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Functions of Respiratory system (6)
- Gas exchange (PRIMARY)
- regulating blood pH
- Filtering inspired air
- Producing sounds
- Elimination of some water and heat
Anatomical classification of respiratory system
- Upper (nose, pharynx and associated)
- Lower (larynx, trachea, bronchi, lungs)
Functional classification of respiratory system
- Conduction portion (most, filters, warms, moistens, and conducts air to and from lungs)
- Respiratory portion (gas exchange)
Conduction portion of respiratory system
- In functional classification.
- Series of connecting tubes that filters, warms, moistens and conducts air to and from lungs. No part in gas exchange
- Nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles.
Respiratory portion of functional classifcation of respiratory system
- Acts in gas exchange.
- Respiratory bronchioles, Alveolar ducts, alveolar sacs, alveoli
1st part of respiratory system
nares. Horses can dilate a LOT, pigs can't. Plays a role in oxygen intake during exercise.
2nd part of respiratory system (after nares)
- paired nasal cavity containing turbinates (thin scrolls of bone covered in mucus membranes)
- Warm and moisten air, cool blood going to brain, allowing the brain temperature to be 2-3 degrees lower than the body temp.
Anatomy of trachea and principle bronchi
dorsally incomplete rings of cartilage united by annular ligament. Trachealis muscle completes the ring. Lined with pseudostratified ciliated columnar epithelium to prevent particles from getting into lungs. Beat stuff upward where it can be swallowed.
holds tracheal cartilage rings together to form a tube
completes the incomplete "C" of the cartilage ring.
terminal bronchioles that contain alveoli
site of gas exchange in lungs. Contains alveolar duct, alveolus and alveolar sac. Lays against capillary endothelium
Pleura of lung
- Parietal pleura lines thoracic cavity.
- Pleural cavity contains a little fluid to help pleura move against each other during respiration
- Visceral pleura lines outside of lungs.
Pressure inside the pleural space is
midsite where 2 pleura meet. Separates the lungs and contains the heart and major vessels
Blood supplies to the lungs
- 2 kinds: Pulmonary arteries oxygenate blood then supply it to the rest of the body. (ventilation perfusion coupling)
- Bronchial arteries arise from the aorta and deliver to the lungs.
Vasoconstriction upon hypoxia. Different from rest of the body. If there is no oxygen in an area, doesn't allow blood to go there.
the pressure within the lungs
the pressure outside the lungs but within the the thoracic cavity (between the visceral and parietal pleura)
- inverse relationship between volume and pressure.
- the pressure inside the lung decreases as the volume of the lung increases
- volume up, pressure down. Pressure down, air in.
- muscular enlargement of the thorax and lungs with accompanying inflow of air.
- Usually an active process.
- Diaphragm contracts down, external intercostals contract, increases volume of thorax, pressure inside lungs decreases, 25% of air rushes in.
Why can lungs increase in volume?
- Elastic structures
- Intrapleural pressure reduces as intrapulmonic pressure reduces.
Energy causing air to leave the lungs is provided by stored elastic energy in the stretched lung and thorax. Usually a passive process using the pressure gradient
In what animal is expiration an active process?
- Horses, even at rest.
- Any animal, if something is impeding outflow of air or breathing is accelerated. There is always a voluntary component.
To permit air to flow out of the lungs:
- intrapulmonic pressure must be positive. Can be due to recoil tendency of lungs.
- Can be produced by elastic fibers within lung or surface tension of fluid that lines alveolar.
- Abdominal and internal intercostals
- Diaphragm relaxes, abdominal muscles contract, internal intercostals contract, increases abdominal pressure, decreases size of thorax, forces diaphragm forward, reduces size of thorax, thoracic pressure increases, air is forced out.
- Reduced total pressure of the intrapleural space is a slight vacuum.
- during breathing the intrapleural pressure gets more negative then eases. Never positive.
goes from negative to more negative to positive to less positive (sin wave)
produced by elastic fibers within the lung and the surface tension of the fluid that lines the alveolar.
Factors that prevent recoil
- Pleural pressure is lower than alveolar pressure to prevent collapse. Air cannot flow into the pleural space, trying exerts a force against the walls of the alveoli, counteracting the tendency of recoil
- Surfactant keeps alveolar from contracting and collapsing, increasing compliancy of lung.
- water lines surface of alveoli and tries to h-bond with other water. This makes alveoli recoil and collapse. Surfactant is produced by typeII alveolar cells, stops H-bonds in water, lowers surface tension, prevents collapse.
- Increases compliancy making ventilation more efficient.
Premature birth and ventilation
surfactant is one of the last things to develop. Premature infants often don't have it. Can't inflate lungs. Treated with synthetic surfactant.
- entry of air into the pleural cavity in sufficient quantity to cause collapse of the lung and consequent respiratory embarrasment.
- 5 types: Closed, open, iatrogenic, spontaneous, tension
- open wound in chest wall, air comes in from outside, kills vacuum, lung collapses. Can be only one, does not have to be both.
- Treatment consists of sealing over chest wound, air-tight, and evacuate air with tool (syringe-type thing like a pic line?)
air leaks in from hole in system (in lung, larynx, etc) killing the vacuum effect.
caused by a doctor, in surgery or similar.
no known cause of air leakage causes collapse of lung
air enters cavity from bronchus but cannot leave the same way, causing a slow collapse
Pneumothorax mediastinal flutter or swing
slight inflation of collapsed lung causes structures of mediastinum to swing towards good lung at each inspiration. Causes serious circulatory issues.
- incomplete expansion of the lung at birth (congenital) or collapse of previously air-filled lung (acquired).
- Blockage of one of the bronchi or bronchioles that lead to lung tissue
- Can be consequence of pleural effusion or pneumothorax, associated with surfactant loss in some conditions.
- Air in alveoli is absorbed into blood, alveoli collapse. Decreased level of oxygen, blood stops going there.
blockage caused by something inside the airway. Complete airway obstruction (inflammation, foreign body, parasites or tumor). Bronchiole gets super skinny.
blockage by something pressing from outside. (pleural, intrathoracic, or intrapulmonary space-occupying lesion like a tumor or enlarged lymph node). Pushes on alveoli, making them small and collapse.
- how easy the lungs are to fill. Distensibility.
- Usually compliance is high due to elasticity of tissue and surfactant.
- Decreased by scar tissue, pulmonary edema from accumulation of fluid, insufficient surfactant, or decrease in ability of thoracic cage to expand.
air way resistance
- Air flow is directly proportional to pressure gradient, indirectly proportional to airway resistance.
- Walls of airways into alveoli (particularly bronchioles) creates resistance to air flow.
- largest diameter has least resistance. Altered by muscle contraction.
Autonomic nervous system and respiration
- Sympathetic nervous system relaxes walls to allow air to enter, lower resistance and increase diameter
- parasympathetic nervous system decreases diameter and increases resistance, lowering inflow.
Disease to increase airway resistance
- Asthma and chronic bronchitis narrow airways and fill them with mucus
- Emphysema makes airways lose elasticity and become distorted and narrowed.
bronchoconstrictor increase resistance and decrease airflow. Less air into alveoli, less air into blood.
respiratory disease. Alveoli become enlarged due to weakened and broken walls. Airways narrow, resistance increases, oxygen cannot get into alveoli.
Two types of breathing
- abdominal (Primary. Visible abdomen movement)
- Costal (rib movement. Caused by pain in abdomen)
normal quiet breathing, no deviation in frequency or depth
difficult breathing in which visible effort is required to breath.
cessation of breathing, usually trasient when in reference to a clinical situation
abnormally slow breathing
excessive rapidity of breathing
- total volume of air breathed per minute
- minute volume = tidal volume * frequency
volume of air inspired in one quiet inspiration
number of breaths each minute
Increase in minute volume
increase in metabolic rate needs more oxygen, so tidal volume or frequency or both must increase
anatomical dead space
conducting airways. No gas exchange. Nares to bronchioles.
alveolar dead space
Lack of gas exchange that occurs within alveoli if they are poorly perfused with blood. Increases with illneses or diseases ike atelectasis, pneumothorax, pulmonary edema, and emphysema
physiological dead space
anatomical dead space + alveolar dead space
- the volume of gas that is inspired but takes no place in gas exchange.
- Dead space plus alveolar ventilation = minute volume
- Used in cooling body (panting) and humidifying.
Layers between alveoli and blood
- 6. Alveolar fluid
- alveolar epithelium
- alveolar basement membrane
- interstitial fluid
- capillary basement membrane
- capillary endothelium
Factors that influence rate of gas diffusion across respiratory membrane (3)
- thickness of membrane
- diffusion coefficient (how easily gas goes across)
- surface area of membrane, partial pressure difference of gas between the two sides of the membrane
Respiratory membrane thickness in gas diffusion
- increasing thickness decreases rate of diffusion
- can be increased by respiratory diseases
- if pulmonary edema fluid accumulates in alveoli, gases must diffuse through thicker-than-normal fluid.
- Pneumonia increases membrane due to mucus build-up, decreasing efficiency.
- measure of how easily a gas will diffuse through a liquid or tissue.
- If diffusion coefficient of oxygen is 1, then coefficient of carbon dioxide is 20. CO2 will go 20 times faster.
Decreased surface area of respiratory membrane in gas diffusion
cause by emphysema and cancer. Destruction of alveoli makes less surface area for diffusion
Partial pressure in gas exchange
- The partial pressure difference of a gas between the two sides of the membrane effects gas exchange in both the alveoli and at the tissue level.
- each gas asserts own pressure.
- Total pressure of gas is the sum of all partial pressures.
- Quantity of gas that will dissolve in a liquid is proportional to its partial pressure and solubility coefficient.
partial pressure of O2 in a gas mixture
partial pressure of O2 dissolved in arterial blood plasma
partial pressure of O2 dissolved in venous blood plasma
partial pressure of O2 in alveoli
why are equal amounts of oxygen and carbon dioxide exchanged?
Oxygen has a higher partial pressure gradient than carbon dioxide but carbon dioxide is more soluble in plasma and alveolar fluid
How many oxygens per hemoglobin?
4 (molecules, so 8 atoms). After one binds it becomes easier for the second to bind
How is CO2 transported in the blood?
most as bicarb (70%), some dissolved (7%) or caraminohemoglobin (22%)
Does partial pressure indicate oxygen level in blood?
No--% can be the same, but less hemoglobin will mean less oxygen to tissues
What percent partial pressure of Oxygen makes the blood saturated?
- Graph flat-lines--very little more gain.
At what percent O2 partial pressure is 25% of O2 saturation of hemoglobin lost in the tissues?
- 40% partial pressure
- Graph drops off steeply
If CO2 or H+ increases or O2 levels decrease, what happens to ventilation?
Increases, returning all to normal.
If CO2 or H+ decreases or O2 levels increase, what happens to ventilation?
Decreases, returning to normal
CNS of respiration
- Brain stem
- Pons: apneustic center (stimulation) and pneumotaxic center (inhibition)
- Medulla: dorsal respiratory group (DRG) (inspiratory) and ventral respiratory group (VRG, expiratory). Respiratory rhythmic center in medulla
Neural control of respiratory
- lung (regulates in and out)
- skin (excitatory)
- cerebral cortex (exercising)
- upper airway passages (pharynx stopping)
- carotid and aortic bodies (inhibit at high blood pressures. Less inspiration slows blood, lowering BP)
What is humoral control
refers to those factors in the body fluids that influence ventilation (CO2, H+ and O2)
Humoral control of CO2
- CO2 increase = alveolar ventilation increase
- CO2 decrease = alveolar ventilation decrease
Humoral control of H+ ions
- H+ ion increase = alveolar ventilation increase
- H+ ion decrease = alveolar ventilation decrease
Humoral control of Oxygen
- O2 decrease = alveolar ventilation increase
- O2 increase = alveolar ventilation decrease
How H+ ions affect ventilation (physiologically)
H+ ions affect chemosensitive inspiratory area of the medulla, speeding up breathing.
Most important chemical factor that affects ventilation in normal circumstances
Most important chemical factor that affects ventilation during disease states (pneumonia and pulmonary edema)
Carotid and aortic bodies
- bilateral chemosensitive areas below medulla that respond to changes in the partial arterial pressure of oxygen in the blood, very important in disease states.
- When PO2 is VERY low (30-60mmHg) they send a signal to ventilate. Body is usually at 80-100mmHg