ANATOMY OF THE KIDNEYS

1. ANATOMY OF THE KIDNEYS FATUROTI MOFOLUWAKE

2. OUTLINE INTRODUCTION GROSS ANATOMY RELATIONS TISSUES SUPPORTING THE KIDNEY BLOOD and NERVE SUPPLY EMBROLOGY HISOLOGY FUNCTIONS CONCLUSION

3. INTRODUCTION The urinary system consist of the kidneys ,ureter, bladder and urethra The kidney: is a bilaterally bean shaped organ These urinary organs remove excess water ,salt and waste protein metabolism from the blood while returning nutrients and chemicals to the blood. It conveys the waste product from the blood to the urine through the ureters to the urinary bladder. The kidneys lie retropritoneally on the posterior abdominal wall. They are both found indivdually found on th T3 throughL3 vertebra

4. GROSS ANATOMY The kidneys lie in a retroperitoneal position in the superior lumbar region The right kidney is lower than the left because it is crowded by the liver The lateral surface is convex; the medial surface is concave The renal hilus leads to the renal sinus Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the hilus.

5. GROSS ANATOMY The kidneys lie retroperitoneally on the posterior abdominal wall; the right kidney is 0.5 in (12 mm) lower than the left, presumably because of its downward displacement by the bulk of the liver. Each measures approximately 4.5 in (11 cm) long, 2.5 in (6 cm) wide and 1.5 in (4 cm) thick

6. Relations Relations Posteriorly�the diaphragm (separating pleura), quadratus lumborum, psoas, transversus abdominis, the 12th rib and three nerves�the subcostal, (T12), iliohypogastric and ilio-inguinal (L1). Anteriorly�the right kidney is related to the liver, the 2nd part of the duodenum (which may be opened accidentally in performing a right nephrectomy), and the ascending colon. In front of the left kidney lie the stomach, the pancreas and its vessels, the spleen, and the descending colon. Superiorly, the suprarenals sit on each side as a cap on the kidney�s upper pole. The diaphram is above it. The medial aspect of the kidney presents a deep vertical slit, the hilum, which transmits, from before backwards, the renal vein, renal artery, pelvis of the ureter and, usually, a subsidiary branch of the renal artery

7. Tissues Supporting theKidney Renal capsule � fibrous capsule that surrounds the kidney. Adipose capsule � cushions the kidney and helps attach it to the body wall. Renal fascia � outer layer of dense fibrous connective tissue that anchors the kidney. The kidneys lie in an abundant fatty cushion (perinephric fat) contained in the renal fascia the renal fascia blends with the fascia over the diaphragm, leaving a separate compartment for the suprarenal.

9. BLOOD and NERVE SUPPLY Blood supply Approximately one-fourth (1200 ml- 1500ml ) of systemic cardiac output flows through the kidneys each minute The renal artery derives directly from the aorta. The renal vein drains directly into the inferior vena cava. The left renal vein passes in front of the aorta immediately below the origin of the superior mesenteric artery. The right renal artery passes behind the inferior vena cava. Lymph drainage Lymphatics drain directly to the para-aortic lymph nodes The nerve supply is via the renal plexus

10. RENAL VASCULAR PATHWAY

11. EMBRYOLOGY Three slightly overlapping kidney systems are formed in a cranial to caudal sequence during intrauterine life in humans: Pronephros Mesonephros Metanephros The first of these systems is rudimentary and nonfuntional (disappears end of 4th wk), the second may function for a short time during the early fetal period and the third forms the permanent kidneys (appears 5th wk) . Early in the fourth week of development, during regression of the pronephric system, the first excretory tubules of the mesonephros appear. They lengthen rapidly, form an S-shaped loop, and acquire a tuft of capillaries that will form a glomerulus at their medial extremity (Fig. 14.3A). Around the glomerulus the tubules form Bowman�s capsule, and together these structures constitute a renal corpuscle. Laterally the tubule enters the longitudinal collecting duct known as the mesonephric or wolffian duct (Figs. 14.2 and 14.3). In the middle of the second month the mesonephros forms a large ovoidEarly in the fourth week of development, during regression of the pronephric system, the first excretory tubules of the mesonephros appear. They lengthen rapidly, form an S-shaped loop, and acquire a tuft of capillaries that will form a glomerulus at their medial extremity (Fig. 14.3A). Around the glomerulus the tubules form Bowman�s capsule, and together these structures constitute a renal corpuscle. Laterally the tubule enters the longitudinal collecting duct known as the mesonephric or wolffian duct (Figs. 14.2 and 14.3). In the middle of the second month the mesonephros forms a large ovoid

12. Collecting system dev from the ureteric bud, which also forms the primitive renal pelvis, and splits into cranial and caudal portions, the future major calyces. The ureteric bud also gives rise to the ureter, the renal pelvis, the major and minor calyces, and approximately 1 million to 3 million collecting tubules.

13. Cortex � the light colored, outer region exhibits cone-shaped medullary(renal) pyramids separated by columns The medullla- The medullary pyramid and its surrounding cortex constitute a lobe which is cone shaped, has a Base Apex or papilla which is surrounded by calyxes forming the pelvicalyceal system The human kidney has about 10-18 lobes Minor calyces- collect the urine from the papilla HISTOLOGY

14. Major calyces Receive the urine from the minor calyces Renal pelvis Funnel shaped tube that collect urine from the major calyces Renal sinus Urine flows through the pelvis and ureters to the bladder HISTOLOGY

15. Nephrons are the structural and functional units that form urine, consisting of:Renal corpuscle � the glomerulus and its Bowman�s capsule Glomerulus � a tuft of capillaries associated with a renal tubule and invarginate into the bowman�s capsule. Glomerular (Bowman�s) capsule � blind,cup-shaped end of a renal tubule that completely surrounds the glomerulus. Within the capsule is the glomerulus is invested by a layervof epithelia cells called podocytes(viseral layer) Glomerular endothelium � fenestrated epithelium that allows solute-rich, virtually protein-free filtrate to pass from the blood into the glomerular capsule THE NEPHRON

16. Cortical nephrons � 85% of nephrons; located in the cortex Juxtamedullary nephrons: Are located at the cortex-medulla junction Have loops of Henle that deeply invade the medulla Have extensive thin segments Are involved in the production of concentrated urine

17. Every nephron has two capillary beds Glomerulus Peritubular capillaries Each glomerulus is: Fed by an afferent arteriole Drained by an efferent arteriole Blood pressure in the glomerulus is high because: Arterioles are high-resistance vessels Afferent arterioles have larger diameters than efferent arterioles

18. Fluids and solutes are forced out of the blood throughout the entire length of the glomerulus Peritubular beds are low-pressure, porous capillaries adapted for absorption that: Arise from efferent arterioles Cling to adjacent renal tubules Empty into the renal venous system Vasa recta � long, straight capillaries of juxtamedullary nephrons

19. Afferent and efferent arterioles offer high resistance to blood flow Blood pressure declines from 95mm Hg in renal arteries to 8 mm Hg in renal veins Resistance in afferent arterioles: Protects glomeruli from fluctuations in systemic blood pressure Resistance in efferent arterioles: Reinforces high glomerular pressure Reduces hydrostatic pressure in peritubular capillaries Vascular Resistance inMicrocirculation

20. The external parietal layer is a structural layer The visceral layer consists of modified, branching epithelial podocytes Extensions of the octopus-like podocytes terminate in foot processes Filtration slits � openings between the foot processes that allow filtrate to pass into the capsular space. Anatomy of the Glomerular Capsule

21. Where the distal tubule lies against the afferent(sometimes efferent) arteriole Arteriole walls have juxtaglomerular (JG) cells Enlarged, smooth muscle cells Have secretory granules containing renin Act as mechanoreceptors Macula densa Tall, closely packed distal tubule cells Lie adjacent to JG cells Function as chemoreceptors or osmoreceptors Mesanglial cells: Have phagocytic and contractile properties Influence capillary filtration Juxtaglomerular Apparatus(JGA)

22. Filter that lies between the blood and the interior of the glomerular capsule It is composed of three layers Fenestrated endothelium of the glomerular capillaries Visceral membrane of the glomerular capsule (podocytes) Basement membrane composed of fused basal laminae of the other layers Filtration Membrane

23. Proximal convoluted tubule (PCT) �composed of cuboidal cells with numerous microvilli and mitochondria Reabsorbs water and solutes from filtrate and secretes substances into it. Loop of Henle � a loop of the renal tubule Proximal part is similar to the proximal convoluted tubule Proximal part is followed by the thin segment(simple squamous cells) and the thick segment (cuboidal to columnar cells) RENAL TUBULES

24. Distal convoluted tubule (DCT) � cuboidal cells without microvilli that function more in secretion than reabsorption The distal portion of the distal convoluted tubule and the collecting ducts have two types of cells: Principal (reabsorbtion of Na and K as well as reabsorbtion of water) Intercalated(secretion of H reabsorbtion HCO3 and are important in the acid base balance

25. Intercalated cells Cuboidal cells with microvilli Function in maintaining the acid-base balance of the body Principal cells Cuboidal cells without microvilli Help maintain the body�s water and salt balance

26. Collecting ducts; it joins the DCTand descend in the medullary rays towards the medulla where it merges withlarge duct of bellini and drain urine from the tip of the renal papilla into the pelvocalyceal system It concentrate urine by passively reabsorbing water into the medullary interstitium following the osmotic gradient created by the counter-current multiplier system The amt of water reabsorbed is controlled by ADH secretion(posterior pituitary gland).the also contain the principal , intercalated cell

27. CLINICAL IMPORTANCE

28. Kidney Functions Filter 200 liters of blood daily, allowing toxins,metabolic wastes, and excess ions to leave the body in urine particularly urea,creatinine,and protein Regulate volume and chemical makeup of the blood Maintain the proper balance between water and salts,and acids and bases Gluconeogenesis during prolonged fasting Production of renin to help regulate blood pressure and erythropoietin to stimulate RBC production Activation of vitamin D

29. CONCLUSION

30. THANK YOU