The Respiratory System Flashcards
How is oxygen obtained in the body?
- is obtained from the air by diffusion across delicate exchange surfaces of lungs
- is carried to cells by the cardiovascular system which also returns carbon dioxide to the lungs
What the primary functions of the respiratory system?
- provides extensive gas exchange surface area between air and circulating blood
- moves air to and from exchange surfaces of lungs
What are the secondary functions of the respiratory systems?
- protects respiratory surfaces from outside environment
- produces sounds
- participates in olfactory sense
- acid-base balance
- body temperature regulation
What does the upper respiratory tract consist of?
upper respiratory tract (above the larynx): filter, warm and humidify incoming air
- nostrils
- nasal passages (nasal cavity)
- paranasal sinuses
- pharynx (throat)
- larynx (voice box)
What does the lower respiratory tract consist of?
from the larynx down:
- trachea (windpipe)
- bronchi
- bronchioles
- alveolar ducts
- alveoli (respiratory portion)
What does the respiratory tract consist of?
a conducting portion: from nasal cavity to terminal bronchioles
a respiratory portion: the respiratory bronchioles and alveoli
What is the respiratory mucosa?
lines conduction portion of respiratory system
is a mucous membrane, consists of:
- an epithelial layer: changes in structure along the respiratory tract from an pseudostratified ciliated columnar epithelium to a simple squamous epithelium
- an areolar layer
What is included in the respiratory defense system?
goblet cells and mucous glands:
- produce mucus that bathes exposed surfaces
cilia:
- sweep debris trapped in mucus toward the pharynx
filtration in nasal cavity:
- hairs removes large particles
alveolar macrophages:
- engulf small particles that reach lungs
Describe the nasal cavity:
air flow from vestibule to internal nares:
- through superior, middle and inferior meatuses
- produce air turbulence: warm and humidify incoming air and trap particles
mucous secretions from paranasal sinus and tears:
- clean and moisten the nasal cavity
superior portion of nasal cavity is the olfactory region:
- provides sense of smell
Describe the pharynx:
a chamber shared by the digestive and respiratory systems
extends from the internal nares to entrances to the larynx and esophagus
What are the divisions of the pharynx?
nasopharynx
- superior part
oropharynx
- middle portion; continuous with oral cavity
laryngopharynx
- inferior portion
- extends from hyoid bone to entrance to larynx and esophagus
Describe the larynx:
inhaled air leaves the pharynx and enters the larynx through the glottis
larynx:
- a cartilaginous structure that surrounds the glottis
-composed of three large cartilages (including epiglottis) and three smaller pairs of cartilage
epiglottis:
- during swallowing: the larynx is elevated and the epiglottis folds back over the glottis
- prevents entry of food and liquids into respiratory tract
Describe the glottis:
two pairs of folds span the glottis:
- the inelastic vestibular folds
- the more delicate vocal folds
air passing through the glottis vibrates the vocal folds, producing sound
Describe the trachea:
extends from the larynx to the primary bronchi
contains C-shaped tracheal cartilages:
- stiffen the tracheal walls and protect the airway
the posterior tracheal wall can distort to permit large masses of food to pass through the esophagus
Describe the primary bronchi:
trachea divides into left and right primary bronchi, which enters the lung
bronchial tree:
- is formed by the primary bronchi and their branches
as bronchi branch, the amount of cartilage in their walls decreases and the amount of smooth muscle increases
Describe the lung:
two functions:
- air distribution
- gas exchange
cone-shaped:
- hilus: where pulmonary nerves, blood vessels, and lymphatics enter lung
- the base: inferior positions of each lung rests on superior surface of diaphragm
- the apex: the tip
- the convex lateral surface
Describe the lobes of the lungs:
lungs have lobes separated by deep fissures
the left lung (two lobes):
- superior (cranial)
- inferior (caudal)
the right lung (three lobes):
- superior (cranial)
- middle
- inferior (caudal)
the lungs of a horse have no lobes
Describe the bronchial tree:
a primary bronchus branches to form a secondary bronchi (lobar bronchi)
- 1 secondary bronchus goes to each lobe
secondary bronchi branch to form tertiary bronchi (segmental bronchi)
- each segmental bronchus supplies air to a single bronchopulmonary segment
- 8-10 segments each lung in humans
each tertiary bronchus branches into 4th, 5th, and 6th order segmental bronchi and eventually multiple bronchioles
Describe the bronchioles:
bronchioles ultimately branch into terminal bronchioles
- each terminal bronchiole delivers air to a single pulmonary lobule
bronchiole structure
- have no cartilage
- are dominated by smooth muscle
autonomic control regulates smooth muscle
- controls diameter of bronchioles
- controls airflow and resistance in lungs
What is the relevance of asthma?
bronchial tree is overly sensitive to certain irritants –> bronchoconstriction
Describe the pulmonary lobules:
are the smallest compartments of the lung
each lobule receives an arteriole and a venule
within the lobule:
- each terminal bronchiole branches to form several respiratory bronchioles
respiratory bronchioles are connected to alveoli along alveolar ducts
What are the alveolus?
are air-filled pockets within the lungs
where all gas exchange takes place
a capillary network surrounds each alveolus
is surrounded by elastic fibers
alveolar epithelium:
- consists of simple squamous epithelium
- contains septal cells that produce surfactant
- patrolled by alveolar macrophages
Describe the respiratory membrane:
the thin membrane of alveoli where gas exchange takes place
3 parts of the respiratory membrane:
1. squamous epithelial lining of alveolus
2. endothelial cells lining an adjacent capillary
3. fused basal laminae between alveolar and endothelial cells
gas diffusion across respiratory membrane is very rapid
- because distance is small
- gasses (O2 and CO2) are lipid soluble
Describe the blood supply to the lungs
- by the pulmonary circuit
- the pulmonary arteries enter the lungs at the hilus and branch with the bronchi
- each lobule receives an arteriole and a venule
- a network of capillaries surrounds each alveolus
- the oxygenated blood from the alveolar capillaries passes through the pulmonary venules and then enters the pulmonary veins, which deliver it to the left atrium
Describe the pleural cavity and the pleural membranes
2 pleural cavities
- are separated by the mediastinum
each pleural cavity
- holds a lung
- is lined with a serous membrane (the pleura)
consists of 2 layers:
- parietal layer
- visceral pleura
pleural fluid:
- lubricates space between 2 layers
Describe external respiration
the exchange of oxygen and carbon dioxide in the lungs
- pulmonary ventilation (breathing)
- gas diffusion across the respiratory membrane
- transport of oxygen and carbon dioxide in the blood
Describe internal respiration
the exchange of oxygen and carbon dioxide between blood and tissue cells
What is pulmonary ventilation?
the physical movement of air into and out of the respiratory tract
- inspiration: move air into the lungs
- expiration moves air out of lungs
What is Boyle’s Law?
as pressure on a gas decreases, its volume expands; as pressure increases, gas volume contracts. P = 1/V
What is respiration?
volume of thoracic cavity changes:
- with expansion or contraction of diaphragm or rib cage
volume changes create changes in pressure
compliance: ability of pulmonary tissues to stretch, making inspiration possible
Describe the mechanisms of pulmonary ventilation
air flows from area of higher pressure to area of lower pressure
the relationship between intrapulmonary pressure and atmospheric pressure (ATM) determines the direction of airflow:
- inspiration: Palveoli < Patm
- expiration: Palveoli > Patm
What is intrapulmonary pressure?
pressure measured inside the respiratory tract, at the alveoli
on inhalation: -1 mmHg
on exhalation: +1 mmHg
What is intrapleural pressure?
pressure measured in the space between the parietal and visceral pleura
-4 mmHg to -18 mmHg
What is the sequence of inspiratory steps?
- inspiratory muscles contract
- thoracic cavity expands
- intrapleural pressure becomes more negative
- transpulmonary pressure increases
- lungs distend
- alveolar pressure falls below atmospheric pressure
- air flows into the lungs until the alveolar pressure becomes equal to atmospheric pressure
What are the respiratory muscles?
the diaphragm
external intercostal muscles of the ribs
accessory respiratory muscles:
- internal intercostal, pectoralis minor, rectus abdominis muscles
- activated when respiration increases significantly
What is quiet breathing (eupnea)?
- involves active inhalation and passive exhalation
- involves the diaphragm and the external and internal intercostal muscles
What is forced breathing (hyperpnea)?
- involves active inhalation and exhalation
- assisted by accessory muscles
What is lung volume?
total lung volume is divided into a series of volumes and capacities useful in diagnosis
What is a spirometer?
instrument used to measure volume of air
What are the 4 pulmonary volumes?
- tidal volume (TV)
- expiratory reserve volume (ERV)
- inspiratory reserve volume (IRV)
- residual volume (RV)
What is tidal volume?
amount of air moving into or out of the lung during a single respiratory cycle
What is expiratory reserve volume?
largest volume of additional air can be forcibly exhaled (human: 1.0-1.2 liters)
What is inspiratory reserve volume?
amount of air that be can forcibly inhaled after normal inspiration (human 3.3 liters)
What is residual volume?
amount of air that cannot be forcibly exhaled (human: 1.2 liters)
What are the 4 calculated respiratory capacities?
- inspiratory capacity: = TV + IRV
- functional residual capacity:
- the amount of air at the end of a normal respiration
- ERV + RV - vital capacity: = IRV + TV + ERV
- total lung capacity
- the total amount of air a lung can hold
- vital capacity + RV
Describe the gas exchange (external respiration) in the lung
occurs between blood and alveolar air
across the respiratory membrane
depends on:
- partial pressures of the gases
- diffusion of molecules between gas and liquid
Describe gas pressure
atmospheric pressure (760 mmHg)
- produced by air molecules bumping into each other
each gas contributes to the total pressure
- in proportion to its number of molecules (Dalton’s law)
partial pressure
- the pressure contributed by each gas in the atmosphere
- all partial pressures together add up to 760 mmHg
What is Henry’s law?
henry’s law: the amount of gas in solution is directly proportional to the partial pressure of that has
the actual amount of a gas in a solution at a given partial pressure and temperature depends on the solubility of the gas in that particular liquid:
- the plasma in a pulmonary vein generally contains 2.62 ml/dl of dissolved CO2; 0.29 ml/dl of dissolved O2, and 1.25 ml/l of dissolved N2
- CO2 is very soluble; O2 is less soluble; N2 has very low solubility
Describe diffusion at the respiratory membrane
- distance involved in gas exchange are small
- O2 and CO2 are lipid soluble
- total surface area is large
- blood flow and air flow are coordinated (blood flow is greatest around alveoli with the highest PO2 values)
- substantial differences in partial pressure across the respiratory membrane
Describe oxygen pickup and delivery
- 98.5% oxygen bind to hemoglobin (Hb) to be transported
- reaction is completely reversible
What are the 3 reactions in CO2 pickup and delivery
- 70% CO2 is transported as bicarbonate (HCO3-)
- 23% binds to Hb
- 7% is transported as dissolved CO2
- reactions 1 and 2 are completely reversible
How is respiration controlled?
under normal conditions: equilibrium between
- absorption of oxygen and generation of carbon dioxide in peripheral cells
- the capillary rates of delivery and removal
- oxygen absorption and carbon dioxide excretion at the lungs
if these rates become unbalanced, homeostatic mechanisms intervene to restore equilibrium:
- changes in blood flow and oxygen delivery that are regulated at the local level
- changes in the depth and rate of respiration under the control of the brain’s respiratory centers
What do local factors (Pco2) regulate?
lung perfusion (blood flow to the alveoli):
- in lung, alveolar capillaries constrict under conditions of low oxygen, so blood flows are directed toward lobules in which the Po2 is relatively high
- the opposite of that is seen in peripheral tissues
alveolar ventilation (airflow):
- bronchioles dilate under conditions of high carbon dioxide, airflow is therefore directed to lobules in which the Pco2 is high
Describe the respiratory centers of the brain;
when oxygen demand rises:
- cardiac output and respiratory rates increase under neural control
respiratory centers in pons and medulla oblongata
motor neurons control respiratory muscles
What sets the pace of respiration?
medulla oblongata
What does the inspiratory center (dorsal respiratory group) of the medulla oblongata do?
- pacesetting inspiratory center
-control inspiratory muscles (diaphragm and external intercostal muscles)
What does the expiratory center (ventral respiratory group) of the medulla oblongata do?
- functions mainly in forced breathing
- control expiratory muscles (internal intercostal muscles and others)
Describe the respiratory refleses:
changes in patterns of respiration induced by sensory input:
- chemoreceptor reflexes
- baroreceptor reflexes
- hering-breuer reflexes
Describe the chemoreceptor reflexes:
chemoreceptors are sensitive to:
- Pco2, Po2, or pH
- of blood or cerebrospinal fluid
leads to increased depth and rate of respiration
Describe baroreceptor refelxes;
- the baroreceptors in the carotid and aortic bodies sense the systemic blood pressure and affects the respiratory centers
- when blood pressure falls, the respiratory rate increases; when blood pressure rises, the respiratory rate declines
What are the hering-breuer reflexes?
stretch receptors in lung
2 reflexes involved in forced breathing;
inflation reflex:
- prevents overexpansion of lungs
- over-inflation of the lung –> vagus nerve –> decreases apneustic center, decreases DRG and increases VRG
deflation reflex:
- prevents over deflation of the lungs
- over-deflation of the lung –> vagus nerve –> increase in DRG, decrease in VRG
- receptors are distinct from those of the inflation reflex
What are the three key concepts of the respiratory system/
- a basic pace of respiration is established between respiratory centers in the pons and medulla oblongata, and modified in response to input from:
- chemoreceptors
- baroreceptors
- stretch receptors - in general, CO2 levels, rather than O2 levels, are the primary drivers of respiratory activity
- respiratory activity can be interrupted by protective reflexes and adjusted by the conscious control of respiratory muscles
