Urinary System Microstructure Quiz

ILM-Urinary System Microstructure: Objectives

• Describe the macrostructure of the kidneys
• Construct the organization of the nephrons and collecting channels
• Describe the histological characteristics of the urinary system passageways (ureter, bladder, urethra)

Kidney: Macroscopic Structure

• Each kidney is bean-shaped with a concave hilum
• Renal sinus contains renal blood vessels, renal pelvis, and adipose tissue
• Renal medulla consists of 8-15 renal pyramids with bases in cortex and apices in the medulla
• Renal papilla is at the apex of the pyramid, and projects into the minor calyx
• Minor calyces collect urine and empty into larger major calyces
• Major calyces empty into the renal pelvis, which is continuous with the ureter
• Renal columns are extensions of cortical tissue between renal pyramids
• Medullary rays are groups of straight tubules extending from the renal pyramid base into the cortex

Kidney: Microscopic Structure

• Renal corpuscle includes the glomerulus and Bowman's capsule
• Proximal convoluted tubule
• Proximal straight tubule
• Descending thin limb
• Ascending thin limb
• Distal straight tubule
• Macula densa located in the final portion of the thick ascending limb
• Distal convoluted tubule
• Connecting tubule
• Arched connecting tubule (juxtamedullary nephron)
• Cortical collecting duct
• Outer medullary collecting duct
• Inner medullary collecting duct

Nephron + Collecting System

• Renal corpuscle (glomerulus + Bowman's capsule)
• Proximal convoluted tubule
• Loop of Henle (descending and ascending limbs)
  • Thick limb (proximal straight tubule)
  • Thin segment
  • Thick limb (distal straight tubule)
• Distal convoluted tubule

Collecting System

• Cortical collecting tubule (connecting tubule)
• Collecting ducts
• Papillary ducts

Nephron: 2 Types

• 15% of total nephrons in humans
• Cortical nephron: short loop of Henle, renal corpuscle in outer cortex
• Juxtamedullary nephron: long loop of Henle, renal corpuscle near medulla

Kidney: Histology

• Kidney parenchyma has an outer renal cortex (darker, with corpuscles & tubules) and an inner renal medulla (aligned tubules and ducts)

Excretory Passages: Histology

• Minor and major calyces, renal pelvis, ureters, urinary bladder, and urethra
• Mucosa lined with transitional epithelium (except some parts of male urethra)
• Dense collagenous lamina propria
• Smooth muscle (inner longitudinal and outer circular)
• Adventitia

Ureter

• Distensible, impermeable transitional epithelium
• Smooth muscle contraction folds the luminal surface into a star-shaped lumen

Urinary Bladder

• Transitional epithelium
• Smooth muscle layer (inner longitudinal and outer circular)

Urethra

• Male: transitional epithelium in pre-prostatic and prostatic parts, pseudostratified or stratified columnar distal to the colliculus seminalis; fossa navicularis lined with stratified squamous epithelium
• Female: initially lined with transitional epithelium, changing to stratified squamous before termination

Test your knowledge on the microstructure of the urinary system, focusing on the kidneys and their organization. Explore the histological characteristics and the macrostructure of renal components like nephrons and passageways. It's an essential quiz for students of anatomy and physiology!