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 cavityReduce 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 cavitySplits into right/left bronchiCartilage rings protect trachea from

collapsing

Lower Respiratory cont.

Bronchial TreePrimary bronchi – right/left branch

into smaller and small bronchiSecondary 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 O2/CO2 diffusion)

Lower Respiratory cont.

Lungs – left/right separated by mediastium, enclosed by diaphragm and thoracic cageRight 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 – exhalationElastic 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 volumeRemains in lungs, mixing with new

air…keeps O2 and CO2 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 mLMax 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 (Px) – 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.

PO2 in alveolar air = 104 mmHg

PO2 in capillary blood = 40 mmHgOxygen diffuses into blood

PCO2 in alveolar air = 40 mmHg

PCO2 in capillary blood = 45 mmHg

CO2 diffuses out of blood

Gas Transport

Oxygen TransportCombines with hemoglobin in red

blood cells to form oxyhemoglobin (red in color)

Oxygen molecules release and diffuse into tissues

CO2 TransportForms include carbaminohemoglobin

and bicarbonate ions