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Biology > Excretion > Flashcards

Excretion Flashcards

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1
Q

Define metabolism

A

The sum of all chemical reactions in the body

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2
Q

Define excretion

A

Excretion is the removal of toxic materials and waste products of metabolism from organisms

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3
Q

Define egestion

A

Egestion is the elimination of undigested materials from the alimentary canal

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4
Q

What is a catabolic reaction

A

A catabolic reaction is a reaction that breaks up complex molecules into simpler molecules

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5
Q

What is an anabolic reaction

A

An anabolic reaction is a reaction that builds up simpler molecules into complex molecules

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6
Q

Why must metabolic waste products be removed from the body

A

Can be harmful and prevent homeostasis of body if accumulated

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7
Q

What are some examples of excretory products

A
  • CO2
  • Excess water
  • Excess minerals and salts
  • Bile pigments
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8
Q

What is the kidney

A
  • Contains numerous nephrons
  • Responsible for osmoregulation
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9
Q

What is the ureter

A

Tube connecting kidney to bladder

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10
Q

What is the bladder

A

Muscular bag that stores urine

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11
Q

What does a nephron consist of

A
  • Glomerulus
  • Bowman’s capsule
  • Proximal convoluted tubule
  • Loop of Henle
  • Distal convoluted tubule
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12
Q

What is the urethra

A

Muscular tube for urine to flow from bladder to exterior

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13
Q

Define ultrafiltration

A

Ultrafiltration is a non-selective filtering process which occurs at the glomerulus

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13
Q

What are the processes involved in urine formation

A
  • Ultrafiltration
  • Selective reabsorption
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14
Q

Describe the process of ultrafiltration

A
  • Renal artery splits into numerous arterioles, and each arteriole splits into a glomerulus
  • Lumen of afferent arteriole bringing blood towards glomerulus is larger than that of efferent arteriole bringing blood away from glomerulus
  • Blood enters glomerulus more readily than it leaves, causing blood to build up and result in high blood pressure
  • This provides the main force required for ultrafiltration
  • Pressure forces blood plasma out of glomerular capillaries and into the Bowman’s capsule
  • Blood plasma forced out contains water and small molecules, forming filtrate in Bowman’s capsule
  • Blood cells, platelets, blood proteins and fats remain in the blood and leaves glomerulus via efferent arteriole
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14
Q

What is the glomerulus

A

A network of blood capillaries

15
Q

What is the average composition of urine

A
  • 96% water
  • 2% urea
  • 1.8% salts
  • 0.2% nitrogenous substances
15
Q

Define selective reabsorption

A

Selective reabsorption is the transport of useful substances from the filtrate back into the bloodstream

16
Q

Describe the process of selective reabsorption

A
  • Selective reabsorption is usually completed at the proximal convoluted tubule
  • All glucose, amino acids and vitamins are reabsorbed
  • 85% of sodium ions, chloride ions and water are reabsorbed at the proximal convoluted tubule
  • Some water and ions are reabsorbed at the loop of Henle
  • Water and smaller concentrations of ion are reabsorbed at the distal convoluted tubule
  • Remaining water required is reabsorbed at collecting duct
16
Q

How are useful solutes reabsorbed back into blood during selective reabsorption

A
  • Facilitated diffusion
  • Active transport
17
Q

How can urine composition vary

A
  • Protein-rich diet > more urea
  • Water-rich diet > more urine
  • Salty food > more salts
  • Cold temperature > more urine
  • Diabetes > glucose present
18
Q

Why is there glucose present in urine of a diabetic

A
  • Diabetic patient unable to store excess glucose as glycogen in body
  • Blood has high glucose concentration
  • Glucose is all filtered at glomerulus
  • Nephrons are unable to reabsorb glucose fast enough
  • Glucose passes out in urine
19
Q

Define osmoregulation

A

Osmoregulation is the maintenance of a constant water potential in the body

20
Q

What controls volume of water in blood

A

Anti-diuretic hormone (ADH)

21
Q

What is ADH

A
  • Produced by hypothalamus
  • Released by pituitary gland
  • Target organ in kidney
22
Q

What happens when water potential of blood increases beyond the norm

A
  • Osmoreceptors in hypothalamus detect increase in blood water potential
  • Osmoreceptors send nerve impulses to hypothalamus
  • Hypothalamus sends nerve impulses to pituitary gland
  • Pituitary gland releases less ADH into bloodstream
  • Walls of distal convoluted tubule and collecting duct become less permeable to water so less water is reabsorbed back into blood
  • Negative feedback sent to hypothalamus via osmoreceptors once water potential of blood decreases back to the norm
23
Q

What happens when water potential of blood decreases below the norm

A
  • Osmoreceptors in hypothalamus detect the decrease in blood water potential
  • Osmoreceptors send nerve impulses to hypothalamus
  • Hypothalamus sends nerve impulses to pituitary gland
  • Pituitary gland releases more ADH into the bloodstream
  • Walls of distal convoluted tubule and collecting duct become more permeable to water
  • More water is reabsorbed back into the blood
  • Negative feedback sent to hypothalamus via osmoreceptors once water potential of blood increases back to the norm
24
Q

What are the features of a dialyser

A
  • Narrow tubing speeds up rate of diffusion between blood and dialysis fluid
  • Direction of dialysis fluid flow is opposite to direction of blood flow, maintaining concentration for removal of waste products
25
Q

Where is blood drawn from for haemodialysis

A

Fistula in patient’s arm

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