1. Structures and Functions
Kidneys and Excretion
Structures and Functions

2. Kidney has 3 main parts Adrenal cortex - outer part of kidney
Adrenal medulle - middle part of kidney
Renal pelvis - inner part of kidney

3. Parts of the Kidney

4. Nephron
functional unit of the kidney, performing the filtering of the blood.
over 1 million per kidney
Extend between the adrenal cortex and the medulla
parts of the nephron:

5. Parts of the Nephron 1. Glomerulus microscopic glob of capillaries
blood circulates at increased pressure, causing fluids to leak out.
this is the process called FILTRATION.

6. A. Filtration
materials are forced out of the blood and into the nephron’s tubules
materials move OUT of the glomerulus and INTO Bowman’s Capsule

7. the filtrate contains both “good” and “bad” materials
water
salts
sugars
amino acids
uric acid
urea

8. two arterioles are involved in increasing the pressure of blood in the glomerulus:
Afferent arteriole:
controls blood flow into the glomerulus
dilates to allow for increased volume.
Efferent arteriole:
controls blood flow out of the glomerulus
constricts to increase pressure

9. Proximal Tubule 2. Bowman’s Capsule
cup-like structure that collects the filtrate
3. Proximal Tubule
some filtrate is put back into the blood = REABSORPTION

10. B. Reabsorption Proximal Tubule
the “good” materials are pulled back out of the tubule into the blood.
water, glucose, amino acids, vitamins, minerals, salts Active Transport is used to reabsorb materials.
special carrier proteins in the walls of the proximal tubule use ATPs to move what is needed.
70% of reabsorption occurs in the proximal tubule.
Proximal Tubule

11. Descending Ascending Loop of Henle 4. Loop of Henle
long tube that extends into the medulla
creates an environment that encourages WATER REABSORPTION (C)
the ascending loop actively transports out sodium ions (Na+)
the positive ions draw negative chlorine ions out after them (Cl-)
the salty environment that results sets up an osmotic gradient for water to move out of the nephron
the descending loop actually absorbs some of the chlorine and sodium ions so that they can be used again.
Descending
Ascending
Loop of Henle

12. Distal tubule 5. Distal Tubule
a winding tube that is found in the cortex
some reabsorption occurs here.
able to remove materials from the blood.
Process is called SECRETION.
Distal tubule

13. D. Secretion actively transports waste materials from the blood.
carrier proteins in the walls of the capillaries near the distal tubule aid in secretion.

14. some secretion occurs here.
6. Collecting Duct
sends the waste (urine) out of the nephron and toward the renal pelvis.
some secretion occurs here.
- urine will then travel down the ureters to the bladder and then down the urethra and out of the body = EXCRETION