What is the function of the nose?
Filtering, defence function (cilia waft inhaled particulates from anterior naries backwards to be swallowed), temperature of inspired air
The anterior nares open into the vestibules. What do they contain?
Vestibules have turbinates. These double the SA of the nose
What are the spaces inbetween the turbinates called?
Meatus (superior, middle, inferior)
What are the paranasal sinuses?
Pneumatised areas of the:
- sphenoid bones
They are arranged in pairs
Where are the frontal sinuses found? What is their innervation?
Within frontal bone, midline septum. Innervated by ophthalmic division of V nerve
Where are the maxillary sinuses found? What is their shape?
Located within the body of the maxilla. Pyramidal shape
Where are the ethmoid sinuses found? What is their innervation?
Between the eyes, semilunar hiatus of the middle meatus. Ophthalmic + maxillary V nerve
Where are the sphenoid sinuses found? What is their innervation?
Medial to cavernous sinus, inferior to optic canal, dura + pituitary gland. Ophthalmic V
What is the pharynx? What is it split into?
- Fibromuscular tube lined with epithelium. Base of skull to C6.
- Nasopharynx, oropharynx + laryngopharynx
What is the function of the larynx? What is it made up of?
Has a valvular function. Prevents liquids + food from entering the lung. Has a rigid structure, 9 cartilages + multiple muscles. Elastic = epiglottis. Hyaline = thyroid, cricoid, arytenoid
What are the single and double laryngeal cartilages?
What is the laryngeal innervation? What does the main nerve split in to?
The vagus (X). This splits into the superior laryngeal nerve + recurrent laryngeal nerve
What does the superior laryngeal nerve supply? What does it divide into?
Inferior ganglion + lateral pharyngeal wall. Divides into internal (sensation) + external (cricothyroid muscle)
What does the recurrent laryngeal nerve supply? Are the left and right the same?
Supplies all muscles except cricothyroid (where pierced if need to get into airway). Right and left laryngeal nerve are different - left is longer than right as it crosses under arch of aorta at the ligamentum arteriosum
What is the general structure of the lower respiratory tract?
Trachea - main bronchi - lobar bronchi - segmental branches - terminal bronchiole - respiratory bronchiole - alveolar ducts + alveoli
Where is the trachea found? What features does it have? Is it conducting or respiratory airway?
- From larynx (C6) to carina (T5)
- Semicircular cartilaginous rings
- Pseudostratified ciliated columnar epithelia with interspersed goblet cells
Which bronchus is more vertical? What do these bronchi split into? Are these conducting airway or respiratory airway?
- Right main bronchus is more vertical than the left - left accommodates aortic arch underneath
- Trachea split to form these at carina
- RMB further divides into lobar bronchi to form 3 lobes (lower, middle + upper)
- LMB divides into lobar bronchi to form 2 lobes (upper lingular + lower)
- Segmental bronchi arise from these lobar divisions
- All conducting airway
What are the two bronchioles? Are these conducting or respiratory airway?
- Terminal (conducting)
- Respiratory = highest restriction to airflow (respiratory)
- Conducting = no gas exchange
- Respiratory = gas exchange
What do alveoli contain?
- Type I (gas exchange) + II (surfactant) pneumocytes
- Adjacent alveoli connected through pores of Kohn - allows movement of alveolar macrophages
- Fused basement membrane with endothelia of capillaries - 1um thick
This is all respiratory. In total, there are 24 divisions from trachea to alveoli
What are the two types of pulmonary plurae? Where do they originate from?
- Visceral - on lung surface, autonomic innervation
- Parietal - on thoracic wall against lungs, pain sensation
- Mesodermal origin, single layer cells
- Continuous with each other at root of lung
- Intrapleural fluid fills space, lubricating surfaces
What is the innervation of the lungs?
- Sympathetic = bronchodilation (T2-4 symp. trunk ganglia)
- Parasympathetic = bronchoconstriction (vagus)
What are the 7 layers of gas exchange?
- Fluid lining alveolus
- Layer of epithelial cells - Type I pneomocytes
- Basement membrane of type I cells
- Interstitial space
- Basement membrane
What are the muscles of inspiration?
- Diaphragm mainly, 70% of volume change (phrenic C3-5 innervation)
- External intercostals - lift ribs 2-12, widen thoracic cavity
- Scalenes, pectoralis major, sternocleidomastoids
What are the muscles of active expiration?
- Passive during quiet breathing
- Internal intercostals = depresses ribs 1-11
- Rectus abdominis = depresses lower ribs, compresses abdominal organs + diaphragm
What happens to the intercostal muscles, diaphragm, volume and pressure during inspiration and expiration?
- Intercostal muscles = contract
- Diaphragm = contract
- Volume = increases
- Pressure = decreases, so air moves in
- Intercostal muscles = relaxes
- Diaphragm = relaxes
- Volume = decreases
- Pressure = increases, so air moves out
What is physiological deadspace? What is it split into?
- It is the volume of inspired air that is not contributing to ventilation. There is anatomical (due to anatomy), that makes up more ml, and alveolar. So, the physiological deadspace = anatomical + alveolar
What happens in gas exchange? What is hypoxia? How is this overcome?
- O2 in, CO2 out
- 1000 capillaries per alveolus, each erythrocyte may come into contact with multiple alveoli
- Capillaries at most dependent parts of lung are preferentially perfused with blood at rest
- Perfusion of capillaries with oxygen depends on pulmonary artery pressure, pulmonary venous pressure etc.
- Hypoxia = where region of body deprived of oxygen. Pulmonary vasoconstriction diverts blood to better-oxygenated lung segments, thereby optimising ventilation/perfusion matching + system oxygen delivery
What do these abbreviations mean:
- Arterial O2/CO2
- Alveolar O2/CO2
- Pressure of inspired O2
- Alveolar ventilation
- CO2 production
What is the equation for CO2 elimination? What are the three ways in which CO2 is carried? What are the physiological causes of high CO2?
- CO2 elimination: PaCO2 = k V'CO2/V'A
- Three ways CO2 is carried:
- Bound to haemoglobin
- Plasma dissolved
- As carbonic acid
- Physiological causes of high CO2:
- V'A reduced = either reduced minute ventilation, increased deadspace ventilation by rapid shallow breathing or increased deadspace ventilation by ventilation/perfusion mismatching
- Increased CO2 production
What is the alveolar gas equation? What are the causes of low PaO2?
- Alveolar gas equation: PAO2 = Pi02 - PaCO2/R (R is respiratory quotient)
- Causes of low PaO2 (hypoxaemia):
- alveolar hyperventilation
- reduced PiO2
- ventilation/perfusion mismatching
- diffusion abnormality