End Show Slide 1 of 36 Biology Mr. Karns Excretory system.
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BiologyMr. Karns
Excretory system
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Each kidney
Is supplied with blood by a renal artery and drained by a renal vein
Figure 44.13a
Posterior vena cava
Renal artery and vein
Aorta
Ureter
Urinary bladder
Urethra
(a) Excretory organs and major associated blood vessels
Kidney
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Functions of the Excretory System
Functions of the Excretory System
Every cell produces metabolic wastes.
The process by which these wastes are eliminated is called excretion.
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Functions of the Excretory System
The skin excretes excess water and salts in the form of sweat.
The lungs excrete carbon dioxide.
The kidneys also play a major role in excretion.
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Functions of the Excretory System
The Kidneys
What are the functions of the kidneys?
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Functions of the Excretory System
The kidneys:
• remove waste products from the blood.
• maintain blood pH.
• regulate the water content of the blood and, therefore, blood volume.
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The Kidneys
The kidneys are located on either side of the spinal column near the lower back.
A tube, called the ureter, leaves each kidney, carrying urine to the urinary bladder.
The urinary bladder is a saclike organ where urine is stored before being excreted.
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The Kidneys
Structure of the KidneysKidney Nephron
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The Kidneys
Blood enters the kidney through the renal artery.
The kidney removes urea, excess water, and other waste products and passes them to the ureter.
The clean, filtered blood leaves the kidney through the renal vein and returns to circulation.
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The Kidneys
Kidney Structure
A kidney has two distinct regions:
• The inner part is called the renal medulla.
• The outer part is called the renal cortex.
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The Kidneys
Cortex
Medulla Renal artery
Renal vein
Ureter
To the bladder
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The Kidneys
The functional units of the kidney are called nephrons.
Nephrons are located in the renal cortex, except for their loops of Henle, which descend into the renal medulla.
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The Kidneys
Artery
Vein
Loop of Henle
Bowman’s capsule
Glomerulus
Capillaries
Collecting duct
To the ureter
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The Kidneys
Vein
Artery
Capillaries
To the ureter
Collecting duct
Each nephron has its own blood supply:
• an arteriole
• a venule
• a network of capillaries connecting them
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The Kidneys
Vein
Artery
Capillaries
To the ureter
Collecting duct
Each nephron releases fluids to a collecting duct, which leads to the ureter.
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The Kidneys
How is blood filtered and removed?
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Excretory Processes
Most excretory systems (4 basic parts)
Produce urine by refining a filtrate derived from body fluids
Figure 44.9
Filtration. The excretory tubule collects a filtrate from the blood.Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.
Reabsorption. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.
Secretion. Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.
Excretion. The filtrate leaves the system and the body.
Capillary
Excretorytubule
Filtrate
Urine
1
2
3
4
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What are the 4 parts?
Say it outloud
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Key functions of most excretory systems are
1. Filtration, pressure-filtering of body fluids producing a filtrate
2. Reabsorption, reclaiming valuable solutes from the filtrate
3. Secretion, addition of toxins and other solutes from the body fluids to the filtrate
4. Excretion, the filtrate leaves the system
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The Kidneys
As blood enters a nephron through the arteriole, impurities are filtered out and emptied into the collecting duct.
The purified blood exits the nephron through the venule.
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The Kidneys
The mechanism of blood purification involves two distinct processes: filtration and reabsorption.
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The Kidneys
Filtration
Passing a liquid or gas through a filter to remove wastes is called filtration.
The filtration of blood mainly takes place in the glomerulus.
The glomerulus is a small network of capillaries encased in the top of the nephron by a hollow, cup-shaped structure called Bowman's capsule.
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The Kidneys
Fluid from the blood flows into Bowman’s capsule.
The materials filtered from the blood include water, urea, glucose, salts, amino acids, and some vitamins.
Plasma proteins, cells, and platelets remain in the blood because they are too large to pass through the capillary walls.
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The Kidneys
Reabsorption
Most of the material removed from the blood at Bowman's capsule makes its way back into the blood.
The process in which liquid is taken back into a vessel is called reabsorption.
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The Kidneys
Almost 99% of the water that enters Bowman’s capsule is reabsorbed into the blood.
When the filtrate drains in the collecting ducts, most water and nutrients have been reabsorbed into the blood.
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The Kidneys
Remaining material, called urine, is emptied into a collecting duct.
Urine is primarily concentrated in the loop of Henle.
The loop of Henle is a section of the nephron tubule in which water is conserved and the volume of urine minimized.
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The Kidneys
As the kidney works, purified blood is returned to circulation while urine is collected in the urinary bladder.
Urine is stored here until it is released from the body through a tube called the urethra.
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Control of Kidney Function
Control of Kidney Function “Homeostasis”
The activity of the kidneys is mostly controlled by the composition of the blood.
In addition, regulatory hormones are released in response to the composition of blood. This is controlled by a hormone ADH from the Pituitary Gland.
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Pituitary Gland feedback system
Pituitary Gland
What is the function of the pituitary gland?
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Pituitary Gland – master control
The pituitary gland secretes nine hormones that directly regulate many body functions and controls the actions of several other endocrine glands.
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Pituitary Gland
The pituitary gland is a structure at the base of the skull.
The gland is divided into two parts: the anterior pituitary and the posterior pituitary.
Remember anterior – front side or ventral
posterior- toward the rear / dorsal side
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Pituitary Gland
The Pituitary Gland
Hypothalamus
Pituitary gland
Posterior pituitary
Anterior pituitary
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Pituitary Gland
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Control of Kidney Function
When you drink a liquid, it is absorbed into the blood through the digestive system.
As a result, the concentration of water in the blood increases.
As the amount of water in the blood increases, the rate of water reabsorption in the kidneys decreases.
Less water is returned to the blood, and excess water is sent to the urinary bladder to be excreted as urine.
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Control of Kidney Function
When the kidneys detect an increase in salt, they respond by returning less salt to the blood by reabsorption.
The excess salt the kidneys retain is excreted in urine, thus maintaining the composition of the blood.
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Antidiuretic hormone (ADH)
Increases water reabsorption in the distal tubules and collecting ducts of the kidney
Figure 44.16a
Osmoreceptorsin hypothalamus
Drinking reducesblood osmolarity
to set point
H2O reab-sorption helpsprevent further
osmolarity increase
STIMULUS:The release of ADH istriggered when osmo-receptor cells in the
hypothalamus detect anincrease in the osmolarity
of the blood
Homeostasis:Blood osmolarity
Hypothalamus
ADH
Pituitarygland
Increasedpermeability
Thirst
Collecting duct
Distaltubule
(a) Antidiuretic hormone (ADH) enhances fluid retention by makingthe kidneys reclaim more water.
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Kidney Disorders
Kidney Disorders
Humans have two kidneys, but can survive with only one.
If both kidneys are damaged by disease or injury, there are two options:
• a kidney transplant
• kidney dialysis
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Kidney Disorders
Kidney dialysis works as follows:
• Blood is removed by a tube and pumped through special tubing that acts like nephrons.
• Tiny pores in the tubing allow salts and small molecules to pass through.
• Wastes diffuse out of the blood into the fluid-filled chamber, allowing purified blood to be returned to the body.
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Kidney Disorders
Kidney Dialysis
Air detector
Dialysis machine
Fresh dialysis fluid
Compressed air
Vein
Artery
Shunt
Blood pump
Blood in tubing flows through dialysis fluid
Used dialysis fluid
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A dialysis machine performs the function of which structure in the excretory system?
a. nephron
b. ureter
c. urethra
d. glomerulus
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In the human body, the kidneys play an important role in
a. producing digestive enzymes.
b. circulating the blood.
c. destroying old red blood cells.
d. maintaining homeostasis.
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In the nephron, most filtration occurs in the
a. renal tubule.
b. capillaries.
c. glomerulus.
d. loop of Henle.
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Urine leaves the body through the
a. loop of Henle.
b. glomerulus.
c. urethra.
d. bladder.
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Materials filtered out of the blood include all of the following EXCEPT:
a. water.
b. urea.
c. amino acids.
d. plasma proteins.
END OF SECTION
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