Anatomy and Physiology of the Respiratory System - Fetal Development and Adult Anatomy

Comprehensive practice flashcards covering fetal lung development phases, neonatal respiratory stats, pulmonary anatomy, and clinical conditions like RDS and Empyema.

Embryonic period

The first phase of lung development occurring in the 26th week after fertilization, where lungs appear as small buds rising from the esophagus.

Pseudoglandular period

A developmental phase from the 6th to 16th week of gestation where segmental, subsegmental, and all lung segments appear, and about 20 generations of airways are present.

Canalicular period

A stage between the 17th and 26th week of gestation where terminal bronchioles proliferate, primitive bronchioles appear, and lungs become highly vascularized.

Terminal sac period

A period from week 26 until full term (40 weeks) where the entire acinus develops and Type I and II alveolar cells become visible.

Alveolar period

Starts at 32 weeks and continues through childhood, during which alveolar-capillaries increase to about 300 million.

Newborn lung compliance

The average measurement is approximately $0.005\,\text{L/cm H}_2\text{O}$.

Newborn airway resistance

The average value is approximately $30\,\text{cm H}_2\text{O/L/sec}$.

Cotyledons

The 15 to 20 segments that anatomically compose the placenta.

Umbilical Arteries

Two vessels that carry deoxygenated blood from the fetus to the placenta.

Umbilical Veins

Vessels through which oxygenated fetal blood flows out of the chorionic villi and returns to the fetus.

Amniocentesis

A procedure used to diagnose fetal abnormalities during early pregnancy, evaluating factors such as lung maturity, bilirubin level, and genetic disorders.

Meconium

The first fetal stool; a thick, sticky, greenish to black material that, if found in amniotic fluid, indicates fetal asphyxia.

Respiratory Distress Syndrome (RDS)

A condition affecting babies born before their Type II alveolar cells can produce adequate pulmonary surfactant ($50\%$ of babies born at 26-28 weeks and $25\%$ at 30-31 weeks).

Vibrassae

Hair follicles located in the vestibule of the nose that act as filters for air entering the body.

Pharyngotympanic tubes

Tubes located in the lateral walls of the nasopharynx that connect to the middle ear to equalize pressure.

Glottis

The narrowest part of the airway in the adult, consisting of the space between the true vocal cords.

Valsalva’s Maneuver

The tight closure of the glottis involving laryngeal walls and vocal cords to stop air from leaving during physical work like lifting or pushing.

Conducting Zone

Airway generations 0–19, extending from the trachea to the terminal bronchioles.

Respiratory Zone

Airway generations 20–28, which serve as the primary site of gas exchange.

Mucociliary Escalator

A transport mechanism where cilia move in an upward wavelike motion through the sol layer to strike the gel layer, moving mucus toward the larynx at a rate of $2\,\text{cm/min}$.

Cellular Immunity

Sensitized lymphocytes responsible for tissue rejection in transplants and the destruction of infected or abnormal cells.

Humoral Immunity

Circulating antibodies involved in allergic reactions and defenses against environmental antigens like pollen or animal dander.

Mast Cells

Cells located in the lamina propria that release substances like Histamine, Heparin, and Leukotrienes when activated, altering bronchial airway diameter.

Type I Pneumocytes

Also known as squamous pneumocytes, these form $95\%$ of the surface area of the alveolar epithelium.

Type II Pneumocytes

Also known as granular pneumocytes, they form $5\%$ of the alveolar epithelium and are the source of pulmonary surfactant.

Arterioles

Referred to as resistance vessels, they supply nutrients to respiratory structures and play an important role in the distribution and regulation of blood.

Hilum

The center of the mediastinal border of the lungs where mainstem bronchi, blood vessels, lymph vessels, and nerves enter.

Empyema

A clinical condition where pus is present in the space between the visceral and parietal pleura.

Diaphragm

The major muscle of ventilation which receives its primary motor innervation from the phrenic nerves.