Excretory System Flashcards

1
Q

What are the main functions of the excretory systems?

A
  • Maintenance of the right concentrations of inorganic solutes in the internal fluids
  • maintenance of an appropriate plasma volume
  • removal of toxic substances
  • removal of hormones
  • maintenance of osmotic and ionic balance
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2
Q

Which organ systems are involved in excretory function and retention?

A
  • Respiratory systems (gills, lungs)
  • digestive systems (liver, intestine)
  • integument (skin) and glands (sweat gland, salt gland)
  • renal organs (protonephridia, antennal glands, kidneys)
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3
Q

What are the fundamental phases of renal excretory processes?

A
  • Filtration
  • secretion
  • reabsorption
  • osmoconcentration
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4
Q

What are protonephridia and where are they found?

A

Protonephridia are excretory structures found in simple animals like

  • rotifers
  • flatworms
  • larvae of annelids
  • molluscs
  • fish
  • amphibians
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5
Q

What is the function of protonephridia?

A
  • They use ultrafiltration driven by cilia
  • along with secretion and reabsorption, to filter body fluids.
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6
Q

What are metanephridia and where are they found?

A

Metanephridia are excretory structures found in

  • adult molluscs
  • annelids
  • crustaceans
  • vertebrates
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7
Q

What is the function of metanephridia?

A

They perform
- ultrafiltration
- secretion
- reabsorption
- sometimes osmoconcentration

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8
Q

How do metanephridia function in annelids?

A

They consist of tubules communicating with the coelomic cavity

  • secreting KCl and other substances
  • (no ultrafiltration)
  • with reabsorption and secretion processes

occurring as the fluid moves through the tubules.

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9
Q

How do metanephridia function in crustaceans?

A

They consist of an

  • end-sac for ultrafiltration
  • a labyrinth for reabsorption and secretion
  • a bladder for urine accumulation and excretion
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10
Q

How do metanephridia function in molluscs?

A

They are

  • tubular or saccular structures
  • filter blood ultrafiltrate through the pericardial cavity
  • reabsorbing glucose and amino acids
  • discharging the final urine into the mantle cavity
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11
Q

What is the functional unit of the vertebrate kidney?

A

The nephron

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12
Q

What are the components of the nephron?

A

Tubules associated with a vascular component for

  • filtration
  • reabsorption
  • secretion processes
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13
Q

What regulates the glomerular filtration rate (GFR) in the kidneys?

A

The juxtaglomerular apparatus, which

  • detects changes in tubular saline concentration (macula densa, distal tube)
  • releases vasoactive factors (ATP and adenosine) by granular cells
  • to modulate arteriole contraction.
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14
Q

How do tubules reabsorb substances from the tubular lumen to the blood?

A

Through transepithelial transport mechanisms, preventing the passage of molecules between cells due to tight junctions.

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15
Q

How is glucose reabsorbed in the proximal tubule?

A
  1. secondary active transport with Na+ at the luminal membrane
  2. facilitated diffusion through the basolateral membrane

same transport mechanisms for amino acids

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16
Q

What happens when the tubular maximum (Tm) for glucose is exceeded?

A

Excess glucose is not reabsorbed and is excreted in the urine

17
Q

What percentage of Na+ is reabsorbed in different parts of the nephron?

A
  • 67% in the proximal tubule
  • 25% in the loop of Henle
  • 8% in the distal tubule and collecting ducts
18
Q

What is the importance of Na+ reabsorption in the proximal tubule?

A

It is essential for the reabsorption of

  • glucose
  • amino acids
  • water
  • chloride
  • urea

and for regulating the volume of extracellular fluid

19
Q

Which system stimulates Na+ reabsorption in the distal tubule?

A

The renin-angiotensin-aldosterone system (RAAS)

20
Q

How does atrial natriuretic peptide (ANP) affect Na+ reabsorption?

A

ANP antagonizes the RAAS, reducing Na+ reabsorption and promoting Na+ excretion

21
Q

How does vasopressin (ADH) regulate urine osmoconcentration?

A

Vasopressin increases the permeability of the distal and collecting tubules to water by promoting the insertion of aquaporins in the cell membranes

22
Q

What triggers the release of vasopressin?

A

Changes in osmotic pressure detected by hypothalamic osmoreceptors

23
Q

What happens after the release of vasopressin? (steps)

A
24
Q

What does NKCC stand for and what is its function?

A

NKCC stands for

Na+-K+-2Cl- cotransporter

which moves

  • sodium
  • potassium
  • and chloride ions

into tubular cells

25
Q

How does the NKCC transporter contribute to ion balance?

A

It helps create an electrochemical gradient that facilitates the diffusion of chloride and sodium ions.

26
Q

Where is the NKCC transporter especially important?

A
  • In the rectal gland of cartilaginous fish
  • the gills of bony fish for salt regulation
27
Q

How do marine mammals’ kidneys differ from those of other mammals?

A

Marine mammals’ kidneys are made up of numerous reniculi, which are small independent lobes with discrete cortical tissue

  • they are shorter
  • reduced NaCl reabsorption
28
Q

How do cartilaginous fish regulate their plasma concentration?

A
  • maintaining a lower plasma concentration of NaCl than seawater
  • eliminating excess NaCl through the rectal gland
  • their osmolarity is equal to/ slightly higher than external environment due to the presence of osmolytes (urea or TMAO)
29
Q

How do bony fish eliminate excess NaCl?

A

Through chloride cells in the gills using a mechanism similar to the NKCC cotransporter

30
Q

What are the three methods reptiles use to conserve water?

A
  1. they eliminate uric acid
  2. reabsorb water in the cloaca
  3. eliminate high salt concentration liquid through the salt gland
31
Q

How do seabirds manage to drink seawater?

A

They possess a salt gland that removes NaCl from the blood without losing water, becoming active when the bird is dehydrated or overloaded with salt

32
Q

How do body systems work together in response to homeostatic challenges

A

All body systems integrate to maintain homeostasis, responding to physiological changes such as injury from a predator attack