The Respiratory System

a.k.a. The Breathing System Breathing is the moving of air into and out of the lungs All cells need oxygen to perform activities (survive), and need to get rid of cellular waste (carbon dioxide). The respiratory system has this function. The average breathing rate = times per minute - it can become faster if necessary

2 Divisions of the Respiratory System 1.Upper Respiratory Tract parts outside the chest cavity: air passages of the nose - has hair just inside nostrils to block dust

nasal cavities - separated by the nasal septum - lined with nasal mucosa - upper portion has the olfactory nerves (senses smells) pharynx larynx upper trachea

2. Lower Respiratory Tract (parts found within the chest cavity) lower trachea lungs - bronchial tubes - alveoli ~ site of oxygen and carbon dioxide exchange between blood and air pleural membranes respiratory muscles - diaphragm - intercostal muscles

Pharynx ~ muscular tube; posterior to nasal and oral cavities; anterior to cervical vertebrae

3 parts 1. nasopharynx - uppermost portion - pathway for air only - composed of the soft palate, uvula, adenoid (pharyngeal tonsil) Eustachian tube opening - extends to the middle ear cavities - permits air to enter or leave middle ear so ear drums can vibrate properly

2. Oropharynx - behind the mouth - composed of the palatine tonsils lingual tonsils - destroys pathogens - part of the swallowing reflex

3. Laryngopharynx - lowest portion - opens into larynx or esophagus - works with oropharynx as part of the swallowing reflex

Larynx (a.k.a. the voice box) - functions: speaking and passageway between pharynx and trachea - composition -9 pieces of cartilage connected by ligaments - largest cartilage = thyroid cartilaqe -uppermost cartilage = epiglottis - during swallowing, closes over top of larynx

-vocal cords - on either side of glottis (opening between the cords) * during breathing, vocal cords are held at the sides of the glottis, so air passes freely into and out of the trachea. * during speaking, muscles of larynx pull vocal cords across the glottis and exhaled air vibrates the vocal cords to produce sound which can be turned in to speech

Trachea - approximately 4-5 inches long with C-shaped cartilage pieces - extends from the larynx to the primary bronchi

Bronchial Tree - branches of the trachea that enter the lungs are: - left and right primary bronchi - within the lungs, each primary bronchi branches into secondary bronchi that lead to the lobes of each lung - secondary bronchi branch into bronchioles (small ) - bronchioles end in alveoli (air sacs of lungs)

Lungs - located on either side of the heart; protected by the rib cage - extends from clavicle to diaphragm - has parietal pleura lining the chest wall and visceral pleura on the lung surface

Alveoli -functional units of the lung -each lung has millions of alveoli - each alveolus is surrounded by a network of pulmonary capillaries to allow for gas exchange through diffusion -since liquid is needed for the diffusion of gases, the alveoli have tissue fluid which make it similar to a wet air bag (side cling to each other) -to keep the cells from sticking together (due to the surface tension of the liquid), alveolar cells secrete a pulmonary surfactant that prevents the cells from sticking together.

Gas Exchange - Respiratory System Gases diffuse from an area of greater concentration to an area of lesser concentration. Gas diffusion occurs at two sites in the human body: the lungs and the body's tissues In the lungs, it occurs between the alveoli and pulmonary capillaries

-called external respiration (because the air is from the external environment) In the body tissues, it occurs between the systemic capillaries and the cells of the body - called internal respiration

The air we inhale is not pure oxygen: approximately 21% = oxygen approximately 0.04% = carbon dioxide approximately 78% = nitrogen -but since the body has no way of using the nitrogen, it is simply exhaled The air we exhale is not pure carbon dioxide: approximately 16% = oxygen approximately 4.5% = carbon dioxide

Diffusion Pathway of Gases Gases begin in the alveoli then go to the pulmonary veins, then to the heart, aorta, arteries, systemic capillaries (where gas is exchanged), veins, vena cava, heart, pulmonary artery, and finally back to the alveoli.

Respiratory Ailments respiratory acidosis = when breathing is not efficient and carbon dioxide accumulates in the body fluids and changes the blood chemistry respiratory alkalosis = when the breathing rate increases and carbon dioxide is very rapidly exhaled and blood chemistry changes - rare - can be caused by: ~ hyperventilation ~ traveling to a higher elevation *both are temporary

pneumonia = inflammation of the lungs caused by bacteria, viruses, or chemicals asthma = constriction of the bronchioles, excessive mucous production, or dyspnea (difficulty breathing); often caused by allergies pulmonary edema = excess fluid in the alveoli causes a decrease in gas exchange

Mechanisms of Breathing Terms ventilation = movement of air into (inhalation) and out of (exhalation) the lungs inhalation = bringing air into lungs; breathing in a.k.a. = inspiration active - requires energy exhalation = air being released from lungs; breathing out a.k.a. = expiration passive = no energy required

The Diaphragm is the muscle that allows rib cage to expand, letting air in. Tidal Volume: air in a normal inhale and exhale Minute Respiratory Volume: (MRV) amount in and out in one minute Inspiratory Reserve: amount past tidal volume. With a deep inhale

Expiratory reserve: amount beyond the tidal. Forceful exhale Residual Air: air remaining in lungs after forceful exhale. Coughing and sneezing are reflexes that remove irritants from the passages

Muscles Diaphragm = dome-shaped muscle below the lungs - flattens and moves downward when it contracts - responsible for bringing air into the lungs External Intercostal Muscles = muscles of ribcage - pull ribs upward and outward -helps expand chest cavity and bring air in Internal Intercostal Muscles = muscle of ribcage - pulls ribs downward and inward - helps constrict chest cavity during exhaling

Sequence of Breathing Events 1. diaphragm contracts and moves downward 2. external intercostal muscles pull ribcage upward and outward 3. lungs expand - causes the air pressure in the lungs to be lower than the air outside the lungs (atmosphere) 4. air in the atmosphere (outside the lungs) goes into the lungs to equalize the air pressure outside and inside the lungs

5. gases (oxygen and carbon dioxide) are exchanged between the alveoli and capillaries 6. diaphragm relaxes and moves upward 7. external intercostal muscles relax 8. lungs and chest cavity become smaller - causes the air pressure in the lungs to be higher than the air outside the lungs 9. air leaves the lungs and goes into the environment (atmosphere)

Reflexes couqhinq = reflex that is stimulated by irritants to the mucosa of the pharynx, larynx, or trachea - purpose: to remove the irritant - exhalation through mouth sneezing = reflex that is stimulated by irritants to the nasal mucosa - purpose: to remove the irritant - exhalation through nose

Disease emphysema = degenerative disease in which lung tissue loses its elasticity, so more energy is needed to exhale, leaving little energy for other activities