Biology 212 Anatomy & Physiology I Dr. Thompson Renal

Renal (Urinary) System Primary function: Disposes of while retaining

Organs of Renal System

Kidney Mass ~ 150g Size ~ 12 cm x 6 cm x 3 cm

Kidney Capsule: Cortex: Medulla: Pelvis:

Kidney:

This is where filtration will occur to begin formation of urine (more on that in a moment).

Each renal artery divides into lobar arteries, interlobar arteries, arcuate arteries, interlobular arteries, afferent arterioles, glomeruli, efferent arterioles, peritubular capillaries Blood then flows into interlobular veins or arcuate veins, interlobar veins, and lobar veins to reach the renal vein which carries it to the inferior vena cava.

This series of tubes is called a nephron. Let’s go back to the glomerulus:

Each kidney contains ~ 1,000,000 nephrons Pattern of nephrons creates pattern of cortex and medulla:

Functions of nephrons:

Thus: Primary function of renal system: Maintains homeostasis by regulating concentrations of both water and solutes in the blood. Disposes of metabolic wastes excess water excess ions toxins while retaining proper amount of water proper concentrations of ions nutrients anything else needed in blood

Two types of “pressure” are involved in these processes of filtration, reabsorption, and secretion. 1) 2)

Two types of “pressure” are involved in these processes of filtration, reabsorption, and secretion. A.

Two types of “pressure” are involved in these processes of filtration, reabsorption, and secretion. B.

Filtration

Structure of Glomerulus

Filtration: a) b) c) Thus: only things smaller than ~ 7 nm can be filtered from blood into urine

Filtration: In general:

This fluid filtered out of the blood flows into

As this filtrate passes through the nephron: a) Most solutes needed by body & most of the water are reabsorbed back into the blood in peritubular capillaries b) Excess solutes & excess water stay in urine c) Additional unwanted ions and molecules secreted into urine

Key Feature of Kidney: Nephrons can concentrate urine by reabsorbing most of the water filtered out of the glomerulus Substance: Amount Amount Reabsorption filtered excreted ( % ) per day per day Water ( L ) Sodium ( g ) Glucose ( g ) Urea ( g )

Key Feature of Kidney: (Nephrons concentrate urine by reabsorbing most of the water filtered out of glomerulus. This requires kidney to create a large concentration gradient in extracellular fluid of medulla, surrounding loops of Henle)

Key Feature of Kidney: (Nephrons concentrate urine by reabsorbing most of the water filtered out of glomerulus. This requires kidney to create a large concentration gradient in extracellular fluid of medulla, surrounding loops of Henle) Low osmolarity (concentration of solutes) closer to cortex High osmolarity (concentration of solutes) deeper in medulla so that As newly formed urine passes through collecting, most of the water will diffuse out of collecting duct, into the extracellular fluid, from which it will diffuse back into blood of the peritubular capillaries, leaving high concentration of solutes in urine which reaches pelvis & leaves kidney

Your text goes into great detail about how this happens (including these diagrams): You don’t need to understand details, but you should understand that it allows the final urine to be concentrated by pulling water out of it as it passes through the collecting duct. How much water gets pulled out can increase or decrease if body needs to retain or lose water. This is under control of

(How much water gets pulled out can increase or decrease if body needs to retain or lose water. This is under control of antidiuretic hormone (ADH) produced by posterior pituitary). Increase in ADH Decrease in ADH

Kidney also has important function in regulating systemic blood pressure.

(Each nephron has a juxtaglomerular apparatus which detects blood pressure in afferent arteriole and secretes hormone renin. The lower the blood pressure in the afferent arteriole, the more renin the juxtaglomerular apparatus will secrete.)

Urine passes from

Urine leaving the pelvis enters

Ureters:

Ureter: Mucosa: Muscularis: Adventitia:

Urinary Bladder:

Mucosa: Muscularis: Adventitia Serosa

Urinary Bladder:

Urethra: Adventitia: Muscularis: Mucosa:

Urine not modified in ureter bladder urethra Thus: Also:

Tonight: On yourself or another person, locate kidneys ureters bladder urethra