I. Urinary System

A. Humans excrete nitrogenous waste (from amino acids) as urea and uric acid.

B. Kidneys remove waste and water from blood.

II. Kidney Anatomy

A. Outer Kidney = Renal Cortex

Inner Kidney = Renal Medulla

B. Nephron – Functional unit of a kidney (Each kidney contains more than 1 Million nephrons)

C. Kidneys connect to ureter and drain to urinary bladder.

Fig. 43.4a, p. 751

renal capsule

ureter

renal pelvis

renal vein

renal artery

kidney cortex

kidney medulla

glomerulus (coded red)

proximal tubule (orange)

start of distal tubule (brown)

loop of Henle (yellow)

collecting duct

orientation of nephrons relative to the kidney cortex and medulla

NEPHRON

Kidney Physiology

A. Nephron Anatomy:

1. Bowman’s capsule (wall of nephron), 2. Glomerular capillaries,

3. Glomerulus (capsul + capillaries),

4. proximal tubule,

5. loop of Henle, and

6.distal tubule (drains to uretur)

Fig. 43.4b, p. 751

Bowman’s capsule

glomerular capillaries at beginning of nephron

collecting duct

peritubular capillaries threading around the nephron’s tubular parts

Steps of Urine Formation:

1. Filtration: Glomerular capillaries force water + solutes through capillary walls.

2. Reabsorption: Water and salt leave filtrate (urine-to-be) as they are pumped out of proximal tubule.

2. Reabsorption (con’t)Nephron tubule impermeable to water after Loop of

Henle, but cells still pump out ions.

Water enters capillaries, reentering blood system (reabsorption).

3. Tubular Secretion: Active transport; reverse of reabsorption.

A

B

C

D

E

1. Where filtration occurs; where reabsorption occurs; where tubular secretion occurs.

2. Where is nephron permeable to water; where is it impermeable to water; where does active transport occur.

3. Where water is reabsorbed; where glucose is reabsorbed; what accounts for changes in filtrate concentration (see handout).

4. Correctly identify components of nephron.

A

B

C

D

E

E

1. Identify A – E.

2. What event occurs at “B”?

3. Explain the physiological reason why proteins aren’t filtered out of the blood at point A.

4. At which points does active transport pump ions out of the nephron?

5. Where is glucose reabsorbed by the capillaries?

6. Explain the physiological reason water leaves the nephron at point B.

A

B

C

D

E

E

1. Identify A – E.

2. Explain the events that occur at “D”?

3. Where is the nephron permeable to water?

4. At which points does active transport pump ions out of the nephron?

5. At which point would you expect the ion concentration of the filtrate to be the highest. Why?

6. Explain the physiological reason why water leaves the nephron at point B.