Respiratory System Flashcards
Learning Objectives for this Lecture (Desired Outcomes):
- Describe the characteristics of the respiratory system.
- Describe the anatomy of the respiratory system and identify the gross and microscopic anatomical features.
- Relate the structure of the components of the respiratory
system to their functions.
Gas exchange occurs via diffusion.
Diffusion = rapid movement of substances over very short distances.
But, diffusion works too slowly to adequately supply most metabolizing cells more than 1 mm from the gas exchange surface. (It would take years for O, to diffuse passively from your lungs to legs)
So gases must be transported away from the gas exchange surface to individual cells via the circulatory system.
Embryological Development
Understanding the embryological development of the lungs makes clear why the respiratory and digestive systems share a common passage way
(pharynx) and why the trachea sits in front of the esophagus
Respiration = the exchange of gases between the environment, blood and the cells.
= delivery of O, to tissues and removal of waste, mainly COz
Respiration in animals with lungs involves:
* movement of air from outside the body into the lungs (inspiration/expiration)
* exchange of gases from the lungs to the blood (external respiration)
* exchange of gases from the blood to the cells (internal respiration)
Functions of the Human Respiratory System Respiratory Functions
Moves air into and from the body (for 02 and CO, exchange)
Requirements for respiration
: Mist sumara (speinimises distance)
* Large surface area (speed)
* Good underlying blood supply (speed)
Ventilation (breathing) requires a pump (lungs)
Perfusion (delivery of blood through an organ) requires a pump (heart)
Principal evolutionary trend in tetrapods has been adaptation to increasing body size
OR metabolic rate by increasing compartmentalisation of the usually paired lungs.
In mammals, lung volume is nearly always proportional to body size
BUT
Alveolar surface area (= respiratory surface) varies with metabolic rate.
e.g. In some primates, total alveolar surface = 8cm? / g of body weight
In mice = 50cm2 / g of body weight
Functions of the Human Respiratory System Non-Respiratory Functions
Non-Respiratory Functions
* Olfaction
* Nonspecific defence against pathogens
* Acid-base balance
* Vocal communication
* Expulsion of abdominal contents
* Blood pressure regulation
* Blood and lymph flow
* Blood filtration
embryological mutations
Upper respiratory tract
= respiratory organs of
the head and neck.
= conducting zone only
nasal cavity photo
Anatomy of the Respiratory System.
Terminology - Functional:
Conducting zone (anatomical dead space) = passages that conduct air (to the)
Respiratory zone = gas exchange regions of the distal airways
Lower respiratory tract
= respiratory organs of
the thorax.
= conducting zone and
Upper Respiratory Tract: Nasal Cavity
turbinate photo
Nasal Cavity: Approximately 10,000 L of ambient air passes through the nasal airway per day and 1 L of moisture is added to this air.
Each fossa = 60cm (= septum + conchae)
Modifies air entering respiratory tract:
nasal cavity functions
- Cleans
- Entry - hairs (vestibule / nostrils)
- Within - cilia + mucus (epithelium)
- Moistens - glands & goblet cells + transudation (= passage of fluid through a membrane)
- Warms - blood sinusoids in CT of underlying
epithelium
prewarms inspired air to 32° C - 34° C
Also performs a thermoregulatory role in mammals.
As body temp Ts, mammals increase respiratory frequency & volume to maximise air movement across an evaporative surface =1d evaporative
heat loss.
upper respiratory tract photo
larynx photo
respiratory tract histology
Eretin case lar tissue (swa ors on the inferior
concha engorges with blood and restricts airflow through
one side.
: The bul of ai flow shits between ightand et nostin
once or twice every hour.
glottis and epiglottis
nasal tract in the mid-sagittal plane
Trachea:
(windpipe)
16-20 C shaped
rings of hyaline
cartilage
cartilage rings
keep trachea
from collapsing
during inhalation
hymen lined by
epithelium
spanned
posteriorly by
smooth muscle =
trachealis (that is how its spelt)
gap in cartilage
allows room for
esophagus to
expand when
food is swallowed
Bronchopulmonary Segments photo
The effect of smoking on epithelium of the conducting zone
- Paralysis of cilial
function - Metaplasia
= decreased mucus
secretion &
ciliary clearance of
particulate matter
lungs photo
Bronchial Tree: photo
btracnicial arteries n shit
bronchial tree lecture slide photo
idk wtf this is for lmao
Learning challenge:
- Explain which features of the epidermis might make it a good respiratory membrane and which would not.
- Describe how air is modified by the nasal cavity before it enters the nasopharynx.
- Describe the epithelium lining the various regions of the pharynx and relate the structure of this epithelium to its function.
- Describe the structure and function of the mucociliary escalator.
- Explain why the lungs are supplied with blood by two different arterial systems.
- Describe the structure and function of the blood-gas barrier.
Blood supply
Lungs receive blood from:
- pulmonary arteries (98%):
whole body physiology:
carry deoxygentated blood from the right ventricle
concerned with systemic physiology (i.e. gas exchange for all tissues of the body)
Pulmonary arteries follow the bronchial tree supply alveoli
- bronchial arteries (2%):
responsible for lung physiology
carry oxygenated blood from the aorta to the lungs supply bronchi, bronchioles, CT, visceral pleura & the larger pulmonary BVs with O2 & nutrients.
more bronchiol artery bs
Learning Objectives:
- Describe the mechanics of breathing.
(Ventilation - inspiration & expiration) - Describe some factors that influence breathing. (Nervous control; chemical & physical influences)
Whole purpose of getting air into lungs is to allow for
alveolar gas exchange.
At the alveolus, blood unloads CO, and loads 02
Efficiency of CO, unloading & 02 loading via RBCs depends on how long it takes for each gas to reach equilibrium (to fully unload or load)
in the capillary blood (=0.25 secs),
compared to how long an RBC spends in in an alveolar capillary:
Usually, at rest = 0.75 secs;
vigorous exercise = 0.3 secs
So even when blood is flowing at maximal speed through capillaries, equilibrium can be reached.
In health: 70m//lung;
alveolar capillaries contain
100ml of blood at any one time
lung diffusion photo
transverse section
Pleura: photo
breathing shity
How do the lungs move?
- Pleura
Thin serous membrane arranged as a double layer
around the lungs.
In between layers the narrow pleural cavity (10-
30um wide) is filled with pleural fluid.
Pleural fluid:
- prevents friction when layers move relative
to each other
- means that the 2 layers of pleural cling to each
other like sheets of wet paper.
So the lungs are stuck to the thorax.
When the thorax moves, the lungs move.
Lungs do not ventilate themselves. Lungs only contain smooth muscle which affects airway diameter.
The muscles that move the lungs are skeletal.
How do the Lungs move?
- Muscles of respiration
Principal muscles of respiration (skeletal)
= diaphragm + intercostal muscles.
Diaphragm: Produces about 2/3ras of pulmonary airflow
Attached to the ribs and costal cartilages (7-12), xiphoid process of sternum; lumbar vertebrae
Innervated by the phrenic nerves - During development these nerves descend into the thorax ahead of the respiratory tree.
When the diaphragm contracts it moves inferiorly (1.5cm in relaxed breathing; up to 12cm in deep breathing)
- increases superior to inferior dimension &
anterior to posterior dimension
(by flattening it pushes outward on the sternum and ribs)
When it relaxes it bulges upwards and compresses the lungs
How do the lungs move? photo
How do the Lungs move? photo
Intercostal muscles: between the ribs
Stiffen the thoracic cage during respiration and prevent it from caving inward when the diaphragm descends (contracts).
Also contribute to enlargement and contraction of the thoracic cage and
contribute about 1/3 of the air that
ventilates the lungs.
Second rib
NOTE: The only muscular effort involved in normal expiration is a braking action to smooth the transition
from inspiration to expiration.
How are the lungs ventilated?
Breathing (pulmonary ventilation) = mechanical process
which moves air into and out of the lungs.
We breathe via aspiration = use a pump to create a
negative pressure to get air into the lungs.
Involves the rhythmically changing the thoracic volume using a repetitive cycle of inspiration (breathing in) and expiration (breathing out).
One cycle of inspiration + expiration = respiratory cycle
Changing thoracic volume changes air pressure inside the
lung relative to the environment.
Breathing in increases the volume of the chest. Creates a negative pressure in the lungs - air flows in.
Breathing out decreases the volume of the chest. Creates a positive pressure in the lungs - air flows out.
boyles law
volume change in the lungs photo
Accessory muscles of respiration
Assist mainly during forced respiration
Deep inspiration is aided by using these muscles to arch the back and elevate the upper
ribs. Increases thoracic volume.
In forced expiration abdominal muscles can pull down on the ribs and sternum while pushing the abdominal contents superiorly to reduce thoracic volume more than normal (singing and public speaking).
Do not need to know the names of accessory muscles.
Accessory muscles of respiration photo
mechanics of breathing photo
Gas Laws
- Boyle’s law - at a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume.
Also contributing to lung expansion is:
- Charles’s law - at a constant pressure, the volume of a given quantity of gas is directly proportional to its absolute temperature.
Neural control of respiratory system:
Breathing requires repetitive stimuli from the brain.
1. Smooth muscle of the airways
- influences speed of airflow
Bronchodilation (airway expansion)
Bronchoconstriction (airway contraction)
Under autonomic nervous control (L06):
Sympathetic (fight or flight) &
Parasympathetic (rest & digest)
2. Breathing - moving air into and out of lungs requires
skeletal muscle contraction and relaxation.
Skeletal muscle needs nervous stimulation to contract.
Under control of brain stem & to some extent the cerebrum.
Neural control of respiratory system:
photo
Neural control of breathing:
- Automatic, unconscious cycle of breathing is controlled by 3 pairs of respiratory centres in the brainstem (medulla oblongata and pons).
Also influenced by higher brain centres. - Voluntary control of breathing
Brain stem respiratory centres include: - Ventral respiratory group (VRG)
= primary generator of respiratory rhythm
* Contains Inspiratory (I) neurons that alternate with Expiratory (E) neurons
to produce a respiratory rhythm of 12 breaths/min.
* When I neurons are firing, E neurons are inhibited.
When I neurons stop firing, E neurons start firing.
* I neurons cause diaphragm and intercostal muscles to contract (~2 secs).
* E neurons facilitate relaxation of these muscles (~3 secs).
Neural control of breathing:
photo
Brain stem respiratory centres
receive input from:
Brain stem respiratory centres
receive input from:
1. Peripheral chemoreceptors
Located in carotid and aortic bodies of the large arteries above the heart.
Respond to mostly to pH
but also to 0, and CO, blood levels
Sensory neurons in the
Glossopharyngeal (carotid body) & Vagus (aortic bodies) nerves synapse with Dorsal Respiratory Group (DRG)
neurons.
DRG = speed and depth of breathing.
Brain stem respiratory centres continued:
- Dorsal Respiratory Group (DRG)
Modifies basic respiratory rhythm of the VRG to adapt to various conditions
Affects depth and rate (speed) of breathing
DRG is an integrating centre that receives in put from:
* Pons (see below)
* Chemoreceptors (medulla, some major arteries)
* Airway stretch and irritant receptors
* Emotional influences (higher brainstem centres) - Pontine Respiratory Group (PRG)
Also affects speed and depth of breathing
Receives input from higher brain centres (e.g. hypothalamus, cerebral cortex)
Adapts breathing to e.g. sleep, exercise, vocalisation, crying, gasping, laughing
Brain stem respiratory centres
receive input from: photo
Brain stem respiratory centres receive input from:
- Irritant receptors
Nerve endings amongst the epithelial cells of the airway.
Respond to cold air, pollen, smoke, dust, chemical fumes &
excess mucus.
Result = coughing, shallower breathing, breath-holding
(mainly via skeletal muscle) & bronchoconstriction (smooth muscle) - Stretch receptors
Found in the smooth muscle of the bronchi and bronchioles
& in the visceral pleura.
Respond to extreme stretching (inflation) of the lungs by stopping inspiration (inhibition of | neurons)
Both irritant and stretch receptors transmit signals to the
DRG via the vagus nerve.
Brain stem respiratory centres receive input from:
Brain stem respiratory centres receive input from:
4. Central chemoreceptors
= brainstem neurons that respond to pH changes in cerebrospinal fluid (CSF)
pH is a measure of hydrogen ions
Metabolism depends on the functioning of enzymes which are very sensitive to pH
Even slight variations from pH can:
* Shut down metabolic pathways
* Alter the structure and function of macromolecules
Acids release Ht ions; bases accept Ht ions
Normal pH = 7.35 - 7.45
Acidosis-blood pH lower than 7.35 (below pH 7 = coma, 6.8 = death)
Alkalosis-blood pH higher than 7.45 (above pH 7.7 = death)
Excessive changes in pH are resisted by physiological and chemical buffer systems in the body.
Buffers minimise changes in pH by releasing or binding H+ ions.
Adjustments to pulmonary ventilation is one of the physiological buffer systems
- Central chemoreceptors continued…
= brainstem neurons that respond to pH changes in (CSF)
How?
CO, crosses blood-brain-barrier and reacts with water in CSF to produce carbonic acid according to the following equation:
СО2 + H20 → Н2СО3 → HCO3 + H+
A stable CSF pH reflects stable blood COz
Adverse shifts in pH - adjusted via pulmonary ventilation which affects the “direction” of the equation and restores pH levels.
(= physiological buffering)
Changes to ventilation can be activated within minutes
- Central chemoreceptors continued… photo
A corrective homeostatic response to acidosis (blood pH < 7.35)
= HYPERventilation (over-breathing)
* “Blowing off” CO, faster than the body produces it
* Pushes reaction to the left:
COz (expired) + H20 < H2CO3 + HCO; + H+
* Reduces H+ (reduces acid), raises blood pH toward
normal
A corrective homeostatic response to alkalosis
(blood pH > 7.45)
= HYPOventilation (under-breathing)
* Allows CO, to accumulate in body fluids faster than
we exhale it
* Shifts reaction to the right:
СО, + Н20 → Н,СО3 → НСО3 + H+
* Raising the H+ concentration, lowering pH to normal
Voluntary Control of Breathing
Important in speaking, singing, breath
holding
Voluntary control originates in the motor cortex of the cerebrum
Bypasses brainstem centres.
Efferent neurons send impulses down the corticospinal tracts to integrating
centres in the spinal cord
(Sound familiar? Nervous system 2
Tutorial)
Holding breath raises COz blood levels until a breakpoint
is reached THEN automatic
controls override.
So breathing will resume,
even if child faints when holding their breath.
Learning challenge:
- Explain the role that each of the 3 subtypes of muscle plays in the respiratory system.
(smooth muscle - airway diameter; skeletal muscle - ventilation of the lungs;
cardiac muscle - propels deoxygenated blood to the lungs via the pulmonary arteries) - Describe the mechanical events of tidal breathing.
Must describe the full cycle - air in and out. - Describe how inspiratory and expiratory neurons of the ventral respiratory group
interact to generate respiratory rhythm. - Explain how the respiratory system responds to acidosis.
Exam Questions
The region of the brain regulating breathing while these children laugh is the:
a. Ventral respiratory group of the medulla oblongata
b. Dorsal respiratory group of the medulla oblongata
c. Pontine respiratory group
d. Motor cortex of the cerebrum
The part of the brain’s ventricular system closest to the Pontine respiratory group is the:
a. Lateral ventricles
b. Third ventricle
c. Cerebral aqueduct
d. Fourth ventricle
