Urinary System Microstructures PDF

ILM-Urinary System Microstructure: Objectives 1. Describe the macrostructure of the kidneys. 2. Construct the organization of the nephrons and collecting channels. 3. Describe the histological characteristics of the urina...

ILM-Urinary System Microstructure: Objectives 1. Describe the macrostructure of the kidneys. 2. Construct the organization of the nephrons and collecting channels. 3. Describe the histological characteristics of the urinary system passageways (ureter, bladder, urethra). 12/3/2020 Manas Das, MD 1  Kidney: Macroscopic Structure Each kidney is bean-shaped, with a concave hilum that consists of the renal sinus and its contents, which include the larger renal blood vessels, the renal pelvis, and adipose tissue. The renal medulla in humans consists of 8-15 conical structures called renal pyramids, whose bases lie in the cortex and whose apices lie in the medulla. The renal papilla is located at the apex of each renal pyramid. It has a perforated tip (area cribrosa) that projects into the lumen of a minor calyx. The minor calyces collect urine and empty into the larger major calyces. These in turn empty into the single, funnel-shaped renal pelvis, which is continuous with the ureter. Renal columns are extensions of cortical tissue between adjacent renal pyramids. Medullary rays are groups of straight tubules that extend from the base of each renal pyramid into the cortex.  Kidney: Microscopic Structure 1, renal corpuscle including the glomerulus and Bowman’s capsule; Renal Cortex contains: 2, proximal convoluted tubule; A. Renal corpuscles 3, proximal straight tubule; B. Proximal convoluted tubules C. Distal convoluted tubules 4, descending thin limb; D. Connecting/collecting tubules 5, ascending thin limb; E. Cortical collecting ducts 6, distal straight tubule; Renal Medulla contains: 7, macula densa located in the final portion of the thick ascending limb; A. Loop of Henle 8, distal convoluted tubule; B. Medullary collecting ducts 9, connecting tubule; C. Papillary ducts 9*, arched connecting tubule (juxtamedullary nephron); 10, cortical collecting duct; Medullary rays comprise: A. Proximal & distal 11, outer medullary collecting duct; and straight tubules 12, inner medullary collecting duct B. Cortical collecting ducts 12/3/2020 Manas Das, MD 3  Kidney (uriniferous tubules) = Can you identify the following Nephron + Collecting System on the image? Nephron i. renal corpuscle (glomerulus + Bowman’s capsule), ii. proximal convoluted tubule, iii. loop of Henle, a. descending limb i. thick limb (proximal straight tubule) ii. thin segment b. ascending limb i. thin segment ii. thick limb (distal straight tubule) iv. distal convoluted tubule Collecting System i. cortical collecting tubule (connecting tubule) ii. collecting ducts iii. papillary ducts 12/3/2020 Manas Das, MD 4  Nephron: 2 Types 15% of total in humans Needed to make highly concentrated urine  Kidney: Histology Cortex Under the light microscope, the parenchyma of each kidney has 1. an outer renal cortex, a darker stained region with many round corpuscles and tubule cross sections, and 2. an inner renal medulla consisting mostly of aligned linear tubules and ducts Medulla 12/3/2020 Manas Das, MD 6  Excretory Passages: Histology The excretory passages include the minor and major calyces and the renal pelvis, located within each kidney, and the ureters, urinary bladder, and urethra, located outside the kidneys. These structures possess a wall composed of: i. mucosa lined by transitional epithelium (except in some parts of the male urethra) ii. dense collagenous lamina propria iii. smooth muscle → inner longitudinal and outer circular iv. adventitia 12/3/2020 Manas Das, MD 7  Lined with a distensible, highly impermeable transitional epithelium continuous with that in the Urinary Bladder. Ureter Contraction of the smooth muscle of the muscularis → the luminal surface is characteristically folded → star-shaped lumen Key: mucosa (Muc), muscularis (Mus), adventitia (Adv), serosa (Ser), urothelium (Ep), connective tissue (CT), adipose tissue (AT), inner longitudinal layer (SM[l]), middle circular layer (SM[c]), outer longitudinal layer (SM[l]) 12/3/2020 Manas Das, MD 8  Urinary Bladder Ureter Key: ureter (U), urothelium (Ep), connective tissue (CT), blood vessels (BV), longitudinal smooth muscle (SM[L]), muscularis (M), binucleate cells (arrows), medium-sized arteries (A) and veins (V) 12/3/2020 Manas Das, MD 9  Urethra Male urethra: lined by transitional epithelium in the pre-prostatic and part of the prostatic portion till the colliculus seminalis and by pseudostratified or stratified columnar epithelium in the parts distal to it. The fossa navicularis, located at the distal end of the penile urethra, is lined by stratified squamous epithelium. Female urethra: initially lined by transitional that changes to stratified squamous before termination. 12/3/2020 Manas Das, MD 10