RESPIRATORY SYSTEM This resource is licensed under the

RESPIRATORY SYSTEM This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License

Objectives Students should be able to : 1. Describe the structure of the conducting and exchange parts of the respiratory system and relate this to function. 2. Compare the microscopic structure of the walls of trachea, bronchi and bronchioles. 3. Examine the structure of the alveolar wall.

SLIDE 62 Trachea (rat) At low magnification identify the principal features. ? ? ? ? ? 1. 0 mm

SLIDE 62 Trachea (rat) At low magnification identify the principal features. Muscle (skeletal) Cartilage of trachea Ventral Dorsal Lumen of trachea Oesophagus Thyroid Line across lumen is a fold in the section 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall What type of cartilage is present? 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall What type of cartilage is present? Hyaline. cartilage lumen 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall Why is there a need for cartilage? cartilage lumen 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall Why is there a need for cartilage? Gives support during inspiration and expiration (radially and longitudinally). Its rigidity prevents collapse of the trachea. cartilage lumen 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall Give two reasons why the cartilage rings are incomplete. cartilage lumen 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall Give two reasons why the cartilage rings are incomplete. Radial expansion of the trachea is possible. Bolus of food can pass down the oesophagus. cartilage lumen 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall Find the trachealis muscle at the dorsal aspect of the trachea. 1. 0 mm

SLIDE 62 Trachea (rat) Tracheal wall What lies immediately dorsal to this? 250 µm

SLIDE 62 Trachea (rat) Tracheal wall What lies immediately dorsal to this? The oesophagus. trachealis muscle oesophagus lumen of oesophagus 250 µm

SLIDE 62 Trachea (rat) Trachealis muscle Classify the type of muscle present. 50 µm

SLIDE 62 Trachea (rat) Trachealis muscle Classify the type of muscle present. Smooth muscle. smooth muscle spindle shaped cells with single, central nucleus 50 µm

SLIDE 62 Trachea (rat) Tracheal wall Examine the epithelium lining the trachea. 1. 0 mm

SLIDE 62 Trachea (rat) Epithelial lining What type of epithelium is it? 25 µm

SLIDE 62 Trachea (rat) Epithelial lining What type of epithelium is it? Pseudostratified, ciliated, columnar epithelium. cilia mucous on surface pseudostratified epithelium 25 µm

SLIDE 151 Trachea epithelial lining Pseudostratified, ciliated, columnar epithelium from cat trachea. 25 µm

SLIDE 62 Trachea (rat) Tracheal wall Are there any glands in the submucosa? 50 µm

SLIDE 62 Trachea (rat) Tracheal wall Are there any glands in the submucosa? Yes. submucosal glands epithelium lumen 50 µm

SLIDE 62 Trachea (rat) Tracheal wall What is their function? submucosal glands epithelium lumen 50 µm

SLIDE 62 Trachea (rat) Tracheal wall What is their function? They are mucoserous glands; secreting mucous. submucosal glands epithelium lumen 50 µm

SLIDE 63 Trachea (cat) Stained for elastic fibres Observe the transversely sectioned elastic fibres. Where are they located? 50 µm

SLIDE 63 Trachea (cat) Stained for elastic fibres Observe the transversely sectioned elastic fibres. Where are they located? Just below the epithelium. Why are the fibres longitudinally arranged, and why are they so abundant? band of black stained elastic fibres in lamina propria. epithelium pseudostratified columnar, ciliated. 50 µm

SLIDE 63 Trachea (cat) Stained for elastic fibres Observe the transversely sectioned elastic fibres. Where are they located? Just below the epithelium. Why are the fibres longitudinally arranged, and why are they so abundant? Part of the elastic continuum of the lung. Add to the elastic recoil of the lungs after inspiration and expiration. band of black stained elastic fibres in lamina propria. epithelium pseudostratified columnar, ciliated. 50 µm

SLIDE 63 Trachea (cat) Stained for elastic fibres Note the presence of lymphocytes. How are they distributed? 25 µm

SLIDE 63 Trachea (cat) Stained for elastic fibres Note the presence of lymphocytes. How are they distributed? Mostly sub epithelial, but some can be seen amongst the epithelial layer. L L : lymphocytes L 25 µm

Dog Lung deflated (adult) Ca Crcr . Crca Left lung in situ. Dog. Crcr - Cranial lobe, pars cranialis Crca - Cranial lobe, pars caudalis Ca - Caudal lobe

Dog Lung inflated (adult) . Left lung inflated in situ.

SLIDE 67 Lung (adult) Examining the lung at low magnification. What covers its surface? Ca Crcr Crca Left lung in situ. Dog. Crcr - Cranial lobe, pars cranialis Crca - Cranial lobe, pars caudalis Ca - Caudal lobe Left lung inflated in situ. 1 mm

SLIDE 67 Lung (adult) Examining the lung at low magnification. What covers its surface? Visceral pleura. outer surface of lung covered by visceral pleura B : blood vessels B B small bronchus 1 mm

SLIDE 67 Lung (adult) Visceral pleura. Surrounds the lungs. surface mesothelium connective tissue layer with elastic fibres 100 µm

Scanning electron micrograph of adult sheep lung Shows cut surface of the lung. B : cut bronchioles B alveoli B 50 µm

Lung How can you distinguish between a bronchus and a bronchiole?

Lung How can you distinguish between a bronchus and a bronchiole? Lining cells Bronchus Bronchiole pseudostratified ciliated columnar epithelium

Lung How can you distinguish between a bronchus and a bronchiole? Bronchus Bronchiole Lining cells pseudostratified ciliated columnar epithelium Cartilage plates of cartilage absent

Lung How can you distinguish between a bronchus and a bronchiole? Bronchus Bronchiole Lining cells pseudostratified ciliated columnar epithelium Cartilage plates of cartilage absent Mucosal glands present absent

Incised Lung Lobe. Dog. 2 larger airways have been opened to show branching of the bronchial tree. V-shaped dark areas are post-mortem artefacts – blood has pooled in dependent areas.

SLIDE 68 Lung (adult) Bronchus Low magnification view of bronchus. Plates of cartilage can be identified. Incised Lung Lobe. Dog. 2 larger airways have been opened to show branching of the bronchial tree. V-shaped dark areas are post-mortem artefacts – blood has pooled in dependent areas. 1. 0 mm

SLIDE 68 Lung (adult) Bronchus Low magnification view of bronchus. Plates of cartilage can be identified. cartilage lumen cut edge of section 1. 0 mm

SLIDE 68 Lung (adult) Bronchus Identify : plates of cartilage smooth muscle glands lining epithelium C 250 µm

SLIDE 68 Lung (adult) Bronchus Identify : plates of cartilage smooth muscle glands lining epithelium C : cartilage G : glands C M : smooth muscle M G epithelium lumen 250 µm

SLIDE 68 Lung (adult) Bronchus Typical respiratory tract epithelium lines the bronchus. Pseudostratified, ciliated, columnar with goblet cells. Further down as the bronchus gets smaller the epithelial lining also reduces in height. 25 µm

SLIDE 68 Lung (adult) Bronchus Typical respiratory tract epithelium lines the bronchus. Pseudostratified, ciliated, columnar with goblet cells. Further down as the bronchus gets smaller the epithelial lining also reduces in height. G : goblet cells RB : blood cells in capillary G mucous on surface G RB cilia 25 µm

SLIDE 68 Lung (adult) Another bronchus from slide 68 0. 5 mm

SLIDE 68 Lung (adult) Identify : epithelium smooth muscle blood vessels glands cartilage Smooth muscle runs in a spiral around the bronchus. 100 µm

SLIDE 68 Lung (adult) Identify : epithelium smooth muscle blood vessels glands cartilage Smooth muscle runs in a spiral around the bronchus. epithelium blood vessel muscle cartilage glands 100 µm

SLIDE 67 Lung (adult) At low magnification identify : bronchus bronchiole large blood vessels 1. 0 mm

SLIDE 67 Lung (adult) At low magnification identify : bronchus bronchiole large blood vessels bronchiole bronchus 1. 0 mm

SLIDE 67 Lung (adult) Bronchus and blood vessels BV BR : bronchus BV : blood vessel BR 0. 5 mm

SLIDE 67 Lung (adult) Although there is little evidence of cartilage in this structure, some glands can be seen suggesting that this is a small bronchus. glands 250 µm

SLIDE 67 Lung (adult) Bronchiole Why is cartilage absent from the wall of a bronchiole? 250 µm

SLIDE 67 Lung (adult) Bronchiole Why is cartilage absent from the wall of a bronchiole? To allow a change in diameter. They must be flexible in a way that minimises ‘dead space’ but does not cause too great a resistance to air flow. M : muscle epithelium M 250 µm

SLIDE 67 Lung (adult) Respiratory Bronchiole Respiratory bronchioles are lined by a cuboidal epithelium. Alveolar ducts open into alveoli. blood vessel alveoli 100 µm

SLIDE 67 Lung (adult) Respiratory duct/sac The lips of the alveoli contain smooth muscle. Respiratory bronchiole → alveolar ducts → alveolar sacs → alveoli. 100 µm

SLIDE 67 Lung (adult) Respiratory duct/sac The lips of the alveoli contain smooth muscle. Respiratory bronchiole → alveolar ducts → alveolar sacs → alveoli. AD alveolar ducts A A AS alveolar sacs AD AS A : alveoli 100 µm

Transmission electron micrograph of adult lung Section through the alveoli of the lung. alveolar type I (flattened, squamous like cells) are the main lining cell of the alveolus. alveolar type II cells form about 10%. Numerous capillaries lined with endothelial cells and blood cells within. 2. 5 µm

Transmission electron micrograph of adult lung Section through the alveoli of the lung. alveolar type I (flattened, squamous like cells) are the main lining cell of the alveolus. alveolar type II cells form about 10%. Numerous capillaries lined with endothelial cells and blood cells within. RB A A : alveolar spaces RB RB : erythrocytes RB A 2. 5 µm

Transmission electron micrograph of adult lung Briefly describe the blood gas barrier in the alveolus. 1. 0 µm

Transmission electron micrograph of adult lung Briefly describe the blood gas barrier in the alveolus. The walls of the alveoli and the walls of the capillaries are only one cell thick. They share a basal lamina so minimising the blood gas barrier. A A : alveolar cell BL E : endothelial cell N : nucleus of endothelial cell E RB BL : basal lamina N RB : red blood cell 1. 0 µm

SLIDE 70 Lung (marsupial mouse) Injected lung for alveolar phagocytes. 25 µm

SLIDE 70 Lung (marsupial mouse) Injected lung for alveolar phagocytes. alveoli phagocytes 25 µm

SLIDE 70 Lung (marsupial mouse) alveolar phagocytes What do they look like? 25 µm

SLIDE 70 Lung (marsupial mouse) alveolar phagocytes What do they look like? Wandering irregular shaped cells. On this slide with prominent dark inclusions. What is their function? P : phagocytes P P 25 µm

SLIDE 70 Lung (marsupial mouse) alveolar phagocytes What do they look like? Wandering irregular shaped cells. On this slide with prominent dark inclusions. What is their function? The lung’s defence mechanism to protect the inner surfaces. P : phagocytes P P 25 µm

SLIDE 71 Lung In this slide the blood vessels have been injected with a red dye. 1 cm

SLIDE 71 Lung injected for blood vessels Note the arrangement of the capillaries supplying the alveoli. What happens to these capillaries during inspiration and expiration? 100 µm

SLIDE 71 Lung injected for blood vessels Note the arrangement of the capillaries supplying the alveoli. What happens to these capillaries during inspiration and expiration? During inspiration the lungs expand the resulting traction to the capillaries increases the blood flow through the capillary bed. Blood is drawn from the pulmonary artery. During expiration resistance to the blood flow increases. 100 µm

SLIDE 72 Lung stained for elastic tissues Examine this section stained for elastic tissue. At low magnification. 1 cm

SLIDE 72 Lung stained for elastic tissues Note the distribution of these fibres throughout the section especially in relation to the alveolar ducts and alveoli. elastic fibres and smooth muscle cells below the cuboidal lining of the alveolar ducts elastic fibres surrounding alveoli 100 µm

SLIDE 72 Lung stained for elastic tissues Why are there so many elastic fibres in the lung? 50 µm

SLIDE 72 Lung stained for elastic tissues Why are there so many elastic fibres in the lung? The lung is stretched during inspiration. The elastic fibres enable the elastic recoil during expiration. elastic fibres 50 µm

SLIDE 72 Lung stained for elastic tissues Why does their distribution differ in different parts of the respiratory tract? elastic fibres 50 µm

SLIDE 72 Lung stained for elastic tissues Why does their distribution differ in different parts of the respiratory tract? There are more fibres in the parts that expand the most, the respiratory ducts and the alveoli. elastic fibres 50 µm

Lectures. First Year Histology. 012. Respiratory. Gross Anatomy Correlates. Histology Slides and Stains. This version. Dr C. Lawson. J. Bredl. 02 -09 -03. S. Frean. 08 -09 -03. Tanya Hopcroft. 2007.