respiratory 3 Flashcards
what does the lungs separate the heart from the ribcage and what are the 5 structures within teh lungs
separate heart from ribcage except at cardiac notch (at about 3rd-5th intercostal space) - feel heartbeat
- base (= diaphragmatic surface): concave surface adjacent to diaphragm
- apex: adjacent to thoracic inlet
- costal surface: convex - in contact with rib cage
- medial surface: indented by heart (region of 3rd-6th ribs) - contact with mediastinum around the heart
- root:
- composed of grouped principal bronchus, pulmonary artery, veins and nerves, wrapped together in pleural covering
- location of tracheobronchial lymph nodes
- enters lung at hilus
how many lobes in most domestic species, dogs and horses and what defines a lobe
dog: 2 left, 4 right - most domestic species
• horse: 2 left; 3 right
• defined as structures supplied by a secondary (lobar) bronchus
what does the connective tissue septa separate, what does it contain and what is the consistency in different species
- separate different lung lobes
- contain collagen, elastin (expansion and remain expanded with decrease in pressure), blood vessels
○ thick in ruminants, pig - infection less readily spread to other lobes
○ thin and incomplete in horse
○ almost non-existent in dog
what is the tracheal bronchus and what is its function
Tracheal bronchus comes straight off trachea before the primary and secondary bronchus splits
- Provides air to cranial lobe of right lung
what is the left and right lung divided into
left lung: 2 lobes 1. cranial - has cranial and caudal portions 2. caudal right lung 1. cranial lobe - ventilated by tracheal bronchus in ruminants and pigs 2. middle lobe - not present in horse 3. caudal lobe 4. accessory lobe
what are the 3 systems of vasculature for the lungs and where do they enter
1) pulmonary arteries - oxygen-depleted blood from right ventricle - pulmonary trunk - left and right arteries - lungs
2) pulmonary veins - oxygen-rich blood from lungs - left atrium, also provides venous return from bronchi
3) bronchial artery - oxygenated blood for the bronchus - arises from aorta
what are the 2 networks of lymphatic drainage
- superficial network: drains subpleural tissue into vessel at hilus of lung
- deep network: drains deeper tissues via vessels running along airways (from level of bronchioles)
where do the 2 networks of lymphatic drainage meet and what are they responsible for
both sets merge at hilus ⇒ tracheobronchial lymph nodes ⇒ cranial mediastinal nodes ⇒ tracheal lymphatic vessels or thoracic duct
• responsible for:
- removal of material phagocytosed by macrophages in airways
- mounting immune response to infectious agents
○ Very important as air breathed in isn’t sterile unlike the blood
what is the innovation for lungs and glands and reflexes
autonomic supply (sympathetic and parasympathetic) from pulmonary plexus within mediastinum:
1) efferent
- regulates activity of bronchial glands
○ Sympathetic - drying up of glands
○ Parasympathetic - secretion from glands
- smooth muscle of bronchi ⇒ broncho-constriction or dilation
2. afferent supply from:
- stretch receptors ⇒ reflex modification of respiration
- mechanoreceptors ⇒ reflex coughing
what are two processes that result in ventilation-perfusion mismatching
1) hypoventilation - insufficient airflow to lungs due to partial obstruction of upper or lower airway (pathological) or holding breath
⇓
O2 depletion and CO2 accumulation in alveoli
⇓
O2 depletion and CO2 accumulation in blood
2) Hyperventilation
• breathing more deeply or rapidly than necessary to maximally oxygenate blood flowing through lungs
- Beyond the animals needs
⇓
surplus fresh air flowing into and out of lungs
⇓
decrease in [CO2] in blood (constant removal from lungs) = hypocapnia
+
only slight increase in [O2] in blood (already almost saturated)
what are the normal mismatching with ventilation-perfusion ratios
1) generally air goes to dorsal region and blood ventral regions in standing animal due to hydrostatic pressure
2) ventilated unperfused lung = alveolar dead space, during anaesthesia of large animals in dorsal recumbancy therefore get pooling of blood in dorsal lung, need to adminster pure O2 to maintain blood PO2
what are the 4 ways in which localised ventilation-perfusion matching occurs
1) local hypoventilation in alveolar airflow - increase PCO2 results in bronchodilation - increase in airflow
2) local hyperventilation in alveolar airflow - decrease PCO2 - bronchoconstriction - decrease in airfow
3) local hypoventilation of capillary blood flow - decrease PO2 - vasoconstriction of arterioles - reduction in blood flow
4) local hyperventilation in capillary blood flow - increase in PO2 in alveolus - vasodilation - increase in blood flow
what are the two types of alveolar epithelial cells and their shape and function
1) type I alveolar epithelial cells:
- very flattened cells - squamous
- cover majority of alveolar wall
- sit on basement membrane
- terminally differentiated (cannot divide)
- allow gas diffusion across cytoplasm
2) type II alveolar epithelial cells:
- cuboidal
- cytoplasmic granules contain surfactant (secreted to coat alveolar lining and reduce surface tension)
divide to replace type I and type II cells
what are alveolar separated by and what does contain and what allows passage of O2
interalveolar septa:
- contain fibroblasts, mast cells, macrophages
- rich in capillaries:- endothelial basement membrane fused with that of alveolar epithelial cells in some places, fused with thin interstitium in others
- alveolar pores - allows O2 movement between adjacent alveoli
what are the 5 structures of the blood-air barrier
- alveolar fluid
- alveolar epithelial cell
- basement membrane of alveolar epithelium (+/- thin interstitium)
- basement membrane of capillary endothelium
- capillary endothelial cell
what are the 3 location pulmonary macrophages are present and what line are they dervied from
- intravascular: associated with endothelium (pigs, ruminants)
- Interstitial - degrade particular material
- alveolar: function to clear alveolar surface; removed via trachea (mucociliary clearance, coughing) or via interstitium ⇒ lymphatic system
• derived from haemopoietic stem cells (monocyte-macrophage lineage)
how to determine partial pressure
e.g. if O2 comprises 20% of a gas mixture with total pressure of 760 mm Hg
partial pressure of a gas is found by multiplying its percentage concentration by the total pressure
e.g. if O2 comprises 20% of a gas mixture with total pressure of 760 mm Hg: ⇒ PO2 = 0.20 X 760 mm Hg = 152 mm Hg
what makes the partial presure of O2 drop in the alveoli
water vapour added to air during inspiration ⇒ change in partial pressures of gases, although total pressure remains the same: - acts as a partial pressure
also diluted by stale air that is maintained within alveoli
what is the total alveolar air replaced with each normal breath and what is the average PAO2 and PACO2 in the alveoli
about 15% total alveolar air replaced with each normal breath
⇒ average PO2 of alveolar air (PAO2) = 100 mm Hg; PACO2 = 40 mm Hg
what determines the partial pressure of gases in liquids and what measures PO2 and PCO2 in the blood
concentration of gas dissolved in the fluid
PO2 - only O2 dissolved in plasma
PCO2 - CO2 (what we are measuring) + H2O ⇔ H2CO3 ⇔ H+ + HCO3
⇒ lowered PCO2 in the blood
does CO2 or O2 diffuse quicker, why and what does this result in
CO2 Has a lower partial pressure gradient than oxygen however has higher diffusion coefficient so diffuses quicker than O2
- factors limiting diffusion may result in hypoxia without hypercapnia - indicates disease results in problem with diffusion
rate of gas transfer in terms of blood flow and what does this result in
gas transfer in alveolar capillary bed usually completed in about 1/3 time it takes for blood to travel past alveolus ⇒ existence of enormous diffusion reserve - capacity to add more oxygen to the blood
what do fish use as gas exchange surface
make use of gills – delicate evaginations (out pocketing) of tissue protruding into surrounding water; consist of thin epidermis highly perfused by circulatory system, providing high surface area for gas exchange between water and blood - equivalent to alveoli
what is the mechanism of fish breathing
- breathing involves taking water into mouth while operculum (gill cover) is shut; the mouth is then shut and operculum opened, thus forcing water over gills and out through operculum
• flowthrough (unidirectional) system