Respiratory System

functions:

• used to intake and expel air
• site of oxygen and carbon dioxide exchange with the blood
• maintains acid and base balance
• speech
• smell and taste senses
• traps and expel pathogens

nose and nasal cavities

• olfactory nerve - sense of smell
• palates- separate nasal and oral cavities
• nasal cavity-
    * warms and moistens inhaled air
    * uses mucus and cilia to trap dust and pathogens

    → removed by sneezing or swallowing

pharynx : throat; small muscular passageway

• three regions:
    * nasopharynx - air
    * orapharyx and laryngopharynx - both food water and air

larynx: 9 pieces of cartilage

• closes off the trachea when food is swallowed (epiglottis)
• produces sound (vocal cords)
• air passage between pharynx and trachea

lower respiratory tract:

• trachea
    * rigid tube supported by rings of cartilage (doesnt collapse)
    * brings air into lungs
• bronchi
    * at the end of trachea, right and left branches of bronchi enter each lung
    * each primary bronchi subdivides into smaller bronchi
• alveoli
    * bronchioles divide into structures called alveoli
    * gas exchange in blood occurs in the alveoli

    → each alveolus is encased by capillaries

    → to facilitate diffusion between alveoli and capillaries, both have thin walls

gas exchange: gasses diffuse from high to low concentration

lungs:

• large, spongy organs that have an opening for bronchi
• role is to expand and contract to facilitate breathing
• no muscle tissue
• depend on nearby muscle in ribs and diaphragm to expand and contract

respiratory muscle:

• intercostals
    * located between ribs
    * pull ribs up and out when contracted
• diaphragm
    * main breathing muscle
    * located under lungs
    * flattens and enlarges the thoracic cavity when contracted (relaxed=dome)

pulmonary ventilation = breathing

• inspiration (breathe in) and expiration (breathe out)
    * both depends on

    → respiratory muscles (lungs have no muscle tissue)

    → difference between air pressure within the lungs and outside the body

inspiration

• air is inhaled
• muscles contract ; diaphragm is flattened, muscles in ribs pull up and out
• this causes expansion in thoracic cavity (more space)
• as a result, low pressure in lungs and high pressure outside
• air flows from high to low pressure; fills lungs

expiration

• muscles relax
• diaphragm bulges upward; rib muscles stop pulling
• this causes a reduction in size in thoracic cavity (less space)
• as a result, high pressure in lungs and low pressure outside
• air flows from high to low pressure; lungs empty ; air is exhaled

pleura

• because lungs expand and contract, its important that friction is reduced
• therefore, lungs surrounded with a lining called pleura
• pleura is filled with serous fluid. this fluid
    * reduces friction
    * maintains pressure needed for breathing
• pleura consists of two linings with a fluid filled space between then

visceral pleura

• covers the surface of lungs

parietal pleura

• lines the thoracic cavity

pleural cavity

• filled with serous fluid, called pleural fluid
• lubricates to reduce friction
• maintains pressure for breathing
• the pressure in pleural cavity allows lung to expand

neural control of breathing

• stimulation to breathe comes from the autonomic nervous system

medulla oblongata

• contains a respiratory center that causes the intercostal and diaphragm to contract

pons

• contains two centers that can influence breathing rhythms

factors that influence breathing

• co2 (main regulator)- high levels signals medulla to high breathing
• oxygen levels- low oxygen signals medulla to high breathing
• hydrogen ions/ ph- low ph signals medulla to high breathing
• stretch- lungs stretching inhibits signals for inhalation
• pain and emotion- limbic system affects breathing in response to emotions

resistance and air flow- like blood flood, greater resistance means less airflow

diameter of bronchioles

• bronchiole dialation- larger diameter and more airflow
• bronchiole constriction- smaller diameter and less airflow

pulmonary compliance

• elasticity of lung tissue allows more airflow

measurement of ventilation

• breathing through a spirometer gives information about lung capacity
• if lungs showing increased resistance and decrease capacity, this can indicate disease

inspiratory reserve volume

• amount of air inhaled during max effort

vital capacity

• amount of air of that can be inhaled and exhaled with max effort

total lung capacity

• vital capacity + residual volume

tidal volume

• amount of air inhaled and exhaled during normal breathing; “quiet breathing”

expiratory reserve volume

• amount of air exhaled during max effort

residual volume

• amount of air that always remains in lungs after exhalation