Physiology [PDF]

Dr. Chris Doumen Lecture 1

2402 : Anatomy/Physiology RESPIRATORY SYSTEM Introduction

TextBook Readings ♦ Pages 830 through 845. ♦ Make use of the figures

in your textbook ; a picture is worth a thousand words !

♦ Work the Problems and

Questions at the end of the Chapter

The respiratory system provides the body with the needed oxygen in order for our cells to carry out aerobic metabolism and generate the needed cellular energy in the form of ATP. In addition, the respiratory system aids in the final disposal of carbon dioxide. Four distinct processes accomplish these functions: • Pulmonary Ventilation • movement of air in and out of the lungs (actual breathing) • External Respiration • gas exchange between air and blood (alveolar function) • Transport of respiratory gases • transport of gases to and from tissues; performed by the C.V. system • Internal Respiration • gas exchange between blood and tissues (capillary function) The First two processes are purely a Respiratory system phenomena while the later two are purely Cardiovascular. Thus the complete process of respiration depends on the close cooperation of the two body system

General Anatomy

Collin County Community College District

1. External nose 2. Nasal cavity 3. Middle concha 4. Superior concha 5. Inferior concha 6. Nasopharynx 7. Oropharynx 8. Laryngopharynx 9. Larynx 10. Trachea 11. Apex of right lung 12. Superior lobe of right lung 13. Horizontal fissure 14. Middle lobe of right lung 15. Oblique fissure 16. Inferior lobe of right lung 17. Diaphragm 18. Left crus of diaphragm 19. Right crus of diaphragm 20. Aortic hiatus 21. Esophageal hiatus 22. Inferior lobe of left lung 23. Lingula 24. Oblique fissure 25. Cardiac notch

2402 : Anatomy/Physiology

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Functional Anatomy Respiratory system consists functionally out of • respiratory zone : actual sites of gas exchange (alveoli, alveolar ducts and respiratory bronchioles) • conducting zone : all other respiratory passage ways; serve as air conduits and air cleaners, humidifiers

Conducting Zone Organs 1. Nose Air enters via nostrils or external nares into nasal cavity. Vestibule area (inner part of nose) contains sweat glands and many hairs filters out coarse particles. Upper portion of Nasal cavity is lined with an olfactory mucosae; the olfactory epithelium lies right under the cribiform plate and contains the smell receptor cells as well as Bowman’s glands that secrete the mucus, trapping the odor molecules ( see figure below). Rest of nasal cavity lined with respiratory mucosa • it has ciliated pseudostratified epithelium • contains goblet cells and ducts from mucous (mucus) and serous (enzyme secreting) glands • Mucus traps dust, debris, bacteria; serous fluid contains lysozyme that destroys bacteria • Ciliated cells move trapped material towards throat where it is swallowed and digested by stomach juices • Cold causes cilia to move sluggish...accumulated mucus and fluid dribble out nose Nasal epithelium is lined with many thin walled veins that fill up with blood when temperature drops • helps in warming up the air ; also explains the easy nosebleeds Nasal Conchae are internal projections that increase mucosal surface area • enhance air turbulence such that heavier air particles are deflected against mucus coated surfaces ( anything bigger than 4 micron will end up in mucus) 2. Pharynx Commonly called the throat and connects nasal cavity with larynx and esophagus. It Serves as a common pathway for food and air. There are Three regions based on location: A. Nasopharynx: • located above point of food entry in body, towards nasal cavity • During swallowing uvula reflects superiorly, closing off naso pharynx • Also contains pharyngeal tonsils (up high, dorsally) B. Oropharynx: • extends from soft palate to epiglottis; it is an area where both fluid and air pass through

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2401 : Anatomy/Physiology

The diag ram sh ows the Ol f act ory Epi theli um with the Ol f act ory Rec ep t or cells. Bet wee n the e pitheli um and t he c ri bif orm pl ate i s a prop ri a l ami na wi th B ow mans glands C. Laryngopharynx • lies posterior to the epiglottis and extends the pharynx • at point of larynx, respiratory and digestive pathways diverge • air enters anteriorly into the larynx but food has "right of way" (air passage stops temporarily when swallowing) Interesting note is the epithelium lining that changes from pseudostratified to stratified sqaumous when going from Naso to Oro and Laryngo-pharynx ; this is an adaptation that reflects the increased friction and chemical trauma that goes with food intake.

3. Larynx • Attaches superiorly to hyoid bone and is posteriorly continuous with trachea • Framework consists out of nine cartilage plates connected by membranes and ligaments • Three important ones are • the large thyroid cartilage = Adam's apple • cricoid cartilage that anchors with the trachea inferiorly • Epiglottis = elastic cartilage structure at the top that seal off the laryngeal inlet during swallowing

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Within the larynx, under the epiglottis and underneath the pharyngeal mucosae are the vocal ligaments that form the core of the true vocal cords • vibrate when air rushes up from the lungs through the opening between the vocal cords (glottis) • speech involves the release of expired air and opening-closing of glottis Vocal folds can perform a sphincter function: glottis closes and inhaled air is retained when abdominal muscles contract; this raises intra-abdominal pressure; associated with emptying bladder, rectum or also used to equalize pressure on ear drums (Valsalva's maneuver).

4. Trachea The trachea is the Windpipe : descends from larynx into the mediastinum and ends by dividing into two primary bronchi Tracheal wall consists out of a typical • Mucosa : contains the pseudo stratified ciliated epithelium with many goblet cells • Submucosa : C.T. with many glands that secrete the mucous sheets within the trachea • Adventitia : C.T. reinforced internally by 16-20 C-shaped rings of hyaline cartilage Open ends of the cartilage rings which face the esophagus are connected by smooth muscle fibers called the t rache alis mu scle • this allows the esophagus to expand into the trachea during swallowing of food • contraction of trachealis muscle also decreases diameter of trachea and causes air to be expelled with greater force; used when we cough Las t cartil age of t rache a at s plit is c alle d Cari na; m uc os a is very s ensiti ve h ere an d forei gn objec t t ouching it c aus es vi ole nt c ou ghing

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2401 : Anatomy/Physiology

5. Bronchi and Subdivisions Division of trachea result in a right and left primary bronchus which penetrate right and left lung Once inside the lung, each divides into secondary bronchi • Right primary divides into 3 secondary to serve the 3 lobes of the right lung • Left primary divides into 2 secondary since left lung has only 2 lobes • Secondary bronchi now divide into smaller and smaller bronchi; about 23 orders of branching occurs Once diameter reaches less than 1 mm, the branches are called bronchioles. They will end into terminal bronchioles. Important changes occur in the walls of these passage ways • cartilage support changes into irregular plates instead of rings and eventually completely vanishing at the bronchiole level • epithelium changes from pseusdostratified to simple columnar and eventually simple cuboidal in the terminal bronchioles; no cilia nor mucus producing cells are present anymore in the bronchioles so that foreign material must be taken care off by macrophages • smooth muscle layer in the walls increases as the passageways becomes smaller

6. Respiratory zone (see Fig. 22-8, 22-9) • starts where the terminal bronchioli feed into the respiratory bronchioles • respiratory bronchioles lead into alveolar ducts that end in clusters of alveolar sacs (=bunch of grapes) • roughly 300 million alveoli account for most of lung volume and surface Res piratory Me mbrane • • • • •

Walls of alveoli are composed of a simple squamous epithelial cells; mostly Type I Cells external surfaces is densely covered with a cobweb of pulmonary capillaries cell wall of capillary and alveolar cells from the respiratory membrane or air-blood barrier gas exchange occurs by simple diffusion scattered among Type I cells are cuboidal type II cells; they secrete a fluid containing surfactant • alveolar macrophages, called dust cells, crawl on internal surfaces of alveoli and keep the lungs sterile • alveolar pores occur between adjacent alveoli to allow equalization of air pressure throughout the lung

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7. The Lungs (fig 22-10) Gross Anatomy • 2 lungs that take up the entire thoracic cavity except for the mediastinum ( occupied by heart, trachea, esophagus..) • The base of the lungs rests on the diaphragm • Left lung is smaller than right one due to presence of heart, the latter making the “cardiac notch impression” into the left lung • Left lung is divided into two lobes by oblique fissure • Right lung into 3 lobes by oblique and horizontal fissure • Each lobe contains pyramid shaped broncho-segments separated by c.t. septa • Each lung contains a total of 10 such segments and one can remove such segments without damaging the rest of the lung Blood Supply • Blood is delivered via the pulmonary artery • arteries branch alongside the bronchi and feed into a pulmonary capillary network surrounding the alveoli • blood returns to the heart via pulmonary veins • bronchial arteries arise from the aorta and supply lung tissue with blood and nutrients themselves • Nerve supply is via the pulmonary plexus that provides parasympathetic activity ( constrict the air tubes ) and sympathetic nerves ( to dilate )