The Anatomy of the Respiratory System: Conception to Maturity

Comprehensive practice flashcards covering fetal lung development, cardiopulmonary anatomy, clinical conditions like RDS and asthma, and the mechanics of the respiratory system based on the lecture transcript.

Embryonic Period

Occurs around the $26^{th}$ day after fertilization where the lungs first appear as small buds rising from the esophagus.

Pseudoglandular Period

Occurs between the $6^{th}$ and $16^{th}$ week of gestation; segmental and subsegmental bronchi are present, and by week $16$, there are around $20$ generations of airways.

Canalicular Period

Includes events between the $17^{th}$ and $26^{th}$ week of gestation where terminal bronchioles proliferate and the lung mass becomes highly vascularized.

Terminal Sac Period

Begins at the $26^{th}$ week of gestation until term ($40$ weeks); the entire acinus develops, and Type I and Type II alveolar cells can be seen.

Alveolar Period

Begins at $32$ weeks and continues through childhood ($8\text{-}10$ years), during which alveolar-capillary units increase to about $300$ million.

Respiratory Distress Syndrome (RDS)

A common newborn disorder developed due to an insufficient amount of pulmonary surfactant produced by Type II cells.

APGAR Scoring System

A system used $1$ and $5$ minutes after delivery to evaluate heart rate, respiratory effort, muscle tone, reflex irritability, and color.

Atelectasis

A condition associated with RDS where the alveoli collapse.

Persistent Pulmonary Hypertension of the Neonate (PPHN)

A syndrome produced when the ductus arteriosus remains open because the infant’s $PaO_2$ remains below $45$ torr.

Cotyledons

The $15$ to $20$ segments that compose the placenta, containing fetal vessels, chorionic villi, and intervillous spaces.

Abruptio Placenta

The premature partial or total separation of the placenta from the uterus, which can be life-threatening to the fetus.

Functional Residual Capacity (FRC)

The volume of air that remains in the lungs after a normal exhalation.

Intrapleural Pressure at First Breath

The negative pressure an infant must generate to initiate the first breath, typically around $-40\text{ cm }H_2O$ and potentially as low as $-100\text{ cm }H_2O$.

Vibrissae

Hair follicles located in the vestibule of the nose that function as the first line of defense for the tracheobronchial tree.

Turbinates

Three bony protrusions (superior, middle, and inferior) on the lateral walls of the nasal cavity that increase surface area for warming and humidifying air.

Epistaxis

The clinical term for nosebleeds, classified as either anterior (more than 90\text{%} of cases) or posterior.

Rhinitis

Inflammation of the mucous membranes of the nasal cavity, often accompanied by swelling, excessive mucus, and nasal congestion.

Vallecula Epiglottica

A depression located between the base of the tongue and the epiglottis, serving as a landmark for endotracheal tube insertion.

Croup Syndrome

A common clinical manifestation in children, also called inspiratory stridor, caused by LTB (laryngotracheobronchitis) or acute epiglottitis.

Valsalva’s Maneuver

The process of tightly sealing the glottis to prevent air from escaping during physical work seperti pushing, lifting, or coughing.

Conducting Zone

The first $0 \text{--} 19$ generations of the tracheobronchial tree (trachea to terminal bronchioles) that only serve as air conductors.

Respiratory Zone

Generations $20 \text{--} 28$ of the tracheobronchial tree where gas exchange takes place.

Mucociliary Escalator

The cleansing mechanism where cilia move a mucous blanket (sol and gel layers) toward the larynx at a rate of $1500$ times per minute.

IgE

The specific immunoglobulin basic to allergic reactions; levels in asthma patients can be $20$ times greater than the normal $200\text{ ng/ml}$.

Mast Cells

Cells found in the lamina propria that release histamine, leukotrienes, and heparin when an antibody/mast cell complex detects an antigen.

Carina

The bifurcation point where the trachea divides into the right and left mainstem bronchi.

Canals of Lambert

Small channels between the inner surface of terminal bronchioles and adjacent alveoli that provide collateral ventilation.

Clara Cells

Cells in the terminal bronchioles that have secretory functions and may detoxify inhaled toxic substances.

Venous Admixture

The mixture of oxygenated blood in pulmonary veins with deoxygenated blood from the bronchial circulation.

Type II Pneumocytes

Granular alveolar cells that make up 5\text{%} of the surface area and are the believed source of pulmonary surfactant.

Pores of Kohn

Small holes in the septa between adjacent alveoli that allow gas to move between them, increasing in size and number with age.

Pulmonary Interstitium

A gel-like substance with collagen fibers that supports alveolar-capillary clusters; it has two compartments known as the tight space and the loose space.

Sympathomimetic Drugs

Agents that mimic the sympathetic nervous system to cause bronchodilation, such as albuterol.

Parasympatholytic Agents

Drugs that block the cholinergic receptors of the parasympathetic nervous system to prevent bronchial smooth muscle constriction.

Pleurisy

Inflammation of the pleural membranes that causes friction and a stabbing pain during inspiration, often resulting in a friction rub sound.

Angle of Louis

The sternal angle or manubriosternal joint which serves as a palpable landmark for identifying the carina.

Diaphragm

The major muscle of ventilation, composed of two hemi-diaphragms held together by a central tendon and innervated by the phrenic nerves.