Module 13: The Respiratory System

Lesson 7: Embryonic Development of the Respiratory System

Phát Triển Hệ Hô Hấp Giai Đoạn Phôi Thai

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Dưới đây là danh sách những thuật ngữ Y khoa của module The Respiratory System.
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Medical Terminology: The Respiratory System

process of adjustment that the respiratory system makes due to chronic exposure to high altitudes
acute mountain sickness (AMS)
condition that occurs a result of acute exposure to high altitude due to a low partial pressure of oxygen
(plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares
alar cartilage
cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae
alveolar dead space
air space within alveoli that are unable to participate in gas exchange
alveolar duct
small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli
alveolar macrophage
immune system cell of the alveolus that removes debris and pathogens
alveolar pore
opening that allows airflow between neighboring alveoli
alveolar sac
cluster of alveoli
small, grape-like sac that performs gas exchange in the lungs
anatomical dead space
air space present in the airway that never reaches the alveoli and therefore never participates in gas exchange
tip of the external nose
apneustic center
network of neurons within the pons that stimulate the neurons in the dorsal respiratory group; controls the depth of inspiration
atmospheric pressure
amount of force that is exerted by gases in the air surrounding any given surface
Bohr effect
relationship between blood pH and oxygen dissociation from hemoglobin
Boyle’s law
relationship between volume and pressure as described by the formula: P1V1 = P2V2
portion of the external nose that lies in the area of the nasal bones
bronchial bud
structure in the developing embryo that forms when the laryngotracheal bud extends and branches to form two bulbous structures
bronchial tree
collective name for the multiple branches of the bronchi and bronchioles of the respiratory system
branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs
decrease in the size of the bronchiole due to relaxation of the muscular wall
increase in the size of the bronchiole due to contraction of the muscular wall
tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs
bound form of hemoglobin and carbon dioxide
carbonic anhydrase (CA)
enzyme that catalyzes the reaction that causes carbon dioxide and water to form carbonic acid
cardiac notch
indentation on the surface of the left lung that allows space for the heart
central chemoreceptor
one of the specialized receptors that are located in the brain that sense changes in hydrogen ion, oxygen, or carbon dioxide concentrations in the brain
chloride shift
facilitated diffusion that exchanges bicarbonate (HCO3–) with chloride (Cl–) ions
conducting zone
region of the respiratory system that includes the organs and structures that provide passageways for air and are not directly involved in gas exchange
cricoid cartilage
portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus
Dalton’s law
statement of the principle that a specific gas type in a mixture exerts its own pressure, as if that specific gas type was not part of a mixture of gases
dorsal respiratory group (DRG)
region of the medulla oblongata that stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration
dorsum nasi
intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone
leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing
(also, exhalation) process that causes the air to leave the lungs
expiratory reserve volume (ERV)
amount of air that can be forcefully exhaled after a normal tidal exhalation
external nose
region of the nose that is easily visible to others
external respiration
gas exchange that occurs in the alveoli
portion of the posterior oral cavity that connects the oral cavity to the oropharynx
fibroelastic membrane
specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers
forced breathing
(also, hyperpnea) mode of breathing that occurs during exercise or by active thought that requires muscle contraction for both inspiration and expiration
endoderm of the embryo towards the head region
functional residual capacity (FRC)
sum of ERV and RV, which is the amount of air that remains in the lungs after a tidal expiration
opening between the vocal folds through which air passes when producing speech
Haldane effect
relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide
Henry’s law
statement of the principle that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas
concave structure on the mediastinal surface of the lungs where blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung
increased rate and depth of ventilation due to an increase in oxygen demand that does not significantly alter blood oxygen or carbon dioxide levels
increased ventilation rate that leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH
(also, inhalation) process that causes air to enter the lungs
inspiratory capacity (IC)
sum of the TV and IRV, which is the amount of air that can maximally be inhaled past a tidal expiration
inspiratory reserve volume (IRV)
amount of air that enters the lungs due to deep inhalation past the tidal volume
internal respiration
gas exchange that occurs at the level of body tissues
intra-alveolar pressure
(intrapulmonary pressure) pressure of the air within the alveoli
intrapleural pressure
pressure of the air within the pleural cavity
laryngeal prominence
region where the two lamine of the thyroid cartilage join, forming a protrusion known as “Adam’s apple”
portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food
bud forms from the lung bud, has a tracheal end and bulbous bronchial buds at the distal end
cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs
lingual tonsil
lymphoid tissue located at the base of the tongue
organ of the respiratory system that performs gas exchange
lung bud
median dome that forms from the endoderm of the foregut
one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity
(plural = nares) opening of the nostrils
nasal bone
bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones
nasal septum
wall composed of bone and cartilage that separates the left and right nasal cavities
portion of the pharynx flanked by the conchae and oropharynx that serves as an airway
olfactory pit
invaginated ectodermal tissue in the anterior portion of the head region of an embryo that will form the nasal cavity
portion of the pharynx flanked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food
oxygen–hemoglobin dissociation curve
graph that describes the relationship of partial pressure to the binding and disassociation of oxygen to and from heme
(Hb–O2) bound form of hemoglobin and oxygen
palatine tonsil
one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces
paranasal sinus
one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses
parietal pleura
outermost layer of the pleura that connects to the thoracic wall, mediastinum, and diaphragm
partial pressure
force exerted by each gas in a mixture of gases
peripheral chemoreceptor
one of the specialized receptors located in the aortic arch and carotid arteries that sense changes in pH, carbon dioxide, or oxygen blood levels
pharyngeal tonsil
structure composed of lymphoid tissue located in the nasopharynx
region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea
concave surface of the face that connects the apex of the nose to the top lip
pleural cavity
space between the visceral and parietal pleurae
pleural fluid
substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing
pneumotaxic center
network of neurons within the pons that inhibit the activity of the neurons in the dorsal respiratory group; controls rate of breathing
pulmonary artery
artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli
pulmonary plexus
network of autonomic nervous system fibers found near the hilum of the lung
pulmonary surfactant
substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made by type II alveolar cells
pulmonary ventilation
exchange of gases between the lungs and the atmosphere; breathing
quiet breathing
(also, eupnea) mode of breathing that occurs at rest and does not require the cognitive thought of the individual
residual volume (RV)
amount of air that remains in the lungs after maximum exhalation
respiratory bronchiole
specific type of bronchiole that leads to alveolar sacs
respiratory cycle
one sequence of inspiration and expiration
respiratory epithelium
ciliated lining of much of the conducting zone that is specialized to remove debris and pathogens, and produce mucus
respiratory membrane
alveolar and capillary wall together, which form an air-blood barrier that facilitates the simple diffusion of gases
respiratory rate
total number of breaths taken each minute
respiratory volume
varying amounts of air within the lung at a given time
respiratory zone
includes structures of the respiratory system that are directly involved in gas exchange
region of the external nose between the eyebrows
thoracic wall compliance
ability of the thoracic wall to stretch while under pressure
thyroid cartilage
largest piece of cartilage that makes up the larynx and consists of two lamine
tidal volume (TV)
amount of air that normally enters the lungs during quiet breathing
total dead space
sum of the anatomical dead space and alveolar dead space
total lung capacity (TLC)
total amount of air that can be held in the lungs; sum of TV, ERV, IRV, and RV
total pressure
sum of all the partial pressures of a gaseous mixture
tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung
trachealis muscle
smooth muscle located in the fibroelastic membrane of the trachea
transpulmonary pressure
pressure difference between the intrapleural and intra-alveolar pressures
true vocal cord
one of the pair of folded, white membranes that have a free inner edge that oscillates as air passes through to produce sound
type I alveolar cell
squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases
type II alveolar cell
cuboidal epithelial cells that are the minor cell type in the alveolar wall; secrete pulmonary surfactant
movement of air into and out of the lungs; consists of inspiration and expiration
ventral respiratory group (VRG)
region of the medulla oblongata that stimulates the contraction of the accessory muscles involved in respiration to induce forced inspiration and expiration
vestibular fold
part of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing
visceral pleura
innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures
vital capacity (VC)
sum of TV, ERV, and IRV, which is all the volumes that participate in gas exchange
Nội dung này đang được cập nhật.
Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
Development of the respiratory system begins early in the fetus. It is a complex process that includes many structures, most of which arise from the endoderm. Towards the end of development, the fetus can be observed making breathing movements. Until birth, however, the pregnant person provides all of the oxygen to the fetus as well as removes all of the fetal carbon dioxide via the placenta.
The development of the respiratory system begins at about week 4 of gestation. By week 28, enough alveoli have matured that a baby born prematurely at this time can usually breathe on its own. The respiratory system, however, is not fully developed until early childhood, when a full complement of mature alveoli is present.

A. Weeks 4–7

Respiratory development in the embryo begins around week 4. Ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. An olfactory pit is one of a pair of structures that will enlarge to become the nasal cavity. At about this same time, the lung bud forms. The lung bud is a dome-shaped structure composed of tissue that bulges from the foregut. The foregut is endoderm just inferior to the pharyngeal pouches. The laryngotracheal bud is a structure that forms from the longitudinal extension of the lung bud as development progresses. The portion of this structure nearest the pharynx becomes the trachea, whereas the distal end becomes more bulbous, forming bronchial buds. A bronchial bud is one of a pair of structures that will eventually become the bronchi and all other lower respiratory structures (Figure 1).

B. Weeks 7–16

Bronchial buds continue to branch as development progresses until all of the segmental bronchi have been formed. Beginning around week 13, the lumens of the bronchi begin to expand in diameter. By week 16, respiratory bronchioles form. The fetus now has all major lung structures involved in the airway.

C. Weeks 16–24

Once the respiratory bronchioles form, further development includes extensive vascularization, or the development of the blood vessels, as well as the formation of alveolar ducts and alveolar precursors. At about week 19, the respiratory bronchioles have formed. In addition, cells lining the respiratory structures begin to differentiate to form type I and type II pneumocytes. Once type II cells have differentiated, they begin to secrete small amounts of pulmonary surfactant. Around week 20, fetal breathing movements may begin.

D. Weeks 24–Term

Major growth and maturation of the respiratory system occurs from week 24 until term. More alveolar precursors develop, and larger amounts of pulmonary surfactant are produced. Surfactant levels are not generally adequate to create effective lung compliance until about the eighth month of pregnancy. The respiratory system continues to expand, and the surfaces that will form the respiratory membrane develop further. At this point, pulmonary capillaries have formed and continue to expand, creating a large surface area for gas exchange. The major milestone of respiratory development occurs at around week 28, when sufficient alveolar precursors have matured so that a baby born prematurely at this time can usually breathe on its own. However, alveoli continue to develop and mature into childhood. A full complement of functional alveoli does not appear until around 8 years of age.
Although the function of fetal breathing movements is not entirely clear, they can be observed starting at 20–21 weeks of development. Fetal breathing movements involve muscle contractions that cause the inhalation of amniotic fluid and exhalation of the same fluid, with pulmonary surfactant and mucus. Fetal breathing movements are not continuous and may include periods of frequent movements and periods of no movements. Maternal factors can influence the frequency of breathing movements. For example, high blood glucose levels, called hyperglycemia, can boost the number of breathing movements. Conversely, low blood glucose levels, called hypoglycemia, can reduce the number of fetal breathing movements. Tobacco use is also known to lower fetal breathing rates. Fetal breathing may help tone the muscles in preparation for breathing movements once the fetus is born. It may also help the alveoli to form and mature. Fetal breathing movements are considered a sign of robust health.
Prior to birth, the lungs are filled with amniotic fluid, mucus, and surfactant. As the fetus is squeezed through the birth canal, the fetal thoracic cavity is compressed, expelling much of this fluid. Some fluid remains, however, but is rapidly absorbed by the body shortly after birth. The first inhalation occurs within 10 seconds after birth and not only serves as the first inspiration, but also acts to inflate the lungs. Pulmonary surfactant is critical for inflation to occur, as it reduces the surface tension of the alveoli. Preterm birth around 26 weeks frequently results in severe respiratory distress, although with current medical advancements, some babies may survive. Prior to 26 weeks, sufficient pulmonary surfactant is not produced, and the surfaces for gas exchange have not formed adequately; therefore, survival is low.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at

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  1. The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood.
  2. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx.
  3. At about this same time, a protrusion of endodermal tissue extends anteriorly from the foregut.
  4. This produces a lung bud, which continues to elongate until it forms the laryngotracheal bud.
  5. The proximal portion of this structure will mature into the trachea, whereas the bulbous end will branch to form two bronchial buds.
  6. These buds then branch repeatedly, so that at about week 16, all major airway structures are present.
  7. Development progresses after week 16 as respiratory bronchioles and alveolar ducts form, and extensive vascularization occurs.
  8. Alveolar type I cells also begin to take shape.
  9. Type II pulmonary cells develop and begin to produce small amounts of surfactant.
  10. As the fetus grows, the respiratory system continues to expand as more alveoli develop and more surfactant is produced.
  11. Beginning at about week 36 and lasting into childhood, alveolar precursors mature to become fully functional alveoli.
  12. At birth, compression of the thoracic cavity forces much of the fluid in the lungs to be expelled.
  13. The first inhalation inflates the lungs.
  14. Fetal breathing movements begin around week 20 or 21, and occur when contractions of the respiratory muscles cause the fetus to inhale and exhale amniotic fluid.
  15. These movements continue until birth and may help to tone the muscles in preparation for breathing after birth and are a sign of good health.
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