Urinary System:
- Kidneys: Urine forming organ
- Ureter: Duct that channels urine from the kidney to the urinary bladder
- Urinary bladder: Smooth muscle-walled sac used for the temporary storage of urine
- Urethra: Tube through which urine is eliminated from the body
- In males, also serves as the duct for the passage of semen for the reproductive system
Primary Function
- Filter the blood, Remove waste products
- Convert the filtrate to urine and Eliminate the urine
Secondary functions
- Formation of calcitriol
- Production and release of erythropoietin
- Regulation of: Ion levels, Acid-base balance and Blood pressure (water levels)
- Potential to engage in gluconeogenesis
- General theme is that kidneys condition the blood
Location of the kidneys:
- Along the posterior abdominal wall
- Partially protected by the rib cage
- Between T12 & L3 vertebrae
- Left kidney sits slightly higher than right kidney
- Posterior to the parietal peritoneum
- Only anterior surface is covered called the retroperitoneal space
- Surrounded and supported by several tissue layers (inside to outside)
- Fibrous capsule
- Renal capsule
- Maintains kidney shape, protects it from trauma, serves as a barrier to pathogens
- Perinephric fat
- External to fibrous capsule
- Provides cushioning and support for kidney
- Renal fascia
- External to perinephric fat and Anchors kidney to surrounding structures
- Perinephric fat: Outermost layer surrounding kidney
Sectional Anatomy of the Kidney:
- Kidney is arranged into two distinct region
- Renal cortex = Outer region
- Renal medulla = Inner region
- Renal columns: Projections of the cortex that project into medulla and subdivide the medulla
into the renal pyramids
- Renal pyramids: Striated appearance
- Corticomedullary junction: Where base of pyramid lies against the cortex
- Renal papilla: Apex of pyramid
- Renal lobe: Another means of subdividing the kidney
- Consists of a pyramid, adjacent columnar material, and the renal cortex to the capsule
- Renal sinus : Urine drainage area, Medially located; organized into:
, - Minor calyces: Smallest; One for each pyramid
- Major calyces: 2-3 per kidney;Form from minor calyces
- Renal Pelvis: Forms from major calyces
- Hilum: Region through which the vessels, nerves, and ureter enter/exit into the kidney
- Renal arteries, Renal veins, Lymph vessels
- Nerves: Parasympathetic nerves from CN X (vagus) and Sympathetic nerves from T10 -
T12 of spinal cord
Nephron: Functional filtration unit of the kidney. Two major units:
- Renal corpuscle: Point of contact between the blood and the “filtering” tubule
- Renal tubule: Modifies the filtrate to create urine
- Both units reside primarily in the cortex
- Exception is the Nephron loop (Loop of Henle)
Renal Corpuscle:
- Glomerulus: Ball like tuft of capillaries
- H2O are solutes are filtered from the blood
- Composition of filtrate is similar to plasma but will eventually be converted to urine by
the tubular component
- Afferent Arterioles: Supply blood to the glomerulus
- Efferent Arterioles: Carry blood not filtered by the tubular component from the glomerulus
- Is an arteriole because no O2 or nutrients are delivered nor wastes picked up by
glomerulus
- Glomerular capsule: aka Bowman’s capsule
- Expanded double-walled invagination cupping the glomerulus
- Visceral layer directly overlays the glomerular capillaaries
- Parietal layer is the external impermeable layer of simple squamous epithelium
- Capsular space receives the filtrate
- Two opposing poles
- Vascular pole: Point where afferent and efferent arterioles connect with glomerulus
- Tubular pole: Point where renal tubule originates
Renal Tubule: Single tube, single layer of cells
- Proximal convoluted tubule (PCT): Located entirely within the cortex
- Contains filtered fluid
- Lined with simple cuboidal epithelium
- Tall, apical microvilli
- Nephron loop: aka Loop of Henle
- Hairpin loop that dips into the medulla
- Descending limb: Enters into medulla
- Ascending limb: Returns to cortex
- Both limbs have thick and thin segments
- Thick segments lined with simple cuboidal epithelium
- Thin segments lined with simple squamous epithelium
- Distal convoluted tubule (DCT): Extends beyond the thick segment of the ascending limb of the
Nephron loop
- Kidneys: Urine forming organ
- Ureter: Duct that channels urine from the kidney to the urinary bladder
- Urinary bladder: Smooth muscle-walled sac used for the temporary storage of urine
- Urethra: Tube through which urine is eliminated from the body
- In males, also serves as the duct for the passage of semen for the reproductive system
Primary Function
- Filter the blood, Remove waste products
- Convert the filtrate to urine and Eliminate the urine
Secondary functions
- Formation of calcitriol
- Production and release of erythropoietin
- Regulation of: Ion levels, Acid-base balance and Blood pressure (water levels)
- Potential to engage in gluconeogenesis
- General theme is that kidneys condition the blood
Location of the kidneys:
- Along the posterior abdominal wall
- Partially protected by the rib cage
- Between T12 & L3 vertebrae
- Left kidney sits slightly higher than right kidney
- Posterior to the parietal peritoneum
- Only anterior surface is covered called the retroperitoneal space
- Surrounded and supported by several tissue layers (inside to outside)
- Fibrous capsule
- Renal capsule
- Maintains kidney shape, protects it from trauma, serves as a barrier to pathogens
- Perinephric fat
- External to fibrous capsule
- Provides cushioning and support for kidney
- Renal fascia
- External to perinephric fat and Anchors kidney to surrounding structures
- Perinephric fat: Outermost layer surrounding kidney
Sectional Anatomy of the Kidney:
- Kidney is arranged into two distinct region
- Renal cortex = Outer region
- Renal medulla = Inner region
- Renal columns: Projections of the cortex that project into medulla and subdivide the medulla
into the renal pyramids
- Renal pyramids: Striated appearance
- Corticomedullary junction: Where base of pyramid lies against the cortex
- Renal papilla: Apex of pyramid
- Renal lobe: Another means of subdividing the kidney
- Consists of a pyramid, adjacent columnar material, and the renal cortex to the capsule
- Renal sinus : Urine drainage area, Medially located; organized into:
, - Minor calyces: Smallest; One for each pyramid
- Major calyces: 2-3 per kidney;Form from minor calyces
- Renal Pelvis: Forms from major calyces
- Hilum: Region through which the vessels, nerves, and ureter enter/exit into the kidney
- Renal arteries, Renal veins, Lymph vessels
- Nerves: Parasympathetic nerves from CN X (vagus) and Sympathetic nerves from T10 -
T12 of spinal cord
Nephron: Functional filtration unit of the kidney. Two major units:
- Renal corpuscle: Point of contact between the blood and the “filtering” tubule
- Renal tubule: Modifies the filtrate to create urine
- Both units reside primarily in the cortex
- Exception is the Nephron loop (Loop of Henle)
Renal Corpuscle:
- Glomerulus: Ball like tuft of capillaries
- H2O are solutes are filtered from the blood
- Composition of filtrate is similar to plasma but will eventually be converted to urine by
the tubular component
- Afferent Arterioles: Supply blood to the glomerulus
- Efferent Arterioles: Carry blood not filtered by the tubular component from the glomerulus
- Is an arteriole because no O2 or nutrients are delivered nor wastes picked up by
glomerulus
- Glomerular capsule: aka Bowman’s capsule
- Expanded double-walled invagination cupping the glomerulus
- Visceral layer directly overlays the glomerular capillaaries
- Parietal layer is the external impermeable layer of simple squamous epithelium
- Capsular space receives the filtrate
- Two opposing poles
- Vascular pole: Point where afferent and efferent arterioles connect with glomerulus
- Tubular pole: Point where renal tubule originates
Renal Tubule: Single tube, single layer of cells
- Proximal convoluted tubule (PCT): Located entirely within the cortex
- Contains filtered fluid
- Lined with simple cuboidal epithelium
- Tall, apical microvilli
- Nephron loop: aka Loop of Henle
- Hairpin loop that dips into the medulla
- Descending limb: Enters into medulla
- Ascending limb: Returns to cortex
- Both limbs have thick and thin segments
- Thick segments lined with simple cuboidal epithelium
- Thin segments lined with simple squamous epithelium
- Distal convoluted tubule (DCT): Extends beyond the thick segment of the ascending limb of the
Nephron loop
