Tiêu đề MOD11-1.1-Renal Histology (Laboratory).pdf ✅

ANAT ● ANATOMY Renal Histology (Laboratory) TRANS 1.1 N MODULE 11 estor S. Calimbahin, M.D., FPSA March 1, 2023 LECTURE OUTLINE I. Kidney A. Arterial Supply B. Venous Drainage C. Medullary Rays (of Ferrein) D. Pars Convoluta (Cortical Labyrinth) E. Renal corpuscles II. Ureter A. Ureter 1 B. Ureter 2 III. Urinary Bladder IV. Urethra A. Female Urethra B. Male Urethra V. Review LECTURE OBJECTIVES 1. Identify the organ from where the section was taken. 2. Delineate the cortex from the medulla in the kidney. 3. Delimit the renal lobe. 4. Demarcate the renal lobule. 5. Delimit a renal pyramid. 6. Locate the pars radiata (medullary ray) and pars convoluta in the cortex of the kidney. 7. Identify the different branches of the renal artery and tributaries of the renal vein: arcuate blood vessels, interlobular blood vessels, glomerular capillaries, afferent and efferent arterioles, peritubular capillaries, and vasa recta. 8. Identify and locate the different components of the nephron. 9. Distinguish collecting tubules from papillary ducts. 10. Delimit the renal papilla. 11. Identify the components of the JG complex. 12. Point to the characteristic features of the urinary passages: calyxes, ureter, urinary bladder, and urethra. 13. Identify the components of the glomerular filtration barrier in electron micrographs. I. KIDNEY ● Maintains the body’s acid-base balance, water, and electrolyte concentrations by filtering the blood through a process that requires the formation of urine ● Produces hormones: Renin and Erythropoietin. ● It also produces active substances including kinins, and calcitriol (calcitriol; 1, 25-dihydroxycholecalciferol; 1, 25- dihydroxy vitamin D3). Figure 1. Renal Lobe Section. Online Histology Slides ● Capsule ○ Connective tissue ○ Note that at higher magnification, there is hardly any connective tissue from the capsule that invades the renal parenchyma ● Cortex ○ Region that is deep to the capsule ○ Occupies the half section ○ Consists of convoluted tubules and renal corpuscles ● Medulla ○ Region on the right half of the specimen ○ Has numerous red streaks because the capillaries are dilated and blood-filled ○ Consists of loops of Henle and collecting ducts ○ Comprised of millions of nephrons (functional unit of kidney) ● Renal papilla ○ Apex of the renal pyramid ○ Tapering region near the edge of the medulla ○ Fits into a cup-shaped structure: Calyx (pocket where Renal Papilla fits) ● Renal pyramid ○ Conical structure ○ About 10 to 15 renal pyramids are found in the medulla of the kidney ● Renal Columns of Bertin ○ Separates renal pyramids ○ Projections of cortical tissue into the medulla ● Renal Lobe ○ Composed of: a. Renal Pyramid b. Cortical tissue (which overlies and immediately surrounds the pyramid) ○ Note: The renal lobe in Figure 1 is a single renal lobe because it consists of a single renal pyramid that is overlain by cortical tissue. ● Arcuate Arteries and Arcuate Veins ○ Large arteries and veins at the cortico-medullary junction. Group 16B | Renal Histology (Laboratory) 1
A. ARTERIAL SUPPLY ● The kidneys receive about a quarter of the total amount of blood in the body for filtering per minute. 1. Abdominal aorta ● Branches to form left and right renal arteries ● Allows blood to flow to the kidneys 2. Renal arteries (left and right) ● Enters to the hilum of the kidney ● It divides into 3 to 5 branches ● Give off a variable number of interlobar arteries 3. Interlobar arteries ● Travel in between the renal pyramids ● “Inter” = between; “lobar” = lobes; “Interlobar” = Between lobes (as mentioned, renal lobes are composed of renal pyramid and cortical tissue, so between renal pyramids) ● Proceed toward the cortex without giving off any branches to the medulla ● End at the corticomedullary junction by giving rise to arcuate arteries 4. Arcuate arteries ● At the level of corticomedullary junction ● Course parallel to the capsule ● Branches off at the right angles and give rise to interlobular arteries 5. Interlobular arteries ● At the level of corticomedullary junction ● Traverse the cortex as they course toward the capsule ● Supply the capsule ● Give rise to afferent arterioles 6. Afferent arterioles ● Run parallel to the capsule and enter the lobules ● Within the lobules, each afferent arteriole breaks up into a clump of capillaries (glomerular capillaries) 7. Glomerular capillaries ● Forms the bulk of the glomerulus ● Drains into a single efferent arteriole 8. Efferent arteriole ● Leaves the glomerulus and break up to form a peritubular capillary network ● However, those associated with the juxtamedullary nephrons break up to form a series of straight capillaries (vasa recta) 9. Peritubular capillary network ● Supplies the proximal and distal tubules and the segments of the loops of Henle that are around them 10. Straight Capillaries (Vasa Recta) Descending Vasa Recta Descend into and supply the medulla Ascending Vasa Recta After supplying the medulla, the capillaries loop and ascend back to the corticomedullary junction to drain the venous blood that they carry either into the interlobular veins or arcuate veins B. VENOUS DRAINAGE ● Venous blood from the capsule and the outer cortex drains into the superficial cortical veins that empty into stellate veins on the surface of the kidney. ● Venous blood from the rest of the cortex drains into the deep cortical veins. ● The stellate and deep cortical veins empty into the interlobular veins that run parallel and close to the interlobular arteries. ● The interlobular veins, in turn, drain into the arcuate veins. ● The arcuate veins are tributaries of the interlobar veins that unite to form the renal vein, which drains into the IVC Figure 2. Venous drainage of the kidney’s histology C. MEDULLARY RAYS (OF FERREIN) ● AKA pars radiata ● Consists of clusters of longitudinally-oriented tubular structures that seem to radiate from the medulla Figure 3. Medullary rays (of Ferrein). Online Histology Slides Group 16B | Renal Histology (Laboratory) 2
Figure 4. Medullary rays (of Ferrein). Online Histology Slides ● Each medullary is made up of tubular structures that run perpendicular to the capsule. Table 1. Composition of a Medullary Ray Straight collecting tubules Lined by a simple cuboidal that is taller than that in the limbs of Henle. Segments of the descending thick limbs of Henle Histologically identical with the proximal convoluted tubule Segments of the ascending thick limbs of Henle Histologically identical with the distal convoluted tubule. ● A collecting tubule is the continuation of a distal convoluted tubule. It starts in the cortex as a short segment that curves towards the medulla (arched collecting tubule) then straightens (straight collecting tubule) and heads for the medulla. ● In the medulla, straight collecting tubules merge and remerge to form successively larger collecting tubules until a papillary duct is formed. Figure 5. Medullary rays of the kidney. Online Histology Slides Figure 6. Corticomedullary junction and arcuate vessel. Online Histology Slides ● The terminal portions of the papillary ducts in a pyramid comprise the renal papilla, which fits into a minor calyx ● The epithelial cells of the collecting tubules: a. Relatively distinct lateral borders b. Faintly eosinophilic cytoplasm. STRUCTURES THAT ARE IN THE MEDULLA a Collecting tubules b Papillary ducts c Segments of the loop of Henle d Vasa recta e Some connective tissue elements Figure 7. Renal pelvis and Vasa recta capillaries. Online Histology Slides NOTE: The collecting tubules vary in caliber and that their epithelial lining ranges from simple cuboidal to simple columnar. Group 16B | Renal Histology (Laboratory) 3
● These tubular structures have bigger lumen than the collecting tubules and that their lining epithelium is simple but tall, columnar. ● Each renal pyramid has about 25 papillary ducts that open into a minor calyx. ● Area cribrosa - The region on the renal papilla that contains the opening of these papillary ducts ● The wall of the thin limbs consists of a simple squamous epithelium. D. PARS CONVOLUTA (CORTICAL LABYRINTH) ● The region between the medullary rays ● Medullary rays consist of: ○ Renal corpuscles ○ Proximal and distal convoluted tubules Figure 8. Pars convoluta (area spanned by the red double arrows). Online Histology Slides E. RENAL CORPUSCLES Figure 9. Renal corpuscles. Online Histology Slides ● Ball-like in between the medullary rays (of Ferrein) surrounded by tubular structures are seen mostly in the cross-section. ● Each kidney has between 1-1.5 million renal corpuscles that are all located in the cortex. ● Made up of: ○ Glomerulus ○ Bowman’s capsule (glomerular capsule) Figure 10. Renal corpuscle. Online Histology Slides 1. Glomerulus ● A globular structure that is made up of capillaries (glomerular capillaries) that are embedded in an amorphous material called the mesangial matrix (mesangium). ● Cells called glomerular mesangial cells are also embedded in the mesangium. ○ Phagocytic cells that are contractile and could decrease the luminal diameter of the glomerular capillaries by contracting. ○ Responsible for the production of the mesangial matrix ● Other cells that comprise the cellular population of the glomerulus: ○ Endothelial cells ○ Podocytes – cells that comprise the visceral layer of the Bowman’s capsule Figure 11. Glomerulus of a renal corpuscle. Online Histology Slides Group 16B | Renal Histology (Laboratory) 4
2. BOWMAN’S CAPSULE Figure 12. Bowman’s capsule of a renal corpuscle. Online Histology Slides A double-walled sac that envelops the glomerulus: Parietal layer Forms the outer boundary of the renal corpuscle Visceral layer Its cells are highly modified and are called podocytes; they envelope the glomerulus intimately ● Both walls of the capsule are made up of a single layer of flattened epithelial cells ● The visceral and parietal layers of Bowman’s capsule are separated by a narrow cavity known as Bowman’s space (capsular space; subcapsular space; urinary space) ○ Blood is filtered as it passes through the glomerular capillaries ○ The filtrate that is produced, which is called glomerular filtrate, goes into the Bowman’s space. Figure 13. Bowman’s capsule with arterioles and poles. Online Histology Slides 3. Poles ● Urinary Pole - renal tubule begins here ○ Parietal layer of Bowman’s capsule is continuous with the epithelium of the proximal convoluted tubule (PCT) ○ Bowman’s space is continuous with the lumen of the PCT ● Vascular Pole - entry site of afferent arteriole and exit site of the efferent arteriole ○ The parietal layer of Bowman’s capsule is continuous with the visceral layer ○ initial segment of distal convoluted tubule (DCT) is in contact with the vascular pole of the renal corpuscle 4. Arterioles AFFERENT ARTERIOLES ● Bigger diameter than the efferent arteriole (this distinction is not enough to distinguish the arterioles) ○ Closely associated to the macula densa ○ Its wall is atypical at the point of contact between the DCT and afferent arteriole ○ No internal elastic lamina ○ Thin tunica adventitia ■ Made up of Juxtaglomerular cells (JG cells) instead of smooth muscle ■ JG cells (Juxtaglomerular cells - polyhedral cells with a spherical nucleus that secrete renin ● Larger than ordinary smooth muscles ■ Extraglomerular mesangial cells - group of flattened, light staining cells that occupy the space between the macula densa and afferent arteriole JUXTAGLOMERULAR COMPLEX ● JG Complex; JG apparatus ● Helps regulate systemic blood pressure ● Comprised of: a. Macula densa b. JG Cells c. Extraglomerular mesangial cells E. RENAL TUBULES ● Proximal and distal convoluted tubules that surround the renal corpuscles. - Segments of renal tubules ● From Bowman’s Capsule: glomerular filtrate flows into a long tube (renal tubule) where it is modified to become urine ● Renal corpuscle + renal tubule = nephron (functional unit of kidney) ● Segments: PROXIMAL CONVOLUTED TUBULE ● receives the glomerular filtrate from the glomerular space ● long, highly-coiled tube that is entirely in the cortex ● drains into the loop of Henle ● longer and more highly-coiled ● comprise a majority of the tubules that are seen in the cortex ● wall of a PCT is made up of a simple cuboidal epithelium ● cells that comprise the epithelium ○ Have a centrally located nucleus ○ Acidophilic cytoplasm Group 16B | Renal Histology (Laboratory) 5