Unit 3 - Respiratory Flashcards
(18 cards)
upper respiratory
nose
nasal cavity.
nasal sinuses
pharynx
larynx
trachea
lower respiratory
bronchi
bronchioles
lungs
functions
- supply oxygen + remove CO2.
- phonation (voice)
- body temp control
- acid-base balance
- olfactory sense
respiration levels
- external: physically breathing in and out
- internal: exchange b/w blood and cells
- cellular: ATP production
external structures
- nose
- nares supported by nasal cartilage
- opened by muscles that let air enter
- dilated = sign that animal is having trouble getting enough oxygen
- lined with hair to filter
- skin around nostril continuous with muzzle, covered w/ hair and sebaceous/sweat glands
- more rigid in rooting animals
- functions: warm, humidity, filter air before lungs
- highly vascular, bleeds a lot.
- sneezing + coughing = debris irritate sensitive mucosa -> expels
- nasal cavity
- hard + soft palates separate it from moth
- turbinates (AKA conchae) = bony scrolls lined w/mucous membranes . protect from noxious gasses/trap particles
~nasal meatus = pathways b/w turbinates~
- ventral nasal meatus: dorsal to hard palate. route for stomach tube -> nasopharynx. very vascular (bleeding risk)
- blood vessels below m. membranes warm air
- nasolacrimal ducts drain excess tears into nasal cavity
- median nasal septum -> R/L halves - paranasal sinuses
- maxillary, frontal, sphenoid, and palatine sinuses
- bilateral symmetry
- m membrane lines + air-filled
- reduce skull weight
- infection prone (in dentistry + dehorning cattle) - pharynx
- passageway connecting oral cavity -> oropharynx (food) / nasal cavity -> nasopharynx (air)
- openings into pharynx = mouth, 2 caudal nares, 2 eustachian (auditory) tubes, esophagus, larynx
- inspired air -> nasal cavity -> caudal nares -> pharynx -> larynx
- food in mouth -> pharynx -> into esophagus through contraction of pharyngeal muscles as larynx is closed by epiglottis
- pharynx + larynx work together to make air/food go down the right tube
- 3 divisions:
a: nasopharynx (part respiratory channel)
- soft palate = floor
- auditory tubes open here connecting to middle ear
- equalize pressure on both sides of ear drum
b: oropharynx (part of GIT)
c: laryngopharynx (respiratory AND GIT passage)
swallowing is series of actions:
- stop breathing
- glottis covers larynx opening
- material -> rear of pharynx
- esophagus opens
- material moves dorsal -> esophagus
- swallow -> larynx opens back up -> breathing resumes
* malfunction of this under anesthesia = aspiration -> pneumonia
- larynx (AKA voice box).
- mucosa lined, cartilage tube joining pharynx + trachea
- hyoid apparatus supports
* cats prone to laryngospasm
- directs air to trachea
- prevents aspiration of food/water
- houses vocal organs
- segments of cartilage (# varies by species) connected + surrounded by muscles
a. epiglottis
b. arytenoid cartilages (2) - attach vocal cords which then run down to floor of thyroid cartilage - forms boundaries of glottis (larynx opening)
c. thyroid cartilage (AKA adams apple) - moves w/hyoid, attaches muscles used for swallowing + phonation
d. cricoid cartilage - connects thyroid cartilage -> trachea, maintains larynx shape so air passes
epiglottis:
- leaf shaped, rostral position, projects forward from ventral larynx
- tip tucked up to dorsal soft palate during breathing
- pulled back to cover larynx (glottis) when swallowing so food doesn’t enter
larynx 3 functions:
1. voice production:
- phonation by relaxing (low pitch/open glottis) + tightening (high pitch/closed glottis) cords as air passes -> they vibrate
2. prevent aspiration
- trapdoor effect of epiglottis + muscle contraction pulling larynx forward -> folding epiglottis back over its opening
- backed up by vocal cords (can meet in midline to close glottis)
3. airflow to/from lungs
- adjusting size of glottis w/vocal folds + closing glottis w/epiglottis
- trachea
- short wide tube from larynx -> thorax
- C shaped hyaline (opening of C = dorsal), allows trachea to change size + prevents it from collapsing on inspiration
- lined w/pseudostratified ciliated mucousa (like nasal passages) that trap foreign bodies -> move them cranial to pharynx where they are swallowed
- increased dust = increased mucous production. irritates trachea lining -> cough to expell
- divides into 2 bronchi at tracheal bifurcation (AKA carnia) at heart level
lower respiratory tract
starts at bronchi, ends at alveoli
- all structures part of lungs
- bronchial tree = gradually gets smaller
- bronchi -> bronchioles -> alveolar ducts -> alveolar sacs (bunch of grapes)
- smooth muscles relaxes for bronchodilation (during increased oxygen) and tightens for bronchoconstriction (when rested)
- bronchoconstriction also when irritants in lungs -> difficulty breathing
* eg. felina asthma (allergic bronchitis), heaves in horses (fungal spore allergy) - alveoli, forming alveolar sac:
- tiny, thin-walled sacs surrounded by capillary network
- site for gas exchange
- contain surfactant: reduces stickiness (surface tension) of walls to help expand during breathing + prevent collapse of lungs
* important with premature babies (surfactant often not properly formed, contributes to their death) - lungs
- exchange O for CO2 in blood
- cone shaped: base at diaphragm, apex at thoracic inlet
- lateral side of each lung connects to thoracic wall (except at cardiac notch -> contact w/heart)
- L cranial + caudal lobes
(L cranial partially subdivided, some may refer to a ‘L middle lobe’) - R cranial, middle, caudal, accessory lobes
- Horse: L and R lobes + accessory
- hilus: small medial area where air, blood, lymph, nerve cells enter/leave
- only ‘fastened in place’ area of lung
- lungs completely fill thoracic cavity from first breath. never collapse regardless of exhale until death
- necropsy to see if stillborn: cut lung piece -> place it in water (floats -> born alive, sinks -> born dead)
- pulmonary circulation: lung blood supply
- blood vessels smaller as they branch down alveoli -> capillaries (network around each alveolus)
- only 1 blood cell passes through at a time (CO2 diffuses from blood cell into alveolus + O from alveolus into blood)
lung boundaries:
1. dorsal: thoracic vertebrae
2. lateral: ribs
3. ventral: sternum
4. caudal: diaphragm
5. cranial: thoracic inlet (1st ribs, 1st thoracic vertebrae, cranial sternum)
- thorax
- contains lungs, heart, large vessels, nerves, trachea, esophagus, lymph vessels/nodes
- diaphragm: primary muscle for respiration (thin sheet of skeletal muscle)
- pleura (thin membrane) covers structures in thorax (visceral) + lines inside of cavity (parietal). space b/w with serous fluid to prevent friction when breathing
- mediastinum: junction of ^ near thoracic midline. in between the two lungs and contains heart + other structures, but not lungs themselves
respiration
air drawn into lungs -> O transferred from alveoli into blood -> CO2 from blood into lungs -> CO2 breathed out
negative intrathoracic pressure
- partial vacuum in thorax keeping lungs against wall
- whenever thorax expands -> lung volume also expands -> air can enter
- lungs are passive, thorax and diaphragm are active
- can hear release if thoracic cavity punctured during surgery
- if air leaks into space b/w lung + wall, pressure is compromised (pneumothorax) -> body can’t expand lungs -> collapse + death
- also problem if fluid accumulates in thorax
- bonus: pressure also helps pull blood into atria
inspiration
AKA inhalation
- powered by diaphragm + external intercostal muscles.
- diaphragm normally dome shaped -> contracts + flattens when breathe in
- external intercostals b/w ribs -> pull ribs up and forward to expand cavity
expiration
AKA exhalation
- diaphragm relaxes (gravity + elasticity of lung tissue and wall help this happen)
- less effort than inspiration, nearly passive
forced expiration: powered by internal intercostal + ab muscles
- internal intercostal deep to externals -> pull back and rotate ribs to decrease thorax volume
- ab muscles contract -> push abdominal organs against diaphragm -> dome shape restored + thorax volume decreased
breathing types
dyspnea: difficult
apnea: absence
hyperpnea: increase rate and/or depth
polypnea/tachypnea: shallow rapid breath
species resp rates
cat: 20-30
dog: 10-30
cow: 18-28
horse: 8-16
auscultation
- little noise if normal, noisy if issue
stridor: high pitch, from upper airway obstruction
stertor: low pitch, flaccid tissue vibrating in airway (like snoring)
respiratory volumes
tidal: volume of air exchanged in one breath
minute volume: volume of air exchanged in one minute
- tidal X # breaths/min
residual: volume leftover after exhale
- never completely empty
vital capacity: max air that can be expired
total capacity: residual + vital
alveolar gas exchange
room air: 20% O, 0.03% CO2
- blood entering lungs HIGH in CO2, LOW in O
- capillary walls use concentration gradient -> CO2 out of blood/into alveoli -> O in alveoli into blood
- concentration gradient maintained by constant flow of CO2 in capillaries + constant breathing refreshing alveoli
- exchange rate affected by distance gas needs to cover (eg. edema in lung impacts amount of O absorbed)
- if part of lung collapses/airway obstructed -> O in alveoli decrease -> local hypoxic vasoconstriction occurs (decreases blood circulating through part of lung that aren’t getting good gas exchange)
- general hypoxia (high altitude): overall vasoconstriction of lungs
- increased vascular resistance -> pulmonary hypertension -> heart pumps harder against resistance -> right heart failure
- high mountain disease in cattle
- hemoglobin becomes saturated with O during this process (even some still leftover in the CO2 blood coming back to lungs)
- things that decrease hgb-O bind: increased temp, increased CO2, reduced pH
- helps Hgb + O dissociate where needed in tissues
partial pressures of gases:
- sum of individual gases pressure = total pressure
ie. each gas accounts for ‘partial’ pressure
- another way of looking at concentration of substances
- substances move DOWN concentration gradient -> partial pressure of O higher in air than blood = O into blood
breath control
- muscles involved = voluntary
- overall process = involuntary, by respiratory center in brainstem (medulla)
- ^ subconscious, but can be overridden by conscious control
medullary rhythmicity area: sets rate
- automatic rhythmic signal for inspiration
- expiration is the passive result of this effort ending
- expiratory area only activated if forced
-> signal travels down phrenic nerve -> diaphragm AND intercostal nerves -> costal muscles
2 systems to control:
1. mechanical
- sets limits on inspiration/expiration
- uses ‘stretch receptor’ in lung
- receptor -> respiratory center -> muscles signalled
- chemical
- chemoreceptors monitor CO2, O, pH for balance
- in brain, carotid artery, aorta
- rising CO2 stimulates breathing more than decrease O because CO2 + pH linked
- CO2 high = pH down -> acidic blood -> increase resp rate to ‘blow off’ excess CO2 -> normal pH
* artificial ventilation if too high during surgery -> risk of blowing off too much CO2 -> animal compensates by holding breath (apnea) -> CO2 rise -> breathing stimulated again
oxygen sensors:
- mild hypoxia: signal to increase
- severe hypoxia: neurons too depressed to signal -> respiratory failure
* in clinic, mechanical receptors in skin cause deeper resp when signalled. newborns can be vigorously rubbed to stimulate this reflex/can also use needle to stimulate philtrum (b/w nose + lips)
terminology
cough: irritation in trachea/bronchi
- pressure against closed glottis -> sudden release
sneeze: irritation in nasal passages
yawn: slow deep breath stimulated by decrease in O levels in blood (or boredom/fatigue/anxiety)
sigh: deep breath stimulated by decrease in O in blood
hiccup: diaphragm spasm -> sudden glottis closure
panting: heat dissipation. increased resp rate + decreased tidal volume
physiological dead space: part of resp system where there’s no gas exchange
* important during anesthesia. long endotracheal tube = increased dead space = reduced gas exchange
- if the tube is too long exhaled air won’t clear it -> rebreathing same air
- careful w/small animals
dive reflex: helps aquatic mammals stay under long time. when air starts to get into air passages -> heart rate changes -> breathing stops -> blood shunted from less essential tissues
emphysema: alveolar membranes destroyed -> larger lung chambers -> decreased surface area for gas exchange
atelectasis: alveoli collapse (often from obstruction or lack of surfactant)
haemoptysis: coughing up blood
pathlogy
sinusitis:
- inflammed paranasal sinuses
- can obstruct drainage -> need trephination
tonsilitis:
- common in dogs (esp. toys and brachysephalics)
- can be secondary to mouth, pharynx, or nasal infections
dorsal soft palate displacement:
- vigorous exercise makes soft palate rise and epiglottis fall below -> nasopharynx diameter reduced
larynx related:
- de-barking: suturing/severing vocal cords
- laryngospasm: when area rubbed while incubating
- laryngeal edema: from irritants, trauma to endotracheal intubations, excessive panting in brachys/obese dogs
- laryngeal hemiplegia: in horses (afflicted known as ‘roarers’), paralysis of laryngeal nerve through genetics or injury -> vocal fold constructs airway and vibrates
- laryngeal hemiplasia: vocal cords obstruct lumen and cause roaring when air passes out
* laryngeal-tieback or laryngeal ventriculectomy
- laryngeal paralysis: same thing as hemiplegia but in dogs
upper respiratory tract infections (URI)
- nuisance usually, not threatening
- coughs can be productive
ex. kennel cough
heaves - recurrent airway obstruction (RAO)
- chronic allergy of horse
- laboured breath, cough, low stamina
- common in stable, not pasture
- onset 9-12 years
- secondary to narrowing of airways
heaves - chronic obstructive pulmonary disease (COPD)
- progressive, changes to lung irreversible
penumothorax
- free air in chest -> lung collapses
- hole in chest wall/punctured lung
pulmonary edema:
- fluid in airways/alveoli
- circulatory associations: L ventricle failure, anaphylactic shock, severe allergies
- may be auscultated
pneumonia:
- lung inflammation
- usually when viral/bacterial infection
- penumonitis: non-infectious version
- more serious than bronchitis
- mucus + fluids can accumulate -> plug lung -> decrease gas exchange
* aspiration pneumonia: anesthetized animal not intubated or extubated too early
diaphragmatic hernia:
- trauma result/congenital
- may not show symptoms depending on severity
- abdominal contents enter chest
- abdomen open -> life-threatening
- small tear from negative thorax pressure can cause abdominal viscera to pass through
