Why does the afferent arteriole have a larger diameter than the efferent?

Explanation: The afferent arteriole is the arteriole that brings blood to the glomerulus. It is larger in diameter than the efferent arteriole. This is to provide for the increased blood pressure in the glomerulus for ultrafiltration to take place.

Why is the efferent arteriole not an Venule?

The afferent-efferent arteriole situation is unique because blood usually flows out of capillaries into venules and not into other arterioles. The efferent arterioles divide to form a network of capillaries, called the , which surround tubular portions of the nephron in the renal cortex.

Why arterioles are the primary site of both resistance and regulation of blood pressure?

Arterioles have muscular walls that usually consist of one or two layers of smooth muscle. They are the primary site of vascular resistance. This reduces the pressure and velocity of blood flow to enable gas and nutrient exchange to occur within the capillaries.

Why is it important that the efferent arteriole has a smaller diameter when compared to the afferent arteriole?

The efferent arteriole carries blood away from the glomerulus. Because it has a smaller diameter than the afferent arteriole, it creates some resistance to blood flow, producing the back-up of blood in the glomerulus which creates higher pressure in the glomerular cavity.

How do afferent and efferent arterioles differ?

Difference between the efferent arteriole and afferent arteriole. Afferent arteriole is a branch of the renal artery that brings in blood to the glomerulus. Efferent arteriole is a branch of the renal artery that drains blood away from the glomerulus. Afferent arteriole carries blood to the glomerulus.

Does capillaries reunite to form arteries?

After diffusion, they carry away carbon dioxide and other nitrogenous waste from the tissue and merge to form veins. So, the correct answer is arteries are best defined as the vessel which carries blood from one visceral organ to another visceral organ and breaks into capillaries which reunite to form a vein.

What capillaries come off the efferent arterioles associated with cortical nephrons?

Throughout the length of the nephron, capillaries called peritubular capillaries lie adjacent to all segments of the tubule. They originate from the efferent arteriole and are important for solute transport throughout the tubule.

Why are capillaries sometimes called the exchange vessels of the cardiovascular system?

Capillaries are tiny vessels that connect arterioles to venules. They have very thin walls which allow nutrients from the blood to pass into the body tissues. Waste products from body tissues can also pass into the capillaries. For this reason, capillaries are known as exchange vessels.

What is the difference between arterioles and capillaries?

Arterioles carry blood and oxygen into the smallest blood vessels, the capillaries. Capillaries are so small they can only be seen under a microscope. The walls of the capillaries are permeable to oxygen and carbon dioxide. Oxygen moves from the capillary toward the cells of the tissues and organs.

What is the relationship between arteries and capillaries?

Eventually, the smallest arteries, vessels called arterioles, further branch into tiny capillaries, where nutrients and wastes are exchanged, and then combine with other vessels that exit capillaries to form venules, small blood vessels that carry blood to a vein, a larger blood vessel that returns blood to the heart.

Why do capillaries have fenestrae in their endothelium?

The capillaries have small openings in their endothelium known as fenestrae or fenestra, which are 80 to 100 nm in diameter. Fenestra have a non-membraneous, permeable membrane, which is diaphragm-like and spanned with fibrils. This arrangement allows quick movement of macromolecules in and out of the capillary.

How do substances move in and out of the capillary walls?

Substances move in and out of the capillary walls as the blood exchanges materials with the cells. Before leaving the tissues, capillaries unite into venules, which merge to form larger and larger veins that eventually return blood to the heart.

What percentage of capillaries are fully filled with blood?

Second, at any give time only a fraction (25\%) of capillaries are fully filled with blood, especially in tissues at rest, as blood flow in microvessels is dependent on the metabolic activity of the tissue and is regulated at the sites of their origin by sphincter muscles.