Question

Blood enters the glomerulus through the _______ and exits the glomerulus through the ___________. a. efferent arteriole \(\ldots\) afferent arteriole b. efferent arteriole \(\ldots\) distal tubule c. proximal tubule \(\ldots\) efferent arteriole d. afferent arteriole \(\ldots\) efferent arteriole

Short answer

d. afferent arteriole \text{...} efferent arteriole

Step-by-step solution

Understand the Structure of a Nephron

The nephron is the functional unit of the kidney. It includes the glomerulus, where blood filtration begins. The glomerulus receives blood from an arteriole and blood exits through another arteriole.

Identify the Input Vessel

The blood enters the glomerulus through the afferent arteriole. This vessel carries blood towards the glomerulus.

Identify the Output Vessel

After filtration in the glomerulus, the blood exits through the efferent arteriole.

Match the Answer

From the given choices, the correct option that states blood enters through the afferent arteriole and exits through the efferent arteriole is option d.

Key concepts

glomerulus

The glomerulus is a tiny ball-shaped structure made of capillary blood vessels, located at the beginning of a nephron in the kidney. It plays a crucial role in the body's filtration process. This intricate network of capillaries is contained within Bowman's capsule.
The primary function of the glomerulus is to filter blood plasma. Small molecules such as water, glucose, salts, and urea are passed through the glomerular membrane, while larger proteins and blood cells remain in the bloodstream.
The process of blood entering the glomerulus and being filtered is known as glomerular filtration. The filtration barrier has three layers:

• Endothelial cells
• Basement membrane
• Epithelial cells known as podocytes

These layers together enable the glomerulus to selectively filter blood, allowing the nephron to perform its essential functions in the kidney.

afferent arteriole

The afferent arteriole is a small artery that carries blood toward the glomerulus of the nephron. It is larger in diameter compared to the efferent arteriole, which helps maintain the necessary pressure for filtration.
After the blood arrives at the nephron via the afferent arteriole, it enters the glomerulus for filtration. The larger diameter of the afferent arteriole compared to the efferent arteriole creates a pressure difference. This pressure is crucial as it drives the filtration of blood through the glomerulus.
Blood carrying a variety of substances such as oxygen, nutrients, and waste products enters the glomerulus through the afferent arteriole. From here, it's filtered inside the glomerulus to form what is known as filtrate, the starting point for urine formation.

efferent arteriole

The efferent arteriole is the blood vessel that carries blood away from the glomerulus after it has been filtered. Unlike veins that carry blood away from organs, the efferent arteriole continues to branch into the blood supply network of the nephron.
This vessel is smaller in diameter compared to the afferent arteriole, creating higher pressure in the glomerulus. This pressure aids in efficient filtration. The efferent arteriole's structure ensures that essential substances like large proteins and blood cells remain in the bloodstream after glomerular filtration.
After leaving the glomerulus, the filtered blood moves through the efferent arteriole to the network of capillaries that surround the nephron tubules. Here, essential ions and nutrients may be reabsorbed back into the blood, making the efferent arteriole essential for maintaining the body's homeostasis.

blood filtration

Blood filtration is a critical process that occurs in the kidneys, mainly within the network of nephrons. It starts in the glomerulus, where blood brought by the afferent arteriole undergoes filtration.
In the glomerulus, the filtration barrier allows water and small solutes such as glucose, amino acids, and ions to pass through while restricting larger molecules like proteins and cells. The resulting filtrate collects in Bowman's capsule and proceeds to the rest of the nephron.
This filtration ensures that various waste products, like urea, creatinine, and excess ions, are removed from the bloodstream, forming the initial stage of urine production. Post-filtration, the remaining blood exits the glomerulus via the efferent arteriole, continuing on to the kidney's capillary network.
The whole process is essential for maintaining fluid balance, electrolyte balance, and overall homeostasis in the body. Efficient blood filtration by the glomerulus is vital for eliminating waste while retaining necessary substances.