Respiratory System Exercises 36 and 37 1 Respiration

Respiratory System Exercises 36 and 37 1

Respiration • Entire process of exchanging gases between the atmosphere and body cells is called respiration. • Breathing or ventilation – moving air in and out of the lungs • External respiration – exchange of gases between the air in the lungs and the blood. • Internal respiration – exchange of gases between the blood and body cells. • Cellular respiration – use of O 2 and 2 production of CO 2 by cells of the body

Organs of the Respiratory System: • Two parts or tracts: • Upper respiratory tract (URT) – nose, nasal cavity, sinuses and pharynx • Lower respiratory tract – larynx, trachea, bronchial tree, and lungs 3

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Pharynx • Muscular tube lined by mucous membrane • Nasopharynx – – Respiration – lined with pseudostratified ciliated columnar epithelium • Oropharynx and Laryngopharynx – digestion and respiration – Nonkeratinized stratified squamous epithelium 7

Larynx • • • Connects pharynx and trachea Passage of air in and out of lungs Prevents foreign objects entering trachea Contains vocal cord – speech Muscle and 9 cartilages connected by elastic tissue 8

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Thyroid cartilage • “Adam’s Apple” • In female more rounded – shorter front to back – shorter vocal cords • In male more “V” shaped – longer front to back – longer vocal cords 10

• Cricoid cartilage – inferior to thyroid cartilage. Marks end of larynx • Epiglottic cartilage – elastic cartilage – Attaches to thyroid cartilage and supports epiglottis • Arytenoid cartilages and • Corniculate cartilages serve as sites for muscles that regulate tension on vocal cords and aid in closing larynx during swallowing • Cuneiform cartilages in mucous membrane – stiffen soft tissue 11

Vocal cords • Two sets of muscle and connective tissue covered by mucous membrane • Upper are “false vocal cords” –close off glottis to keep food out • Lower are true vocal cords – sound produced when air forced across them. • Pitch changed by amount of tension – modified by resonating chambers, and position of lips, mouth and tongue 12

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Trachea • • • “windpipe” Extends from larynx to primary bronchi (T 5) Smooth muscle – trachealis muscle 20 – “C” shaped rings of hyaline cartilage Open end of C posterior to allow esophagus to expand in • Lined with pseudostratifed ciliated columnar epithelium • Ridge – carina – most sensitive areas for 15 triggering cough reflex

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Bronchial Tree • Right and left primary bronchi – Right bronchus shorter, wider, more vertical • Secondary or lobar bronchi – 3 branches on right ; 2 on left • Tertiary or segmental bronchi – 10 branches on right; 8 on left • Bronchi lined with pseudostratified ciliated columnar epithelium • Held open by complete rings of cartilage 21

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Lungs • • Separated by mediastinum Pleural membranes Right has 3 lobes and two fissures, shorter Left has 2 lobes and one fissure, cardiac notch • Apex, base, hilum 24

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Pulmonary ventilation • Air moves depending on a pressure gradient • Before inspiration, pressure in lungs = pressure of atmosphere = 760 mm Hg • Inspiration increases the size of the thoracic cavity and ↓ pressure. • Diaphragm is the most important muscle of inspiration. - 75 % of air 27

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• Diaphragm is innervated by the phrenic nerve. • Decreases pressure 1 -3 mm Hg • Moves 500 ml of air • External intercostals also contract – move ribs up and sternum forward • Strenuous breathing – sternocleidomastoid, scalenes, and pectoralis minor 32

Expiration • Passive process – the diaphragm and external intercostals relax. Elastic recoil of stretched elastic fibers and surface tension of the liquid in the lungs decreases the lung volume and increases the pressure, forcing air out of the lungs. • Forced expiration involves contraction of the internal intercostal and abdominal muscles. 33

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Lung volumes • Clinically, respiration = one inhalation and one exhalation – respiratory cycle • Adult breathes about 12 X/ min. • Air volumes can be measured with a spirometer. 35

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Lung volumes • Tidal volume – air moved by one respiration, about 500 ml. • Inspiratory reserve volume – additional air taken in during maximal inhalation • Expiratory reserve volume – additional air expired during forced exhalation. • Residual volume – amount of air left in alveoli after forced expiration that keeps them inflated. 37

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Respiratory capacities • Inspirational capacity – tidal vol. + inspiratory reserve volume • Functional residual – residual volume + expir. res. vol. • Vital capacity - inspir. Res. + tidal vol. + expir. Res. • Total lung capacity – sum of all volumes 39

Other lung volumes • Anatomic dead space – due to conducting parts of system 40

Regulation of the Respiratory Center • Respirations can be modified by factors from inside and outside the brain. • Chemical influences: – Central chemoreceptors in medulla oblongata – Sensitive to changes in conc. of CO 2 and p. H – CO 2 + H 2 O ↔ H 2 CO 3 ↔ H+ + HCO 3 carbon + dioxide water carbonic hydrogen bicarbonate acid ion 41

Peripheral Chemoreceptors • Carotid bodies and aortic bodies • Stimulated by oxygen concentration decrease • Send impulses to respiratory centers, and breathing increases • Not triggered until O 2 is very low (50 mm Hg) 42