pleura & lungs Flashcards
what are the boundaries of the thoracic cavity?
thoracic cavity is bounded by thoracic inlet, thoracic wall (ribs) & diaphragm
what is the pleura?
a thin serous membrane that lines the thoracic cavity & forms 2 pleural sacs
what are the 2 layers of the pleura?
- serous layer (simple squamous epithelium & thin laminar propria)
- subserous layer (loose connective tissue)
what does the pleura release and what is the function of this fluid?
- serous-fluid (also called exudate)
- lubricates & reduces friction during movement of lungs
what is the mediastinum?
- mediastinum is where the plural sacs come together medially
- it is a partition comprising 2 serous membranes with connective tissue between
what type of pleura covers the lungs?
pulmonary visceral pleura covers lungs
name the type of pleura that forms the walls of the pleural sacs
parietal pleura
costal pleura, diaphragmatic pleura, mediastinal pleura
what is the pleural space and what fluid does it contain?
- pleural space is the very narrow space left between the pulmonary visceral pleura (lining lungs) & parietal pleura (lining pleural cavity)
- pleural space contains pleural fluid
function of pleural space & fluid (IMPORTANT)
- pleural space & fluid make lungs stick to inside of thoracic cavity (pleural space needs to be sealed)
- allows thoracic wall to move in & out with lungs stuck to pleura
- pulls lungs with expanding thoracic cavity during breathing
- lubricates for lung movement against inside of thoracic wall
what organs are not contained in the mediastinum
lungs, caudal vena cava & right phrenic nerve
what organs does the cranial mediastinum (pre-heart) contain?
- part of trachea
- part of oesophagus
- blood vessels
- nerves (sympathetic trunk, vagus, phrenic & recurrent laryngeal nerves)
- lymph nodes
- thymus
what organs/structures does the middle mediastinum (at level of heart) contain?
- heart & pericardium
- descending aorta
- part of oesophagus & trachea
- vagus & phrenic nerves
what organs/structures does the caudal mediastinum contain?
- aorta
- part of oesophagus
- dorsal & ventral vagal trunks
- LEFT PHRENIC NERVE
- caudal mediastinal lymph nodes
- pelica vena cava
- mediastinal recess
- pulmonary ligament
what is the pelica venae cavae?
a fold of pleura that connects caudal vena cava to mediastinum & contains the right phrenic nerve
what is the mediastinal recess and which lung lobe does it house?
- a small pouch formed between mediastinum & pelica venae cavae
- houses accessory lobe of right lung
what is the pulmonary ligament?
- a pleural fold connecting the mediastinum w medial surface of lung
which species have an opening in the ventral aspect of the caudal mediastinum? what is the clinical significance of this if the integrity of one side is interrupted?
- dog, cat & horse
- getting air in one side of the pleural cavity will lead to a bilateral lung collapse
what is the cupulae pleurae?
cranial most part of pleural sacs
what is the cost-diaphragmatic recess?
space between the diaphragmatic & costal pleura where no lung is present after lungs have expanded
do the lungs fill the pleural space completely?
lungs fill that pleural space completely, only leaving a capillary space between the pulmonary visceral pleura & parietal pleura
name the surfaces of the lungs
- costal surface (contact thoracic wall)
- medial surface (contacts mediastinum)
- diaphragmatic
what are the 3 borders of the lungs?
- dorsal (vertebral) border
- ventral (costal) border with cardiac notch
- basal (diaphragmatic) border - moves in & out of costa-diaphragmatic recess during breathing
which structures ventilate each lung lobe
each lobe is ventilated a large SECONDARY BRONCHUS which arise from a principal bronchus or trachea
name the lobes of the right lung
- cranial lobe
(tracheal bronchus in pigs & ruminants, has cranial & caudal segments in ruminants) - middle lobe (no middle lobe in horse)
- caudal lobe
- accessory lobe (in mediastianal recess)
name the lobes of the left lung
- left lung has 2 lobes in all species
- cranial lobe - has cranial & caudal segments (except horse)
- caudal lobe
what is the hilus of the lung?
- the hilus is the root of the lungs that
- anchors the lungs to the trachea & heart
- each root is formed by structures that enter & leave the lung at the hilus (principal bronchus, pulmonary & bronchial vessels, lymphatic vessels & nodes & nerves)
name the conducting structures of the lungs (tubes that move air along bronchial tree that are not involved in O2 exchange)
- trachea
- principle bronchi
- secondary bronchi + tracheal bronchus in pigs & ruminants
- tertiary bronchi
- bronchioles
name the respiratory structures of the lungs that are involved with oxygen exchange
- respiratory bronchioles
- alveolar ducts
- alveolar sacs & alveoli
describe the interstitial framework (stroma) of the lungs
- lobes are divided into lobules which are small units of pyramidal-shaped lung tissue surrounded by interlobular connective tissue
- pleura on the surface of the lung is simple squamous epithelium with a thin laminar propria
- elastic connective tissue provides elasticity for lungs to contract during expiration
describe the steps in inspiration & expiration
inspiration
- chest wall expands & diaphragm is pulled back during contraction
- creates negative pressure in pleural space
- lung walls are sucked outwards
- expands lungs & creates negative pressure in lungs
- air flows into lungs
expiration
- thoracic wall & diaphragm relax
- elasticity causes lungs to contract
- creates a positive pressure in lungs & expels air
what morphological changes occur as the duct system of the lungs branches?
- decrease in tube diameter
- mucosa is less folded
- pseudo-stratified columnar epithelium becomes simple columnar & then cuboidal
- reduction in cartilage
- changes in relative amount of muscle & connective tissue
- presence of alveoli
describe the mucosal layers of the bronchi & note the differences to trachea?
epithelium? laminar propria? beneath LP? smooth muscle? submucosa? last layer?
epithelium - is pseudostratified columnar ciliated with goblet cells (but fewer goblet cells than trachea)
laminar propria - loose connective tissue w lymphocytes & capillary network
beneath LP - thick layer of longitudinal elastic fibres
smooth muscle - circular to spiral arrangement
submucosa - contains sero-mucous bronchial glands (fewer than trachea) that produce a thin watery mucous that traps dust & humidifies air
fibroelastic/cartilaginous layer - cartilage plates (less continuous than trachea)
how are bronchioles different to a bronchus?
- smaller (less than 1 diameter)
- cartilage is absent
- epithelium is simple columnar or cuboidal
- decreasing number of goblet cells, cilia, lymphocytes, elastic fibres & muscle
what is the importance of the muscle layer in the bronchioles
muscle layer controls resistance to air flow & distribution of air to alveoli
which structure makes up the largest surface area of the respiratory system?
bronchioles are small but there are many of them giving them the largest cross-sectional area of the airway
what are the two type of bronchioles
- terminal bronchioles - end of the conducting part of the airway
- respiratory bronchioles - have alveoli budding off them
name the type of cell that replaces goblet cells in the respiratory bronchioles & their function
club cells replace goblet cells & secrete lipoprotein surfactant
- surfactant reduces water tension and allows a thin film of water to line alveoli without forming droplets
what are the 3 cell types of the alveoli & their functions
- squamous alveolar epithelial cells (type I) - flat & thin to maximise gas exchange & are in very close contact with capillaries
- cuboidal alveolar epithelial cells (type II) - contain surfactant which reduces surface tension (allows alveoli to easily expand)
- alveolar macrophages - remove dust particles & other unwanted material
describe the blood gas barrier (important!)
oxygen must travel across the blood-gas barrier to be absorbed into the blood
blood gas-barrier consists of 3 cell layers:
- type 1 epithelial cells
- basement membrane
- endothelial cells of the capillaries
what is the function of the alveoli?
- alveoli are delicate to enable gaseous exchange
- > air must be carefully conditioned (warmed, humidified & filtered to remove dust) before reaching alveoli to avoid damage
- > air must be delivered & removed at correct rate (aided by smooth muscle in airways)
describe the functional blood supply of the lungs
- provides oxygenated blood for rest of body
- provides nutrition to alveoli
- consists of pulmonary arteries & veins
describe the nutritional blood supply to the lungs (bronchial circulation)
- bronchial circulation provides nutrition & O2 to bronchial tree, stroma & pleura
- blood vessels arise from broncho-oesophageal artery which drains into bronchial arteries, capillary beds, venous plexuses & then either the bronchial veins (azygous vein) or pulmonary veins (left atrium)
name the 2 lymphatic networks of the lungs of the lungs
- superficial network - in the sub pleural connective tissue
- deep network - follows the bronchial tree & contains lymph nodes
which nerves innervate the lungs & what are their actions?
- vagus (parasympathetic) - responsible for bronchi-constriction
- sympathetic - responsible for broncho-dilation & vasoconstriction of bronchial arteries (nutritional blood supply to bronchial tree)
- nerves follow bronchial tree with vessels
which nerves innervate the lungs & what are their actions?
- vagus (parasympathetic) - responsible for bronchi-constriction
- sympathetic - responsible for broncho-dilation & vasoconstriction of bronchial arteries (nutritional blood supply to bronchial tree)
- nerves follow bronchial tree with vessels
which part of the lung is the last to mature during embryonic development and how does this affect premature mammals?
- alveoli are last to develop
- premature mammals may have poorly formed alveoli that do not produce enough surfactant, resulting in breathing difficulties
