Ch. 23 - The Respiratory System Flashcards
What is respiration?
exchange of gasses between atmosphere, blood, and cells
What are the 3 steps that respiration requires?
- pulmonary ventilation (breathing; movement of gases in and out of lungs)
- pulmonary respiration (gas exchange between lung alveoli and blood)
- tissue respiration (bt blood and cells)
What does the upper respiratory system comprise of?
nose, pharynx, associated structures
What does the lower respiratory system comprise of?
larynx, trachea, bronchi, lungs
What are the functional divisions of the resp system?
conducting portion (~150 mL) and respiratory portion (~5-6 L)
What is the conducting portion and what does it comprise of?
- filter and moisten air and conduct into lungs
- nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
What is the respiratory portion and what does it comprise of?
- tissue w/i lungs where gas exchange occurs
- resp bronchioles, alveolar ducts, alveolar sacs, alveoli
RECALL: how is the nasal cavity divided? What is this division composed of?
nasal septum: septal cavity, vomer, perpendicular plate of ethmoid bone
What is the anterior portion inside the nostrils called?
nasal vestibules
How does the nasal cavity communicate with the pharynx?
posteriorly through 2 openings called internal nares
Which ducts open into the internal nose?
paranasal sinuses and nasolacrimal ducts
What are the functions of the nose?
- warm, moisten, filter air
- olfaction
- modify speech
How does air pass through the nostrils?
through vestibule lined with coarse hairs that filter dust particles
What is the function of the conchae?
- subdivide each side of nasal cavity into series of passages –> sup, middle, inf meatuses
- cause air to swirl for increased contact w mucous membrane that lines cavity and conchae
What is the pharynx composed of and where is it located? (throat)
- tube of sk muscles lined w mucous membranes
- internal nares and extends to cricoid cartilage of larumx
What are the 3 regions of the pharynx and where are they each locate?
- nasopharynx: internal nares to soft palate
- oropharynx: soft palate to hyoid
- laryngopharynx: hyoid to esophagus
What is the function of the pharynx?
- houses tonsils
- passageway for air and food
- resonating chamber for speech
What is the larynx composed of and where is it located? (voicebox) What does it connect?
- extrinsic and intrinsic muscles & thyrohyoid membrane
- anterior to esophagus (C4-C6)
- connects laryngopharynx to trachea
What are the 3 main cartilage pieces in the larynx?
- thyroid C (Adam’s apple)
- cricoid C (ring at top of trachea)
- epiglottis (elastic C; covers glottis during swallowing)
What are the 2 pairs of folds the mucous membrane of the larynx forms?
- vestibular folds (false vocal cords)
2. vocal folds (true vocal cords)
What is the function of vestibular folds?
- holding breath against pressure in thoracic cavity
* do not produce sound
What are vocal folds attached to?
ligaments that are attached to muscles responsible for speech/sounds
How do vocal cords produce speech and sound?
- muscles contract and stretch the vocal folds during speech
- folds vibrate when air is directed against them and produce sounds
What is the trachea composed of and where is it located?
- smooth muscle and C-shaped rings of C (rings keep airway open!)
- lined with pseudostratified ciliated columnar epithelium
- extend from larynx to primary bronchi
What is the function of cilia in the trachea?
sweep mucus/debris away from lungs and back to throat to be swallowed
List the airway branchings in the conducting zone (from trachea)
- main bronchi (primary)
- lobar bronchi (secondary)
- segmental bronchi (tertiary)
- bronchioles
- terminal bronchioles
List the airway branching in the respiratory zone (from terminal bronchioles)
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
Describe briefly the change in epithelium from the main bronchi to the alveolar sacs
- pseudostratified ciliated columnar w/ goblet cells in main bronchi
- simple non-ciliated cuboidal w/o goblet cells in terminal bronchioles
- simple squamous epithelium line alveolar sacs
What separates each lung?
mediastinum
What encloses each lung?
pleural (serous) membrane
- visceral pleura covers lung
- parietal pleura lines wall of thoracic cavity
- pleural cavity (between layers) contains pleural fluid
What is the function of the pleural cavity?
- fluid lubricates to prevent friction
- provides surface tension to help breathing
What is pleuritis?
inflammation of pleura
- causes pain due to friction between membranes
What is pleural effusion?
when fluid accumulates in pleural cavity
- impairs breathing bc lungs cannot inflate properly
What are alveoli composed of? (small air sacs)
- type I alveolar cells
2. type II alveolar cells
How do the 2 types of alveolar cells differ?
- type I form simple squamous epithelium
- type II secrete alveolar fluid and contain surfactant (decreases surface tension and allows ease of alveolar inflation)
What covers each alveolus?
blood capillaries for gas exchange
What is the respiratory membrane composed of?
- alveolar wall (type I cells)
- epithelial basement membrane
- capillary basement membrane
- capillary endothelium
Describe the blood supply to the lungs
- de-O2 blood arrives through pulmonary arteries from R ventricle
- bronchial arteries branch from aorta to supply O2 blood to lung tissue
How do external (pulmonary) and internal (tissue) respiration differ?
E - pulmonary capillary picks up O2 and loses CO2
I - systemic capillary loses O2 and gains CO2
How does air move in and out of the lungs?
- moves IN when pressure inside lungs is less than atmospheric pressure
- moves OUT when pressure inside lungs is greater than atmospheric pressure
What is pulmonary ventilation controlled by?
contraction/relaxation of resp muscles
What is Boyle’s law?
- as size of closed container decreases (less space for molec to move), the pressure inside the container increases
How is Boyle’s law related to pulmonary ventilation?
- during breathing, size of lungs change
- change in size causes pressure change inside lungs
- pressure change causes air to move from area of high pressure to area of low pressure
How do the contraction of resp muscles function in normal/quiet inhalation?
- contraction of ext intercostals makes ribs move UPWARDS
- contraction of diaphragm flattens it downwards, allowing lungs to expand vertically
What additional muscles are involved in forced/laboured inhalation?
- accessory muscles of inspiration are recruited: sternocleidomastoid, scalenes, pectoralis minor
- further elevate sternum and ribs allowing more space for lung inflation
How do relaxation of resp muscles function in normal/quiet exhalation?
- relaxation of diaphragm causes it to move up
- relaxation of ext intercostals move ribs down and inward
**reduce intrathoracic cavity size
What additional muscles are involved in forced exhalation?
- contraction of abdominal muscles (move inf ribs downward and compress abdominal viscera) and internal intercostals (pull ribs inferiorly)
What are 3 factors affecting pulmonary ventilation? (ease of breathing)
- surface tension of alveolar fluid
- compliance of lungs (ease of expanding)
- airway resistance (diameter of airways)
How does surface tension of alveolar fluid affect breathing? What can it be reduced by?
- water molecules attract to each other and cause alveoli to collapse (like a wet plastic bag)
- surfactant (mixture of P-lipids and lipoproteins)
What is respiratory distress syndrome in infants?
RDS is due to lack of surfactant
How does compliance of lungs affect breathing?
- results from high elasticity and low surface tension
- decreased compliance can result from fluid in lungs, deficient surfactant production, physical impairment of lung expansions
How does airway resistance affect breathing?
- contraction of smooth muscles in airways causes constriction reducing airway size
How does airway resistance relate to asthma?
absence of C in small airways contribute to airway constriction
How do you calculate vital capacity (VC)?
TV + IRV + ERV = VC
How do you calculate total lung capacity?
VC + RV = TLC
What are some factors that affect the rate of diffusion?
- partial pressure difference
- SA available for gas exchange
- diffusion distance
- solubility of gases
What would happen to the rate of diffusion at high altitudes?
difference in pressure
What would happen to the rate of diffusion in a patient with emphysema (breakdown of alveoli)?
:)
How much O2 is dissolved in the plasma? Where does the rest go to?
- 1.5% dissolves in plasma
- 98.5% binds to heme complexes on Hb
How many O2 molecules can each Hb molecule carry?
4
What are the normal saturation levels of Hb?
95-100%; all heme groups bound to O2
**less than 90% is considered low
How does the binding of O2 to Hb differ in pulmonary and systemic capillaries and why?
P - O2 must strongly bind to Hb to bee transported in the blood
S - O2 must loosely bind to/dissociate from Hb to diffuse into tissue cells
What is affinity? (of Hb to O2)
how tightly Hb binds to O2
What are 4 factors that affect binding and dissociation?
- partial pressure of O2
- acidity (pH)
- partial pressure of CO2
- temperature
What are characteristics of metabolically active tissues? Would these increase or decrease affinity of Hb for O2?
increase since O2 is most needed by metabolically active tissues
How does partial pressure affect affinity?
the greater the PO2, the more O2 will combine with Hb
- higher Hb saturation = less O2 dissociation
- lower Hb = more dissociation; can be used by tissues
How do shifts of curve affect affinity?
shift to R - decreased affinity
shift to L - increased affinity
How does pH affect affinity?
as acidity increases, affinity of Hb for O2 decreases
- H+ binds to Hb and alters shape; O2 dissociates more readily
- metabolically active cells produce acid, which enhances O2 release at tissues
How does partial pressure of CO2 affect affinity?
as PCO2 rises (with metabolic activity), O2 affinity for Hb decreases
- increased CO2 levels in blood make blood more acidic; decreases affinity
How does temperature affect affinity?
as temperature increases, Hb affinity for O2 decreases (O2 is more readily released)
At rest, why is temperature higher near tissue cells than in arteries?
- metabolic activity; generates heat
- allows O2 to dissociate more easily
Does fetal Hb or maternal Hb have a higher affinity for O2?
fetal because the baby needs the O2; different a.a (eventually diff proteins) determine affinity differences for maternal and fetal Hb
What causes carbon monoxide poisoning? How can it be counteracted?
CO binds to Hb heme group more strongly than O2
- administering pure O2; use pressure to cause more O2 to dissolve in blood (hyperbaric oxygen)
How is CO2 transported in the blood?
- dissolving in plasma (7%)
- bound to globin part of Hb (23%)
- transported in plasma as part of bicarbonate ion (70%)
What is the formula for the conversion of CO2 to HCO3
CO2 + H20 —- H2CO3 (carbonic acid) —– H+ _ HCO3
In systemic capillaries, CO2 is converted into what? How does this affect blood?
excess CO2 is converted into H+ and HCO3 for transport, making blood more acidic
In pulmonary capillaries, H+ and HCO3 are converted into what?
combined to reform CO2 so gas molecules can diffuse out of capillaries and be exhaled
What are respiratory muscles controlled by?
neurons from the pons and medulla (under autonomic control)
What is the function of the medullary rhythmicity area?
- controls basic resp rhythm (quiet inhalation)
- specialized cells in dorsal resp group (DRG) and ventral resp group (VRG)
What do the cells in DRG and VRG respectively do?
DRG - autorhythmic cells innervate diaphragm and ext intercostals for contraction (active 2 sec) and relaxation (inactive 3 sec)
VRG - neurons only active during forced ventilation; innervates accessory muscles
What is the pontine respiratory group? (PRG)
located in pons, oversees signals to DRG
- transmits nerve impulses to DRG to modify respiratory rhythm when needed (e.g. when exercising, sleeping)
How do signals from the cerebral cortex affect breathing patterns?
- voluntarily alter patterns; allow conscious control of respiration for protection (e.g. holding breath, swimming)
What is voluntarily breath holding limited by?
overriding stimuli of increased PCO2 and [H+]
- stimulates DRG, triggering inhalation
What is the role of central chemoreceptors in chem regulation of respiration? (in medulla)
respond to changes in PCO2 or [H+] in cerebrospinal fluid
What is the role of peripheral chemoreceptors in chem regulation of respiration? (in walls of aorta and carotid arteries)
respond to changes in PO2, PCO2, [H+]
How does negative feedback function in regulation of breathing?
- stimulus: increase in arterial PCO2
- stimulate receptors
- stimulates DRG
- muscles of resp contract more frequently and forcefully
- PCO2 decreases
What is the inflation reflex?
detects over-expansion of lungs with stretch receptors in bronchioles
- inhibit DRG; allow for exhalation to take place
- after exhalation, stretch receptors no longer stimulated –> DRG no longer inhibited –> inhalation occurs
**protective mechanism; not part of normal breathing
What other factors influence the respiratory rate?
- anticipation of exercise, excitement, fear, anxiety all cause limbic system to excite DRG; increase resp rate
- temperature: increase in temp increases rate
- pain: sudden pain causes brief apnea; prolonged pain increases resp rate; visceral pain slows rate
What does the irritation of respiratory mucosa do?
stops inspiration, triggers coughing or sneezing
Why does breathing increase at the beginning of exercise?
- proprioceptors of joints/muscles activate DRG
- axon collaterals sent to DRG from motor neurons in primary motor cortex area
Why does breathing gradually increase as exercise progresses?
- decreased PO2 due to increased use of O2 (hypoxia)
- increased PCO2 due to increased CO2 production (hypercapnia)
- increased metabolic activity leads to increased temp
