Chapter #16: Respiratory System
Respiration:The respiratory system consists of tubes that _filter__ incoming air and __transport_ it intothe microscopic
alveoli where gases are _exchanged___. What are the four processes of respiration? Ventilation, external
respiration, gas transport between the lungs and body cells, and internal respiration
Oxygen use and CO2 production by the cells is called _cellular_ _respiration_.
Respiratory Organs:
The organs of the respiratory tract can be divided into two groups: the upper respiratory tract (nose, nasal cavity,
sinuses, and pharynx), and the lower respiratory tract (larynx, trachea, bronchial tree, and lungs).
Nose:
The nose, supported by _bone___ and cartilage, provides an entrance for air in which air is filtered by coarse
___hairs___ inside the nostrils.
Nasal cavity:
The nasal cavity is a space posterior to the nose that is divided medially by the _nasal septum__.
Nasal conchae:
What are they? Turbinate bones, which curl in from the walls of the nasal cavity, dividing it into passages
What is their function? To divide the nasal cavities into three passageways, and increase surface area to warm
and filter incoming air
Cilia:
Particles trapped in the mucus are pushed to the __pharynx___by ciliary action, swallowed, and carried to the
_stomach___, where gastric juice destroys any microorganisms in the mucus.
Paranasal sinuses:
What four bones are they found in? Maxillary, frontal, ethmoid, sphenoid
What is their function? Reduce weight of skull, serve as resonating chambers for voice quality
Pharynx:
The pharynx is a common passageway for __air_____ and __food____, and it aids in producing
sounds for __speech______.
Larynx:
The larynx is an enlargement in the airway, superior to the _trachea__ and inferior to the _pharynx__.
It helps keep particles from entering the trachea and houses the vocal cords.
The larynx is composed of a framework of _muscle____ and _cartilage___ bound by elastic tissue.
What is the largest cartilage called? (Hint: it is known as the Adam’s apple). Thyroid cartilage
Inside the larynx, two pairs of folds of muscle and connective tissue covered with mucous membrane make up
the __vocal cords__. What is the upper pair called? False vocal cords (vestibular folds)
What is their function? To help close larynx during swallowing
What is the lower pair called? True vocal cords
What is their function? To vibrate to produce sounds when air is forced between them
What is the name of the triangular slit, through which air passes? Glottis
What closes this space off when swallowing? Epiglottis
Trachea:
The trachea extends downward anterior to the __esophagus_and into the thoracic cavity, where it splits into
right and left _bronchi___.
What is the inner wall lined with? Ciliated mucous membrane
Why? It filters incoming air and moves trapped particles upwards into the pharynx
The tracheal wall is supported by 20 incomplete cartilaginous rings. Why are they incomplete and not complete?
The open area at the back permits expansion of esophagus when swallowing food
Bronchial tree:
The bronchial tree consists of branched tubes leading from the _trachea__ to the _alveoli___.
The bronchial tree begins with the two primary ___bronchi____, each leading to a lung.
Where do these lead? To secondary bronchi
How many secondary bronchi are on each side? Three on right and two on left
What are the smallest branches of the bronchial tree called? Bronchioles
Do they have cartilage in their walls? No
Where does the actual gas exchange take place? In the alveoli
Lungs:
The right and left soft, spongy, cone-shaped lungs are separated medially by the __mediastinum__ and are
enclosed by the _diaphragm_____ and thoracic cage. Aprimary bronchus and large blood vessels enter each
lung.
A layer of serous membrane, the visceral ___pleura__, attached to the lung, folds back to form the
__parietal pleura_.
The __parietal__ pleura lines the thoracic cavity; serous fluid lubricates the pleural cavity between these
two membranes.
Each lobe is composed of lobules that contain air passages, alveoli, nerves, blood vessels, lymphatic vessels, and
connective tissues.
Breathing Mechanism:
__Ventilation__ (breathing), the movement of air in and out of the lungs, is composed of 2 processes:
__inspiration___ and _expiration__.
Inspiration:
__Atmospheric_____ pressure is the force that moves air into the lungs.
What happens when pressure on the inside of the lungs decreases? Air flows in from the atmosphere
Air pressure inside the lungs is decreased by __increasing___ the size of the thoracic cavity; due to
surface tension between the two layers of pleura, the lungs follow along with the chest wall and _expand__.
What are the muscles involved in inspiration (expanding the thoracic cavity)? Diaphragm and external
intercostals
What keeps the alveoli from sticking to each other and collapsing? A lipoprotein called surfactant
Expiration:
The process of expiration results from the elastic _recoil_ of lung and muscle tissues, and from the surface
tension within the alveoli.
Forced expiration is aided by __internalintercostal_ muscles, and abdominal wall muscles that compress the abdomen
against the diaphragm.
Respiratory Volumes and Capacities:
The measurement of different air volumes is called __spirometry__, and it describes four distinct respiratory
volumes.
Define each of the following volumes and capacities.
- Tidal volume (TV): The volume of air that enters or leaves the respiratory passages in one normal
- Inspiratory reserve volume (IRV): The additional volume of air that could be inhaled by forceful
- Expiratory reserve volume (ERV): The additional volume of air that could be exhaled by forceful
- Residual volume (RV): The volume of air remaining in the respiratory passages after forceful
- Vital capacity (VC): Maximum volume of air that can be exhaled after a forceful inspiration;
- Inspiratory capacity (IC): The maximum volume of air that could be inhaled after a normal expiration;
- Functional residual capacity (FRC): The volume of air that remains in the lungs after a normal
- Total lung capacity (TLC): The total volume of air that the lungs and respiratory passages can hold;
Anatomic Dead Space: Volume of air that never reaches the gas exchange area of the lungs
Control of Respiration:
Normal breathing is a rhythmic, involuntary act, even though the muscles are under __voluntary___ control.
The respiratory centers in the __medulla___ & __pons___ sends impulses to controlrespiration. This process is
controlled primarily by the level of __carbon dioxide__ in the blood. The level of __oxygen__plays only a
minor role (only when levels are extremely low).
An inflation reflex, triggered by stretch receptors in the visceral pleura, bronchioles, and alveoli, helps to prevent
__overinflation__ of the lungs during forceful breathing.
Hyperventilation lowers the amount of _carbon dioxide__ in the blood.
Gas Exchange:
The __alveoli__ are the only sites of gas exchange between the atmosphere and the blood. They are tiny sacs
clustered at the distal ends of the __alveolar_____ ducts.
The ___respiratory__ membrane consists of the epithelial cells of the alveolus, the endothelial cells of
the capillary, and the fused basement membranes of these layers.
Gases diffuse from areas of __higher___ pressure to areas of __lower___ pressure.
In a mixture of gases, each gas accounts for a portion of the total pressure; the amount of pressure each gas exerts
is called its partial pressure.
When the partial pressure of oxygen is higher in the alveolar air than it is in the capillary blood, oxygen will
diffuse into the _blood___. When the partial pressure of carbon dioxide is greater in the blood than in the alveolar
air, carbon dioxide will diffuse out of the __blood_____ and into the __alveoli___.
What factors favor increased diffusion across the respiratory membrane? Increased surface area, increased partial
pressure gradient, shorter diffusion distance, greater solubility
O2 transport:
Over 98% of oxygen is carried in the blood bound to _hemoglobin___ of red blood cells, producing
__oxyhemoglobin_. This chemical is unstable in areas where the concentration of oxygen is low, and
gives up its oxygen molecules in those areas.
More oxygen is released as the blood concentration of carbon dioxide increases, as the blood becomes more
acidic, and as blood temperature increases.
A deficiency of oxygen reaching the tissues is called _hypoxia__, and has a variety of causes.
CO2 transport:
Carbon dioxide may be transported _dissolved__ in blood plasma, as _carbaminohemoglobin__, or as
___bicarbonate____ ions. Which is most common? Bicarbonate ions
When carbon dioxide reacts with water in the plasma, _carbonic__ acid is formed slowly. Much
of the carbon dioxide enters red blood cells, where the enzyme _carbonic anhydrase__ speeds up this reaction.
The resulting acid dissociates immediately, releasing bicarbonate and hydrogen ions.
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