"Histology Chapter 19: Urinary System, HS142, Spring2024" PDF

HS142 Spring2024 1st Lecture Histology Chapter 19: Urinary System Dr. Ahlam Ellafi, MBBCh, I.C. dipl, MSc Lecturer ( Assist) in Histology and Genetics Head of Quality & Performance Evaluation Department [email protected]  Learnin...

HS142 Spring2024 1st Lecture Histology Chapter 19: Urinary System Dr. Ahlam Ellafi, MBBCh, I.C. dipl, MSc Lecturer ( Assist) in Histology and Genetics Head of Quality & Performance Evaluation Department [email protected]  Learning Objectives (ILOs): Describe the functions of kidney. Compare kidney architecture. Explain Filtration Barrier. Describe the structure and functions ureter, urinary bladder, and urethra. Describe and critically evaluate the clinical applications of urinary system. kidney Each kidney is bean-shaped, with a concave hilum where the ureter &the renal artery &vein enter. The ureter divides &subdivides into several major and minor calyces, around which is located the renal sinus containing adipose tissue. Attached to each minor calyx is a renal pyramid, a conical region of medulla delimited by extensions of cortex. The cortex and hilum are covered with a fibrous capsule. Renal functions Regulation of the balance between water and electrolytes (inorganic ions) and the acid-base balance Involved in forming urine through filtration, absorption, and excretion Produce enzyme renin to regulate blood pressure and maintain proper filtration pressure in glomeruli Synthesize erythropoietin to stimulate erythrocyte production in red bone marrow in response to hypoxia Excretion of many bioactive substances, including many drugs; Excretion of metabolic wastes along with excess water Conversion of the prohormone vitamin D, initially produced in the skin, to the active form (1,25-dihydroxyvitamin D3 or calcitriol). Gluconeogenesis during starvation or periods of prolonged fasting, making glucose from amino acids to supplement this process in the liver. Nephrons Each kidney contains 1-4 million functional units called nephrons, each consisting of a corpuscle and a long, simple epithelial renal tubule with three main parts along its length are: Renal corpuscle, an initial dilated part enclosing a tuft of capillary loops and the site of blood filtration, always located in the cortex. Proximal tubule, a long convoluted part, located entirely in the cortex, with a shorter straight part that enters the medulla. Loop of Henle (or nephron loop), in the medulla, with a thin descending and a thin ascending limb. Nephrons Distal tubule, consisting of a thick straight part ascending from the loop of Henle back into the cortex and a convoluted part completely in the cortex. Connecting tubule, a short minor part linking the nephron to collecting ducts. These converge in the renal papilla, where they deliver urine to a minor calyx. Cortical nephrons are located almost completely in the cortex while juxtamedullary nephrons (about one- seventh of the total) lie close to the medulla and have long loops of Henle. Renal Vasculature The renal corpuscle. Renal Filtration Barrier Filtration, occurs through a structure with three parts: The fenestrations of the capillary endothelium, which blocks blood cells and platelets The thick, combined basal laminae, or GBM, which restricts large proteins and some organic anions The filtration slit diaphragms between pedicels, which restrict some small proteins and organic anions  Mesangial Cells Attached to capillaries in the renal corpuscle and serve important functions Produce extracellular matrix and provide structural support for glomerular capillaries Serve as phagocytes in glomerulus and phagocytose antigen–antibody complexes Produce interleukins in response to glomerular injury or damage Regulate blood pressure as a result of their contractile function Extraglomerular cells form part of the juxtaglomerular apparatus  The cells of PCT have: Apical brush border Acidophilic cytoplasm Many mitochondria Interdigitating lateral border Basal striations with many mitochondria Na+/K+-ATPase (sodium pump) in basolateral membrane Apical canliculi between the bases of microvilli to increase the capacity for absorption Apical endocytosis ( pinocytotic vesicles contain small plasma proteins ) Structural characteristics of the renal tubule. Convoluted tubule epithelia Structural characteristic s of the collecting system The juxtaglomerular apparatus. Cortical and juxtamedullary nephrons The renin-angiotensin-aldosterone system  Medical application Lysosomal storage disorders are inherited metabolic diseases usually due to a mutation leading to a missing or deficiency of one of the digestive enzymes present in lysosomes, or defects due to faulty posttranslational processing. Fabry's disease Is a X-linked recessively inherited, caused by a deficiency of α-galactosidase A which leads to the progressive intra-lysosomal accumulation of ceramide trihexoside in different cell types. Johannes Fabry (1860 - 1930) was a German dermatologist. William Anderson (1842 – 1900) was an English surgeon & Professor of Anatomy MEDICAL APPLICATION 1. Polycystic kidney disease is an inherited disorder in which normal cortical organization of both kidneys is lost due to the formation of multiple, large, fluid- filled cysts. The cysts may arise from any epithelial cells of the nephron and can lead to gross kidney enlargement and loss of renal function. 2. Inflammation within the glomeruli, or glomerulonephritis, which can range from acute or chronic, usually stems from humoral immune reactions. MEDICAL APPLICATION 3. In diseases such as diabetes mellitus and glomerulonephritis, the glomerular filter is altered and becomes much more permeable to proteins, with the subsequent release of protein into the urine (proteinuria). Proteinuria is an indicator of many potential kidney disorders MEDICAL APPLICATION 4. Diabetic glomerulosclerosis, the thickening and loss of function in the GBM produced as part of the systemic microvascular sclerosis in diabetes mellitus, is the leading cause of (irreversible) end-stage kidney disease in the United States. Treatment requires either a kidney transplant or regular artificial hemodialysis. 5. Sickle cell nephropathy, one of the most common problems caused by sickle cell disease, occurs when the affected erythrocytes sickle in the vasa recta, because of the low oxygen tension there. The nephropathy results from renal infarcts, usually within the renal papillae or pyramids. 6. A common problem involving the ureters is their obstruction by renal calculi (kidney stones) formed in the renal pelvis or calyces, usually from calcium salts (oxalate or phosphate) or uric acid. Problems caused by such stones can be corrected by either surgical removal of the stone or its disintegration using focused ultrasonic shock waves in a procedure called lithotripsy, although this treatment can cause significant renal damage.  Bacterial infections of the urinary tract can lead to inflammation of the renal pelvis and calyces, pyelonephritis. In acute pyelonephritis, bacteria often move from one or more minor calyx into the associated renal papilla, causing accumulation of neutrophils in the collecting ducts Q. Identify all the green areas? KEN HUB Q. Identify all the green areas? Q. Where are the Renal tubules ? Q. Mention at least five structures? Q. Where are the Distal tubule? Q. Where is the mesangial cell? Q. Identify the structures of the Renal Filtration Barrier?  Q. Describe the histological structures of proximal tubule?  Q. Describe the Collecting tubule (duct) cytology? https://jbioleng.biomedcentral.com/articles/10.1186/s13036-022-00299-4 Q. A 14-year-old patient presents in the nephrology clinic with fatigue, malaise, anorexia, abdominal pain, and fever. She reports a loss of 6 lb in the past 2 months. Serum gamma globulin and the immunoglobulins IgG, IgA, and IgM are all elevated. Her serum creatine is 1.4 mg/dL (normal 0.6-1.2 mg/dL) and urinalysis of glucose and protein are 2+ on a dipstick test, confirmed by laboratory at 8.0 g/ dL and 0.95 g/dL, respectively. A renal biopsy is prepared for light microscopy, and an infiltrate containing lymphocytes, plasma cells, and eosinophils is found among tubules having cells with prominent brush borders. Which one of the following statements correctly pertains to these epithelial cells? a. Impermeable to water despite presence of ADH b. The primary site for the reduction of the tubular fluid volume c. The site of the countercurrent multiplier d. The site of action of aldosterone e. Indirectly involved in the release of renin  HS142 Spring2024 2nd Lecture Histology Chapter 19: Urinary System Dr. Ahlam Ellafi, MBBCh, I.C. dipl, MSc Lecturer ( Assist) in Histology and Genetics Head of Quality & Performance Evaluation Department [email protected] Ureters, Bladder, & Urethra Urine is transported by the ureters from the renal pelvis to the urinary bladder where it is stored until emptying by micturition via the urethra. The walls of the ureters are similar to that of the calyces and renal pelvis, with mucosal, muscular, and adventitial layers and becoming gradually thicker closer to the bladder. The mucosa of these organs is lined by the uniquely stratified urothelium or transitional epithelium. Cells of this epithelium are organized as three layers: 1. A single layer of small basal cells resting on a very thin basement membrane, 2. An intermediate region containing from one to several layers of cuboidal or low columnar cells, and Ureters, Bladder, & Urethra 3. A superficial layer of large bulbous or elliptical umbrella cells, sometimes binucleated, which are highly differentiated to protect the underlying cells against the potentially cytotoxic effects of hypertonic urine. The thick muscularis of the ureters moves urine toward the bladder by peristaltic contractions and produces prominent mucosal folds when the lumen is empty. Umbrella cells (up to 100 μm in diameter) are especially well developed in the bladder (contact with urine is greatest). Have extensive intercellular junctional complexes surrounding unique apical membranes. Most of the apical surface consists of asymmetric unit membranes in which regions of the outer lipid layer. Ureters, Bladder, & Urethra These regions are composed of lipid rafts containing mostly integral membrane proteins called uroplakins = stiffened plaques. The abundant membranous plaques + the tight junctions, allow this epithelium to serve as an osmotic barrier protecting its cells and the cells of surrounding tissues from hypertonic urine and preventing dilution of the stored urine. Urothelium + folded lamina propria + submucosa + a dense sheath of interwoven smooth muscle layers and adventitia. Lipid rafts Membrane proteins that are components of large enzyme complexes are usually less mobile, especially those involved in the transduction of signals from outside the cell. Located in specialized membrane patches with higher concentrations of cholesterol & saturated fatty acids which reduce lipid fluidity. Bladder The bladder’s lamina propria and dense irregular connective tissue of the submucosa are highly vascularized. The muscularis consists of three poorly delineated layers, collectively called the detrusor muscle, which contract to empty the bladder. Three muscular layers are seen most distinctly at the neck of the bladder near the urethra. The ureters pass through the wall of the bladder obliquely, forming a valve that prevents the backflow of urine into the ureters as the bladder fills. All the urinary passages are covered externally by an adventitial layer, except for the upper part of the bladder that is covered by serous peritoneum. Urethra The urethra is a fibromuscular tube that carries the urine from the bladder to the exterior. The urethral mucosa has prominent longitudinal folds, giving it a distinctive appearance in cross section..  Urethra In men, the two ducts for sperm transport during ejaculation join the urethra at the prostate gland The male urethra is longer & consists of three segments: 1. The prostatic urethra, 3-4 cm long, extends through the prostate gland and is lined by urothelium. 2. The membranous urethra, a short segment, passes through an external sphincter of striated muscle and is lined by stratified columnar & pseudostratified columnar epithelium. 3. The spongy urethra, about 15 cm in length, is enclosed within erectile tissue of the penis & is lined by stratified columnar & pseudostratified columnar epithelium, with stratified squamous epithelium distally. Ureters, Bladder, & Urethra In women, the urethra is exclusively a urinary organ. The female urethra is a 3- to 5-cm-long tube, lined initially with transitional epithelium which then transitions to nonkeratinized stratified squamous epithelium continuous with that of the skin at the labia minora. The middle part of the urethra in both sexes is surrounded by the external striated muscle sphincter. MEDICAL APPLICATION Cystitis, or inflammation of the bladder mucosa, is the most frequent problem involving this organ. Such inflammation is common during urinary tract infections, but it can also be caused by immunodeficiency, urinary catheterization, radiation, or chemotherapy. Chronic cystitis can cause an unstable urothelium, with benign urothelial changes involving hyperplasia or metaplasia. Bladder cancer is usually some form of transitional cell carcinoma arising from unstable urothelium Urinary tract infections, usually involving coliform bacteria or Chlamydia, often produce urethritis and in women often lead to cystitis because of the short urethra. Such infections are usually accompanied by a persistent or more frequent urge to urinate, and urethritis may produce pain or difficulty during urination (dysuria).  Q. Identify this section? Q. What is (4) indicates? Q. Is this section indicates the urinary bladder? Why? Q. (5) indicates the….. Intended Learning Objectives: Identify and describe the histological characteristics of urinary system by microscopic examination. Apply safety and infection control measures during Laboratory practice. Possess the ability to use a computer to search for information related to the course. Use critical thinking and problem-solving skills Self- learning ability. Manage time effectively. Respect colleagues. Working within the team.  Eosinophilic cuboidal with brush border Flat epithelium cells stain weakly pink low cuboidal cells without a brush border cuboidal to columnar cells, well-defined boundaries between cells, cytoplasm only weakly stained or unstained Urinary bladder(filled, empty) Ureter International day of Histology 10.3.2024