Nephron

Article

May 28, 2022

Nephron - the basic functional and structural unit of the kidney. It consists of two main parts: the renal corpuscle (glomerulus + glomerular capsule) and the renal tubule. The human kidney consists of about a million nephrons, their number is an individual feature - it may vary from 1 to 4 million.

Renal body (Malpighi body)

The renal corpuscle (corpusculum renis) is composed of the glomerulus of the strange network and the surrounding capsule (Bowman's). Primary urine (it is filtered blood devoid of proteins and morphotic elements) is produced in the renal body by physical filtration (the so-called glomerular filtration). During the day, both kidneys produce 110-220 liters of primary urine (for comparison, the final urine is only about 1.5 liters).

Glomerulus

The strange (miraculous) network consists of two arteries - an incoming with greater lumen and an outlet with a narrower lumen, which is important in filtering the blood as pressure builds up. The network consists of about 30 loops of capillary (capillary) blood vessels.

Glomerular Purse (Nephron Purse)

The glomerular capsule (capsula glomeruli - bowmani capsula) consists of 2 gills. The inner (visceral) lamina is adjacent to the glomerulus; it is made up of a single-layer squamous epithelium and cells called epicytes, which have trabecular projections that increase the surface area. The outer (wall) lamina is also made of a single-layer squamous epithelium, but of cells higher than the epicites, having a basal membrane. Between the two laminae of the capsule there is a lumen of the glomerular capsule, where the primary urine flows. The place where the outer lamina changes into the inner lamina is called the vascular pole, and the place where the lumen of the capsule passes into the proximal (proximal) tubule is called the urinary pole. Primary urine - unconcentrated urine - is formed in the nephron capsule.

Renal tubule (nephron tubule)

The entire length of the tubule is made of a single-layer cobblestone (isoprismatic) epithelium. This type of epithelium has the ability to easily and intensively transport ions and organic compounds. Final urine is produced in the tubule (which occurs through the process of resorption and secretion - absorption of water and salt ions). The renal tubule is divided into 3 characteristic sections.

First order spiral tubule (proximal tubule)

First order tortuous tubule (proximal; tortuous proximal; tubulus contortus I ordinis) - it arose from the narrowing of the capsule; Like it, it has a characteristic brush border. The length of this part is approximately 14 mm, thickness 40-60 μm. It is followed by obligatory (obligatory) feedback resorption and tubular secretion. Water, ions (eg Na +, K +, Ca2 +, Mg2 +, Cl−) and organic compounds (glucose, organic acids, amino acids) return to the blood, while some substances (eg uric acid) are secreted into the tubular lumen.

Nephron loop (Henle loop)

Nephron loop (Henle's loop) - consists of the descending and ascending arms (which, unlike the proximal and distal tubules, are located in the spinal part of the kidney). The descending arm epithelium is permeable to water, while the ascending epithelium is permeable to salt ions (actively resorbs ions and passively resorbs urea). In this part of the nephron, the urine becomes concentrated (the longer the loop, the more concentrated the urine), because the body does not want to lose water. This mechanism is called a countercurrent amplifier. The diameter of the loops is 15 μm, but the length varies (it ranges between 4–8 mm). Reptile kidneys do not have a loop, and in birds it is shorter and does not always have a descending loop (this type of loop is called a short loop). Second row winding tubule