1. Presentation title slide

2. UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System
Chapter 10: Circulatory System and Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System: Section 13.2
Chapter 14: Reproductive System

3. Chapter 13: Urinary System
UNIT B
Chapter 13: Urinary System
Chapter 13: Urinary System
What is the role of the kidneys in the body?
How would problems in the collecting ducts of the nephrons cause kidney failure?
Polycystic kidney disease seems to cause more serious problems in people of African descent, especially those who have sickle cell disease. Sickle cell is mainly a disease of the red blood cells. What does this have to do with the kidneys?
Born with Bad Kidneys. The kidney on the left is normal. The kidney on the right is from a person who has polycystic kidney disease (PKD). In PKD, cysts form within the collecting ducts of the nephrons, which can lead to kidney failure. A kidney transplant is required to treat PKD.
Chapter opener figure background:
Polycystic kidney disease (PKD) is a genetic disorder that results in cysts (small, fluid-filled sacs) forming within the collecting ducts of the nephrons in the interior of the kidneys. PKD causes kidney failure. Therefore, a kidney transplant is required for treatment.
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4. 13.2 Anatomy of the Kidney and Excretion
UNIT B
Chapter 13: Urinary System
Section 13.2
13.2 Anatomy of the Kidney and Excretion
The kidney’s blood supply is supported by many branches of the renal vein and renal artery.
Figure 13.3 Anatomy of the kidney. a. A lengthwise section of the kidney showing the blood supply. Note that the renal artery divides into smaller arteries, and these divide into arterioles. Venules join to form small veins, which form the renal vein.
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5. A kidney has three regions. Renal cortex: outer, granulated layer
UNIT B
Chapter 13: Urinary System
Section 13.2
A kidney has three regions.
Renal cortex: outer, granulated layer
Renal medulla: contains cone-shaped tissue masses called renal pyramids
Renal pelvis: central space that is continuous with the ureter
Figure 13.3 Anatomy of the kidney. c. The same section as (a) without the blood supply. Now it is easier to distinguish the renal pelvis, medulla, and cortex, which connects with the ureter.
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6. UNIT B Chapter 13: Urinary System Section 13.2
Figure 13.3 Anatomy of the kidney. a. A lengthwise section of the kidney showing the blood supply. Note that the renal artery divides into smaller arteries, and these divide into arterioles. Venules join to form small veins, which form the renal vein. b. An enlargement showing the placement of nephrons. c. The same section as (a) without the blood supply. Now it is easier to distinguish the renal pelvis , medulla, and cortex, which connects with the ureter. d. A lengthwise section of an actual kidney.
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7. Anatomy of a Nephron UNIT B
Chapter 13: Urinary System
Section 13.2
Anatomy of a Nephron
The kidney is composed of over 1 million nephrons, also known as renal or kidney tubules.
Figure 13.3 Anatomy of the kidney. b. An enlargement showing the placement of nephrons.
nephrons: microscopic kidney units made up of a glomerular capsule, the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting duct
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8. Blood Supply in a Nephron
UNIT B
Chapter 13: Urinary System
Section 13.2
Blood Supply in a Nephron
Figure 13.4 Nephron anatomy. a. You can trace the path of blood through a nephron by following the black arrows.
Each nephron has it own blood supply.
From the renal artery, an afferent arteriole leads to the glomerulus, a knot of capillaries inside the glomerular capsule
Blood leaving the glomerulus enters the efferent arteriole, which takes blood to the peritubular capillary network, before exiting through the renal vein
glomerulus: a knot of capillaries inside the glomerular capsule
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9. Parts of a Nephron UNIT B Glomerular capsule (Bowman’s capsule)
Chapter 13: Urinary System
Section 13.2
Parts of a Nephron
Glomerular capsule (Bowman’s capsule)
Inner layer composed of cells called podocytes
Spaces between podocytes allow small molecules from the glomerulus to enter the glomerular capsule
glomerular capsule: a cuplike structure that is the initial portion of a nephron
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10. Parts of a Nephron UNIT B Proximal convoluted tubule (PCT)
Chapter 13: Urinary System
Section 13.2
Parts of a Nephron
Proximal convoluted tubule (PCT)
Lined with cuboidal epithelial cells that have packed microvilli to increase the surface area for reabsorption
Also contain several mitochondria to carry out active reabsorption of substances
proximal convoluted tubule: portion of a nephron following the glomerular capsule where tubular reabsorption of filtrate occurs
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11. Parts of a Nephron UNIT B Loop of Henle
Chapter 13: Urinary System
Section 13.2
Parts of a Nephron
Loop of Henle
Also known as the loop of the nephron
Consists of a descending limb and an ascending limb
Lined with simple squamous epithelium
loop of Henle: portion of a nephron between the proximal and distal convoluted tubules
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12. Parts of a Nephron UNIT B Distal convoluted tubule (DCT)
Chapter 13: Urinary System
Section 13.2
Parts of a Nephron
Distal convoluted tubule (DCT)
Composed of cuboidal epithelial cells that lack microvilli but have many mitochondria
Helps move molecules from the blood into the tubule (tubular secretion)
The DCTs of many nephrons enter one collecting duct
Collecting ducts carry urine to the renal pelvis
distal convoluted tubule: final portion of a nephron that joins with a collecting duct
collecting ducts: carry urine to the renal pelvis
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13. UNIT B Chapter 13: Urinary System Section 13.2
Figure 13.4 Nephron anatomy.
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14. UNIT B
Chapter 13: Urinary System
Section 13.2
Urine Formation
Urine formation is divided into the following processes:
Pressure filtration: water, salts, nutrients, and wastes move from the glomerulus to the inside of the glomerular capsule
Selective reabsorption: nutrient and salt molecules are actively reabsorbed from the convoluted tubules into the blood of the peritubular capillary network
Tubular excretion: certain molecules are actively secreted from the blood in the peritubular capillary network into the convoluted tubules
pressure filtration: part of urine formation; occurs when whole blood enters the afferent arteriole and the glomerulus
selective reabsorption: part of urine formation; occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network
tubular excretion: part of urine formation; a way by which substances are removed from blood in the peritubular network and added to the tubular fluid
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15. UNIT B Chapter 13: Urinary System Section 13.2
Figure 13.5 Processes in urine formation. The three main processes in urine formation are described in boxes and colour-coded to arrows that show the movement of molecules into or out of the nephron at specific locations. In the end, urine is composed of the substances within the collecting duct (see blue arrow).
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16. Pressure Filtration UNIT B
Chapter 13: Urinary System
Section 13.2
Pressure Filtration
Pressure filtration occurs when blood enters the afferent arteriole and the glomerulus.
Due to blood pressure, water and small molecules move from the glomerulus to the inside of the glomerular capsule
These filterable blood components form the glomerular filtrate
pressure filtration: part of urine formation; occurs when whole blood enters the afferent arteriole and the glomerulus
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17. Selective Reabsorption
UNIT B
Chapter 13: Urinary System
Section 13.2
Selective Reabsorption
In selective reabsorption, nutrients and ions from the glomerular filtrate in the convoluted tubules are reabsorbed into the blood of the peritubular capillary network.
Examples:
Na+ ions are actively reabsorbed into the blood, with Cl- ions following passively
This reabsorption of salt (NaCl) results in water moving passively from the tubule into the blood
Glucose and amino acids are actively reabsorbed into the blood almost exclusively at the proximal convoluted tubule
selective reabsorption: part of urine formation; occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network
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18. UNIT B
Chapter 13: Urinary System
Section 13.2
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19. Selective Reabsorption
UNIT B
Chapter 13: Urinary System
Section 13.2
Selective Reabsorption
The glomerular filtrate that enters the proximal convoluted tubule is divided into two portions.
Reabsorbed filtrate components: reabsorbed from the tubule into blood
Nonreabsorbed filtrate components: continue to pass through the nephron to be processed into urine (become the tubular fluid that enters the loop of Henle)
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20. Tubular Excretion UNIT B
Chapter 13: Urinary System
Section 13.2
Tubular Excretion
Tubular excretion is another way substances are removed from blood in the peritubular capillary network and added to the tubular fluid.
Hydrogen ions, potassium ions, creatinine, and certain drugs are removed by active transport from the blood in the peritubular capillary network into the convoluted tubules
The resulting urine contains:
Substances that have undergone glomerular filtration but have not been reabsorbed
Substances that have undergone tubular excretion
tubular excretion: part of urine formation; a way by which substances are removed from blood in the peritubular network and added to the tubular fluid
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21. Check Your Progress UNIT B
Chapter 13: Urinary System
Section 13.2
Check Your Progress
Identify the parts of a nephron that are found in the renal cortex and the renal medulla.
Explain the difference in microscopic structure which suggests that the PCT, but not the DCT, is specialized for reabsorption.
ANSWERS
1. The renal cortex contains Bowman’s capsules, proximal convoluted tubules, and distal convoluted tubules. The renal medulla contains the Loops of Henle and portions of the collecting ducts.
2. The epithelium of the PCT has many microvilli, which increases the surface area for reabsorption. The DCT is composed of cuboidal epithelial cells that are not designed for reabsorption.
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22. Check Your Progress UNIT B
Chapter 13: Urinary System
Section 13.2
Check Your Progress
Explain how the kidney uses the processes of diffusion, passive transport, and active transport.
Explain where in the nephron, and by what process, glucose is normally returned from the glomerular filtrate to the blood.
ANSWERS
3. The kidney uses diffusion to move non-polar molecules from PCT back into the blood. The kidney uses passive transport (or facilitated transport) to move polar molecules such as glucose and amino acids. The kidney uses active transport to move other molecules against their concentration gradient. Active transport occurs during selective reabsorption, and tubular excretion.
4. Glucose is returned to the blood at the proximal convoluted tubule in a process called selective reabsorption. Some is returned to the blood by passive reabsorption and the rest (up to threshold levels) is returned by active transport.
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23. UNIT B
Chapter 13: Urinary System
Section 13.2
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24. UNIT B
Chapter 13: Urinary System
Section 13.2
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