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DAT Bio > The Excretory System > Flashcards

The Excretory System Flashcards

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1
Q

What is the path of the excretory system?

A

The path of the excretory system is:

  • Kidneys
  • Ureter
  • Bladder
  • Urethra

Sphincter muscles control micturation

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2
Q

Where does the kidney receive blood and where does it discharge it?

A

The kidney receives blood at the Renal Artery.

The kidney discharges blood through the Renal Vein

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3
Q

What are the two regions of the kidney?

A

The kidney is composed of the:

  • Cortex: Outer Kidney
  • Medulla: Inner Kidney
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4
Q

What are the urinary system’s functions?

A

The urinary system:

  • removes toxic by-products of metabolism from the bloodstream
  • reabsorbs essential salts, glucose, proteins, ions, and water from glomerular filtrate
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5
Q

What is glomerular filtrate?

A

Glomerular filtrate is the substance pulled from the blood from the kidneys at the renal artery. It contains many things such as:

  • Urea
  • Amino Acids
  • Water
  • Salts
  • Glucose
  • Ions
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6
Q

How does glomerular filtrate differ from blood plasma?

A

NB FOR THE DAT:

Glomerular filtrate contains the same substances as blood plasma, except for the larger proteins which the filtrate lacks.

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7
Q

How much urine is produced a day?

A

1.5 L of urine are produced a day

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8
Q

What two hormones are produced by the kidney?

A

The kidney produces two hormones:

  • EPO (erythropoietin)
  • Renin
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9
Q

What is EPO?

A

EPO (Erythropoietin) is a hormone that stimulates red blood cell production

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10
Q

What is Renin?

A

Renin is a hormone that is involved with regulating blood pressure

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11
Q

How much time does it take for all our blood to pass through our kidneys?

A

It takes 5 minutes for all our blood to pass through our kidneys

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12
Q

What is a nephron?

A

A nephron is the functional unit of the kidney

  • Each kidney contains about one million of them
  • Similar to an earthworms nephridia in that they are closely associated with capillaries.
  • Originates in the cortex and extends into the medulla
  • Contains a hollow section called the Bowman’s capsule that gathers the glomerular filtrate from the glomerulus
  • Contains many tubes and ducts
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13
Q

What is the path of filtrate in the kidney?

A

NB for the DAT

The path of filtrate in the kidney is:

  • Glomerulus
  • Bowman’s Capsule
  • Proximal Convoluted Tubule
  • Loop of Henle
  • Distal Convoluted Tubule
  • Collecting Duct
  • Renal Pelvis (innermost hollow kidney chamber)
  • Ureter

Bottom line: Before it becomes urine, we must filter the blood and reabsorb the good stuff (glucose, ions, etc) and excrete waste products like urine.

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14
Q

What are the afferent and efferent arterioles?

A
  • Afferent arterioles bring blood to the glomerulus

- Efferent arterioles provide the path for blood to leave the glomerulus.

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15
Q

What are the four processes of the excretory system?

A

The four processes of the excretory system are:

  • Filtration
  • Reabsorption
  • Secretion
  • Excretion
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16
Q

Describe the glomerulus’s function

A
  • The glomerulus is where the afferent arterioles enter the kidney from the renal artery.
  • The glomerulus has a large surface area due to a great number of capillaries.
  • These capillary walls are more permeable than most capillaries to ions, H20, and small solutes. It is not permeable to the large proteins in blood plasma.
  • In a process known as glomerular filtration, the H20, solutes, and ions pass through the endothelial layer of the capillaries, and through a basement membrane into the Bowman Capsule.
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17
Q

What is the function of the Bowman’s capsule?

A

The Bowman’s capsule collects the glomerular filtrate from the glomerulus. The filtrate includes:

  • Ions
  • Glucose
  • Amino Acids
  • Small solute molecules
  • Nitrogenous wastes like Urea
  • Vitamins
  • Salts
  • H20

Bowman’s capsules contain cells called podocytes that extend like tentacles up to the basement membrane of the glomerulus and help with filtering.

The filtrate moves to the Proximal convoluted tubule from the Bowman’s capsule.

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18
Q

What is the function of the Proximal Convoluted Tubule?

A
  • The proximal convoluted tubule (PCT) receives glomerular filtrate from the Bowman’s Capsule.
  • Most reabsorption takes place here and they are packed with Mitochondria to supply ATP
  • Glucose, drugs, amino acids, other ions, and essential nutrients are transported out of the proximal tubule by active transport to the interstitial fluid and then into the peritubular capillaries.
  • Usually 100% of glucose in the glomerular filtrate is absorbed here, unless glucose levels are extremely high (diabetes mellitus). If they aren’t absorbed they are expelled in the urine.
  • About 65% of water, small plasma proteins, and vitamins are absorbed here
  • We see NH3 buffering with H+ ions to form NH4+. This helps remove some H+ ions. HCO3- is also reabsorbed as well. Both work to help balance pH
  • 75% of Na ions leave the cells through a Na+/K+ ATPase pump. Cl- follows through passive charge diffusion and water follows through osmosis.
  • The PCT descends into the descending loop of Henle
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19
Q

Describe in detail how the pumping of Na+ ions through the ATPase pumps helps drive reabsorption.

A

Along the PCT is a lumen of waving cell membranes that maximize surface area. On the other side of the cells of the PCT are the peritubular capillaries that surround the PCT and is where the PCT places things in the blood.

  • A Na+/K+ ATPase pump takes Na+ out of the cell and puts it into the blood through Active transport. K+ also comes in, but then leaks back out of the cell.
  • The concentration of Na+ leaving the cell pulls Na+ from the lumen of the PCT into the cell.
  • When Na+ enters into the cell it’s usually through proteins that also bind to things like Glucose or Amino Acids. Both the Na+ and the glucose (Amino Acids) are brought into the cell through cotransport
  • Cl - and H20 diffuse passively through the cell following the flow of Na+ ions.
  • Once in the cell they either diffuse passively, actively, or with facilitated diffusion through the basal membrane.
  • Urea is only partly reabsorbed at a much slower rate than H30+
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20
Q

What is the function of the descending loop of Henle?

A

The descending loop of Henle:

  • More H20 is reasbsorbed
  • Aquaporins in this region make the apical membrane very permeable to water
  • Has a low permeability to salts, so as the glomerular filtrate moves through this region, it becomes more and more concentrated with salt.
  • The urine becomes hypertonic with salts
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21
Q

What is the function of the ascending loop of Henle

A

The ascending loop of Henle

  • This region is impermeable to water
  • NaCl moves out to the blood, but the water doesn’t follow.
  • The solution goes from being hypertonic to hypotonic with salts
  • Creates a ion gradient that the descending loop of Henle can use to push water into the interstitial fluid.
22
Q

What is the function of the Distal Convoluted Tubule?

A

The Distal Convoluted Tubule

  • The fluid here is not very salty, it is hypoosmotic to normal body fluids bringing ions into the filtrate.
  • Like the PCT, the DCT helps to regulate pH
  • Involved with Secretion of:
  • K+
  • H+
  • NH4+
23
Q

What is aldosterone and what is its role in kidney function?

A

Aldosterone is a hormone made in the adrenal cortex of the adrenal gland that regulates the Na+/K+ pumps controlling the rate of Na+ reabsorption and K+ secretion. As Aldosterone levels rise, so does pump activity.

24
Q

What is the juxtaglomerular apparatus?

A

The juxtaglomerular apparatus is a special structure formed by the distal convoluted tubule and the afferent arteriole.

  • Along the afferent arteriole close to the glomerulus the tunica media smooth muscle cells become specialized as juxtaglomerular cells. These cells secrete a hormone called renin, as well as retaining their smooth muscle function. They are a type of cell called myoendocrine.
  • If blood pressure drops, the blood volume drops and the juxtaglomerular cells release a hormone called renin into the afferent arteriole.
  • When blood pressure drops there are several ways that juxtaglomerular cells are triggered.
  • pressure sensors on the juxtaglomerular cells will sense the drop in pressure and stimulate the release of renin
  • Parasympathetic nerve endings that terminate right next to juxtaglomerular cells, can trigger them to release renin.
  • DCT cells called Macula Densa sense a low amount of Na+ (indicative of low blood pressure) and send prostaglandin to juxtaglomerular cells to increase renin release.
25
Q

How does Renin help increase blood pressure?

A
  • The Liver produces a long amino acid chain called angiotensinogen. It floats through the blood waiting to be activated.
  • Renin in the blood finds angiotensinogen in the blood and activates it to become angiotensin 1, by cleaving off most of the amino acids leaving 10.
  • Angiotensin 1 floats along in the blood until it reaches capillaries with Angiotensin Converting Enzyme (ACE) these convert Angiotensin 1 into Angiotensin 2 which is an active hormone that works to increase blood pressure/
26
Q

How does Angiotensin II work to increase blood pressure?

A

Angiotensin II works in four ways to increase blood pressure:

  • Stimulates smooth muscle to undergo vasoconstriction
  • Stimulates the kidneys to reabsorb more Na+, H20 follows the Na+ ions increasing blood pressure
  • Stimulates the adrenal glands to release more aldosterone which increases the Na+/K+ ATPase pump to increase its rate of pumping in the DCT, putting more Na+ ions into the blood, and H20 follows it in.
  • Stimulates the pituitary to release ADH (Anti-Diuretic hormone), which opens up channels in the H20 impermeable sections of the nephron to allow water reabsorption
27
Q

What is the collecting duct?

A

The filtrate from the DCT moves into the collecting duct

  • When water levels are low, water can move out of the collecting duct by osmosis, concentrating the solutes left in the filtrate.
  • In the presence of ADH a lot of water is moved out of the collecting duct and reserved for the body to use. The urine becomes hypertonic in the presence of ADH.
  • In the presence of ADH some Urea is also reabsorbed from the collecting duct.
  • The urine flows from the collecting duct into the renal pelvis.
28
Q

What does alcohol do to ADH levels?

A

Alcohol reduces ADH levels, which leads to an increase in urination.

29
Q

What is the renal pelvis?

A

The renal pelvis is the collecting funnel for all the urine flowing through the collecting ducts. The renal pelvis connects to the ureter.

30
Q

What is the ureter?

A

The ureter connects the renal pelvis to the urinary bladder

31
Q

What is the urinary bladder?

A

The urinary bladder is the storage site of urine before micturition occurs. The bladder is connected to the outside world through the urethra.

32
Q

How is the length of the loop of Henle related to water retention?

A

The longer the loop of Henle, the more water can be reabsorbed.
- You see very long loops of Henle in desert animals.

33
Q

What does a diuretic do to decrease water reabsorption?

A

A diuretic increases urination rate by:
- Decreasing permeability of collecting ducts
or
- Decreasing ADH production

Coffee, Tea, and alcohol are all diuretics

34
Q

What is urine composed of?

A

Urine is composed of:

  • 95% water
  • urea
  • uric acid
  • creatinine
35
Q

How is the rate of glomerular filtration influenced by filtration pressure? What are the mechanisms that control filtration pressure?

A

The rate of glomerular filtration is directly proportional to filtration pressure.

The afferent arteriole is under sympathetic nervous system control. If the afferent arteriole becomes constricted:

  • Glomerular hydrostatic pressure decreases
  • Filtration rate decreases
  • Volume of urine flow decreases, thus urine output decreases

If the efferent arteriole is constricted blood cannot flow past the constriction and blood backs up on the glomerulus

  • Glomerular hydrostatic pressure increases
  • Filtration rate increases
  • Urine output increases
  • Potential urine output increases
36
Q

What pH is urine?

A

There is no exact pH of urine. It really has to do with the solute content and water content. It hovers around a little above and below 7.

37
Q

What is Micturition?

A

Micturition is the process by which urine is expelled.

  • As the bladder fills up with urine, stretch receptors are stimulated and the need to urinate occurs.
  • The micturition reflex center is located on the spinal cord.
38
Q

Explain the counter-current mechanism and counter-current multiplier

A

The counter current mechanism is as follows:

  • Blood vessels move in the opposite direction of the loop of Henle.
  • At the ascending portion of the loop of Henle, Na+ and Cl- ions are pumped into the interstitial fluid through active transport. The membrane is impermeable to water here. The ions then move into the blood vessels passively through a concentration gradient.
  • In the presence of ADH water from the collecting ducts will also flow into the interstitial fluid of the medulla and then into the blood because of the same ion gradient formed.
  • The blood that had the ions pumped into it, is now traveling in toward the descending loop of the loop of Henle. Here, ions are impermeable to the membrane and water travels passively through the membrane into the interstitial fluid and then into the blood because of the gradient formed by the increased Na+ and Cl- ions in the blood.
  • The currents of glomerular filtrate and blood go in opposite directions, thus the name counter current.
39
Q

What does PTH do to the kidney?

A

Parathyroid Hormone (PTH) causes the ascending loop of Henle and DCT to release more Ca++ into the blood.

40
Q

What is the main nitrogenous waste of Birds, Reptiles, Insects, and land snails?

A

Birds, Reptiles, and land snails secrete Uric Acid as their nitrogenous waste.

Uric acid is in the form of crystals and is water soluble and less toxic than ammonia or urea.

41
Q

What is the main excretory structure in insects?

A

The main excretory structure in insects is the Malphigian tubule.

42
Q

What is the main nitrogenous waste of Mammals and Mature Amphibians?

A

Mammals and Mature Amphibians secrete Urea as their nitrogenous waste.

43
Q

What do aquatic animals secrete as nitrogenous waste?

A

Aquatic animals secrete Ammonia as their nitrogenous waste.

44
Q

What are the three types of nitrogenous waste?

A

The three types of nitrogenous waste are Urea, Uric Acid, and Ammonia

45
Q

What is a nephridium?

A

Similar to a kidney in vertebrates, nephridium’s are the waste filtration organ of many types of invertebrates, including:

  • annelids
  • Mollusks
46
Q

What is a contractile vacuole?

A

A contractile vacuole is a structure or organelle used for osmoregulation and waste removal.

These are found in:

  • Paramecium
  • Amoeba
  • Some Algea
  • Some Fungi
  • Hydra
47
Q

What is a flame cell?

A

Flame cells function as excretory cells in flatworms (platyhelminthes) and rotifers (microscopic, multicelled aquatic animals). They function essentially like a kidney.

48
Q

How do freshwater and saltwater fish differ in their urine content?

A

Freshwater fish’s skin contains more salt than the freshwater they live in, meaning their bodies continually draw in water from their environment through their skin. This way, they drink very little water and produce a lot of very diluted urine to avoid having excess water in their bodies. Freshwater fish create large amounts of urine that is more dilute than their body fluids

The body tissues of saltwater fish contain less salt than the water in their environment. The saltwater draws water from the fish’s body tissues through its skin in a process called osmoregulation. To prevent dehydration, saltwater fish drink large amounts of saltwater and produce small amounts of very salty urine. They also secrete salt through their gills. In this way they’ve adapted to their super salty surroundings. Saltwater fish create a small amount of urine that is slightly less concentrated than their body fluids

NB for the DAT

49
Q

Why do women get UTIs more than men?

A

Women have a shorter urethra, so bacteria have a shorter path to get in and cause infection.

50
Q

What are the symptoms of a UTI?

A

Symptoms of a UTI could include:

  • painful urination
  • burning sensation when urinating
  • feeling the urge to urinate, but you can’t
  • malaise (general feeling of being unwell)
  • cloudy or dark urine that smells bad
  • blood in urine (hematuria)
51
Q

What is hematuria?

A

Hematuria is blood in the urine. Sometimes it is not visible to the naked eye, and can only be detected by a lab.

DAT Bio (46 decks)

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