The Respiratory System Breathe in… Breathe out…

Respiration Respiration – process of gas exchange between the atmosphere and body cells Events include: 1. Ventilation (air in/out) 2. Gas exchange (blood/air) 3. Gas transport (blood) 4. Gas exchange (blood/body cells)

Organs of Respiratory System Upper respiratory tract: nose, nasal cavity, paranasal sinuses, pharynx Lower respiratory tract: larynx, trachea, bronchial tree, lungs

Upper Respiratory Tract Nose – internal hairs guard nostrils Nasal cavity – hollow space behind nose Nasal septum – divides cavity into right/left portions Nasal conchae – bones that support mucous membrane Mucous membrane is rich in pseudostratified epithelium w/ goblet cells (mucus to trap dust etc), and it helps moisten and warm air

Upper Respiratory cont. Paranasal sinuses – air filled spaces w/ in maxillary, frontal, ethmoid, and sphenoid bones that open into nasal cavity Reduce weight of skull Pharynx – behind oral/nasal cavity; passageway for food to esophagus or air to larynx

Lower Respiratory Tract Larynx – top of trachea; conducts air in/out of trachea and prevents foreign objects from entering trachea Houses vocal cords Thyroid cartilage = Adam's apple Epiglottis – helps prevent food/liquid from entering air passages Laryngitis – mucous membrane of larynx becomes inflamed due to infection  causes hoarseness or lack of voice

Lower Respiratory cont. Trachea – windpipe; flexible, cylindrical tube (2.5 cm in diameter) that extends downward in front of esophagus into thoracic cavity Splits into right/left bronchi Cartilage rings protect trachea from collapsing

Lower Respiratory cont. Bronchial Tree Primary bronchi – right/left branch into smaller and small bronchi Secondary bronchi, tertiary bronchi, lead to bronchioles which then branch into alveolar ducts  alveolar sacs  alveoli (provide large surface area for simple squamous epithelial cells for O 2 /CO 2 diffusion)

Lower Respiratory cont. Lungs – left/right separated by mediastium, enclosed by diaphragm and thoracic cage Right lung (3 lobes) larger than left lung (2 lobes) Contains air passageways, alveoli, blood vessels, connective tissue, lymphatic tissue, and nerves

Breathing Mechanism Inspiration – inhalation Atmospheric pressure (760 mmHg at sea level) due to weight of air forces air into lungs when pressure on lungs decreases Diaphragm contracts (moves downward) and external intercostal muscles contract to expanding thoracic cavity and thus lowering pressure on lungs  air rushes into lungs

Breathing Mechanism cont. Expiration – exhalation Elastic recoil of tissues from surface tension results when diaphragm and external intercostals relax  increasing pressure above normal mmHg (forcing air out) Internal intercostal and abdominal muscles are used when forceful expiration is needed  squeezing air out of lungs

Respiratory Air Volumes and Capacities Respiratory cycle – one inspiration and the following expiration Tidal volume – volume of air that enters (or leaves) the lungs during a single cycle 500 mL of air is the resting tidal volume Inspiratory reserve volume – volume taken up by air from forced inspiration This extra air is appx 3,000 mL max

Respiratory Volumes cont. Expiratory reserve volume – volume of air that can be forced out after the resting tidal volume (1,100 mL) Even after the most forceful expiration, 1,200 mL remains  residual volume Remains in lungs, mixing with new air…keeps O 2 and CO 2 levels from fluctuating greatly

Respiratory Volumes cont. Respiratory capacities – result of combining 2 or more of the “volumes” Vital capacity – inspiratory reserve (3,000), tidal volume (500), and expiratory reserve (1,100) = 4,600 mL Max amt of air a person can exhale after taking the deepest possible breath

Respiratory Volumes cont. Inspiratory capacity – tidal volume plus inspiratory reserve volume = max volume of air a person can inhale after a resting expiration (3,500) Functional residual capacity – expiratory reserve plus residual volume = air that remains in the lungs following exhalation of tidal volume (2,300) Total lung capacity – vital capacity plus residual volume = total amount of air the lungs can hold (5,800)

Can you abbreviate? TV IRV ERV RV IC FRC VC TLC Tidal volume Insp. reserve vol Exp. reserve vol Residual vol Insp capacity Func residual cap Vital capacity Total lung cap Table 16.2 Summarizes

Control of Breathing Respiratory center: located in pons and medulla oblongata Neurons in medullary rhythmicity area activate muscles for breathing (muscles relax so body may passively exhale) Neurons in pneumotaxic area of pons control breathing rate

Alveolar Gas Exchanges 2+ thicknesses of epithelial cells separate air in sacs from blood in capillary (Respiratory membrane) Partial pressure (P x ) – amt of pressure each gas contributes to the total Concentrations of dissolved gases in liquid (blood) is proportional to the partial pressure Gases diffuse from higher partial pressure to lower partial pressure til equilibrium is reached

Gas Exchange cont. P O2 in alveolar air = 104 mmHg P O2 in capillary blood = 40 mmHg Oxygen diffuses into blood P CO2 in alveolar air = 40 mmHg P CO2 in capillary blood = 45 mmHg CO 2 diffuses out of blood

Gas Transport Oxygen Transport Combines with hemoglobin in red blood cells to form oxyhemoglobin (red in color) Oxygen molecules release and diffuse into tissues CO 2 Transport Forms include carbaminohemoglobin and bicarbonate ions