Excretion

Excretion

#1. Excretion

A. Excretion-the process of removing metabolic wastes

-Without excretion toxic wastes would continue to circulate throughout the body

B. Metabolism –all chemical reactions that occur in our bodies

-produces useful products and waste products

C. Examples of wastes

1. Nitrogenous wastes in urine

2. carbon dioxide from lungs

3. Oxygen is excreted from plant via the stomata (daytime only)

#1. Excretion

#2. Nitrogenous wastes and animal habitats

A. Nitrogenous wastes1. Produced when amino acids are broken

down to be used for energy2. Produce ammonia, which is extremely basic

and toxic

B. Freshwater organisms (fish)1. Take in surplus of water2. Excess water provides a medium for

ammonia to be diluted and flushed out with the excess water

C. Marine mammals

1. Do not take in excess water

2. Must convert ammonia to a less toxic substance

3. They convert ammonia to urea and trimethyline oxide


D. Adult amphibians

1. conserve water and convert ammonia into urea

E. Birds

1. Birds cannot carry excess water for dilution of ammonia

2. Convert ammonia into insoluble uric acid (the white stuff in bird feces)


F. Mammals

1. excrete urea (produced in the liver)

2. Urea is produced from ammonia by the ornithine cycle (the urea cycle)

3.


100,000 times less toxic than ammonia

#3. The Excretory System (an overview)

A. Filtration-separation of products from body fluids

B. Reabsorption-return of useful products to the body

C. Secretion-solutes (wastes) are removed from the body and added to the filtrate

D. Excretion-discarding of waste products

**Accumulation of wastes (no excretion) could lead to death because toxins build up in the body

(Remember PKU?)

#4. The Human Kidney

A. Kidney structure

1. humans have two kidneys

2. each has a renal artery leading to it

3. each has a renal vein and ureter leading away from it

4. renal vein takes away clean blood

5. the ureter leads urine to the bladder

A. Kidney structure-

6. Inside the kidney there are two regions

a. renal cortex-outer

b. renal medulla-inner

*The cortex and medulla are packed with nephrons

7. Nephrons –functional units of the kidneys

B. Animation

#4. The Human Kidney

http://www.kidneypatientguide.org.uk/site/HKWanim.php

• Kidneys from behind with spine removed

http://en.wikipedia.org/wiki/Image:Kidneys_from_behind.jpg

ASSIGNMENT

1. Draw, label and annotate a diagram of the human kidney. Include the following:cortex, medulla, pelvis, ureter and renal blood vessels

2. Draw, label and annotate a diagram of a nephron. Include the following:glomerulus (bowman’s capsule, basement membrane, podocytes), renal artery (distinguish between afferent and efferent vessels), renal vein, distal tubule, proximal tubule, loop of Henle, collecting duct

A. Jobs of the nephron – ultrafiltration, reabsorption, secretion

B. Ultrafiltration-part of fluid from the blood is pushed into the nephrons and filtered

C. Reabsorption-molecules that the body ‘wants’ to keep, such as, glucose are reabsorbed into the blood

D. Secretion-undesired substances are released into the filtrate by the nephrons

#4. The Nephron

E. There are about 1,000,000 nephrons per kidney and about 80km of tubules

F. Every nephron has a glomerulus, a Bowman’s capsule, a proximal tube, a loop of Henle and a distal tube

#4. The Nephron

#5. Blood flow in the nephron

A. Blood enters kidneys through renal artery

B. Renal artery splits into smaller vessels1. Afferent vessels

2. Efferent vessels

C. Afferent vessels-carry blood to the glomerulus

D. Efferent vessels carry blood to other parts of the nephron

E. Glomerulus-ball of capillaries in the nephron

-surrounded by Bowman’s capsule

-where the proximal tube ends


http://upload.wikimedia.org/wikipedia/commons/3/30/Gray1130.svg

http://upload.wikimedia.org/wikipedia/commons/f/fd/Gray1129.png

Glomerulus and Bowman’s capsule

F. Ultrafiltration

1. Blood pressure in the glomerulus forces water, salt, urea and other minerals into Bowman’s capsule

2. The filtrate must pass through a layer of three barriers to get there

a. wall of glomerulus (endothelial cells)

b. basement membrane of the glomerulus

c. podocytes


3. Wall of the glomerulus (endothelium) is fenestrated

-it has small pores that allow blood plasma to pass through


http://upload.wikimedia.org/wikipedia/commons/6/66/Inner_view_of_fenestrae_in_capillary_of_glomerulus_in_Scanning_Electron_Microscope%2C_magnification_100%2C000x.GIF

F. Ultrafiltration

4. Basement membrane-a protein membrane outside of the cells

-has no pores

-acts as a dialysis membrane by stopping large molecules from entering the Bowman’s capsule


F. Ultrafiltration

5. Bowman’s capsule (inner wall)

-made of podocytes

-podocytes have:-many extensions which fold around blood vessels

-networks of filtration slits to hold back blood cells

-fluid produced by ultrafiltration is collected by Bowman’s capsule

-from there it flows to the proximal tubule


The Glomerulus

Glomerulus and podocytes

G. Osmoregulation

1. The control of water balance in blood, tissue and cytoplasm of cells in living organism

2. An internal adjustment

#6. Filtrate flow in the nephron

H. Reabsorption1. After ultrafiltration the filtrate leaves Bowman’s capsule and enters the proximal convoluted tubule where most reabsorption occurs2. The fluid is made of glucose, amino acids, vitamins, hormones, urea, salt ions and water3. most of the fluid is reabsorbed into the blood


I. Reabsorption and the structure of proximal convoluted tubule

Orange arrow - Distal tubule Blue arrow - Proximal tubule

Proximal tubule -invaginated outer membrane -has microvilli (brush border) -large lumen that carries filtrate -basement membrane


J. Reabsorption in the proximal tubule1. Water is reabsorbed by osmosis2. Sodium and glucose are reabsorbed via active transport3. Chlorine passively follows the sodium ion4. To facilitate the movement, the lumen wall is lined with microvilli5. Microvilli increase the surface area 6. Mitochondria are present in these cells to facilitate active transport


K. Loop of Henle-creates an area of high solute concentration in the cells and tissue fluid of the medulla-found in medulla-descending and ascending limbs are opposite in permeability1. Descending loop of Henle

-water leaves the nephron via osmosis-the descending limb is permeable to water but not salt-NaCl becomes more concentrated


K. Loop of Henle2. Ascending loop of Henle

-made of two segments (thick and thin)-both segments are

impermeable to water-the thin section

permeable to NaCl-NaCl diffuses out of the limb and into the

interstitial fluid causing high osmolarity


K. Loop of Henle

2. Ascending loop of Henle

-Thick segment continues the transfer of NaCl, but through active transport

-Salt removed from Henle’s loop helps maintain a concentration gradient in

the medulla


L. Vasa recta -blood vessels running along Henle’s loop

-maintains the concentration gradient of the medulla by countercurrent exchange

-countercurrent exchange-the path of the vasa recta and the loop of Henle flow opposite of each other

-there is no direct exchange of fluids between the filtrate and the blood


L. Vasa recta

-Substances pass through the interstitial fluid of the medulla

-Blood entering the medulla will lose water to the region via osmosis and absorb salt and urea via diffusion

(in the descending capillary of the vasa recta)


L. Vasa recta

-the opposite happens in the ascending capillary of the vasa recta

-movement of fluid requires no energy because it happens via diffusion and osmosis


M. Distal tubule-regulates potassium and salt concentration of body fluids by varying the amount of potassium secreted into the filtrate and the amount of salt absorbed from the filtrate-ions are exchanged between blood and filtrate to maintain concentration gradients


N. Collecting duct-epithelium of collecting duct is permeable to water but not salt-duct carries filtrate back towards medulla and renal pelvis-as the filtrate moves along water is lost and the filtrate becomes more concentrated-the bottom of the collecting duct is permeable to urea


N. Collecting duct

-some of the urea diffuses into the interstitial fluid in the medulla

-causes high osmolarity of the medulla

-high osmolarity of the interstitial fluid allows the kidney to conserve water by excreting urine that is hyperosmotic to the general body fluids


***Collecting duct and the loop of Henle maintain the osmolarity in the interstitial tissue of the kidney

-this makes it possible to concentrate the urine

***After the collecting duct the filtrate moves to the:

renal pelvis→ureters→bladder→urethra


1. Renal artery

2. Glomerulus(epithelium, basement membrane, podocytes)

3. Bowman’s capsule

4. Proximal tubule

5. Descending loop of Henle (water leaves through osmosis/salt becomes more concentrated)

#7. Filtrate in the nephron (quick review)

6. Ascending loop of Henlea. Thin-impermeable to water/permeable to

salt/salt diffuses outb. Thick-impermeable to water/permeable to

salt/salt moves out through active transport

7. Vasa recta-blood vessels along loop of Henle

a. Uses countercurrent exchange to maintain concentration gradient in the medulla

8. Distal tubule

#5. Blood flow in the nephron (quick review)

9. Collecting duct (permeable to water but impermeable to salt)

a. water diffuses out through osmosis

b. salt stays and makes urine more concentrated

c. some urea diffuses out (causes high osmolarity of interstitial fluid which increases the amount of osmosis which makes urine hyperosmotic to body fluids)

#7. Filtrate in the nephron (quick review)

AssignmentDue Tomorrow

1. Get a red book.2. Outline negative feedback in regards to ADH

and osmoregulation.3. If you wish . . .

a. the first two people may present their outlines and receive 5 points of E.C.b. the presentations must be accurate and detailedc. the class should be able to take notes from your workd. you have to put your outline on transparencies or PowerPoint

#8. Blood Composition of Renal Artery and Renal Vein

A. Renal artery

1. oxygen rich

2. contains more urea, salt and water than the set value

B. Renal vein

1. oxygen poor

2. contains correct amount of water and salts and very little urea

A. Glomerular filtrate1. No proteins

2. Contains glucose, sodium and small amounts of urea

B. Urine1. Has no proteins and no glucose

2. Has large amounts of urea and sodium

#9. Blood Composition of Glomerular Filtrate and Urine

Contents of Fluids in the Kidney

Units=mg per 100 ml of blood

Renal artery

Renal vein

UrineGlomerular

filtrate

Glucose 90 90 0 90

Urea 30 24 2000 30

Proteins 740 740 0 0

Sodium ions

900 720 1200 900

#10. Kidney failure and dialysis

A. If the kidneys fail, waste cannot be removed from the body

B. There are two main types of kidney failure

1. Acute-rapid onset

2. Chronic-long duration/slow progress

C. If the kidneys fail, a person will become dependent on a dialysis machine

#11. Dialysis Machines

A. The concept: lead patients blood through a machine that will clean it and return it to the body

B. Dialysis involves the diffusion of solutes from a high to low concentration through a semi-permeable membrane

C. The dialysis membrane used in the machines is usually made of cellulose acetate or cellulose nitrate (the membrane acts as a filter)

D. The filter has small pores that allow small solute particles through (blood and large proteins cannot fit through)

E. Blood flows on one side of the dialysis membrane and dialysis fluid flows on the other

F. The dialysis fluid contains solute concentrations in found in healthy blood


G. The dialysis fluid contains no urea or other excretory fluids

-these diffuse from the patients blood into the dialysis fluid

H. Glucose and other desired substances found in the dialysis fluid do not diffuse into the blood

I. Dialysis fluid contains dextran

-Excess water is removed by osmosis from the blood to the dialysis fluid to neutralize it


J. During dialysis blood flow through tubes and between sheets of dialysis membrane

K. Blood is taken and returned via needles in the person’s arm

L. The dialysis fluid is continuously replaced during a session to maintain a continuous concentration gradient

M. Most patients spend about 4 hours, 3 times a week in dialysis treatment


1. ADH animation 1

• Dialysis animation 2

• Dialysis animation 3

http://www.kidneypatientguide.org.uk/site/HDanim.php

http://www.ski.group.shef.ac.uk/health/dialysis.html

#12. Acute renal failureA. Caused by serious illness or operation which

can reduce the amount of blood flow to the kidneys

B. Blood flow to the kidneys can be reduced by:-blood loss-decrease in blood pressure-severe dehydration-lack of salt

C. Acute kidney damage can also be caused as a side effect to medication

D. The cause is treated and the kidneys will often return to normal(dialysis may be necessary until full function is restored)

#13. Chronic renal failure

A. Can be caused by:-inflammatory conditions of the kidney tissue

(a complication of type I diabetes)

-chronic blockage to the drainage of the kidney

-inheritance

B. Often the cause cannot be identified because it occurred so long ago

C. Chronic failure is often irreversible

D. Often requires a dialysis machinefrcx

p. 239 #1, 3, 4

Due at the end of class.

Education

Excretion