HISTO OF URINARY SYSTEM

Q: What are the two main compositions of the kidney? A: The kidney is composed of the outer renal cortex and the inner renal medulla1.

Q: What is the site of the kidney? A: The kidney is retro-peritoneal1.

Q: What is the shape of the kidney and what feature is located on its medial side? A: The kidney is bean shape. It has a concave medial hilum where the ureter, nerves, blood & lymph vessels enter and exit1.

Q: What structures compose the renal medulla? A: The renal medulla is composed of 10-18 medullary pyramids2.

Q: What structures separate the medullary pyramids? A: The medullary pyramids are separated by extensions from the renal cortex called renal columns2.

Q: What is the apex of each renal pyramid called? A: The apex of each pyramid is called the renal papilla2.

Q: What structures receive urine from the renal papillae? A: 7-10 minor calyces receive urine from the renal papillae2.

Q: What structures receive urine from the minor calyces? A: 2-3 major calyces receive urine from the minor calyces2.

Q: Define a renal lobe. A: A renal lobe consists of a medullary pyramid and the overlying cortical tissue2.

Q: Define a renal lobule. A: A renal lobule consists of a medullary ray and the overlying cortical tissue3.

Q: What are the two main components of the histological structure (parenchyma) of the kidney? A: The parenchyma of each kidney contains around 1 million functional units called Nephrons and Collecting ducts3.

Q: What are the four main divisions of the nephron? A: The divisions of the nephron are the Renal Corpuscle, Proximal Tubule, Loop of Henle, and Distal Tubule3.

Q: What is the Renal Corpuscle formed of? A: The Renal Corpuscle is formed of Bowman's capsule and Glomerular capillaries3.

Q: What is the space between the two layers of Bowman's capsule called? A: The space between the two layers of Bowman's capsule is the Capsular (Bowman’s) space3.

Q: What are the two poles of Bowman's capsule and what are their functions? A: Bowman's capsule has two poles:

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Vascular pole: Site of entry of the afferent arteriole and exit of the efferent arteriole4.

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Urinary pole: Connected to the Proximal tubule4.

Q: Describe the two layers of Bowman's capsule. A: Bowman's capsule has two layers:

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Parietal layer (outer): Simple squamous epithelium4.

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Visceral layer (inner): Formed of podocytes4.

Q: What are podocytes? A: Podocytes are stellate-shaped cells that rest on the glomerular capillaries4.

Q: Describe the processes of podocytes. A: Podocytes have Primary processes that arise from the cell body and curve around the glomerular capillary, and Secondary processes (pedicels) that arise from the primary processes and are implanted on the basement membrane of glomerular capillaries4....

Q: What are filtration slit pores? A: Filtration slit pores are pores located between the secondary processes (pedicels) of podocytes, covered by slit diaphragms5.

Q: What are the components of the filtration membrane? A: The filtration membrane is composed of:

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Fenestrations of capillary endothelium: Hold back blood cells5.

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Thick glomerular basement membrane (GBM): Formed by the fusion of the basal lamina of capillary endothelium and that of podocytes. Holds back some large proteins & organic anions5.

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Filtration slit pores (between secondary processes) covered by slit diaphragms5.

Q: Where are mesangial cells located and what are their functions? A: Mesangial cells are located in the renal corpuscles between the glomerular capillaries6. Their functions include:

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Secreting components of the mesangial matrix to support the glomerular capillaries6.

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They are contractile and can modify the diameter of glomerular capillaries, playing an important role in controlling blood flow6.

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Continuous turnover of the GBM6.

Q: List the parts of the renal tubules. A: The renal tubules consist of the Proximal convoluted tubule, Loop of Henle, Distal convoluted tubule, Connecting tubules, and Collecting ducts7.

Q: Where does the proximal convoluted tubule start and what does it become continuous with? A: The proximal convoluted tubule starts at the urinary pole of the renal corpuscle and becomes continuous with the loop of Henle7.

Q: Describe the light microscopy features of the Proximal Convoluted Tubule (PCT). A: Features of PCT under light microscopy include:

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Long & highly convoluted7.

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Large diameter7.

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Narrow lumen, which may be obliterated by the brush border7....

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Cuboidal cells7.

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Apical brush border7....

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Cytoplasm is strong acidophilic7....

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Nuclei are round & central, with 3-5 nuclei in each cross-section7....

Q: Describe the electron microscopy features of the cells of the Proximal Convoluted Tubule (PCT). A: PCT cells have features of ion-transporting cells, including:

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Dense apical microvilli (heavy brush border)9....

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Numerous basal folds9....

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Present lateral interdigitations9....

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Numerous mitochondria9....

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Lysosomes9.

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Pinocytotic vesicles9.

Q: What are the main functions of the proximal tubule? A: The functions of the proximal tubule are Reabsorption and Secretion9.

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Reabsorption includes over half of water and electrolytes, and all organic nutrients (glucose, amino acids, vitamins, etc.)9.

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Secretion includes some organic anions and cations (bile salts, creatinine, drugs, etc.) into the renal filtrate11.

Q: Describe the light microscopy features of the Distal Convoluted Tubule (DCT) and compare them to the PCT. A: Features of DCT under light microscopy include:

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Less convoluted than PCT8....

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Smaller diameter than PCT8....

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Wide lumen8....

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Cuboidal cells11.

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No brush border8....

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Cytoplasm is less acidophilic than PCT8....

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Nuclei are round, with 5-10 nuclei in each cross-section8....

Q: Describe the electron microscopy features of the cells of the Distal Convoluted Tubule (DCT) and compare them to the PCT. A: Features of DCT cells under electron microscopy include:

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Apical microvilli are few, nearly absent (compared to dense and long in PCT)8....

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Lateral interdigitations are not well-formed (compared to present in PCT)8....

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Basal folds are more prominent than in the proximal tubule8....

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Elongated mitochondria (less numerous than in PCT)8....

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Nucleus is round & euchromatic8.

Q: What is the main function of the distal tubule? A: The distal tubule performs much less reabsorption than the proximal tubule8. It is involved in the reabsorption of sodium ions by an active process regulated by aldosterone hormone8.

Q: Describe the structure of the Loop of Henle. A: The Loop of Henle is a U-shaped structure10. It has a descending limb and an ascending limb10.

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The descending limb has an initial thick part (pars recta of PCT) and a thin descending limb10.

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The ascending limb has a thin ascending limb and a thick ascending limb (simple cuboidal cells like DCT cells)10.

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The U-shaped thin parts are lined by simple squamous epithelium10.

Q: What are the functions of the thin parts and the thick ascending limb of the Loop of Henle? A: The functions are:

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Thin parts: Passive reabsorption of sodium & chloride ions12.

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Thick ascending limb: Active reabsorption of sodium & chloride ions12.

Q: Where are collecting ducts located and what do they merge to form? A: Collecting ducts are located in the medullary ray12.

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In the outer medulla, they merge to form large ducts called ducts of Bellini, which are lined by simple columnar epithelium12.

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In the renal papilla, the ducts of Bellini merge to form papillary ducts, which lead to the minor calyx13.

Q: What are the types of cells found in the collecting ducts and their characteristics/functions? A: The collecting ducts are lined by simple cuboidal epithelium and contain two types of cells13:

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Principal cells: Pale staining cells that can respond to ADH, serving as the final site of water reabsorption13.

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Intercalated cells: Dark staining cells that help maintain acid-base balance13.

Q: What are the components of the Juxtaglomerular apparatus (JGA)? A: The JGA is composed of Juxtaglomerular cells (JG), Macula densa (MD), and Lacis cells (L)13.

Q: What are Juxtaglomerular cells (JG)? A: JG cells are modified smooth muscle cells of the afferent arteriole that become secretory cells containing granules of renin13....

Q: What is the Macula densa (MD)? A: The Macula densa is a part of the distal tubule located between the afferent and efferent arterioles and the renal corpuscle. It consists of crowded columnar cells with a lost basement membrane14.

Q: What are Lacis cells? A: Lacis cells, also known as Polar cushion, are supportive mesangial cells14.

Q: What is the main function of the Juxtaglomerular apparatus (JGA)? A: The main function of the JGA is the regulation of blood pressure through the renin-angiotensinogen system14.

Objective: To illustrate the histological structure of the ureter and urinary bladder.1

Q: What are the layers of the ureter wall? A: The ureter wall has three layers: Mucosa, Muscularis, and Adventitia15.

Q: Describe the Mucosa layer of the ureter. A: The mucosa of the ureter is folded. It consists of Transitional epithelium (urothelium) with a thin basement membrane and Lamina propria14....

Q: Describe the Muscularis layer of the ureter. A: The muscularis of the ureter consists of irregular bundles of smooth muscles separated by abundant loose connective tissue15.

Q: What are the layers of the urinary bladder wall? A: The urinary bladder wall has three layers: Mucosa, Muscularis, and Adventitia16.

Q: Describe the Mucosa layer of the urinary bladder. A: The mucosa of the urinary bladder is folded. It consists of Transitional epithelium (urothelium) with a thin basement membrane and Lamina propria16.

Q: Describe the Muscularis layer of the urinary bladder and its name. A: The muscularis of the urinary bladder consists of three loosely arranged layers of smooth muscles: inner longitudinal, middle circular, and outermost longitudinal. These layers are separated by loose connective tissue and are collectively called the detrusor muscle16.

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