Urinary/respiratory Flashcards
Respiration vs ventilation
Respiration = the exchange of gases at the alveoli
Ventilation = the movement of air through the airways
Pleura
Double layer of simple squamous epithelium lying on connective tissue - lining the thoracic cavity
Layers of the pleura
Visceral pleura - invests the tissue of the lung
Parietal pleura - lines the remaining structures of the thorax
The two layers are continuous with each other, forming a sealed pleural sac
pneumothorax
When a hole is made in the pleura so air rushes in, causing the lung to collapse on that side
Larynx
A structure supported by multiple cartilages, lined by a mucous membrane.
It connects the pharynx and trachea and is involved in:
- Protection of the lower airways
- Phonation
- Swallowing
- Coughing and eructation/vomiting
Lobes of the lungs
Right:
- Cranial
- Middle
- Caudal
- Accessory
Left:
- Cranial
- Caudal
What epithelium are the airways of the ventilation system lined with?
Pseudostratified ciliated columnar epithelium
Type 1 alveolocytes
Flattened simple squamous epithelial cells of the alveolus
Nerve supply of the lungs
The lung receives sympathetic and parasympathetic supply via the pulmonary plexus.
The vagus nerve provides the parasympathetic portion.
The sympathetic nerve supply to the lung only innervateds the blood vessels, the smooth muscle of the airways has β₂ adrenoreceptors which respond to circulating adrenaline and noradrenaline.
Eupnoea
Normal, resting breathing - at a normal rate, depth and effort
Tachypnoea
An increased respiratory rate
Hyperpnoea
Increased respiratory depth
Dyspnoea
Laboured breathing
Compliance
The degree to which a change in transpulmonary pressure causes a change in the volume of the lung
C=𝞓V/𝞓P
It depends on the elasticity in the lung tissue and the surface tension of the alveoli
Surfactant
To counteract resistance, type II alveolar cells produce surfactant.
It is a mixture of phospholipids, proteins and Ca²⁺ which reduce the formation of H bonds between water molecules
Carbon dioxide transport
CO₂ is transported in the blood in 3 ways:
- Dissolved in plasma (5%)
- As carbamino compounds (30%)
- As bicarbonate ions (65%)
it is ~20x more soluble than oxygen
Carbamino compounds
CO₂ combined with Hb (or other proteins)
CO₂ binds more strongly to deoxyHb meaning that the offloading of O₂ in the tissues facilitates loading of CO₂
Carbonic anhydrase
The majority of CO₂ combines with water to form carbonic acid under the influence of carbonic anhydrase.
Carbonic acid quickly dissociates into bicarbonate and hydrogen ions.
The chloride shift
When the HCO₃₋⁻ produced in the carbonic anhydrase reaction is transported out into the plasma in exchange for chloride ions to maintain the electrochemical neutrality of the erythrocyte
Pulmonary vascular responses
The net effect of sympathetic stimulation is usually vasoconstriction.
Parasympathetic stimulation has a net effect of vasodilation.
Nitric oxide
It is an important vasodilator.
Its release from vascular endothelial cells is stimulated by the parasympathetic nervous system and by the action of mediators such as Bradykinin. it is also released from the endothelium in direct response to an increased speed of flow.
Alveolar hypoxia
Potent vasoconstrictor.
A low PAO₂ occurs where ventilation of alveoli is reduced - this alveolar hypoxia causes vasoconstriction of the small arteries supplying that portion of the lung.
This response reduces blood flow to poorly oxygenated alveoli and increases flow t well oxygenated alveoli.
This response becomes problematic if the alveolar hypoxia is not localised but generalised, leading to a generalised vasoconstriction of the pulmonary circulation.
This increases the after load on the RHS of the heart and can lead to right congestive heart failure.
Respiratory receptors
- Pulmonary stretch receptors
- Irritant recepotors
- Muscle spindle stretch receptors
- Peripheral chemorecptors
- Central chemoreceptors
Pulmonary stretch receptors
- Associated with the smooth muscle of the airways
- Participate in the Hering Breuer reflex
- They send impulses in increasing frequency throughout inspiration via myelinated axons to the pons to signal degree of lung inflation