Test 2- Respiratory

Question 1

Lung Development

Answer 1

• Immaturity of respiratory tract major cause of morbidity and mortality in preme infants
• Surfactant production begins after 20wks
• 25-28 wks of gestation sufficient alveoli present
• At birth 20-50 mil alveoli
• 300 mil at 3-7 yrs
• 700 mil at adulthood
• Lack of stiff structural support make infants more susceptible to lung collapse( atelectasis) and obstruction

Question 2

Airway Resistance

Answer 2

• Infant airways smaller with more resistance to air flow
• Neonates primarily nose-breathers
• Nasal flaring- sign of increased resp. resistance
• Mucus, edema, airway constriction dramatically reduce airflow

Question 3

Respiratory disorders in Neonates

Answer 3

-Resp. disorders in infants cause reduced lung compliance( ability to stretch/recoil) or increased airway resistance

Signs of above:

• Tachypnea ( ^ resp. rate)
• grunting
• nasal flaring
• retraction( skin sucked in around ribs)
• stridor (sound of increased turbulence of air moving thru trachea/ large airways)
• wheezing( sound of increased turbulence thru smaller airways)

Question 4

Airway Structures

Answer 4

Upper airway

• Nasopharynx
• Oropharynx
• Laryngopharynx

Lower Airway

• Larynx
• Trachea
• Bronchi
• Acinus

Question 5

Nasal Cavity Functions

Answer 5

• Conducts gases to/from lungs
• Filters, warms, humidifies air
• Turbinates convoluted/ vascular

good heat exchanger

water evaporatesfrom surface to humidify air

• Rigid structure prevents collapse
• Vibrissae (large hairs) trap particles
• Mucosal epithelial cilia sweep mucous to nasopharynx then swallowed or expectorated

Question 6

Sinuses

Answer 6

Four paranasal sinuses: maxillary, frontal, ethymoid, spenoid

• contribute to speech resonance, heat, and water vapor exchange
• mucociliary action (remove bacteria/ debris)

Question 7

Eustachian Tubes

Answer 7

• Allows pressure equalization of middle ear
• Open during swallowing (closed otherwise)
• Horizontal position/ shorter length in children predisposes to otitis media

Question 8

Conducting Airways

Answer 8

-Consists of: nasal/oral pharynx, laynx, trachea, bronchi, bronchioles (nonrespiratory/ respiratory)

Functions:

• direct air to respiratory exchange zones of lung
• warm, filter, humidify air
• no gas exchange across conducting airways (only across respiratory bronchi/ alveoli)

Question 9

Conducting Airway Epithelium

Answer 9

Ciliated columnar mucosal epithelial cells

• cilia beat in sweeping motion
• mucociliary transport (primary defense mech.) move inhaled particles/ mucous to espophogus for swallowing/ coughing

Ciliary function impaired by: smoking, ethanol, cold/ hot air, low humidity, hypo/hyperthermia, anesthetics, corticosteroids, viral infections, excess mucous prod.

Goblet cells: produce mucous

• mucous is 95% water
• hydration status important to production
• children have more goblet cells than adults (more mucous)

Question 10

Larynx

Answer 10

Functions: sound production, valve to control air mvmnt. out of lungs (expel foreign substances), prevent foreign subs. entering trachea/lungs

-Hyoid bone: horseshoe shaped- from which larynx suspended

Cartilages:

• Thyroid: v-shaped contain vocal folds
• Cricoid: ring shaped- connected to trachea- supports arytenoid posteriorly
• Arythenoid: vocal folds connet on posterior

Vocal Folds: vibrate when air passes- forming sound (longer folds- lower sound/ tighter fold- higher sound)

Question 11

Lungs: Basic Anatomy

Answer 11

Trachea divides to R/L mainstem bronchi at carina

Right lung: R mainstem bronchus divides to 3 lobular bronchi- RUL, RML, RLL

Left Lung: L mainstem divides to 2 lobular bronchi- LUL, LLL

Lobular bronchi -> segmental bronchi -> bronchopulmonary segments -> terminal bronchioles (smallest units)

Question 12

Alveoli

Answer 12

Terminal bronchioles lead to alveoli

Alveoli form on respiratory bronchioles

Adults- 350 mil alveoli per lung (700 mil total) and 75 sq. meters of SA

Surface for O²/ CO² exchange

Alveolar cells

• Type 1: squamous epithelial (pneumocytes) form gas exchange surface
• Type 2: produce surfactant (lowers surface tension/ fascilitate gas exchange)
• Type 3: alveolar macrophages (phagocytize microbes that reach alveoli)

Question 13

Pleura

Answer 13

• Thin continous membrane covering lungs (visceral) and thoracic cavity (parietal)
• Membranes seperated by small amount of serous fluid to lubricate
• Intrapleural space at negative pressure (keeps lungs pressed against thorax wall)

Question 14

Nervous Innervation

Answer 14

Autonomic nervous system

• Parasympathetic: vagus nerve (CN10) stimuates bronchioconstriction
• Sympathetic: sympathetic innervation (T1-T4) and epi/norepi causes relaxation of bronchial muscle
• mediated by B-2 adrenergic receptors

Question 15

Cough Reflex

Answer 15

• Defense against excessive secretions/ foreign substance
• Diminishing cough reflex increases risk of aspiration (cough suppress. meds, brainstem injury, age)

Question 16

Cough

Answer 16

Initiated by cough receptors in carina and coordinated in brainstem (medulla oblongata)

Cough produced when vocal folds/ epiglottis close against air trapped in lungs

Expiratory muscle contract- increase pressure against closed vocal folds/ epiglottis

High pressure air escapes (ejecting debris/ mucus)

Question 17

Dual Pulmonary Circulation

Answer 17

Bronchial artery system

• Arise from thoracic aorta (oxygenated arterial blood)
• Supplies oxygenated blood to to bronchi

Question 18

Dual Pulmonary Circulation (cont.)

Answer 18

Pulmonary artery system

• Arises from pulmonary artery (delivers unoxygenated blood from R ventricle)
• Huge capillary network for gas exchange

–Fewer capillaries in elderly/ infants (less efficient gas exchng)

–Low pressure arterial system

–blood flow increased/ reduced to adjust gas exchng needs

-Oxygenated blood exists thru pulmonary vein into L atrium

Question 19

Influences on Pulmonary Circulation

Answer 19

Two mechanisms to increase capillary perfusion:

• Recruiting: opening previously closed capillaries
• Increasing arteriolar blood flow
• Pulmonary arterioles constrict in response to alveolar hypoxia (low O²/ high CO²) rerouting blood to alveoli that are well-ventilated

Question 20

Pulmonary Fluid Balance

Answer 20

Fluid balance in lung tissue regulated by 3 factors:

• Hydrostatic pressure (BP vs tissue pressure)
• Colloid (oncotic) pressure related to protein concntrn)
• Capillary permeability (leakiness between endothelial cells lining capillaries)

Question 21

Ventilation

Answer 21

• Process of moving air into/out of lungs
• To allow O² absorption/ removal of CO²
• Ventilation influenced by:
• Age (reduced when old)
• body size/ shape (reduced with obesity)
• body position (reduced in supine)

Question 22

Measures of Lung Volume

Answer 22

Tidal volume (TV): volume of air breathed in/out without conscious effort (normal)- 500cc

Inspiratory reserve volume (IRV): volume above TV that can be inhaled w/ max effort after normal (3L)

Expiratory reserve volume (ERV): volume above TV that can be forcibly exhaled w/ max effort after normal exhalation (1.2L)

Residual volume (RV): volume left in lungs after max exhalation (1.2L)

Question 23

Measures of Lung Capacity

Answer 23

Vital capacity (VC): total volume that can be exhaled after max inhalation (VC= TV+IRV+ERV)

Inspiratory capacity (IC): total volume that can be inspired after normal exhalation (IC=TV+IRV)

Functional residual capacity (FRC): total volume in lungs following normal exhalation (FRC=ERV+RV)

Total lung capacity (TLC): amount of air in lungs at max inspiration (TLC= IRV+TV+ERV+RV)

Question 24

Minute Ventilation

Answer 24

Volume of air thats exchanged each min.

• Respiratory rate (surrogate) 12-18/min normal for healthy adults
• Increased minute ventilation (hyperventilation)- increased need for O²/excess CO² or increased respiratory drive.
• Decreased (hypoventilation)- reduced need for O²/low CO² or reduced respiratory drive

Question 25

Respiratory Function

Answer 25

Primary objective of respiration- get O² in blood and CO² out 3 Primary contributors to gas exchange: - Neuromuscluar function (mechanics of inspiration/expiration) - Ventilation (gas mvmnt in/out of lungs) - Diffusion/ perfusion of gases (mvmnt of gas across exchange surfaces) Alterations of these functions cause pathology

Question 26

Mechanics of breathing

Answer 26

- Airway resistance affects gas mvmnt in/out of lungs - Lung compliance (ability to stretch/ recoil when pressure released)- natural response is recoil/collapse (normal compliance) - Surfactant decreases alveolar surface tension (prevents alveoli fully emptying/ collapsing- atelectasis)

Question 27

Mechanics of breathing (cont.)

Answer 27

Inspiration (active process) - diaphragm contracts/ moves downward - intercostal muscles contract during active inspiration- elevating ribs/ expanding thoracic volume Expiration (passive process) - diaphragm/ intercostal muscles relax - lungs passively recoil - active expiration requires contraction of different intercostal muscles than used for inspiration

Question 28

Alveolar ventilation and Blood oxygenation

Answer 28

- slow, deep breathing- increased alveolar ventilation vs. rapid shallow reathing - partial pressure of O² in alveoli (100mm Hg) greater than arterial O² tension (95-100mm Hg) - large difference between alveolar and arterial O² indicates poor diffusion of alveolar O² into blood (caused by fluid in alveoli/ interruption in blood flow)

Question 29

Ventilation-Perfusion

Answer 29

Anatomic dead space - pulmonary areas that dont participate in gas exchange (bronchi/ bronchioles) - increased w/destruction of alveoli (emphysema) Alveolar dead space -ventilated but nonperfused (pulmonary embolus) Physiologic dead space (functional) -anatomic dead space + alveolar dead space

Question 30

Airway resistance

Answer 30

Ease of which air moves in/ out of lungs Influenced by: - Airway diameter - Turbulence: turbulent air flow creates more resistance (nose-highest, bronchioles- low) - Space filling materials/ obstructions: decrease airway diameter- increase turbulence (mucous, tumor, foreign bodies)

Question 31

Effects of gravity

Answer 31

Upper portion of lungs have: - less blood flow (less gas exchange) - larger, partially inflated alveoli - lesser ventilation capacity (less air mvmnt per alveolus due to partially inflated at all times)

Question 32

Compliance

Answer 32

How easily lungs expand and contract - high lung compliance (lung stretches/ passively contracts easily (normal healthy lungs) - Low lung compliance (lung has difficulty expanding/ doesnt passively contract) Causes: pulmonary fibrosis, edema, insufficient surfactant, COPD, recurrent infections

Question 33

O² and CO² diffusion

Answer 33

- moving gasses from alveoli blood (O²). blood to alveoli (CO²) - impaired by decreased SA (emphysema) - impaired by increased thickness of exchange surface (pulmonary edema)

Question 34

CO² Transport

Answer 34

- small amount dissolved in plasma - some bind to hemoglobin (carbaminohemoglobin) - Most of CO² diffuses into RBCs- converted to carbonic acid by carbonic anhydrase

Question 35

O² Dissociation

Answer 35

Affinity of hemoglobin for O² depends on local conditions (oxyhemoglobin) - Increased tissue metabolism (increased O2 demands) increases pCO2/ H+ (low blood pH)- result in decreased Hb affinity for O2 - Asblood reaches alveolar capillaries CO2 diffuses out of blood into alveoli- increasing blood pH- increasing O2 binding Affinity of CO binding to Hb higher than O2/CO2

Question 36

Neurologic control of breathing

Answer 36

Diaphragm doesnt have inherent pacemaker properties - requires input from resp. center in pons/medulla - primary regulator low pH (^ CO2) - secondary is low O2 Suppression of resp. feedback- hypoventilation (opiate OD)

Question 37

Neurologic control of breathing (cont.)

Answer 37

Chemoreceptors - Central: affect resp. center - primary responds to low extracellular pH (^ CO2 cncntrn)- increased ventilation - Secondary response to reduced O2 cncntrn - Peripheral: carotid/ aortic bodies - hypoxia triggers increased resp. center activity Lung Receptors -stretch, irritant, hypoxia (decreased O2- increased ventilation)