Anooshka's Blog

Arteries distribute blood to specific regions of the body. Once oxygen-rich blood reaches capillary beds, gas exchange occurs between capillaries and tissues. After gas exchange has occurred, how does carbon dioxide-rich blood return back to the heart? The answer lies in a network of vessels about 80,000 miles long: veins ! Veins tend to merge into larger vessels as they get closer to the heart. Their walls get thicker and their diameter of their lumen (central portion of blood vessels through which blood travels) also increases. Venules,  the smallest veins, have a diameter ranging from 0.008 to 1 mm. Postcapillary venules*  drain capillary beds. Just like porous capillaries, they are permeable to fluids and white blood cells. During inflammation, white blood cells often adhere to the endothelium of the postcapillary venule, and then they diffuse through the venule's wall to reach the inflamed tissue.  Figure 2: Venules drain capillary beds and gradually merge into larger veins As

Capillary beds are found in nearly every tissue and organ of the body. Capillaries are minuscule exchange sites where oxygen, nutrients, and hormones pass from the bloodstream into the interstitial fluid (space between capillary walls and cells), and carbon dioxide and metabolic wastes pass from the interstitial fluid back to the bloodstream.  A  capillary bed  is an interconnected network of capillaries. Capillary beds contain different types of capillaries (read about continuous, fenestrated, and sinusoidal capillaries in my previous blog) depending on the organ in which they are located. Blood flow through a capillary bed is called  microcirculation. A capillary bed consists of true capillaries , which are the hundreds of tiny capillaries in which gas and nutrient exchange occurs between the capillary wall and interstitial fluid, and a vascular shunt , which bypasses the true capillaries.  The main arteriole that leads into the capillary bed is called the terminal arteriole . The te

Whenever we hear the phrase "blood vessels", we always think of arteries and how they distribute blood to cells and tissues. However, we hardly think about the billions of microscopic capillaries, the real vessels that supply cells and tissues with blood and nutrients. It is no doubt that arteries branch into arterioles and capillaries, but it is mainly through capillary walls that gases, nutrients, and metabolic wastes diffuse. The tiniest blood vessels, capillaries have a diameter ranging from .008 to .01 mm, roughly 1/1000 the diameter of arteries and 1/18th the diameter of a strand of hair.  Capillaries lack a both a tunica adventitia and tunica media, and consist of a tunica intima so small in diameter that they can fit only one red blood cell at a time, forcing the RBCs to move in a single file. Although capillaries are found in most tissues, some tissues lack these vessels. For instance, the cornea of the eye does not contain many capillaries. It acquires oxygen and nu

How do cells in different regions of the body acquire the nutrients you digest from your sandwich? The answer lies in a long network of blood vessels approximately 62,000 miles long, nearly 2.5 times the circumference of Earth! Blood vessels are integral components of the circulatory system, which serves as a group of "highways" for oxygen and nutrients to travel to various organs of the body. Arteries transport oxygen and nutrients to bodily organs , whereas veins transport deoxygenated blood from cells back to the heart . Blood that contains metabolic wastes from cells is filtered by the renal arteries, and these metabolic wastes leave the body through urine. Anatomy and Physiology of Blood Vessels All blood vessels, except the smallest arterioles, capillaries, and venules, contain three main layers referred to as  tunics .  Figure 2: Anatomy of Blood Vessels Tunica Externa  The outermost layer of a blood vessel is known as the tunica externa  and is formally referred to

On a hot summer day, you go jogging outside and notice that your cheeks are gradually turning red. What causes them to become red? It is the arteries in your cheeks dilating in an attempt to release the heat in your body. Not only do arteries help regulate body temperature, but they also play a crucial role in delivering blood to organs, keeping you alive. Damage to arteries can have life-threatening consequences. For instance, cerebral arteries that are ruptured or obstructed in a stroke can block blood supply to the brain, resulting in death if immediate action to restore blood supply is not taken. To recap, arteries transport blood (rich in oxygen and nutrients) from the heart to bodily organs. As arteries carry blood away from the heart, they branch into smaller vessels. Arteries are classified into three types based on their size and proximity to the heart: elastic, muscular, and arterioles. Elastic Arteries Elastic arteries are closest to the heart and have the largest diameter,