Which of the following is NOT a component of the genitourinary system?

Correct Answer: C

Rationale: The rectum is part of the digestive system, not the genitourinary system. The genitourinary system comprises organs involved in reproduction and urine formation and excretion, such as the kidneys, urethra, and bladder. Choices A, B, and D are all components of the genitourinary system. The kidneys filter blood and produce urine, the urethra is a tube that carries urine from the bladder out of the body, and the bladder stores urine before it is excreted.

Correct Answer: C

Rationale: The majority of nutrient absorption occurs in the small intestine. The small intestine is where the final stages of digestion take place, and it is specialized for absorption with its large surface area and villi that increase nutrient absorption efficiency. The mouth is responsible for mechanical digestion through chewing, the stomach primarily aids in digestion through mixing and breakdown of food, and the large intestine mainly absorbs water and electrolytes, with minimal nutrient absorption.

Correct Answer: D

Rationale: The correct answer is D. The immune system's primary function is to help the body avoid, detect, and eliminate infections. It does so by recognizing and responding to harmful pathogens, such as bacteria and viruses, to maintain the body's health and well-being. Choices A, B, and C are incorrect because the immune system is not controlled by the hypothalamus, its main role is not to filter toxins out of the blood, and while it can stimulate the production of certain immune cells, it does not directly stimulate the production of blood cells in response to infections.

Correct Answer: B

Rationale: The correct answer is B - a gene. Genes are the smallest units that can encode for a trait as they contain the specific instructions for producing a particular characteristic or protein. While codons are sequences of nucleotides that code for specific amino acids in a protein, they are not the smallest unit that encodes for a trait. Nucleotides are the building blocks of DNA and RNA, and chromosomes are made up of DNA and proteins, containing many genes.

Correct Answer: D

Rationale: Long bones are characterized by their elongated shape and include bones like the ulna, fibula, and humerus. These bones are crucial for providing support, structure, and facilitating movement in the human body. The sacrum, clavicle, and patella are not classified as long bones. The sacrum is a triangular bone at the base of the spine, the clavicle is a collarbone, and the patella is the kneecap. While these bones have important functions, they do not fit the definition of long bones due to their shape and structure.