneumocytes? What’s their other name and their role?
- They are originally monocytes (macrophages in tissue) – thus they are Immune cells
- Also called alveolar macrophages
- These are originally monocytes that migrate to the pulmonary interstitium and migrate between the Type I pneumocytes through the alveolar pore of kohn to enter the alveolar lumen
- In the tissue they become macrophages
- Their function is to phagocytose dust and debris and prevent infection in alveoli as they have no cilia
- Type I pneumocytes pass down dust particles to the alveolar macrophages through pinocytic vesicles
What is the role of surfactant? What secretes it? What does it mainly prevent from happening? When does it start being produced
- To reduce surface tension within the alveoli
- Secreted by lamellar bodies in type 2 pneumocytes
- Prevents the collapse of alveolar sacs
- It prevents Atelectasis –> Which is the complete or partial collapse of the lung when alveolar sacs become deflated or filled with fluid (like if you breathe in water accidentally - if no surfactant - since water is cohesive - alveolar sacs will collapse)
- Type II pneumocytes develop after 24 week gestation period – if not developed - can cause respiratory distress in newborns due to surfactant not being produced.
Which cell forms 95% of the alveolar SA/allow for gas exchange/are simple squamous/are fused to capillary membrane?
Type I pneum.
What type of cells produce surfactant/ are produced after 24 week gestation/ prevent lung from collapsing?
Type II pneum.
What cells in the alveoli produce ACE 2?
Type II pneum.
What can type II pneum. differentiate into?
Type I pneum.
What immune cells are present in alveoli? What cell do they originate from? How do the enter the alveolar lumen?
- Alveolar macrophages
- From monocytes in the blood
- They enter the alveolar lumen by passing thru the alveolar pore of kohn
What is the distance gases have to diffuse thru in alveoli?
0.5-1.5 micrometers
Area and volume of alveoli?
70-80 m2
2.5 L
Describe the innervation of the respiratory system
Both divisions of the ANS supply the resp system:
- Sympathetic division —> Dilate airways, constrict BVs and inhibit glands
— By the cervical ganglion
— They relax the smooth musc in the airway (beta-2 receptors - adrenaline + noradrenaline)
— They constrict blood vessels
— They inhibit gland secretions
- Parasympathetic division —> Constrict airways, dilate BVs and stimulate glands
— By the vagus nerve
— Cause constriction of the airways (muscarinic receptors - ACh)
— Dilates Blood vessels
— Stimulate gland secretions
Pulm stretch receptors
J receptors
How does airway defence work against airborne particles?
Airborne particles:
– filtered in nasal passages thru nose hair
– Sneeze reflex
– Cough reflex —> Trachea/bronchi stimulated - inhale - close glottis and epiglottis - forced expiration - sudden opening of glottis and epiglottis — 100 mph exhalation of air
How does the Mucociliary escalator act as a mechanism of airway defence?
- This action occurs in all but smallest bronchioles —-> Bronchoalveolar fluid is cleared thru the movement of ciliary action posteriorly towards the oral cavity
- Particles smaller than 3 micrometers
- Alveolar macrophages engulf these particles
How does the Immune response act as a mechanism of airway defence?
Immune response from:
– Loose lymphoid tissue beneath resp. epithelium in larger airways
– Lymphatic drainage to lymph nodules – lymphatic system allows for traffic of immune cells
Where are lymphatics absent in the respiratory system?
The alveolar walls
Define Microbiota
The microbial community membership associated with a particular habitat such as the human body
Define microbiome
The genetic information (genomes) and the inferred physicochemical properties of the gene products of a microbiota
Define human microbiome
The microbiome collectively found in internal and external habitats of the human body
What are the 3 key factors determining the respiratory microbiome? What do each of these depend on?
1) Microbial immigration
– Microaspiration
– Inhalation of bacteria
– Direct mucosal dispersion
2) Microbial elimination
– cough
– Mucociliary clearance
– Innate and adaptive immune responses
3) Relative rate of microbial reproduction:
– Depends on the regional growth conditions: pH, temp, oxygen, nutrients available, local microbial competition, activation and concentration of inflammatory cells
What are the main factors that determine the respiratory microbiome in healthy individuals and those with lung disease?
Healthy – Immigration/elimination of microbes
Lung disease – Regional growth conditions
—> There’s loss of diversity
—> Dysbiosis (imbalance of microbial species) depending on severity of disease
AEROSOLS
What are the 2 ways mucocilliary function can be impaired?
- Mucus – too much/ change in composition
– chronic bronchitis (excess)
– Cystic fibrosis ( Na/cl )
– Asthma - Impairment of cilia:
—- Paralysis by toxic gas
— bronchial epithelium destroyed (cold - temporary)
—ciliary dyskinesia
What occurs as a result of smoking (impairs what)?
- Impairment of mucociliary function
- Impairment of macrophages
State whether someone with the following will have a high or low number of ACE 2:
- COPD
- smokers
- Hypertension
- COPD/smokers —-> High ACE2
- Hypertension —–> Low ACE2 (as ACE2 causes vasoconstriction)
What nerves are involved in the initial response of the diving reflex?
Trigeminal and glossopharyngeal nerves.
What is responsible for producing a fluid envrmt around the cilia?
The bowman’s glands/olfactory glands::
- Release secretions that create a fluid envrmt arnd the cilia allowing for them to clear dirt
- Produce a number of olfactory binding proteins.
What is responsible for producing a fluid envrmt around the cilia?
The bowman’s glands/olfactory glands::
- Release secretions that create a fluid envrmt arnd the cilia allowing for them to clear dirt
- Produce a number of olfactory binding proteins.
Where are lymphatics and lymphoid tissue present in our resp. tract? Where are they absent?
- LNs at hilus
- LNs at airway branch points
- Layer of loose lymphoid tissue under the epithelium of larger airways
- Lymphatics in airway walls and beneath pleura
—> They are absent in alveolar walls.
Where would aerosols with the following particle sizes deposit and by which mechanism?
1) >0.5-3 micrometer
2) >3 micrometer
3) <0.5 micrometer
1) >0.5-3 micrometer
Location:: Tertiary bronchi+ bronchioles
Mechanism:: Sedimentation (gravity)
2) >3 micrometer
Location:: Primary+secondary bronchi
Mechanism:: Impaction (inertia)
3) <0.5 micrometer
Location:: Alveoli
Mechanism:: Brownian motion (diffusion)
