Excretory System

An organism’s way of breaking down nitrogenous wastes

When proteins are broken down, they form ammonia

Birds and reptiles convert ammonia to uric acid and mammals convert it to urea

Malpighian tubules are found in arthropods Nephridia are found in earthworms Flame cells are found in flatworms

Human Excretory System

Kidney regulate excretion Kidneys are made up of nephronsAreas of the nephronRenal cortex1. Bowman’s capsule2. Proximal convoluted tubule3. Collecting ductRenal Medulla4. Loop of Henle5. Distal convoluted tubule

Figure 15.3a

Renal cortex

Renal medulla

Renal pelvis

Renalcortex

Ureter

Renalmedulla

Corticalnephron Fibrous capsule

Collectingduct

Proximalconvoluted tubuleGlomerulusDistalconvoluted tubuleLoopof Henle

Juxtamedullarynephron

(a)

Flow of blood through a nephron Blood enters at the Bowman’s capsule The renal artery leads to the kidney and

branches into arterioles then into a ball of capillaries called the glomerulus

Blood is filtered and plasma passes from the capillaries into the Bowman’s capsule – it is now called a filtrate

Path of the filtrate

Passes through the B. capsule, through the proximal convoluted tubule, then the loop of Henle, then the distal tubule, and finally the collecting duct.

As it travels, it is modified to form urine. Then the urine travels through ureters to

the bladder, to the urethra

Figure 15.3b

Proximalconvolutedtubule (PCT)Glomerular

capillaries

Glomerular(Bowman’s) capsule

Efferent arteriole

Afferent arteriole

Cells of thejuxtaglomerularapparatus

Cortical radiate artery

Arcuate artery

Cortical radiatevein

Arcuatevein

Collecting duct

Loop of Henle

Distalconvolutedtubule(DCT)

Peritubularcapillaries

(b)

How urine is made

1. Filtration – small substances such as ions, water, nutrients, salts pass from the glomerulus to the Bowman’s capsule, proteins and blood cells are too big

2. Reabsorption – as the filtrate moves through the proximal convoluted tubule, the small substances are re-absorbed by the blood in the peritubular capillaries (what remains is urine)

3. Secretion – as the filtrate moves through the remaining tubules, H ions, K ions, ammonium ions are secreted from the capillaries into the tubule

Figure 15.5

Proximal tubuleGlomerularcapsule

Blood

FiltrateH2OSalts (NaCl, etc.)HCO3

– (bicarbonate)H+

UreaGlucose; amino acidsSome drugs

Reabsorption

Active transportPassive transportSecretion (active transport)

Urine (to renal pelvis)

Glucose andamino acids

HCO3–

H2ONaCl

Some drugsand poisons

H+

Cortex

Medulla

Distal tubule

NaCl

K+ andsomedrugs

Loop ofHenle

H2O

NaCl

NaCl

H2O

Urea

K+

NaCl H2O

Collectingduct

Figure 15.1a

Hepatic veins (cut)

Inferior vena cava

Adrenal gland

Aorta

Iliac crest

Rectum (cut)

Uterus (partof femalereproductivesystem)

(a)

Renal artery

Renal hilum

Renal vein

Kidney

Ureter

Urinarybladder

Urethra

Hormones of the Kidney

Regulation occurs primarily by hormones Antidiuretic hormone (ADH) - vasopressin

Prevents excessive water loss in urine Causes more water re-absorption from the

collecting duct If you are dehydrated, ADH will work to re-

absorb the water and urine will be concentrated

If your fluid intake is high, ADH will be low, the body won’t re-absorb most of the water and your urine will be dilute

Hormones cont.

Aldosterone Regulates sodium ion content of the distal

convoluted tubule Sodium is the electrolyte most responsible for

osmotic water flows Aldosterone promotes reabsorption of sodium

ions Remember, water follows salt!

Skin

Epidermis, dermis, subcutaneous layers Sweat glands are found in the dermis Stratum corneum is in the epidermis and

forms are barrier against invading microorganisms

Hair shaft

Epidermis

Papillarylayer

Reticularlayer

Dermal papillae

Pore

Adipose tissue

Cutaneous vascular plexus

Dermis

Hypodermis(superficial fascia)

• Sensory nerve fiber• Lamellar corpuscle• Hair follicle receptor (root hair plexus)

Nervous structures

Appendages of skin• Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair root

Figure 4.3

Excretory Bingo

1. Ammonia2. Uric acid3. Urea4. Malpighian tubules5. Nephridia6. Nephron7. Renal cortex8. Renal medulla9. Bowman’s capsule10. Loop of Henle11. Renal artery12. Glomerulus13. Filtrate

14. Ureters15. Bladder16. Urethra17. Filtration18. Reabsorption19. Secretion20. ADH (vasopressin)21. Aldosterone22. Epidermis23. Dermis24. Subcutaneous layer