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Biology 🦠 > Chapter 8: Excretion in Humans > Flashcards

Chapter 8: Excretion in Humans Flashcards

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1
Q

Metabolic waste products

A
  1. Carbon dioxide
  2. Urea
  3. Mineral salt/ions
  4. water
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2
Q

Carbon dioxide as a metabolic waste product

A
  • product or aerobic respiration
  • carbon dioxide levels in out blood is usually not harmful
  • in certain cases, when there is an abnormally high level of carbon dioxide in blood, a condition, hypercaruin occurs
  • they may suffer from headaches, confusion, rapid breathing and premature heartbeats
  • excreted via lungs as gas in expired air
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3
Q

Urea as metabolic waste product

A
  • produces when excess amino acids is deaminated in liver
  • concentration of urea in blood is not usually harmful
  • however, abnormally high levels of urea in blood may cause abdominal pain, nausea or vomiting
  • can even cause irregular heartbeat and muscle cramps in rare cases
  • excreted via kidneys and skin as urine and sweat
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4
Q

Mineral salt & ions as metabolic waste products

A
  • excess salt/ion in blood can be harmful
  • they lower water potential in blood plasma
  • water may pass out of tissue cells into blood by osmosis and cells become dehydrated and may even die
  • excreted via kidneys and skin as urine and sweat
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5
Q

Water as metabolic waste substance

A
  • excess water increases water potential in the blood plasma
  • by osmosis, water will enter the tissue cells
  • cell may swell and burst
  • excreted via kidneys and skin as urine and sweat
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6
Q

Excretion

A
  • the removal of metabolic waste products, toxic substances and substances in excess of the body’s requirements
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7
Q

Human urinary system

A
  1. kidney
  2. ureter
  3. urinary bladder
  4. urethra
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8
Q

Kidneys

A
  • bean-shaped organs that are embedded in a mass of fat in the abdominal cavity
  • average size of a human kidney is 10 to 13 cm long and about 5 to 7 cm wide
  • lies just above the waistline
  • left kidney is slightly higher than the right kidney
  • main function is to excrete urea and excess salt and water as urine
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9
Q

Ureter

A
  • narrow tube that connects the kidney to the urinary bladder
  • urine from each kidney passes through the ureter to the urinary bladder
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10
Q

Urinary bladder

A
  • elastic muscular bag located at the front of the rectum
  • stores urine
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11
Q

Urethra

A
  • duct through which the urine passes from the bladder to outside the body
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12
Q

Nephron

A
  • a lot of them in the kidney
  • basic functional unit of the kidney
  • tiny kidney tubules where urine is formed
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13
Q

Structure of a nephron

A
  1. Afferent arteriole
  2. Glomerulus
  3. Efferent arteriole
  4. Bowman’s capsule
  5. proximal convoluted tube
  6. Loop of henlé
  7. distal convoluted tube
  8. collecting duct
  9. blood capillaries
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14
Q

Afferent arteriole

A
  • a small branch of the renal artery that carries blood into glomerulus
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15
Q

Glomerulus

A
  • a knot of blood capillaries in the Bowman’s capsule
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16
Q

Efferent arteriole

A
  • transports blood away from the glomerulus
17
Q

Blood capillaries

A
  • blood continues into the blood capillaries surrounding the nephrone
  • they eventually lead into a branch of the renal vein
18
Q

Ultrafiltration

A
  • first stage of urine formation
  • afferent arteriole being wider than the efferent arteriole creates a high blood pressure in glomerulus
  • blood plasma is forced out of glomerular blood capillaries into Bowman’s capsule
  • filtered blood plasma is the glomerular filtrate
  • contains small soluble substances, not large one
19
Q

How is the glomerulus suited for ultrafiltration

A
  • it is a knot/network of blood capillaries, providing large surface area for filtration
  • blood capillaries have 1 cell thick walls. there are tiny pores in the capillary wallys
  • blood capillaries are covered by a thin partially permeable membrane 👉 it only allows when small, soluble substances to pass through. it is impermeable to blood cells, platelets and large molecules
20
Q

selective reabsorption

A
  • as glomerular filtrate passes along nephron, useful substances are reabsorbed into surrounding blood capillaries
  • most of water is reabsorbed by osmosis
  • some salts are reabsorbed by active transport
  • all glucose and amino acids are reabsorbed by active transport
  • waste products such as urea and excess water and mineral salts are passed out of the nephron as urine
21
Q

Selective reabsorption at proximal convoluted tubule

A
  • most of the water is reabsorbed by osmosis
  • all of the glucose and amino acids are reabsorbed by active transport
  • most mineral salts are re absorbed by diffusion and active transport
22
Q

Selective reabsorption at Loop of Henlé

A
  • some water is reabsorbed by osmosis
  • some mineral salts are reabsorbed by active transport
23
Q

Selective reabsorption at distal convoluted tubule

A
  • some water is reabsorbed by osmosis
  • some mineral salts are reabsorbed by active transport
24
Q

Selective reabsorption at collecting duct

A
  • reabsorbs some water by osmosis
25
Q

Osmoregulation

A
  • the control of water potential and solute concentration level in the blood to maintain a constant water potential in body
  • controlled by antidiuretic hormone (ADH) which is produced by a region of the brain called the hypothalamus. It is released by the pituitary gland and increases water reabsorption at nephrons
26
Q

What happens when water potential in blood decreases

A
  • hypothalamus in brain is stimulated
  • pituitary gland releases more ADH into bloodstream
  • cells in walls of collecting duct becomes more permeable to water & more water is reabsorbed from collecting duct into blood capillaries
  • smaller volume of urine is produced and it is more concentrated
  • water potential of blood returns to normal
27
Q

What happens when water potential in blood increases

A
  • hypothalamus in brain is stimulated
  • pituitary gland releases less ADH into bloodstream
  • cells in walls of collecting duct becomes less permeable to water
  • less water reabsorbed from collecting duct into the blood capillaries
  • larger volume of urine produced and it is more diluted
  • water potential returns to normal
28
Q

Why are kidneys important

A
  1. They are excretory organs, so they play important role in excreting metabolic waste products in the form of urine
  2. Kidneys are osmoregulators and they regulate the solute concentration and water potential in the blood, maintaining a constant water potential in blood
    - one can live with 1 healthy kidney, but they will die if both fails
29
Q

What causes kidneys to fail

A
  • high blood pressure
  • diabetes
  • alcohol abuse
  • severe accidents that physically damage the kidneys
  • complications from undergoing major surgery
  • the only way to survive kidney failure is kidney transplant and dialysis with dialysis machine
30
Q

How does dialysis machine work

A
  1. blood is drawn from vein in patient’s arm and is pumped through the tubing in the dialysis machine
  2. tubing is bathed in a special controlled dialysis fluid. walls of the dialysis tubing are partially permeable
  3. small molecules such as urea and other metabolic waste products diffuse out of the tubing into the dialysis fluid. Blood cells, platelets and large molecules remain in tubing
  4. Filtered blood is then returned to vein in patient’s arm
31
Q

Features of dialysis machine

A
  1. Dialysis fluid contains same concentration of essential substances as healthy blood
  2. Dialysis fluid does not contain metabolic waste products
  3. Tubing in machine is narrow, long and coiled
  4. Direction of blood flow is opposite to flow of dialysis fluid
32
Q

Why does the dialysis fluid contain same concentration of essential substances as healthy blood?

A
  • ensures that essential substances do not diffuse out of the blood and into the dialysis fluid
  • if patient’s blood lacks these essential substances, these substances will diffuse from dialysis fluid into blood
33
Q

Why does dialysis fluid not contain metabolic waste products

A
  • this sets up a concentration gradient, allowing waste products to diffuse out of the tubing into the dialysis fluid
  • wast products are removed from blood
  • maintains the correct solute composition & water potential of the blood
34
Q

Why is the tubing in the dialysis machine narrow, long and coiled

A
  • increases the surface area-to-volume ratio which helps to speed up rate of exchange of substances between the patient’s blood and the dialysis fluid
35
Q

Why is the direction of blood flow opposite to flow of dialysis fluid

A
  • this maintains the concentration gradient for removal of waste products

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