Chapter six Flashcards
Path of air through the respiratory system
nares of the nose → nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli
Pharynx
For food and air
Larynx
Lies just below the pharynx, allowing only air to pass through.
To keep food out of this tract, the opening is the glottis which is covered by the epiglottis during swallowing.
There are also two vocal cords here.
Trachea and bronchi
Contain ciliated epithelial cells to catch materials that have made it past
Surfactant
This is the coating surrounding each of the alveoli. It is a detergent that lowers surface tension and prevents collapsing
Thoracic cavity
Contains both the lungs and the heart. The chest wall is right outside of this cavity.
Pleurae
Membranes that surround each of the lungs, forming sacs in which the lungs expand against.
The surface closest to the lung is the visceral pleura and the surface closest to the outside of the parietal pleura.
The space in between the lung and the pleura is the intrapleural space, which is filled with fluid.
Diaphragm
A thin, muscular structure that divides the thoracic cavity from the abdominal cavity. It is under somatic control, even though breathing itself is under autonomic control.
Process of inhalation
This is an active process that uses our diaphragm and the external intercostal muscles (muscles between the ribs) to expand the thoracic cavity.
As the diaphragm flattens and the chest expands outwards, the intrathoracic volume increases.
Increase in volume leads to a decrease in pressure, and air will be sucked in from a higher-pressure environment (outside) – known as negative-pressure breathing
Exhalation
This does not have to be an active process. Rather, it can be passive because the simple relaxation of the muscles can just reverse the process of the exhalation.
Decrease in volume leads to increase in pressure, and the air will be pushed out.
We can speed up the process by using our internal intercostal muscles and abdominal muscle, which oppose the external intercostal muscles and pulls the rib cage down
Spirometers
These are used to assess lung capacities and volumes. Although you cannot measure the amount of air remaining in the lung after exhalation (residual volume), it can provide other information.
Total lung capacity (TLC)
The maximum volume of air in the lungs when you inhale completely, usually around 6 to 7 litres
Residual volume (RV)
The volume of air remaining after exhalation
Vital capacity (VC)
The difference between the minimum and maximum volume of air in the lungs (TLC - RV)
Tidal volume (TV)
The volume of air inhaled or exhaled in a normal breath
Expiratory reserve volume (ERV)
The volume of air that can be forcibly exhaled after a normal exhalation
Inspiratory reserve volume (IRV)
The volume of air that can be forcibly inhaled after a normal inhalation
How is ventilation controlled by the nervous control centre?
Ventilation is regulated by medulla oblongata that fires rhythmically to cause regular contraction of respiratory muscles. These neurons contain chemoreceptors that are sensitive to carbon dioxide concentration.
As CO2 rises in the blood (hypercarbia or hypercapnia), the respiratory rate will increase so that more CO2 is exhaled
Same for oxygen during hypoxemia (low oxygen concentration)
Hypercarbia or hypercapnia
As CO2 rises in the blood, the respiratory rate will increase so that more CO2 is exhaled
Hypoxemia
When there is a low oxygen concentration in blood
How does gas exchange work?
The capillaries around the alveoli bring in deoxygenated blood from the pulmonary arteries, which originate from the right ventricle of the heart. The walls of the alveoli are one cell thick, which facilitates diffusion. Oxygenated blood returns to left atrium of the via the pulmonary veins
Driving force is the pressure difference, transferring down the concentration gradient (high CO2 → low CO2, low O2 → high O2). Because of this, no energy is required.
What would happen if we moved to higher altitudes where less oxygen is available?
First, we would breathe more rapidly. Second, the binding dynamics of hemoglobin would be altered to facilitate the unloading of oxygen at the tissue.
Short term, the body would make more red blood cells to ensure adequate delivery of oxygen.
Long term, the body would develop more blood vessels to facilitate distribution of oxygen to tissues.
How does the respiratory system contribute to thermoregulation?
Heat is regulated by vasodilation and vasoconstriction/ As capillaries expand, more blood can pass through these vessels and a larger amount of energy can be dissipated.
The respiratory system can also transfer heat to the environment through evaporation of water in mucous secretions – dogs take advantage of this by panting
Nasal cavity immune function
The first line of defense is the nasal cavity, which has hairs and mucous. This also contains enzyme lysozyme which is able to attack the walls of gram-positive bacteria.
Mucociliary escalator
This line of defense occurs in the internal airways which are lined with mucous, trapping larger invaders. The underlying cilia can propel the mucous up into the respiratory tract or the oral cavity where it can be expelled or swallowed.
Immune function of macrophages
These immune cells are found in the lungs and alveoli. They engulf and digest pathogens, and also signal to the rest of the system that there is an invader.
IgA antibodies
Mucosal surfaces contain IgA antibodies that help to protect against pathogens that contact the mucous membrane
Mast cells
These are found within the lungs. They are cells that have performed antibodies on their surfaces. When something attaches, it releases inflammatory chemicals into the surrounding area to promote immune response.
These are often reactive to pollen and mold.
Bicarbonate buffer system
Controls pH balance
CO2 (g) + H2O (l) → H2CO2 (aq) → H+ (aq) + HCO3 - (aq)
The body attempts to maintain a pH between 7.35 and 7.45
Low pH in the body (acidemia)
When the pH is lower, hydrogen ion concentration is higher (acidemia). Acid-sensing chemoreceptors just outside of the blood-brain barrier sends signals to the brain to increase the respiratory rate. This generates additional carbon dioxide. As respiratory rate increases, more carbon dioxide is blown off.
This pushes buffer equation to the left and allows H+ concentration to drop back to normal
Results in a higher pH (more basic)
High pH in the body (alkemia)
If blood is too basic (alkemia), the body will increase the acidity. The respiratory rate is slowed, and more carbon dioxide will be retained. This shifts the equation to the right and results in a lower pH (more acidic).
