The Respiratory System
Respiration Cellular respiration-occurs in the
mitochondria, and releases energy from the breakdown of food molecules (ch. 9)
Respiration-process of gas exchange; blood carries oxygen from lungs to tissues and carries carbon dioxide in the opposite direction
Human respiratory system Includes
Nose pharynx Larynx Trachea Bronchi Lungs
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Air Into Lungs
Path of air Air enters nose and moves to the pharynx
(passageway for food and air) From pharynx, air moves to the trachea or
windpipe (epiglottis covers trachea when you swallow)
At these early places, air is warmed, moistened, and filtered by hairs in nasal cavity and mucus produced in cells in the nasal cavity and trachea to keep air clean
Path of air cont. From trachea, air moves to larynx (vocal
cords) and then into 2 passageways in the chest called bronchi (each leads to a lung)
Each large bronchus subdivides into smaller bronchi and those into bronchioles
Bronchioles subdivide into millions of alveoli or air sacs (150 million in each lung)
Each alveoli is surrounded by capillaries
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Aveoli
Gas exchange Alveoli provide huge surface area for gas
exchange Oxygen dissolves in moisture on inner
surface of alveoli and diffuses across capillaries into blood
Carbon dioxide in blood diffuses in the opposite direction
Air Inhaled air is 21% oxygen and .04% carbon
dioxide Exhaled air is <15% oxygen and 4% carbon
dioxide Lungs remove 1/3 of the oxygen and
increase carbon dioxide content 100 times
Oxygen in blood Oxygen dissolves easily and moves into
blood without difficulty Hemoglobin (oxygen-carrying protein in
blood) increase efficiency by increasing oxygen-carrying capacity of blood more than 60 times
Breathing structures Lungs sealed in two pleural membranes or
sacs in the chest cavity Below the chest cavity is the diaphragm, a
large flat muscle
Inhaling Diaphragm contracts Rib cage rises up to expand volume of
chest cavity Creates a partial vacuum in the chest cavity Atmospheric pressure pushes air into lungs
Exhaling Rib cage lowers Diaphragm relaxes Pressure in chest becomes greater than
atmospheric pressure Air is pushed back out
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How A Diaphragm Works
Control of breathing Controlled by medulla oblongata of brain Cells monitor amount of carbon dioxide in
blood As CO2 levels rise, nerve impulses from
breathing center cause diaphragm to contract and fill lungs with air