urea – моча
stroma – строма
parenchyma – паренхима
fibrous capsule – волокнистая капсула
delicate – тонкий
interstitial – промежуточный
49. The urinary system: kidney vascular sypply
Vascular supply begins with the renal artery, enters the kidney the hilum, and immediately divides into interlobar arteries. The arteries supply the pelvis and capsule before passing direct between the medullary pyramids to the corticomedullary junction. The interlobar arteries bend almost 90 degrees to form shoarching, arcuate arteries, which run along the corticomedullary junction. The arcuate arteries subdivide into numerous fine interlobul arteries, which ascend perpendicularly to the arcuate arteries through the cortical labyrinths to the surface of the kidney. Each interlobular artery passes midway between two adjacent medullary rays.
The interlobular arteries then give off branches that become the afferent arterioles of the glomeruli.
As the afferent arteriole approaches the glomerulus, some its smooth muscle cells are replaced by myoepithelio—id cells, which are part of the juxtaglomerular apparatus. The juxtaglomerular apparatus consists of juxtaglomeru—lar cells, polkissen cells, and the macula densa.
Cells of the distal convoluted tubule near the afferent arteriole are taller and more slender than elsewhere in the distal tubule.
The juxtaglomerular cells secrete an enzyme called re—nin, which enters the bloodstream and converts the circulating polypeptide angiotensinogen into angiotensin I. An—giotensin I is converted to angiotensin II, a potent vaso constrictor that stimulates aldosterone secretion from the adrenal cortex. Aldosterone increases sodium and water reabsorption in the distal portion of the nephron.
Their nuclei are packed closely, so the region appear darker under the light microscope. The macula densa is thought to sense sodium concentration in the tubular fluid.
Polkissen cells are located between the afferent and ef—fer ent arterioles at the vascular pole of the glomerulus, adja cent to the macula densa.
Their function is unknown. Efferent glomerular arteriole divides into a second system of capillaries, the peritub—ufar plexus, which forms a dense net work of blood vessels around the tubules of the cortex.
Arterial supply of the medulla is provided by the efferent arte rioles of the glomeruli near the medulla. The arterio—lae rectae and the corresponding venae rectae with their respective capillary networks comprise the vasa recta, which supplies the medulla. The endothelium of the venae rectae is fenestrated and plays an important role in maintaining the osmotic gradi ent required for concentrating urine in the kidney tubules.
New words
renal artery – почечная артерия
renal veins – почечные вены
expanded upper – расширенный верхний
minor calyces – незначительные чашечки
to supply – снабжать
arcuate arteries – дугообразные артерии
to subdivide – подразделять
numerous – многочисленный
interlobul – междолевой
to ascend – поднимать
perpendicularly – перпендикулярно
arcuate arteries – дугообразные артерии
50. The urinary system: ureters, uretra
The calyces, renal pelves, and ureters constitute the main excretory ducts of the kidneys. The walls of these structures, in particular the renal pelvis and ureter, consist of three coats: an inner mucosa, middle muscularis, and an outer adventitia.
Mucosa of the calyces and ureter is lined by a transitional epithelium, which varies in thickness with the distention of the ureter. In the collapsed state, the cells are cuboidal with larger с shaped cells in the superficial layer. In the relaxed state, the lumen of the ureter is thrown into folds that generally disappear when the organ dilates during urine transport. Muscularis consists of an inner longitudinal and an outer circular layer of smooth muscle. In the distal ureter, an additional discontinuous outer longitudinal layer is present.
Adventitia consists of loose connective tissue with many large blood vessels. It blends with the connective tissue of the surrounding structures and anchors the ureter to the renal pelvis. The urinary bladder functions as a strong organ for urine. The structure of the wall of the bladder is similar to but thicker than of the ureter. Mucosa of the urinary bladder is usually folded, depending the degree of the bladder distention. The epithelium is transitional and the number of apparent layers depends on the fullness of the bladder. As the organ becomes distended, the superficial epithelial layer and the mucosa become flattened, and the entire epithelium becomes thinner. At its fullest distention, the bladder epithelium maybe only two or three cells thick. Lamina propria consists of connective tissue with abundant elastic fibers. Muscularis consists of prominent and thick bundles of smooth muscle that are loosely organized into three layers. Adventitia covers the bladder except on its superior part, where serosa is present. Male urethra serves as an excretory duct for both urine and semen. It is approximately 20 cm in length and has three anatom ic divisions. The prostatic portion is lined by transitional epithelium similar to that of the bladder. The prostatic urethra is surrounded by the fibromuscular tissue of the prostate, which normally keeps the urethral lumen closed. In the membranous and penile portions, the epithelium is pseudostratified up to the glans. At this point, it becomes stratified squamous and is continuous with the epidermis of the external part of the penis. The membranous urethra is encircled by a sphincter of skeletal muscle fibers from the deep transverse perineal muscle of the urogenital diaphragm, which also keeps the urethral lumen closed. The wall of the penile urethra contains little muscle but is surrounded and supported by the cylindrical erectile mass of corpus spongiosum tissue. Female urethra is considerably shorter than that of the male urethra. It serves as the terminal urinary passage, conducting urine from the bladder to the vestibule of the vulva. The epithelium begins at the bladder as a transitional variety and becomes stratified squamous with small areas of a pseudostratified columnar epithelium. The muscularis is rather indefinite but does contain both circu lar and longitudinal smooth muscle fibers. A urethral sphincter is formed by skeletal muscle as the female urethra passes through the urogenital diaphragm.
New words
ureter – мочеточник
renal pelvis – почечная лоханка
calyces – чашечки
urethra – уретра
51. The kidney's function
The kidneys are filters which remove waste products from the blood. In the human each is a bean— shaped organ, some four inches long and about two inches wide. The two are situated high up on the posterior abdominal wall behind the peritoneum and in front of the lats ribs and the upper two lunbar transverse processes. Each is invested by a fibrous capsule surrounded by more or less peri—nephric fat. On the upper pole of each is a supra—renal gland. On the medical side is a notch called the hilum where the vessels and the ureter are attached.
Vertical selections through a kidney discloses three more or less concentric zones. The other light—colored zone is the renal cortex, within this is the darker renal medulla and within this again is a space – the renal sinus which is normally occurred by a fibrous bag called the renal pelvis. The pelvis opens below into the ureter. The cortex extends inwards in a series of renal columns which divide the medulla into a number of renal pyramids. Each pyramid has a free rounded projection – a renal papilla – which lies in a cap – like extension, of the pelvis cal led a renal calyx. The pelvis is lined by transitioual epithelium, which extends the calyces and covers the papillae.
Within the cortex each minute artery presents along its course a convoluted knot, called a glomerulus; the branch which enters the knot is the afferent vessel, that which leaves is she efferent vessel. Each glomerulus
