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7. Respiratory System.pdf

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McGill University
Anatomy & Cell Biology
ANAT 261
Craig Mandato

Naveen Sooknanan McGill Fall 2011 Respiratory System: The function of the respiratory system is to provide oxygen and remove carbon dioxide from the blood. There are three segments of the respiratory system: Conduction portion: o Consists of the nasal cavity, nasopharynx, oropharynx, larynx ,trachea, bronchi and bronchioles Includes regular and terminal bronchioles We will only look at the system starting at the trachea The transitional portion is made up of respiratory bronchioles, which have a discontinuous wall The conducting portion consists of the alveolar duct, alveolar sac and lung alveoli The conducting portion is meant to warm, humidify and clean the air of any debris It possesses glands which secrete liquids, to humidify, and mucous, to cling on to any floating debris Ciliated cells also help remove any foreign particles The transitional portion has an intermediate function between conducting and respiratory portions Some gas exchange occurs because of the discontinuous walls, but it also has the same functions as for the conduction portion This marks the beginning of gas exchange (no gas exchange occurs in the conducting portion) The respiratory portion is where the most gas exchange occurs Like in blood vessels, many of the peripheral components of the general respiratory structure will be missing, allowing for easier transfer of gases If a particle was missed by the conducting system, it will be ingested by a macrophage in the lungs, and we can see these in histological slides We will make a general structural plan for the respiratory system with the trachea, which contains all of the necessary components. As we go deeper, these components will start to go missing. Working from the trachea lumen out: Mucosa: o A pseudostratified ciliated columnar epithelium with goblet cells 1 Naveen Sooknanan McGill Fall 2011 The cilia act as hairs to trap particles The goblet cells secrete liquid which keeps the surface moist Goblet cells are very pale staining o Lamina propria Loose CT with fibroblasts and fibrocytes, elastic fibers and capillaries Loose CT has more cells, less fibers Elastic fibers allow extension and retraction of the tissue as you inhale/exhale Capillaries bring by warm blood which warms the air Submusosa: o Loose and dense irreg. CT o Serous and mucous glands (we will see what they are in a bit) o An outer layer of hyaline cartilage shaped like a horseshoe Connecting the two ends of cartilage is a region of smooth muscle known as the Trachealis muscle The opening of the cartilage is at the posterior (back) end Remember, no elastin fibers in hyaline cartilage Adventitia o The same as other adventitias; dense irreg. CT (type I collagen) with BVs The adventitias are all continuous with one another, and are generally made of the same materials o As the trachea branches out into deeper layers, these components are lost Looking closer at the wall of the trachea, we can see that there are 2 types of glands located in the submucosa. Both types of glands here are acinus (we will go over glandular structure later on) There are two types of secretion: serous and mucous o Serous secretion is thin and aqueous, meant to humidify the air as it comes into the system o Mucous is thick and slimy, and is meant to cover and protect the epithelium, as well as stick to foreign material Serous acinus glands are the smaller of the two glands o They are very acidophilic, meaning they stain a very dark pink o They have 1 layer of pyramidal cells which have a round nucleus located either in the middle or towards the outer base o Surrounded by myoepithelial cells which contract and squeeze, just like the sweat gland o They have aqueous (watery) secretion Mucous acinus glands are much larger than serous glands 2Naveen Sooknanan McGill Fall 2011 o They stain very poorly in H&E, making them appear very faded in slides This is due to the presence of many glycoproteins Just by this feature, they can be easily distinguished from serous cells o They also have 1 layer of pyramidal cells, but the cells are larger and paler o The nuclei are flattened and pushed towards the base of the cell o Thick, mucous secretion Both of these glands may appear disconnected from the surface because of place of section o In reality, they all connect and secrete into the lumen of the trachea Lamina Propria Trachea mucosa at high mag. Trachea at low mag.Mucous acinus Cilia (hairs) Goblet Cell Pseudostratified columnar epithelium
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