A patient is recovering from a bone fracture. Which dietary component is crucial for promoting bone healing during this time?

A. Providing energy:Carbohydrates are broken down into glucose, which is the body’s preferred and most efficient fuel source for cellular respiration (ATP production), especially for the brain and muscles during exercise.

B. Building tissues:While some carbohydrates are found in cell markers, the primary "building blocks" of body tissues (muscles, skin, organs) are proteins.

C. Regulating hormones:While some hormones are glycoproteins, the major class of molecules used to synthesize steroid hormones are lipids (specifically cholesterol), and many others are protein-based.

D. Insulating organs:Thermal insulation and physical cushioning of organs is the primary function of lipids (adipose tissue/fat).

A. Cardiac muscle:Cardiac muscle is found only in the heart. It is striated and involuntary with unique intercalated discs and autorhythmicity; it is notthe muscle that lines most hollow organs (like intestines, bladder, blood vessels).

B. Smooth muscle:Smooth muscle is non-striated, involuntary muscle located in the walls of hollow organs (e.g., gastrointestinal tract, bladder, uterus), blood vessel walls, and bronchi. It generates slow, sustained contractions for peristalsis, vasomotion, and other automatic functions.

C. Skeletal muscle:Skeletal muscle is striated and under voluntary control, attached to bones to produce movement; it is not the primary muscle of hollow organ walls.

D. Striated muscle:“Striated muscle” is a descriptive term that includes skeletal and cardiac muscle (both have striations). Since the question asks specifically about involuntary muscle in hollow organs, striated muscle is not the correct category.