Lower Respiratory Tract: Structure and Function PDF

Dr Julie Townsend Senior Lecturer, [email protected] Lower Respiratory Tract: Structure and Function Animal Health and the Veterinary Profession, VETS10022 Intended Learning Outcomes: Outline the borders of the thoracic cavity and recall the importance of the pleura Describe the location, com...

Dr Julie Townsend Senior Lecturer, [email protected] Lower Respiratory Tract: Structure and Function Animal Health and the Veterinary Profession, VETS10022 Intended Learning Outcomes: Outline the borders of the thoracic cavity and recall the importance of the pleura Describe the location, composition and innervation of the diaphragm Recall the location and structure of the trachea Explain the branching of the tracheobronchial tree and the segmentations of the lungs Identify the lung lobation and lobulation patterns of different species Explain the blood supply (pulmonary vs systemic) and lymphatic drainage of the lungs Signposting: Bony thorax – thoracic vertebrae and ribcage – introduction to bones, imaging & terminology practical (week 2/3) Bony landmarks – Body Systems 1 practical (week 4) Introduction to respiratory system lecture (week 7) Dissection 1 : respiratory practical (week 7) You will use this information in the following CBLs: Coughing calf week 7 Poorly performing horse week 8 Snuffly rabbit consolidation case week 12 Boundaries of the thoracic cavity Difficult to visualise externally Cavity smaller than you may think! Bony Landmarks Tuber coxae A reminder! You covered this in Body Systems 1 practical Cranial and Caudal angle of scapula Olecranon Costal arch Factors limiting the size of the thoracic cavity Proximal forelimb & pectoral musculature Thoracic vertebrae spinous processes & epaxial muscles Cranial bulge of the diaphragm Pleurae: serous membranes – a recap Thoracic cavity o 2 pleural cavities o mediastinum Pleural cavities and lungs within them surrounded by pleura o Parietal pleura o Visceral pleura Functions of pleura o Reduce friction o Ventilation of lungs o Pleurisy/pneumothorax parietal pleura visceral pleura mediastinum thoracic wall pleural cavity Parietal Pleura: Consists of: – costal pleura - lines medial surface of ribs – mediastinal pleura – lines medial border of pleural cavity (which is the mediastinum) – diaphragmatic pleura – lines cranial surface of diaphragm Cupula pleurae Costal pleura Mediastinal pleura Remember all parts continuous with each other Cupula pleurae – extends beyond thoracic inlet – vulnerable to injury Diaphragmatic pleura Pleural recesses: Tranverse section of canine thorax Costodiaphragmatic recess Costomediastinal recess Clinically relevant Oesophagus Pleural cavity Left lung Aorta Right lung Heart Costal pleura costomediastinal recess Diaphragmatic pleura Costodiaphragmatic recess Diaphragm Schematic dorsal section of canine thorax Fig 4-21 Dyce Caudal vena cava Diaphragm: most important respiratory muscle Central Tendon Muscular periphery Lumbar vertebrae (crura) Caudal ribs Sternum Diaphragm position Arterial supply Musculophrenic a. (from internal thoracic a.) Phrenico-abdominal aa Venous drainage Phrenic veins Nerve supply Phrenic Intercostal nerves Fig 5.84: Done, Goody, Evans, Stickland. Colour Atlas of Veterinary Anatomy Diaphragmatic openings aortic hiatus Azygous Vein oesophageal hiatus Cisterna Chyli Aorta Dorsal Vagal Trunk Oesophagus Ventral Vagal Trunk caval foramen Caudal Vena Cava Right Phrenic Nerve Left Phrenic Nerve Trachea: Runs from cricoid cartilage to bifurcation at base of heart - Cricotracheal ligament Cartilaginous rings – – Incomplete dorsally Connected by elastic CT (annular ligaments) Trachealis muscle – bridges gap in cartilage ring – SMOOTH muscle – controls diameter of trachea – species variation in position trachealis muscle mucosa Respiratory Mucosa – pseudostratified columnar ciliated epithelium – contains mucous glands Honking Yorkies! cartilage Tracheal position within thoracic cavity: Trachea Oesophagus Cd Cr Fig 5.28: Done et al. Colour Atlas of Veterinary Anatomy Tracheobronchial Tree: L R L R Trachea Primary Primary bronchi Lobar (2o) bronchi Segmental (3o) bronchi System of airways allowing passage of air to lungs Decrease in size as branch distally Species differences - Tracheal bronchus found in pigs and ruminants Segmental bronchi aerate broncho-pulmonary segments Discrete portions of lung supplied by identifiable bronchi and blood vessels More clinical relevance in human at present? Distal tracheobronchial tree: bronchioles and alveoli – a reminder alveoli (sing - alveolus) Lungs: Free except at hilus (root), attached by…. Primary bronchus Pleurae Arteries and veins (pulmonary and bronchial) Nerves Lymphatics Expandable - no fixed size/shape, right larger Soft spongy texture, crepitate Colour depends on amount of blood in lung tissue Lung surfaces: Cranial view of canine lungs Lobation: C C A U D A L R Caudal lobe A Cranial lobe N Diaphragm I Middle lobe Heart A L Fig 5.24: Done et al. Colour Atlas of Veterinary Anatomy Left Lung Costal surface dog horse Left Lung Medial surface dog Horse NB: Cranial lobe not subdivided) Right Lung – costal and medial surfaces: A = cranial, B = middle, C = caudal and D = accessory lobes D O G C O W Right Lung- horse: (NB: no middle lobe) Lobulations: Lobules of lung tissue are surrounded by connective tissue – demarcates tissue Horse Carnivore Pig Sheep Cow Carnivores, Horse and Sheep: Framework is evenly distributed Pig and Cow: Lobules are distinctly demarcated Goat: Only the cranial and middle lobes are demarcated Lobulation of lung tissue: Blood Supply: Lungs receive TWO types of blood supply: Pulmonary Circulation Pulmonary Artery - deoxygenated blood Pulmonary Vein - oxygenated blood Systemic Circulation Bronchial Arteries - oxygenated blood Bronchial Veins - deoxygenated blood Thoracic lymphocentres: Dorsal thoracic centre Ventral thoracic centre Bronchial centre Mediastinal centre Thoracic duct (from cisterna chyli) Right Lymphatic Duct Adapted from Fig 5.27: Done et al. Colour Atlas of Veterinary Anatomy Lymphatic drainage of lungs: Pulmonary nodes Tracheobronchial nodes Bronchial lymphocentre Mediastinal lymphocentre Thoracic duct (L)/right lymphatic duct (R) Cranial vena cava Intended Learning Outcomes: Outline the borders of the thoracic cavity and recall the importance of the pleura Describe the location, composition and innervation of the diaphragm Recall the location and structure of the trachea Explain the branching of the tracheobronchial tree and the segmentations of the lungs Identify the lung lobation and lobulation patterns of different species Explain the blood supply (pulmonary vs systemic) and lymphatic drainage of the lungs