Lecture 10 - Gross Structure of the Lungs Flashcards
How does inspiratory ventilation of the gross lung occur?
expands passively due to change in volume of thoracic cavity –> inflow of oxygen rich air
how does expiratory ventilation of the gross lung occur?
contracts due to elastic tissue throughout the lung –> outflow of carbon dioxide rich air
the lungs seperate the heart from the rib cage except for at what point?
at the cardiac notch - 3-5th intercostal space
what is the base of the lung?
the diaphragmatic surface - concave
where is the apex of the lung located?
adjacent to the thoracic inlet
is the costal surface convex or concave?
convex - against thoracic wall
what is the medial surface?
surface facing and indented by the heart - region of the 3rd - 6th ribs
what does the root of the lung contain?
- grouped, principle bronchi, pulmonary artery, veins and nerves all wrapped together in pleural covering
- also the location of the tracheobronchial lymph nodes
where does the root enter the lung?
at the hilus
how many lung lobes does the dog have?
2 left lobes,
4 right lobes
how many lung lobes does the horse have?
2 left
3 right
How are lobes defined?
defined as structures supplied by a secondary lobar broncos, subdivided into lobules by connective tissue (septa)
what do lobules contain? what are the implications for spread of infection?
contain collagen, elastin, blood vessels vary in consistency - implicates spread of infection thick in ruminant and pig thin and incomplete in horse almost non existent in dog
what are the two lobes of the left lung?
- cranial lobe - has cranial and caudal portions in species other than the horse
- caudal lobe
what are the lobes of the right lung?
divided into 3-4 lobes
- cranial lobe
- middle lobe - not present in horse, separated from cranial lobe by cardiac notch
- caudal lobe - in contact with diaphragm
- accessory lobe - located in mid-ventral region of right lung
in ruminants and pigs what is the cranial right lobe ventilated by?
the tracheal bronchus
describe the path of the pulmonary arteries
oxygen depleted blood from the right ventricle, into the pulmonary trunk into the L and R pulmonary arteries –> lungs
follow bronchi down to the level of the alveolus
describe the path of the pulmonary veins
oxygen rich blood from the lungs into the left atrium
also provides venuous return from the bronchi
variable in number - usually 1 from each lobe
where does the bronchial artery arise from?
arises from the aorta to supply the bronchi and CT - tissues not participating in gas exchange
what are the 2 networks of lymphatic vessels within the lung?
superficial network - drains sub pleural tissue into vessel at hills of lung
deep network - drains deeper tissues via vessels running along airways
where do both sets of lymphatic networks merge? what is the common pathway after merging?
at the hilus –> tracheobroncial lymph nodes –> cramoal mediastinal nodes –> tracheal lymphatic vessels or thoracic duct
what are the 2 lymphatic networks responsible for?
removal of material phagocytosed by macrophages in airways
mounting an immune response to infectious agents
how are the lungs innervated?
autonomic supply from pulmonary plexus within the mediastinum
efferent: regulates activity of bronchial glands, smooth muscle of bronco (constriction, dilation)
afferent supply from: stretch receptors –> sneezing, mechanoreceptors –> coughing
where is the location of the lung within the bird, does it wrap around the heart?
dorsally located against vertebrae and ribs - does not wrap around heart
are the lungs of birds involved with ventilation
no - they are fixed volumes, air sacs expand for inspiration and ventilatin
what is hypoventilation?
insufficient airflow to the lungs due to partial obstruction of upper or lower airways = O2 depletion and CO2 accumulation in alveoli –> accumulation in blood
what is hyperventilation?
breathing more rapidly or deeply than necessary to maximally oxygenate blog floor
= surplus of fresh air into and out of lungs –> CO2 decrease in blood –> only slight increase in O2 in blood; almost already saturated
is ventilation uniform within the lung?
no
what are some localised variationsin alveolar perfusion?
- blood flow depend on body position (greater in ventral position due to hydrostatic pressure diff)
- pulm artery pressure may fall below alveolar pressure in dorsal part of lung –> capillaries squashed flat preventing blood flow
- during anaesthesia of large animal mismatching occurs due to pooling of blood in dorsal lung need to administer pure O2
how does alveolar airflow regulate in response to local hypoventilation
local hypoventilation = increased PCO2 in alveolus –> dilation of bronchiole –> localised increase in air flow
how does capillary blood flow regulate in response to local hypoventilation
local hypoventilation = decrease PO2 in alveolus = vasoconstriction of arterioles (hypoxic pulmonary vasoconstriction) –> localise reduction in blood flow
no point having blood to regions of lung without enough air, want blood going to regions with insufficient blood and too much air
how does alveolar airflow regulate in response to local hyperventilation
local hyperventilation = decrease in PCO2 in alveolus –> bronchiolar constriction –> localised decrease in airflow
how does capillary blood flow regulate in response to local hyperventilation
location hyperventilation = increase in PO2 in alveolus –> vasodilation –> localised increase in blood flow
