FR1-Respiration Flashcards
What is the The respiratory quotient (RQ)?
What is RQ when carbohydrate is being used?
What is RQ when fat is used?
What is RQ when protein is used?
The ratio of CO2 produced to O2 consumed, varies depending on the foodstuff consumed.
- When carbohydrate is being used, the RQ is 1—that is, for every molecule of O2 consumed, one molecule of CO2 is produced
- For fat utilization, the RQ is 0.7
- for protein, it is 0.8.
What is the average oxygen consumption?
What is the average carbon dioxide production?
- Resting O2 consumption averages about 250 mL/min
- CO2 production averages about 200 mL/min, for an average RQ of 0.8:
Explain the steps of external respiration
- Air is alternately moved into and out of the lungs so that air can be exchanged between the atmosphere (external environment) and air sacs (alveoli) of the lungs. This exchange is accomplished by the mechanical act of breathing, or ventilation. The rate of ventilation is regulated to adjust the flow of air between the atmosphere and alveoli according to the body’s metabolic needs for O2 uptake and CO2 removal.
- O2 and CO2 are exchanged between air in the alveoli and blood within the pulmonary (pulmonary means “lung”) capillaries by the process of diffusion.
- The blood transports O2 and CO2 between the lungs and the tissues.
- O2 and CO2 are exchanged between the tissue cells and blood by the process of diffusion across the systemic (tissue) capillaries
The respiratory system does not accomplish all steps of respiration; it is involved only with ventilation and exchange of O2 and CO2 between the lungs and blood (steps 1 and 2 ). What is involved in step 2 and carries out steps 3 and 4?
The circulatory system
Nonrespiratory Functions of the Respiratory System:
What is moistening of inspired air is essential to prevent?
The alveolar linings from drying out; O2 and CO2 cannot diffuse through dry membranes
Nonrespiratory Functions of the Respiratory System:
Explain how it It removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation
(angiotensin II and prostaglandins)
- All blood returning to the heart from the tissues must pass through the lungs before being returned to the systemic circulation.
- Thus the lungs are uniquely situated to act on specific materials that have been added to the blood at the tissue level before these substances have a chance to reach other parts of the body by means of the arterial system.
- For example, prostaglandins, a collection of chemical messengers released in many tissues to mediate particular local responses may spill into the blood, but they are inactivated during passage through the lungs so that they cannot exert systemic effects.
- By contrast, the lungs activate angiotensin II, which is part of the renin–angiotensin–aldosterone hormonal pathway that plays an important role in regulating Na+ concentration in the ECF
Is the nose part of the respiratory system?
Yes
What are the components of the respiratory system?
The respiratory system includes:
- the respiratory airways leading into the lungs,
- the lungs themselves,
- the respiratory muscles of the thorax (chest) and abdomen involved in producing movement of air through the airways into and out of the lungs.
What are the respiratory airways?
The respiratory airways are tubes that carry air between the atmosphere and the air sacs, the latter being the only site where gases can be exchanged between air and blood
Describe the structure of the airways (from nose to alveoli)
The airways begin with the nasal passages (nose)
The nasal passages open into the pharynx (throat), which serves as a common passageway for both the respiratory and digestive systems.
Two tubes lead from the pharynx—the trachea (windpipe), through which air is conducted to the lungs, and the esophagus, the tube through which food passes to the stomach.
Air normally enters the pharynx through the nose, but it can enter by the mouth as well when the nasal passages are congested—that is, you can breathe through your mouth when you have a cold. Because the pharynx serves as a common passageway for food and air, reflex mechanisms close
off the trachea during swallowing so that food does not enter the airways.
The esophagus stays closed except during swallowing to keep air from entering the stomach during breathing.
The larynx, or voice box, is located at the entrance of the trachea.
The anterior protrusion of the larynx forms the “Adam’s apple.”
The vocal folds, two bands of elastic tissue that lie across the opening of the larynx, can be stretched and positioned in different shapes by laryngeal muscles.
Air passes into the larynx through the space between the vocal folds.
This laryngeal opening is known as the glottis.
Beyond the larynx, the trachea divides into two main branches, the right and left bronchi, which enter the right and left lungs, respectively.
Within each lung the bronchus continues to branch into progressively narrower, shorter, and more numerous airways, like the branching of a tree.
The smaller branches are known as bronchioles. Clustered at the ends of the terminal bronchioles are the alveoli
What is similar about the trachea and larger bronhi?
They are fairly rigid, nonmuscular tubes encircled by a series of cartilaginous rings that prevent these tubes from compressing
Do smaller bronchioles have cartilage to hold them open?
What factors affect bronchiolar smooth muscle?
- No
- Their walls contain smooth muscle that is innervated by the autonomic nervous system and is sensitive to certain hormones and local chemicals. These factors, by varying the degree of contraction of bronchiolar smooth muscle
How are the lungs ideally suited for gas exchange and how does their comply with Ficks law?
According to Fick’s law of diffusion, the shorter the distance and the greater the surface area through which diffusion takes place, the greater the rate of diffusion
Explain the structure and arrangemet of alveoli:
What is the space between an alveolus and the surrounding capillary called?
What is different about type II alveolar cells?
What permits airflow between adjoining alveoli?
- The alveolar walls consist of a single layer of flattened, Type I alveolar cells
- Each alveolus is surrounded by a network of pulmonary capillaries, the walls of which are also only one cell thick
- The interstitial space between an alveolus and the surrounding capillary network is extremely thin. Thus, only a 0.5 mm barrier known as the alveolar–capillary membrane separates air in the alveoli from blood in the pulmonary capillaries
- The total surface area thus exposed between alveolar air and pulmonary capillary blood is about 75 m2
- In addition to the thin, wall-forming Type I cells, 5% of the alveolar surface epithelium is covered by Type II alveolar cells. These cells secrete pulmonary surfactant, a phospholipoprotein complex that facilitates lung expansion
- Minute pores of Kohn exist in the walls between adjacent alveoli. Their presence permits airflow between adjoining alveoli
What is the only muscle within the lungs?
smooth muscle in the walls of the arterioles and the walls of thr bronchioles
Are their muscles present within the alveolar walls?
No muscle is present within the alveolar walls to cause them to inflate and deflate during the breathing process.
Instead, changes in lung volume (and accompanying changes in alveolar volume) are brought about through changes in the dimensions of the thoracic (chest) cavity
What structures are in the thoracic cavity?
- The lungs occupy most of the volume of the thoracic (chest) cavity, the only other structures in the chest being the heart and associated vessels, the esophagus, the thymus, and some nerves.
- The outer chest wall (thorax) is formed by 12 pairs of curved ribs, which join the sternum (breastbone) anteriorly and the thoracic vertebrae (backbone) posteriorly.
- The rib cage provides bony protection for the lungs and heart.
- Skeletal muscles connect these bony structures and enclose the thoracic cavity.
- The diaphragm, which forms the floor of the thoracic cavity, is a large, domeshaped sheet of skeletal muscle that separates the thoracic cavity from the abdominal cavity
Label the diagram showing an alveolus and surrounding
(a) A single layer of flattened Type I alveolar cells forms the alveolar walls. Type II alveolar cells embedded within the alveolar wall secrete pulmonary surfactant. Wandering alveolar macrophages are found within the alveolar lumen. The size of the cells and respiratory membrane is exaggerated compared to the size of the alveolar and pulmonary capillary lumens. The diameter of an alveolus is actually about 600 times larger (300 mm) than the intervening space between air and blood (0.5 mm)
Label an Immunofluorescent photomicrograph of several alveoli
Draw a diagram and annotate the relationship of lungs to pleural sacs, thoracic wall, and diaphragm
Give a suitable annaology
Pleural sac. (a) Pushing a lollipop into a small water-filled balloon produces a relationship analogous to that between each double-walled, closed pleural sac and the lung that it surrounds and separates from the thoracic wall. (b) One layer of the pleural sac, the visceral pleura, closely adheres to the surface of the lung (viscus means “organ”) and then reflects back on itself to form another layer, the parietal pleura, which lines the interior surface of the thoracic wall (paries means “wall”). The relative size of the pleural cavity between these two layers is grossly exaggerated for the purpose of visualization
Explain the function of the transmural pressure gradient
The intra-alveolar pressure, equilibrated with atmospheric pressure at 760 mm Hg, is greater than the intrapleural pressure of 756 mm Hg, so a greater pressure is pushing outward than is pushing inward across the lung wall.
This net outward pressure differential, the transmural pressure gradient, pushes out on the lungs, stretching, or distending, them (trans means “across”; mural means “wall”)Because of this pressure gradient, the lungs are always forced to expand to fill the thoracic cavity, no matter its size. As the thoracic cavity enlarges, the lungs enlarge—that is, the lungs follow the movements of the chest wall
Describe important pressure changes in ventilation
What are the lungs stretched by?
The lungs are stretched by the transmural pressure gradient that exists across their walls because the intrapleural pressure is less than atmospheric pressure.
The intrapleural pressure, in turn, is subatmospheric because the stretched lungs tend to pull away from the larger thoracic wall, slightly expanding the pleural cavity and dropping the intrapleural pressure below atmospheric pressure
What is pneumothorax?
What happens to the transmural pressure gradient?
What happens to the lungs?
- Normally, air does not enter the pleural cavity because there is no communication between the cavity and either the atmosphere or the alveoli.
- However, if the chest wall is punctured (for example, by a stab wound or a broken rib), air flows down its pressure gradient from the higher atmospheric pressure and rushes into the cavity
- The abnormal condition of air in the pleural cavity is known as pneumothorax (“air in the chest”).
- Intrapleural and intra-alveolar pressure are now both equilibrated with atmospheric pressure, so a transmural pressure gradient no longer exists across the lung wall.
- With no force present to stretch the lung, it collapses to its unstretched size
- Similarly, pneumothorax and lung collapse can occur if air enters the pleural cavity through a hole in the lung produced
Draw a diagram to show the changes in lung volume and intra-alveolar pressure during inspiration and expiration
(a) Before inspiration, at the end of the preceding expiration, intra-alveolar pressure is equilibrated with atmospheric pressure, and no air is flowing.
(b) As the lungs increase in volume during inspiration, the intra-alveolar pressure decreases, establishing a pressure gradient that favors the flow of air into the alveoli from the atmosphere—that is, an inspiration occurs.
(c) As the lungs recoil to their preinspiratory size on relaxation of the inspiratory muscles, the intra-alveolar pressure increases, establishing a pressure gradient that favors the flow of air out of the alveoli into the atmosphere—that is, an expiration occurs
What are the steps in the intra-alveolar and intrapleural pressure changes throughout the respiratory cycle
- During inspiration, intra-alveolar pressure is less than atmospheric pressure.
- During expiration, intra-alveolar pressure is greater than atmospheric pressure.
- At the end of both inspiration and expiration, intra-alveolar pressure is equal to atmospheric pressure because the alveoli are in direct communication with the atmosphere, and air continues to flow down its pressure gradient until the two pressures equilibrate.
- Throughout the respiratory cycle, intrapleural pressure is less than intra-alveolar pressure. Thus, a transmural pressure gradient always exists, and the lung is always stretched to some degree, even during expiration.
Airway resistance influences airflow rates:
What is the equation that supports this statement?
What is the primary determinant to resistance to airflow?
- The primary determinant of resistance to airflow is the radius of the conducting airways
