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Home , Peritubular capillaries

النسج 2 The الجهاز البولي

محاضرة 9 أ. د. رائدة الخاني The Urinary System

. Two kidneys

. A for each

.

.

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 . (=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: >> glomerular capillaries >> efferent arterioles.

10 . 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 . 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 االنبوب البولي Uriniferous tubule (functional unit for forming urine) Nephron: includes جسيم الكلية . الكبيبة - (tuft of capillaries) محفظة الكبيبة Glomerular capsule - (Bowman’s capsule) . Tubular section االنبوب الملفف Proximal convoluted tubule – القريب/الداني عروة هانلة – االنبوب الملفف البعيد/القاصي – 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 الخاليا القدمية - -Simple squamous cells form parietal layer of capsule . Glomerular capillaries arise from afferent arteriole & form a ball of capillaries before emptying into

16 . Proximal convoluted tubule . Confined to . 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 . 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)

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Juxtaglomerular Apparatus الجهاز المجاور للكبيبة 1. (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

. 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) . (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). . : 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 , 3–4 cm long, extends through the prostate gland; lined by urothelium . The , a short segment, passes through an external sphincter of striated muscle and is lined by stratified columnar and pseudostratified epithelium . The , 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 . . 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

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