النسج 2 The Urinary System الجهاز البولي محاضرة 9 أ. د. رائدة الخاني The Urinary System . Two kidneys . A ureter for each kidney . Urinary bladder . Urethra 2 Kidneys: . Dimensions: about 10x6x3cm . Protected by . Ribs 11 + 12 . Lateral surface is convex . Medial surface is concave ,contains: vessels سرة الكلية Renal Hilus . ureter and nerves . An adrenal gland lies superior to each kidney 3 4 Function . Filtration of blood (1700 L/day) and excreting urine (1L) . Eliminate waste products of metabolism in the urine . Regulating body fluid and salt balance . maintains the appropriate acid balance of plasma . Regulation of blood pressure . Hormone secretion: Endocrine function . Renin secretion: Regulation of blood pressure Function . Erythropoietin secretion: Kidney is the main organ for production of erythropoietin in postnatal life. Secreted by the interstitial fibroblasts in close association with the peritubular capillaries and proximal convoluted tubules. The steroid prohormone vitamin D, initially produced in skin keratinocytes, is hydroxylated in kidneys to an active form (1,25- dihydroxyvitamin D3 or calcitriol ) involved in regulating calcium balance. 6 . Kidney has two regions outer : القشر Cortex . inner : اللب Medulla . -Columns of cortex divide medulla into “pyramids”Darker, cone-shaped medullary or renal pyramids include collecting tubules 7 . Renal pelvis (=basin) . Superior part of ureter كؤيسات Branches to form two or three major calices . divide again, minor calices: collect urine from papillae of pyramids 8 Renal Arteries Right and left renal arteries are branches of the Aorta. They enter the kidney in the hilus and divide>> segmental A. >>9 segmental A. >> interlobar A. >> arcuate A. >> >>cortical radiate A. >> glomerular arterioles: afferent arterioles >> glomerular capillaries >> efferent arterioles. 10 Nephrons . The number of nephrons in a kidney is determined in utero, and it remains constant after birth. The final number is dependent on gestational age and a favorable intrauterine environment . 15,000 at 15 weeks of gestation to >740,000 by 40 weeks . In adults: ranging from 227,000 to over 2,000,000 11 Two types of nephrons – o Cortical nephron . 80-85% of nephrons . Renal corpuscles are in outer cortex and loops of Henle lie mainly in cortex o Juxtamedullary nephrons . 15-20% of nephrons . Renal corpuscles close to medulla and long loops of Henle extend into deepest medulla اﻻنبوب البولي Uriniferous tubule (functional unit for forming urine) Nephron: includes جسيم الكلية Renal corpuscle . الكبيبة Glomerulus - (tuft of capillaries) محفظة الكبيبة Glomerular capsule - (Bowman’s capsule) . Tubular section اﻻنبوب الملفف Proximal convoluted tubule – القريب/الداني عروة هانلة Loop of Henle – اﻻنبوب الملفف البعيد/القاصي Distal convoluted tubule – 13 القناة الجامعة Collecting duct 14 Structure of Renal Corpuscle :with a capsular space lined by محفظة بومان Bowman’s capsule . cover capillaries to form visceral layer الخﻻيا القدمية Podocytes- -Simple squamous cells form parietal layer of capsule . Glomerular capillaries arise from afferent arteriole & form a ball of capillaries before emptying into efferent arteriole 16 . Proximal convoluted tubule . Confined to renal cortex . Cuboidal epithelial cells with long microvilli, rich in mitochondria, rich in glycogen . Resorption of water, ions and solutes . Loop of Henle is composed of : . Descending limb . Thin segment . Thick ascending limb . Distal convoluted tubule . Confined to the renal cortex . Simple cuboidal epithelium with short villi . Selective secretion and resorption of ions 17 . Collecting duct: . Each receives urine from several nephrons . Run straight through cortex into the deep medulla . At papilla of pyramid ducts join to form larger papillary ducts . Empty into minor calices . Role: conserve body fluids . ADH (antidiuretic hormone) increases the permeability of the collecting ducts to water >> water reabsorption . This decreases the total volume of urine . Alcohol inhibits the release of ADH >> less water is reabsorbed >> more urine 18 20 Renal corpuscule 21 22 Function of the Renal Nephron A. Filtration: in glomeruli fluid is squeezed out of the glomerular capillary bed B. Reabsorption: in proximal tubules; most nutrients, water and essential ions (Na+,..) are returned to the blood of the peritubular capillaries. C. Secretion: in distal tubules Moves additional undesirable molecules into tubule from blood of peritubular capillaries (effect of aldosterone) 24 25 Juxtaglomerular Apparatus الجهاز المجاور للكبيبة 1. macula densa(dense spot): specialized epithelial cells of the distal tubule: Monitor electrolyte concentration 2. juxtaglomerular cells: modified smooth muscle cells in the wall of the afferent arteriole. Respond to changes in blood pressure: >> Renin 3. Extraglomerular mesangial cells: Respond to hypoxia >>Erythropoietin . Number of Nephrons remains constant after birth. If injured, no replacement. Dysfunction is not evident until function declines by 25% of normal (other Nephrons handle the extra work) . Removal of one kidney causes enlargement of the remaining until it can filter at 80% of normal rate of 2 kidneys The Ureters . tubes about 25 cm long leaving each renal pelvis . 1-10mm diameter . One for each kidney; they carry urine to the bladder . Enter posterolateral corners of bladder 29 Three layers . Transitional epithelium of mucosa stretches when ureter fill . Muscularis . Inner longitudinal, outer circular layers . Inferior 3rd with extra longitudinal layer) . Adventitia (external) 30 31 Urinary Bladder . Collapsible muscular sac . Stores and expels urine . Lies on pelvic floor posterior to pubic symphysis . Males: anterior to rectum . Females: just anterior to the vagina and uterus . If full: bladder is spherical and extends into abdominal cavity (holds about 500 ml ) . If empty: bladder lies entirely within pelvis with shape like upside-down pyramid 32 33 Urinary Bladder is a smooth flat area bordered by 2 المثلث المثاني Trigone . ureteral openings and one urethral opening. Bladder wall has 4 layers . Mucosa with distensible transitional epithelium and lamina propria (can stretch). Submucosa: thin layer of vascularized connective t. Thick muscularis: . 3 layers of smooth muscle . Fibrous adventitia, except upper part (serosa) 35 Urethra . Females . length about 3-4 cm, opens between clitoris & vagina . histology . transitional changing to nonkeratinized stratified squamous epithelium, lamina propria with elastic fibers & circular smooth muscle . Short length is why females have more urinary tract infections than males by ascending bacteria from stool contamination . Males . About 20 cm in long . Divided into 3 regions Male Urethra . The prostatic urethra, 3–4 cm long, extends through the prostate gland; lined by urothelium . The membranous urethra, a short segment, passes through an external sphincter of striated muscle and is lined by stratified columnar and pseudostratified epithelium . The spongy urethra, 15 cm in length, is enclosed within erectile tissue of the penis and is lined by stratified columnar and pseudostratified columnar epithelium, with stratified squamous in the end. 37 . Urethral sphincters . Internal: involuntary sphincter of smooth muscle . External: skeletal muscle inhibits urination voluntarily until proper time _________trigone 1. Prostatic urethra__________ 2. Membranous urethra____ 3. Spongy or penile urethra_____ female 38 39 .