Glomerular capsule

Renal corpuscle—contains the glomerular capsule, which is vascular and plays a critical role in filtration of the blood... 

Upon leaving the glomerular capillaries, the filtrate enters the first portion of the tubule, Bowman s capsule. The glomerulus is pushed into Bowman s capsule, much like a fist pushed into a balloon or a catcher s mitt. From Bowman s capsule, the filtrate passes through the proximal tubule,... 

Figure 19.2 Basic renal processes. These processes include filtration, reabsorption, and secretion. (1) Filtration is the movement of fluid and solutes from the glomerular capillaries into Bowman s capsule. (2) Reabsorption, which takes place throughout the nephron, is the movement of filtered substances out of the tubule and into the surrounding peritubular capillaries. (3) Secretion is the movement of selected unfiltered substances from the peritubular capillaries into the renal tubule for excretion. Any substance that is filtered or secreted, but not reabsorbed, is excreted in the urine.

The first step in the formation of urine is glomerular filtration. The barrier to filtration is designed to facilitate the movement of fluid from the glomerular capillaries into Bowman s capsule without any loss of cellular elements or plasma proteins. Maximizing GFR has two advantages ... 

The main filtering units of the kidneys are called nephrons-, about one million nephrons are present in each kidney. Each nephron consists of a renal corpuscle and a unit called a tubule. Blood carrying normal metabolic wastes such as urea and creatine moves through a portion of the corpuscle called the glomerulus, where a filtrate forms that contains water, normal metabolic products, and also waste products the filtrate collects in another unit called Bowman s capsule. Glomerular filtrate then moves into a highly convoluted and multifaceted set of tubes - the tubule - where most useful products (water, vitamins, some minerals, glucose, amino acids) are taken back into the blood, and from which waste products are collected as urine. The relative amounts of water and minerals secreted or returned to the blood are under hormonal control. 

The smallest functional unit of the kidney is the nephron. In the glomerular capillary loops, ultrafiltration of plasma fluid into Bowman s capsule (BC) yields primary urine. In the proximal tubules (pT), approx. 70% of the ultrafiltrate is retrieved by isoosmotic reabsorption of NaCl and water. In the thick portion of the ascending limb of Henle s loop (HL), NaCl is absorbed unaccompanied by water. This is the prerequisite for the hairpin countercurrent mechanism that allows build-up of a very high NaQ concentration in the renal medulla In the distal tubules (dT), NaCl and water are again jointly reabsorbed. At the end of the nephron, this process involves an aldosterone-controlled exchange of Na+ against 1C or H. In the collecting tubule (C), vasopressin (antidiuretic hormone, ADH) increases the epithelial permeability for water, which is drawn into the hyperosmolar milieu of the renal medulla and thus retained in the body. As a result, a concentrated urine enters the renal pelvis. 

Emtricitabine (FTC) is a fluorinated analog of lamivudine with a long intracellular half-life (> 24 hours), allowing for once-daily dosing (Figure 49-2). Oral bioavailability of the capsules is 93% and is unaffected by food, but penetration into the cerebrospinal fluid is low. Elimination is by both glomerular filtration and active tubular secretion. 

Extracellular Collagen Skin Tendon Aorta Glomerular basement membrane Lens capsule 58,59,71 60 61 62,64,74 63... 

Figure 29.3. (A) Glomerular capillaries are positioned between two arterioles that regulate hydrostatic pressure and blood flow through the capillaries, thereby controlling glomerular filtration rate. (B) The glomerular basement membrane consists of three layers the capillary endothelium, the capillary basement membrane, and podocytes from epithelial cells of Bowman s capsule. The capillary basement membrane also contains three layers the lamina rara interna (blood side), lamina densa, and lamina rara externa (epithelial side). (From Guyton, A. C., and Hall, J. E. Textbook of Medical Physiology, 11th ed. Elsevier Saunders Company, Philadelphia, 2006. Reproduced with permission.)...

Pccap = glomerular-capillary hydrostatic pressure IIbc - oncotic pressure in Bowman s capsule Pbc = hydrostatic pressure in Bowman s capsule Ifccap - oncotic pressure in the glomerular capillary... 

---