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Ch. 28 Pregnancy and Human Development
Hoehn - Marieb Human Anatomy & Physiology, 12th edition
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 28, Problem 2

Most systems are operational in the fetus by four to six months. Which system is the exception to this generalization, affecting premature infants?
(a) the circulatory system
(b) the respiratory system
(c) the urinary system
(d) the digestive system

Verified step by step guidance
1
Step 1: Understand the general development timeline of fetal organ systems. Most major systems such as circulatory, urinary, and digestive systems become functional between four to six months of gestation.
Step 2: Identify the system that is typically not fully operational by this time and is known to cause complications in premature infants.
Step 3: Recall that the respiratory system, particularly the lungs, matures later in fetal development and often remains underdeveloped in premature infants.
Step 4: Recognize that this underdevelopment of the respiratory system leads to difficulties in breathing and oxygen exchange in premature babies, making it the exception to the general rule.
Step 5: Conclude that the respiratory system is the system that is not fully operational by four to six months and affects premature infants the most.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Fetal System Development Timeline

Most organ systems in a fetus develop and become functional between four to six months of gestation, preparing the infant for life outside the womb. Understanding this timeline helps identify which systems are mature at birth and which may still be underdeveloped, especially in premature infants.
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Timeline of the Prenatal Period

Respiratory System Maturity in Premature Infants

The respiratory system is often underdeveloped in premature infants because the lungs and surfactant production mature late in gestation. This immaturity can cause breathing difficulties, making the respiratory system a common exception to the general fetal system readiness by four to six months.
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Affinity Maturation

Impact of System Immaturity on Premature Infant Health

Immature organ systems in premature infants can lead to complications such as respiratory distress syndrome or feeding difficulties. Recognizing which systems are typically immature helps in managing and treating premature newborns effectively.
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What is the Reproductive System?
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