Final answer:
The letter that indicates the visceral layer of the glomerular capsule is D. Therefore, the correct option is 4.
Step-by-step explanation:
The correct answer is D, indicating the visceral layer of the glomerular capsule. This layer, composed of podocytes, forms the inner portion of Bowman's capsule and plays a crucial role in the renal filtration process.
Podocytes have intricate pedicels that create a filtration membrane, facilitating the selective passage of substances during glomerular filtration. The visceral layer's specialized structure contributes to the kidney's ability to regulate and filter blood, essential for maintaining fluid and electrolyte balance in the body.
Understanding the anatomical components of the glomerular capsule is fundamental for comprehending renal function and filtration processes in the kidneys.
Therefore, the correct option is 4.