Urinary System Overview

Urinary System Overview

• The urinary system consists of kidneys, renal pelvis, calyces, ureters, bladder, urethra, and sphincters.
• Kidneys are paired organs responsible for filtering blood and producing urine.
• Each kidney has a convex lateral border and a concave medial border (hilum) where blood vessels, nerves, and lymph vessels enter and exit.
• The renal pelvis is the expanded upper end of the ureter, which collects urine from the kidneys.
• Two or three major calyces arise from the pelvis, and several smaller minor calyces branch from these.
• A connective tissue capsule surrounds the kidneys, and perirenal fat cushions them.

Kidney Structure

• The kidney is divided into a cortex and medulla.
• The renal medulla contains medullary pyramids, which drain into the minor calyces.
• Renal columns are tissues in the cortex that separate the renal pyramids.
• The renal papilla is the apex of a renal pyramid that drains urine into a minor calyx.

Uriniferous Tubules

• The functional units of the kidneys are nephrons.
• Each kidney contains approximately one million nephrons.
• A nephron is composed of a renal corpuscle and a renal tubule.
• The renal corpuscle includes a glomerulus and Bowman’s capsule.
• Bowman's capsule contains the glomerulus (a tuft of capillaries).
• The renal tubule has several parts: proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

Nephron Structure

• Each nephron is comprised of the renal corpuscle (glomerulus and Bowman's capsule), proximal convoluted tubule, loop of Henle (descending and ascending limbs), distal convoluted tubule, and collecting duct.
• The collecting ducts empty into the renal pelvis.

Renal Corpuscle

• The renal corpuscle, or Malpighian corpuscle, is the initial filtering structure of the nephron.
• The glomerulus is a network of capillaries.
• Bowman's capsule surrounds the glomerulus and collects the filtered fluid.
• The glomerulus is composed of fenestrated capillaries (with small openings).
• Bowman’s capsule consists of a visceral layer (podocytes), a parietal layer (simple squamous epithelium) and a basement membrane.
• The renal corpuscle has two poles: a vascular pole (where afferent and efferent arterioles enter/exit) and a urinary pole (where the proximal convoluted tubule begins).

Proximal Convoluted Tubule (PCT)

• The proximal convoluted tubule is lined by tall cuboidal cells with prominent brush border (microvilli), which increases the surface area for reabsorption.
• Key function: reabsorption of water, electrolytes, and nutrients from the filtrate.

Loop of Henle

• The loop of Henle consists of a descending limb, a thin segment, and an ascending limb (thick segment); both ascending and descending limbs are connected.
• The descending limb is permeable to water but impermeable to solutes.
• The ascending limb is impermeable to water but actively transports solute out of the tubule filtrate.

Distal Convoluted Tubule (DCT)

• The distal convoluted tubule has low cuboidal cells with fewer microvilli.
• Actively regulates the electrolyte and water balance in the filtrate.
• Plays a role in blood pressure regulation, secretion of waste products; and reabsorption of essential substances and elimination of harmful ones.

Collecting Ducts

• Several nephrons empty into a collecting duct.
• The collecting ducts are lined by columnar and cuboidal principle cells plus intercalated cells.
• They actively reabsorb water.
• They conduct urine to minor calyces.

Prostate Gland

• The prostate gland is an accessory gland of the male reproductive system.
• Located below the bladder and surrounding the urethra.
• Histologically, it's encapsulated by a fibromuscular capsule and contains trabeculae.
• The gland consists of secretory units called acini arranged in three zones (peripheral, submucosal, and mucosal).
• Corpora amylacea (prostatic concretions) are acidophilic lamellated calcified secretory material in the acini; their prevalence increases with age.

This quiz covers the anatomy and functions of the urinary system, including the kidneys, renal pelvis, ureters, bladder, and other related structures. It explores the components, functions, and structural divisions of the kidneys, emphasizing their role in urine production and blood filtration.