Question 1: Renal Anatomy

Which of the following structures will filtrate enter after it leaves the distal convoluted tubule?

• Correct Answer: D. Collecting duct

• Explanation: In the flow of the nephron, the distal convoluted tubule (DCT) is the final segment of the tubule itself. Once the filtrate leaves the DCT, it empties into the collecting duct, which then transports the processed fluid toward the renal pelvis.

Question 2: Immune System Cells

Which of the following cells is not a nonspecific phagocytic white blood cell?

• Correct Answer: A. T lymphocytes

• Explanation: Neutrophils, macrophages, and monocytes are all part of the innate immune system and act as nonspecific phagocytes to ingest pathogens. In contrast, T lymphocytes are part of the adaptive immune system; they are highly specific and do not function as phagocytes.

Question 3: Nervous System Support

Which of the following cells controls the blood-brain barrier?

• Correct Answer: A. Astrocytes

• Explanation: Astrocytes are star-shaped glial cells that play a critical role in maintaining the homeostatic environment of the CNS. They wrap their "foot processes" around capillaries to help form and regulate the blood-brain barrier, controlling which substances can pass from the blood into the brain tissue.

Question 4: Skeletal System Joints

Which of the following is classified as a fibrous joint?

• Correct Answer: C. Cranial suture

• Explanation: Fibrous joints are connected by dense connective tissue and typically allow for little to no movement. Cranial sutures, which join the bones of the skull, are the classic example of this joint type. (In contrast, the elbow is a synovial joint, while the symphysis pubis is cartilaginous).

Quick Concept Review

• The Osteon: The functional unit of bone. The Haversian canal runs through the center, housing blood vessels and nerve fibers.

• Muscle Contraction: Calcium ions are the primary trigger for contraction; they bind to the troponin-tropomyosin complex, shifting it to reveal active sites on the actin filament.

• Sensory Neurons: Use the mnemonic "A" for Afferent to remember that these neurons are Arriving at the Central Nervous System with sensory information.

In which of the following structures will filtrate enter after it leaves the distal convoluted tubule?

A. glomerulus

B. proximal convoluted tubule

C. loop of Henle

D. collecting duct