Functional Anatomy Respiratory Flashcards
What are the functions of the nose? (7)
- Olfaction
- Humidification and warming of inspired air
- Filter of inspired air
- Reclamation of expired moisture
- Sneezing (protective reflex)
- Speech
- 1-2 cmH2O PEEP
What is the blood supply to the nose?
External carotid artery
- Facial artery branch
- Maxillary artery branch
Venous drainage
- Facial vein, cavernous sinus, pterygoid plexus
Kieselbach’ plexus = where epistaxis occurs
How does humidification and warming in the nose occur?
- Humidification - Superior, middle and inferior tubrinates on the lateral wall of the nose increase the surface area and generate turbinate flow
- This allows for maximal vapourisation of air
- Water comes from the nasal mucosa - Warming - heat transfer from the vascular cavernous plexus arranged longitudinally
How long is the pharynx?
12cm
What are the four layers of the pharynx?
- Mucous membrane
- Submucous layer
- Muscular layer
- Buccopharyngeal layer
What are the functions of the pharynx? (4)
- Swallowing
- Immune function (Waldeyer’s ring)
- Phonation
- Separates the digestive and respiratory tract
What is the narrowest point of the pharynx?
Where the inferior pharyngeal constrictor muscle attaches to the cricoid cartilage
What is the blood supply to the larynx?
- Upper half
- Arterial supply: superior laryngeal branch of the superior thyroid artery
- Venous drainage: Superior laryngeal vein of the superior thyroid vein - Lower half
- Arterial supply: inferior laryngeal branch of the inferior thyroid artery
- Venous drainage: Inferior laryngeal vein of the inferior thyroid vein
What is the innervation of the larynx?
Recurrent laryngeal nerve
EXCEPT:
Cricothyroid muscle = EXTERNAL branch of the superior laryngeal nerve
What doe the INTERNAL branch of the superior laryngeal nerve supply?
Sensory ABOVE the vocal cords
What are the 4 borders of the larynx?
Superior = hyoid bone (C4)
Posterior = Laryngopharynx
Inferior = trachea (T4)
Anterior = Thyroid cartilage
What are the functions of the larynx? (4)
- Phonation
- Conductive airways (respiration)
- Cough reflex
- Swallowing
List the cartilages of the larynx (paired and unpaired)
Unpaired (3)
- Thyroid
- Cricoid (level C6)
- Epiglottis
Paired (3)
- Arytenoid
- Cuneiform (suspended in quadrangular membrane)
- Corniculate (Superior to arytenoid)
List the ligaments of the larynx (intrinsic and extrinsic)
Intrinsic (2)
- Quadrangular membrane: forms the vestibular fold = false vocal cords
- Cricothyroid ligament: forms the vocal fold = true vocal cord
Extrinsic (3)
- Thyrohyoid membrane (Between thryoid cartilage and hyoid bone)
- Hyoepiglottic ligament (Between the hyoid bone and epiglottis)
- Cricotracheal ligament (Between cricoid cartilage and trachea)
Which ligament does the MAC blade put tension on to move the epiglottis out of the way?
Hyoepiglottic ligament
Which is superior? The quadrangular membrane of the cricothyroid ligament?
Quadrangular membrane
What are the intrinsic muscles of the larynx? (6 but 4 categories)
- Cricothyroid muscle
- Between cricoid cartilage and thyroid cartilage
- Action: pull thyroid cartilage down and forward = tense vocal cords = high pitched sounds
- Acts on the cricothyroid joint - Cricoarytenoid muscles
A) Posterior part - swivels arytenoid cartilage LATERALLY = OPENS rima glottis (Think O in posterior for Opens)
B) Lateral part - swivels arytenoid cartilages MEDIALLY = CLOSES rima glottis - Interarytenoid muscles
A) Oblique = CLOSES LARYNGEAL inlet
- There are fibres that continue past the arytenoid to the epiglottis
B) Transverse = ADDUCT VOCAL cords - Thyroarytenoid muscle
- Also has an attachment to the epiglottis = thyro-epiglottic part
- Action: Decreased tension on vocal cords = low pitched sounds
- Vocalis muscle (sometimes considered separate muscle): fine tunes tension of vocal cords
How long and wide is the trachea?
11cm long, 1.8cm diameter
How many tracheal rings are there?
22 C shaped cartilaginous rings
What is the posterior muscle of the trachea called?
Trachealis muscle
What type of mucosa is the trachea lined by?
Pseudostratified ciliated columnar epithelium
What are the functions of the trachea? (2)
- Conducting airways
- Mucocilliary elevator
What are the surface landmarks of the trachea?
Cricoid cartilage (C6) - superior aspect
Sternal angle (T4) or second ribs = carina
What are the related structures of the trachea?
Organs
- Thyroid gland - isthmus crosses trachea at 3rd tracheal ring
- Oesophagus - L) posterior border
Bone
- Vertebral bodies - R) posterior border
Nerves
- Recurrent laryngeal nerve - R) under R) subclavian artery to cricoid, L) under arch of aorta to cricoid cartilage
Vessels
- Brachiocephalic artery (Anterolateral surface)
- L) common carotid artery (L) lateral border)
- SVC (R) lateral border
- Azygous vein (R) lateral border, joins SVC)
- Pulmonary trunk (Anterior to carina)
What is the blood supply to the trachea?
Upper trachea
- Inferior thyroid arteries
Lower trachea
- Bronchial arteries from aorta
Venous drainage = inferior thyroid plexus
What is the innervation of the trachea?
Vagus nerve
Sympathetic chain (T2-T6)
What are the alveolar cell types
Type 1
- 95% surface area
- No organelles
- Do NOT replicate
- Sensitive to damage with increased FiO2
Type 2
- Function not structural cells
- Cuboidal with microvilli and contain lamellar bodies (vesicles with surfactant)
What are the functions of type 1 alveolar cells?
- Gas exchange - super thin
- Barrier with tight junctions and impermeable to water
What are the functions of type 2 alveolar cells?
- Secrete surfactant
- Replenish type 1 cells (transform into type 1 cells over 48-72 hours)
Other than alveolar cells, what other cells are in the alveoli?
- Capillary endothelial cells
- Macrophages
- Mast cells
- Fibroblasts
What are pores of Kohn?
Holes (30microm) in alveolar walls
Absent in newborns and develop at age 4
Increase in size and become confluent with age
Mostly filled with surfactant
Function = collateral ventilation
When does cartilage become absent in the airways?
Bronchioles onwards
What generations are the conducting airways and what is the volume of anatomical dead space?
1 to 16, 150ml
What generations are the respiratory airways and what is their volume?
17-19 = respiratory bronchioles
20-22 = alveolar ducts
23 = alveolar sacs
3000ml
When does flow in the airways become laminar? (What generation?
Turbulent flow up until generation 11 - beyond this the flow becomes laminar
How does gas move in the airways?
In the conducting airways via forward velocity, in the respiratory airways via diffusion
Describe the cough reflex
Function = clear the airway of debris before reaching lungs, involuntary but can be initiated by voluntary control
Sensors = Irritant receptors in the epithelium of the respiratory tract (trachea, pharynx, carina, less prominent in the distal airways and absent beyond respiratory bronchioles)
Afferent pathway = INTERNAL branch of the superior laryngeal nerve vis VAGUS nerve to the MEDULLA
Central control = no cough centre
Efferent pathway = Cranial nerve X and SUPERIOR LARYNGEAL NERVE
Effectors = glottis, external intercostals, diaphragm and major inspiratory/expiratory muscles
Response = Three phases of the cough reflex
What are the three phases of the cough reflex?
- Inspiratory phase
- Diaphragm (phrenic N.) and External intercostals (segmental IC N.) contract
- Large negative intrathoracic pressure
- Inflow of air –> Close to vital capacity taken - Compressive phase
- Glottis closes and vocal cords contract (recurrent laryngeal nerve)
- Abdominal muscles and expiratory muscles contract
- Rapid increase in intrapleural pressure (>100mmHg) - Expulsive phase
- Glottis and vocal cords open = air expelled at rapid velocity (up to 80kph)
- Collapse of bronchi and non cartilaginous postions of trachea = clearance of material attached to respiratory lining
What reduces the effectiveness of the cough reflex (4)
- Respiratory muscle weakness + neurological conditions
- Tracheostomy
- Vocal cord pathology
- Anaesthesia/paralysis
What is the expiration reflex?
Same as the cough reflex but NO inspiration phase
Stimulus is at the laryngeal inlet and you do not want to inhale something here
Describe the glottic closure reflex/laryngeal adductor reflex/laryngospasm
Brainstem mediated involuntary reflex arc
Sensors = Mechano- and chemoreceptors in laryngopharyngeal mucosa
Afferent = INTERNAL branch of the SLN via vagus
Integration = Medulla
Efferent = Recurrent laryngeal nerve
Effect = Adduction of vocal cords (thyroaretenoids & lateral cricoarytenoids)
Laryngospasm = prolonged maladaptive manifestation of this reflex
Occurs with stimulation of upper airway during light anaesthesia
Describe the sneeze reflex
Same as cough reflex except:
- irritation in nasal cavity
- Afferent pathway = cranial nerve V
- Uvula is depressed resulting in rapid airflow through nose
What are the effects of anaesthesia on airway reflexes?
- Irritation of airways = promote airway reflexes
- Stimulation of airway may cause transient central apnoea (breath holding)
Volatiles
- >1-1.3 MAC = dose dependent suppression of airway reflexes
- Light = increased laryngospasm (esp children)
- Desflurane & Isoflurane = more irritant = more bronchoconstriction
Propofol
- Decreased laryngospasm
- Increased incidence of coughing
What is absolute humidity?
Mass of water vapour in a given volume of air
gH2O/m3 or mgH2o/L
Temperature INDEPENDENT (except when saturated with maximal amount of water)
What is relative humidity?
Ratio of the absolute to the mass required to fully saturate that volume of air at a given temperature
Relative humidity = (Absolute humidity)/(humidity at saturation) X 100%
Temperature DEPENDENT
(Decreasing temperature increases relative humidity)
Describe how humidification happens in the airways
Inspired air = 10g/kg (50% humidity at 22 degrees)
Turbinates = turbulent flow which increases evaporative heat exchange
Lower pharynx = 100% relative humidity T33 degrees
Inspired air = body temperature at the isothermic point which occurs 5cm below the carina
Alveolus = 44mg/L 100% humidity at 37 degrees
During expiration - return some heat and water via condensation
At nares 100% humidified, 32 degrees
What would happen in an intubated patient without a HME filter and without warming of the air inspired?
Inspiration of dry air
- Insippation of secretions leading to atelectasis and V/Q mismatch
- Impaired mucocillary function from mucosal dehydration
- Increased heat loss
What are the non ventilatory functions of the lung? FIRMTAP
F = filtration
1. Blood - receives entire cardiac output and filters particles >10microm (venous thromboemboli, microbes, tumour cells)
2. Gas - filtering and particle impaction of upper airways, sedimentation in lower airways
I = immunological
- Alveolar macrophages
- Secretory IgA
- Mast cells
- Lymphoid tissue in the lungs (BALT - bronchus associated lymphoid tissue)
- Barrier functions (mucous and mucociliary escalator)
R = Reservoir
1. Blood (Approx. 450ml with 20% in pulmonary capillaries)
2. Gas - FRC is an oxygen reservoir
M = Metabolism
- Vasoactive substances
- Protein synthesis, carbohydrate metabolism
- Removal of proteases
- Production of surfactant
T = thermo and water regulation
A = Acid base balance
P = Pharmacological
- Administration and elimination of drugs
- Sequesters drugs with first pass uptake
