The Urinary System and Renal Physiology PART I

Chapter 25

Kidneys

Maintain and regulate the composition of the body’s extracellular fluids by filtering the blood:

• Total body water volume and concentration of solutes in water

• Concentration of ions in ECF

• Acid-base balance

• Toxin and waste disposal

• Hormone production

Retroperitoneal Organs

Structures located behind the peritoneum, lining of the abdominal cavity

Renal Hilum

Indentation in the media portion of the kidney

• Where ureters, renal blood vessels, lymphatics, and nerves enter

Adrenal Gland

Structure that sits immediately superior to each kidney

Renal Fascia

Structure that anchors kidneys to surrounding structures to keep them from moving around

• Made of dense connective tissue

Perirenal Fat Capsule

Fat mass surrounding kidneys, acting as a cushion from physical trauma

Fibrous Capsule

Thin, transparent layer that prevents disease from spreading to kidneys from other parts of the body (except at the hilum)

Renal Cortex

Renal structure that provides area for glomerular capillaries and blood vessel passage

• Contains tubule cells that are responsible for the production of Erythropoietin (EPO)

Renal Medulla

Renal structure that allows for some water reabsorption, electrolyte balance, disposal of waste and H+ ions

• Contains several renal pyramids

Renal Pyramids

Structures that are packed with capillaries and urine-collecting tubules

Renal Pelvis

The open space in the center of each kidney, where it branches to form major calyces → minor calyces at tip of each renal pyramid

Calyces

Collects urine from renal medulla, along with the renal pelvis

Renal Arteries

Deliver blood to the kidneys

• Divide into smaller blood vessels to serve major regions of kidneys

Segmental Arteries

Set of five arteries that are the initial set → they allow for blood to reach throughout the entire kidney

Interlobar Arteries

Arteries that travel between renal pyramids

Arcuate Arteries

Arteries that arc over the bases of the renal pyramids

Cortical Radiate Arteries

Arteries that supply the renal cortex

• Important for glomerular capillaries, blood production, and renin production

Renal Plexus

Network of autonomic nerve fibers and ganglia → adjusts diameter of renal arterioles to adjust blood flow to glomeruli

Sympathetic Vasomotor Fibers

These regulate blood supply to each kidney

Nephron

The functional unit of the kidney that is responsible for forming filtrate and eventually urine in the kidneys

• If part of this is destroyed, you will lose function of the entire kidney

Renal Corpuscle

Renal structure located entirely within renal cortex that filters blood to form the filtrate

Renal Tubule

Renal structures that reabsorbs some substances from the filtrate formed and secretes other substances into filtrate

Filtration

The mass movement of solutes and water from the plasma into the renal corpuscle and renal tubules

Reabsorption

The process by which nephrons remove water and solutes from the filtrate formed from filtration and return it to the blood

Secretion

The process by which excess ions (K+, H+, etc.) and waste products are pumped back into the filtrate after it has been reabsorbed

Glomerulus

Subdivision of the renal corpuscle → cluster of porous capillaries (allow for fluid and substances in blood to be easily filtered)

Afferent Arteriole

Blood enters glomerulus via this artery

Efferent Arteriole

Blood leaves the glomerulus via this artery

Filtrate

Raw fluid material used to produce urine

• Produced by the glomerulus

Glomerular Capsule

Subdivision of the renal corpuscle where it is a double-layered structure that completely surrounds glomerular capillaries

Podocytes

Structure within the inner layer of the glomerular capsule that is important for the filtering mechanism of the glomerular capillaries, along with foot processes

Proximal Convoluted Tubule (PCT)

Subdivision of the renal tubule → leads immediately off from glomerulus

• Located in renal cortex

• Large cuboidal epithelial cells with dense microvilli

Nephron Loop (Loop of Henle)

Subdivision of the renal tubule that travels between the renal cortex and renal medulla

Descending Limb

Of the nephron loop → leads off from PCT

• High permeability to H2O (NOT solutes)

Ascending Limb

Of the nephron loop → continuous with DCT

• High permeability to solutes (NOT H2O)

Distal Convoluted Tubule (DCT)

Subdivision of the renal tubule that is located in the cortex

• Composed of small cuboidal epithelial cells

• Smaller diameter, no microvilli

Collecting Ducts

Receives filtrate from tubules of multiple nephrons

• Fuse together, dump urine into minor calyces

Principle Cells

Cell type in the collecting ducts that maintain Na+ balance in body

• Influences how much water you reabsorb

Intercalated Cells

Cell type in the collecting ducts that help maintain acid-base balance

Cortical Nephron

Type of nephron that is located almost entirely in the cortex

• Small portion of nephron loop found in renal medulla

Juxtamedullary Nephrons

Type of nephron whose loop deeply invades the renal medulla

• Significantly longer → can better vary urine concentration

Glomerulus

Maintains high pressure to increase filtrate production

Peritubular Capillaries

Capillaries that are low pressure, arise from efferent arteriole to reabsorb water and solutes from tubule cells

• Cling to proximal and distal tubules of cortical nephrons → empty into cortical radiate veins for filtered blood to return to circualtion

Vasa Recta

Run parallel to and found only on juxtamedullary nephrons

• Helps form concentrated urine

Juxtaglomerular Complex

Portion of nephron where portion of ascending limb lies against afferent and efferent arterioles

• Regulates blood pressure and filtration rate of the glomerulus

Macula Densa

Chemoreceptor cells in the JGC that monitor NaCl content of filtrate entering the DCT

Granular Cells

Specialized smooth muscle cells of the JGC that can sense blood pressure in afferent arteriole

• Stimulated by macular densa cells

  • Prevent too much filtrate from forming → cause vasoconstriction

Renin

Hormone released by granules when there is low NaCl concentration and low arteriole pressure

• Mostly affects the efferent arteriole

Extraglomerular Mesangial Cells

Cells of the JGC that are packed between tubule and arterioles that maybe are messenger cells that are telling granular cells when to contract

• Function is not really known