Which populations are at a higher risk for dehydration?

A. The onset of menstruation (menarche) in adolescent females results in regular blood loss each month, increasing iron requirements to replace lost hemoglobin and prevent iron-deficiency anemia. This is the primary physiological reason adolescent girls need more iron than their male peers. Adequate iron intake is essential for oxygen transport, energy metabolism, and proper growth during adolescence.

B. Rapid skeletal growth occurs in both adolescent males and females, but it is not the main reason for higher iron needs in females. Bone growth primarily requires calcium, phosphorus, and vitamin D rather than iron.

C. Basal metabolic rate (BMR) may fluctuate during adolescence, but a decline in BMR does not increase iron requirements. Iron needs are linked to blood production, not changes in metabolism.

D. While thyroid hormones regulate metabolism, their increased production is not the primary factor driving higher iron requirements in adolescent females.

A. The small intestine is the primary site of nutrient absorption in the digestive system. After food is mechanically broken down in the mouth and chemically digested in the stomach, it moves into the small intestine, where most nutrients are absorbed into the bloodstream or lymph. The inner lining of the small intestine contains finger-like projections called villi, which are covered by even smaller microvilli, forming the brush border. This structure greatly increases the surface area for absorption. Carbohydrates are broken down into simple sugars, proteins into amino acids, and fats into fatty acids and glycerol, all of which are absorbed here. Additionally, vitamins, minerals, and water are also absorbed in the small intestine, making it essential for overall nutrition and energy supply.

B. The gall bladder stores and concentrates bile produced by the liver. Bile is released into the small intestine to emulsify fats and aid in their digestion, but the gall bladder itself does not participate in nutrient absorption.

C. The bile duct is a conduit that transports bile from the liver and gall bladder to the small intestine. While it plays an important role in fat digestion, it does not directly absorb nutrients from food.

D. The oropharynx is part of the throat located behind the mouth, responsible for swallowing and directing food from the mouth to the esophagus. It has no role in nutrient absorption, which occurs further along in the digestive tract.