Excretory System Flashcards
What are the main functions of the excretory systems?
- 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
Which organ systems are involved in excretory function and retention?
- Respiratory systems (gills, lungs)
- digestive systems (liver, intestine)
- integument (skin) and glands (sweat gland, salt gland)
- renal organs (protonephridia, antennal glands, kidneys)
What are the fundamental phases of renal excretory processes?
- Filtration
- secretion
- reabsorption
- osmoconcentration
What are protonephridia and where are they found?
Protonephridia are excretory structures found in simple animals like
- rotifers
- flatworms
- larvae of annelids
- molluscs
- fish
- amphibians
What is the function of protonephridia?
- They use ultrafiltration driven by cilia
- along with secretion and reabsorption, to filter body fluids.
What are metanephridia and where are they found?
Metanephridia are excretory structures found in
- adult molluscs
- annelids
- crustaceans
- vertebrates
What is the function of metanephridia?
They perform
- ultrafiltration
- secretion
- reabsorption
- sometimes osmoconcentration
How do metanephridia function in annelids?
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.
How do metanephridia function in crustaceans?
They consist of an
- end-sac for ultrafiltration
- a labyrinth for reabsorption and secretion
- a bladder for urine accumulation and excretion
How do metanephridia function in molluscs?
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
What is the functional unit of the vertebrate kidney?
The nephron
What are the components of the nephron?
Tubules associated with a vascular component for
- filtration
- reabsorption
- secretion processes
What regulates the glomerular filtration rate (GFR) in the kidneys?
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.
How do tubules reabsorb substances from the tubular lumen to the blood?
Through transepithelial transport mechanisms, preventing the passage of molecules between cells due to tight junctions.
How is glucose reabsorbed in the proximal tubule?
- secondary active transport with Na+ at the luminal membrane
- facilitated diffusion through the basolateral membrane
same transport mechanisms for amino acids
Which system stimulates Na+ reabsorption in the distal tubule?
The renin-angiotensin-aldosterone system (RAAS)
How does vasopressin (ADH) regulate urine osmoconcentration?
Vasopressin increases the permeability of the distal and collecting tubules to water by promoting the insertion of aquaporins in the cell membranes
What happens after the release of vasopressin? (steps)
How does the NKCC transporter contribute to ion balance?
It helps create an electrochemical gradient that facilitates the diffusion of chloride and sodium ions.
How do body systems work together in response to homeostatic challenges
All body systems integrate to maintain homeostasis, responding to physiological changes such as injury from a predator attack
