Urinary System Flashcards
Structures of the Urinary System
- 2 Kidneys
- 2 Ureters
- 1 Urinary bladder
- 1 Urethra
Functions of Urinary System (Regulates)
- Blood volume
- Blood pressure
- pH (concentrations of H+ and HCO3-)
- Concentrations of each ion in the blood (Na+, Ca++, K+, Cl-)
- Secretion of renal hormones
Functions of Urinary System (Eliminates)
- Wastes e.g. urea, uric acid
- Hormones
- Drugs (e.g. antibiotics)
- Toxins
Structures of the Urinary System
- Kidneys
- Nephrons
- Juxtaglomerular Complex (Apparatus)
- Ureters
- Urinary Bladder
- Urethra
Kidneys
- External Anatomy of Kidneys
- Internal Anatomy of Kidneys
External Anatomy of Kidneys
- Retroperitoneal
- Right lower than left
- Supported and protected by 3 layers of connective tissue
- Renal Hilus (Hilum)
3 Layers of Connective Tissue (External Anatomy - Kidney)
- Fibrous Capsule
- Outer layer
- Perirenal Fat Capsule
- Middle layer
- Renal Fascia
- Inner layer
Renal Hilus (Hilum)
- Medial indentation
- Entry point of:
- Renal artery (superior)
- Renal Vein (Inferior)
- Ureter
- Nerves
Internal Anatomy of Kidneys
- Renal Cortex (superficial layer)
- Renal Medulla
- Renal Pelvis
Renal Cortex (superficial layer)
- Contains parts of nephrons
- Contains afferent and efferent arterioles as well as capillary beds called glomeruli
Renal Medulla
- Renal pyramids
- Renal Columns
Renal pyramids
- Apex of pyramid is called the renal papilla
- Contain parts of nephrons
Renal Columns
- Projections of cortex into the medulla
- Separate pyramids
- Contains arteries, veins and nerves that supply the cortex
Renal Pelvis
- Central collecting chamber for filtrate/urine
- Receives filtrate/urine from major calyces
- Major calyces receive filtrate/urine from minor calyces which are small cup shaped structures that surround the renal papilla
Nephron
- Functional unit of kidney (microscopic)
- Composed of:
- Renal Corpuscle
- Renal Tubules
Renal Corpuscle
- In cortex
- Site of blood filtration (first step in urine formation)
- Parts:
- Glomerulus
- Afferent Arteriole - enters glomerulus
- Efferent Arteriole - exits glomerulus
- Glomerular (Bowman’s) Capsule
Glomerulus
- = Capillary bed (endothelium formed of simple squamous epithelium)
- Has many fenestrations (pores) between cells
Afferent Arteriole - enters glomerulus
Carries blood delivered to kidney from the renal artery
Efferent Arteriole - exits glomerulus
Drains into peritubular (of cortical nephrons) and vasa recta (of juxtaglomerular nephrons)
Glomerular (Bowman’s) Capsule
- Surrounds and collects filtrate (filtered blood plasma) from glomerulus
- 2 layers:
- Outer layer is a simple squamous epithelium
- Inner layer is made of cells called podocytes that wrap around glomerular capillaries
What does the Filtration Membrane consists of?
- Glomerular endothelium (capillaries)
- Fenestrations in the simple squamous epithelium allow plasma through, but not formed elements and most large proteins
- Shared basement membranes of i) and iii)
- Podocytes (of glomerular capsule)
- Have many finger-like projections that form a network of filtration slits
Renal Tubules
- 4 parts with specific cell types and functions:
- Proximal Convoluted Tubule (PCT)
- Nephron Loop
- Distal Convoluted Tubule (DCT)
- Collecting Ducts
Proximal Convoluted Tubule (PCT)
- In cortex
- Receives filtrate from glomerular capsule
- Cells are cuboidal epithelium with dense microvilli
- Reabsorbs most useful substances (e.g. glucose, amino acids) from the filtrate
- Secretes waste products into filtrate
Nephron Loop
- In the medulla
- Descending limb (thin)
- Simple squamous epithelium, highly water permeable
- Ascending limb (thick)
- Simple cuboidal epithelium, water-impermeable
Distal Convoluted Tubule (DCT)
- In cortex
- Cuboidal epithelium
Collecting Ducts
- In cortex & medulla
- Drain filtrate from numerous nephrons into minor calyces
- Contain cells that regulate water and Na+ reabsorption and acid/base balance of the blood
2 Types of Nephrons
- Cortical
- Juxtamedullary
Cortical
- Make up majority of nephrons
- Renal corpuscles near kidney surface in cortex
- Short nephron loop that dips into the outer medulla
- Has peritubular capillaries that branch from efferent arteriole and surround DCT and PCT
Juxtamedullary
- Renal corpuscles in cortex near medulla
- Long nephron loops that penetrate deep into medulla
- Allow for production of dilute or concentrated urine depending on need
- Has capillaries that branch from efferent arterioles called vasa recta that run parallel to the nephron loop
Juxtaglomerular Complex (apparatus)
- Regulates the rate of filtrate formation
- Point of contact between end of ascending limb, afferent and efferent arterioles at renal corpuscle of same nephron
- Parts
- Tubular Portion - macula densa
- Vascular (Arteriolar) Portion
Tubular Portion - macula densa
- Modified (tall and narrow) distal convoluted tubule cells
- Monitor filtrate composition
Vascular (Arteriolar) Portion
- Afferent and efferent arteriolar portion = granular (juxtaglomerular cells)
- Modified smooth muscle cells that monitor blood pressure
- Secrete an enzyme/hormone that helps to regulate blood pressure and ion balance
Ureters
- Transports urine from renal pelvis to bladder
- Retroperitoneal
Histology (Ureters)
- Mucosa
- Transitional epithelium (stretches)
- Muscularis Externa
- Smooth muscle
- Adventitia
- Connects ureter to body wall
Urinary Bladder
- Short term storage of urine
- Retroperitoneal
Histology (Urinary Bladder)
- Mucosa
- Transitional epithelium with rugae
- Muscularis externa
- = Detrusor muscle - smooth muscle
- Contraction of detrusor muscle causes urination
- Adventitia/Serosa
- Mostly adventitia
- Serosa covers the superior surface
Urethra
- Drains urine from bladder
- Transports urine and when testes are present, also transports semen
Histology (Urethra)
- Mucosa
- Transitions from transitional epithelium to stratified squamous epithelium
- Muscularies externa
- Is smooth muscle
- Adventitia only
2 Sphincters (Urethra)
- Internal urethral sphincter (smooth muscle)
- Thickening of detrusor muscle at base of bladder
- External urethral sphincter (skeletal muscle)
- In urogenital diaphragm
Filtrate Movement of the Urinary System
Several DCTs
↓
Collecting ducts (exit at renal papilla)
↓
Minor Calyx
↓
Major Calyx
↓
Renal Pelvis
↓
Ureter
↓
Urinary Bladder
↓
urethra
Related Medical Conditions
- Urinary Tract Infection (UTI)
- Glomerulonephritis
Urinary Tract Infection (UTI)
Bacterial infection of the mucosa of the bladder and/or urethra (most common). Can also involve ureters and kidneys (less common).
Glomerulonephritis
Inflammation of the glomeruli ans structures of the filtration membrane that impairs their ability to filter blood plasma
