Respiratory System Flashcards
Describe the location and function(s) of the major components of the human respiratory system.
You will notice in the diagram that air first enters the respiratory tract through the external nares that are openings which are commonly referred to as nostrils.
Air then enters the nasal cavity, where it is filtered by hairs and mucus that can trap dust and other particles. The nasal cavity also serves to moisten and to warm the air and contains sensors for our sense of smell.
Air leaves the back of the nasal cavity through the internal nares located behind the soft pallet in the roof of the mouth.
The air then passes into the pharynx that is a common passageway for air from the nasal cavity and from the buccal cavity.
Air passes from the pharynx through the glottis into the larynx (the first part of the trachea). The glottis, which is an opening to the trachea, is protected by a flap of cartilage called the epiglottis
The anterior wall of the larynx consists of two large plates of cartilage called the thyroid cartilage. This is commonly called the Adam’s apple. The larynx contains vocal chords, which are responsible for the production of sound. After passing through the larynx, air continues down the trachea.
The trachea extends about 12 cm to the level of the 5th thoracic vertebra and then the trachea divides to form two primary bronchi.
The right primary bronchus serves the right lung; the left primary bronchus serves the left lung. Each primary bronchus again divides to form secondary bronchi.
The lungs are located in the thoracic cavity. The diaphragm forms the bottom of the thoracic cavity.
Explain the mechanism of ventilation (inspiration and expiration) in humans, including the roles of the structures involved.
Inspiration (inhalation) refers to the process of taking air into the lungs that is, breathing in.
Expiration (exhalation) refers to the removal of air from the lungs or breathing out.
Describe the nervous control of breathing.
The parts of the brain regulating breathing are the pons and the medulla oblongata. These brain structures control inspiration and expiration by regulating the skeletal muscles involved in breathing-the diaphragm and the intercostals.
Describe how carbon dioxide, oxygen and hydrogen ions control the rate of breathing.
The ultimate purpose of respiration is to maintain proper levels of oxygen and carbon dioxide in the body. In order to maintain these levels the body is responsive to certain chemical stimuli and these in turn will determine how fast we breathe.
The chemistry of the blood is monitored by peripheral chemoreceptors in the walls of certain blood vessels and by central chemoreceptors in the medulla oblongata of the brain.
Interpret a spirogram and define the respiratory volumes and capacities a spirogram depicts.
a) The tidal volume represents the volume of air breathed at rest. It is the amount of air that is breathed in or out with each breath and amounts to about 500 ml.
b) The expiratory reserve volume is the amount of air which can be forced out of the lungs after a person has finished a normal, relaxed exhalation. It is about 1000 ml or 1 litre. After a normal relaxed inhalation, a person can still inhale a further considerable amount of air.
c) The inspiratory reserve volume is the air volume that can be inhaled after normal inhalation and accounts for about 3000 ml or 3 litres.
d) The vital capacity is the total amount of air that can be maximally exhaled after a maximal inhalation. It represents the total ability of an individual to exchange air with the atmosphere. The vital capacity is the sum of the tidal volume and the expiratory and inspiratory reserve volumes. It comes to 4500 ml or 4.5 litres. This is considerably more than the normal 500 ml tidal volume and represents the ability of an individual to increase metabolic activity
during exertion such as heavy exercise.
e) Residual volume is the amount of air that remains in the lungs after a maximum exhalation. It amounts to 1500 ml and represents air that is in the lungs but is not exchanged during respiration because the chest cavity is not completely collapsed.
f) Adding residual volume to the vital capacity gives us the figure of 6000 ml or 6 litres, which is the total lung capacity. A final respiratory volume is the dead air space. This is air that never enters the alveoli but rather remains in the air passageways (i.e. the trachea, bronchi and bronchioles). It amounts to 150 ml and it represents a volume of air unavailable to the body for gas exchange. Remember that gas exchange only occurs in the alveoli of the lungs.
Explain the basic principle governing the reciprocal exchange of gases between the alveoli and the blood, and between the blood and individual cells.
Gas exchange occurs by diffusion.
There is a high concentration of oxygen in the alveolus and a lower concentration of oxygen in the blood. The oxygen will therefore diffuse from the alveolus to the blood. Once oxygen gets into the capillaries surrounding the alveoli, it travels in the blood from the lungs to the heart via the pulmonary veins. From the heart it is pumped through arteries through the body. These arteries eventually end up in tissue capillaries. From the capillaries, oxygen diffuses into the cells where it is needed for respiration.
Carbon dioxide also diffuses from the cells of the tissues into the capillaries where it is then carried by the veins back to the heart.
Describe the mechanisms by which oxygen and carbon dioxide are transported in the blood.
Oxygen Transport:
Hemoglobin: The majority of oxygen (about 98.5%) is carried through the blood bound to hemoglobin, a protein present in red blood cells. Each hemoglobin molecule can bind to four oxygen molecules. This binding occurs in the lungs, where oxygen concentration is high, and releases oxygen in tissues where oxygen concentration is low due to metabolic activities.
Dissolved in Plasma: A small fraction of oxygen (around 1.5%) dissolves directly in the plasma, not bound to hemoglobin. This dissolved oxygen contributes to the overall oxygen content but is much less significant compared to the oxygen bound to hemoglobin.
Carbon Dioxide Transport:
Dissolved in Plasma: Like oxygen, a small amount of carbon dioxide dissolves directly in the plasma, contributing to CO2 transport in the blood.
As Bicarbonate (HCO3-): The majority of carbon dioxide (around 70%) diffuses into red blood cells, where an enzyme called carbonic anhydrase facilitates its reaction with water to form carbonic acid (H2CO3). Carbonic acid rapidly dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). The HCO3- ions are transported out of the red blood cells into the plasma in exchange for chloride ions (the chloride shift). This process helps in CO2 transport and pH regulation.
Bound to Hemoglobin: A small portion of CO2 (about 20-25%) binds directly to hemoglobin molecules in the blood. This binding does not occur at the same site as oxygen, and it contributes to the overall transport of carbon dioxide.
Define hyperventilation and specify some of its causes and physiological consequences.
Hyperventilation is defined as an increase in the rate of breathing, the depth of breathing or both, beyond what is metabolically necessary for the normal exchange of gasses.
The main effects of reduced carbon dioxide in the blood are:
Alkalosis: The lowered carbon dioxide levels mean that less carbonic acid is formed in the blood and there are fewer hydrogen ions present. This makes the blood more alkaline producing undesirable chemical or physiological effects.
Lower blood pressure: Reduced muscle tone causes decreases in blood pressure that may reduce the blood supply to certain tissues. Blood pressure is partially regulated by the degree of smooth muscle constriction in the walls of blood vessels. Blood vessel diameter is controlled by the vasomotor centre in the medulla oblongata. This center receives information on blood CO2 levels from peripheral chemoreceptors. At relatively normal blood CO2 levels, the smooth muscle fibres are partially contracted. If CO2 levels increase, vasoconstriction increases and blood pressure increases. If CO2 levels drop, vasodilation occurs and blood pressure drops.
Dizziness or unconsciousness may occur: Low carbon dioxide interferes with the ability of hemoglobin to release oxygen to the tissues. This particularly affects the brain, and may result in dizziness or unconsciousness.
Define hypoxia and specify some of its causes and physiological consequences
Define hypoxia and specify some of its causes and physiological consequences
Hypoxia is defined as a reduced amount of oxygen reaching the tissues, literally means that the oxygen levels are too low.
