What shifts with age
Before you read
Test yourself first: 3 questions
Question 1 of 3
Gas exchange in the lungs occurs across the:
Answer: A. Oxygen and carbon dioxide diffuse across the thin barrier between an alveolus and its surrounding capillary. The bronchi and trachea only conduct air.
Question 2 of 3
Which vessel type is the site of gas and nutrient exchange?
Answer: A. Capillaries have walls one cell thick, which is what allows oxygen, nutrients and wastes to diffuse across. Arteries and veins transport blood but do not exchange across their walls.
Question 3 of 3
Homeostasis is best defined as the body's ability to:
Answer: A. Homeostasis is the maintenance of stable internal conditions — temperature, pH, glucose, fluid balance — despite changes outside the body. It is usually achieved by negative feedback.
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