Chapter 11.3 Flashcards
What is excretion?
The removal from the body of the waste products of metabolic activity
What are the functions of the excretory system?
The removal of nitrogenous wastes which may be toxic in large concentrations, as well as the removal of excess water to maintain osmolarity in cells and tissues
How are nitrogenous wastes produced?
From the breakdown of nitrogen-containing compounds like amino acids and nucleotides
What does the type of nitrogenous base depend on in animals?
Based on evolutionary history of animal and habitat
How do aquatic animals eliminate their nitrogenous waste?
As ammonia
Why is ammonia preferably excreted in aquatic animals?
Due to its high water solubility, therefore can be easily flushed into the aquatic habitat
How do terrestrial animals eliminate their nitrogenous waste?
As urea which is less toxic so can be stored at high concentrations
How do reptiles and birds eliminate wastes?
As uric acid which is non toxic but requires more energy to make
How is water produced and consumed?
It is produced via condensation reactions and consumed via hydrolysis reactions
What is tissue viability dependent on?
Osmolarity of tissue
What are osmoconformers?
Maintain internal conditions that are equal to the osmolarity of their environment
What are osmoregulators?
Keep their body’s osmolarity constant, regardless of environmental conditions
Why is less energy required to maintain internal osmolarity in osmoconformers?
Due to the fact that the environment and cell share same conditions, then water movement will be minimized in and out of cell
Why is more energy required to maintain internal osmolarity in osmoregulators?
It ensures internal osmotic conditions are always tightly controlled
What is special about the excretory and digestive systems of insects?
They are connected to each other
What is the name of the circulating fluid system in insects?
The hemolymph
From where and how do the Malpighian tubules uptake nitrogenous wastes and water?
Malpighian Tubules branch off the intestinal tract of insect to absorb materials from hemolymph
What will the Malpighian tubules do when they have absorbed materials?
They will pass them to the gut where they will mix with digested food
What is reabsorbed by the hemolymph and what is excreted via anus?
Solutes, water and salts are reabsorbed while nitrogenous wastes as well as undigested food will be excreted
What are the different functions of the kidney?
-Water balancing system
-Blood filtration system
-Removes nitrogenous wastes
How does blood enter and exit the kidney?
Enters via the renal artery and exits via renal vein
What structures are responsible for the filtration of blood?
Nephrons and they produce urine
How is the urine transported and to where?
Transported via the ureter and will be stored in baldder
How will the blood differ from the renal artery to the renal vein?
In the renal vein, the blood will have less urea, solutes, water, glucose, oxygen and more carbon dioxide
What makes up the nephron?
-Bowman’s capsule: first part of the nephron where blood is initially filtered (to form filtrate)
-Proximal convoluted tubule: folded structure connected to the Bowman’s capsule where selective reabsorption occurs
-Loop of Henle: a selectively permeable loop that descends into the medulla and establishes a salt gradient
-Distal convoluted tubule: a folded structure connected to the loop of Henle where further selective reabsorption occurs
How is blood entered and exited in Bowman’s capsule?
Enters via the afferent arteriole and exits via efferent arteriole
Where inside the Bowman’s capsule is the blood filtered?
At the glomerulus
What does the efferent arteriole form?
A blood network which will aid in the selective reabsorption of filtrate components by nephron
What is the collecting duct?
It feeds into the renal pelvis
What is the function of nephron?
Filter blood and then reabsorb useful materials from the filtrate
What does the process of filtration involve?
-Ultrafiltration: Blood is filtered out of glomerulus at Bowman’s capsule to form filtrate
-Selective reabsorption: Usable materials are reabsorbed in convoluted tubules
-Osmoregulation: The loop of Henle establishes a salt gradient, which draws water out of the collecting duct
What is the structure of Bowman’s capsule?
Blood enters the kidney via the afferent arteriole into the glomerulus which is encapsulated by cells known as podocytes that wrap around the blood vessel of the glomerulus using their cellular extensions.
Where is the basement membrane found and what is its job?
It is found between the podocytes and the blood vessel and is responsible for filtration
What features allow the blood to be easily filtered?
The fact that the blood vessels are fenestrated so blood will move easily out of vessel, and podocytes have space in between the pedicles allowing fluid to move freely in nephron, In addition, the basement membrane is size selective and restricts the flow of blood and large proteins
Why is high hydrostatic pressure created within glomerulus?
Due to the fact that blood enters glomerulus via a wide afferent arteriole and exit via a narrow efferent arteriole
What increases the surface area available for filtration?
The narrow extensive branches within glomerulus
What does selective reabsorption involve?
It involves the reabsorption of useful materials from filtrate and occurs mostly in proximal convoluted tubule
How does the structure of the convoluted tubule aid in its function?
-The proximal convoluted tubule has a microvilli cell lining to increase the surface area for material absorption from the filtrate.
-The tubule is a single cell thick and connected by tight junctions, which function to create a thin tubular surface with no gaps
-There are also a large number of mitochondria within these tubule cells, as reabsorption involves active transport. Substances are actively transported across the apical membrane. Substances then passively diffuse across the basolateral membrane
What and how does the tubule reabsorb materials?
-Mineral ions and vitamins are actively transported by protein pumps and carrier proteins respectively
-Glucose and amino acids are co-transported across the apical membrane with sodium (symport)
-Water follows the movement of the mineral ions passively via osmosis
What is osmoregulation?
The control of the water balance of the blood, tissue or cytoplasm of a living organism
Where does osmoregulation occur?
In the Loop of Henle
What events occur in osmoregulation?
-The loop of Henle establishes a salt gradient (hypertonicity) in the medulla
-Anti-diuretic hormone (ADH) regulates the level of water reabsorption in the collecting duct
How does the Loop of Henle establish a salt gradient?
The descending limb of the loop of Henle is permeable to water but not salts. The ascending limb of the loop of Henle is permeable to salts but not water. This means that as the loop descends into the medulla, the interstitial fluid becomes more salty and hypertonic. Additionally, the vasa recta blood network that surrounds the loop of Henle flows in the opposite direction. This means that salts released from the ascending limb are drawn down into the medulla, further establishing a salt gradient
How is water reabsorption controlled?
As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis. The amount of water released from the collecting ducts to be retained by the body is controlled by anti-diuretic hormone (ADH). ADH is released from the posterior pituitary in response to dehydration. ADH increases the permeability of the collecting duct to water, by upregulating production of aquaporins. This means less water remains in the filtrate, urine becomes concentrated and the individual urinates less. When an individual is suitably hydrated, ADH levels decrease and less water is reabsorbed
What is dehydration?
Is a loss of water from the body such that body fluids become hypertonic
What are the consequences of dehydration?
-Individuals will experience thirst and excrete small quantities of heavily concentrated urine
-Blood pressure will drop (less water in plasma) and the heart rate will increase to compensate for this
-The individual will become lethargic and experience an inability to lower body temperature
-Severe cases of dehydration may cause seizures, brain damage and eventual death
What is overhydration?
Over-consumption of water makes body fluids hypotonic
What are the consequences of overhydration?
-Individuals will produce excessive quantities of clear urine in an effort to remove water from the body
-The hypotonic body fluids will cause cells to swell, which can lead to cell lysis and tissue damage
-Overhydration can lead to headaches and disrupted nerve functions in mild cases
-Overhydration may lead to blurred vision, delirium, seizures, coma and eventual death
What is the length of the Loop of Henle correlated with?
Positively correlated with the need for water conservation in animals
What are kidney diseases based off?
Kidney’s ability to filter waste products from the blood
What do individuals with kidney disease face?
Individuals with kidney diseases will demonstrate a reduced glomerular filtration rate (GFR)
What does the presence of glucose in urine mean?
Diabetes
What does the presence of proteins in urine mean?
Disease such as PKU or hormonal conditions such as hCG
What does the presence of blood in urine mean?
Infection or cancer
What are ways to treat kidney diseases?
Hemodialysis and kidney transplant
What is hemodialysis?
Involves the external filtering of blood in order to remove metabolic wastes in patients with kidney failure
How does hemodialysis work?
Blood is removed and pumped through a dialyzer, contains a porous membrane that is semi-permeable, introduces fresh dialysis fluid and removes wastes to maintain an appropriate concentration gradient
How is kidney transplant undergone?
The transplanted kidney is grafted into the abdomen, with arteries, veins and ureter connected to the recipient’s vessels, Donors must typically be a close genetic match in order to minimize the potential for graft rejection, Donors can survive with one kidney and so may commonly donate the second to relative suffering kidney failure
