Chapter 10.1 Flashcards
What does the excretory system consist of
-it consists of kidneys, ureters, bladder and urethra
What is the difference between the cortex and the medulla of the kidneys
Cortex
->kidney’s outermost layer
Medulla
->it sits within the cortex
Where do the renal artery, renal vein and ureter enter/exit from
-they enter/exit from the renal hilum
Describe the movement of blood through the kidneys
- renal artery branches out
- > passes through the medulla
- > enter the cortex as afferent arterioles
- > then the afferent arteriole enters capillaries known as the glomeruli
- after blood passes through glomerulus
- > then it goes to the efferent arterioles
What is the vasa recta
-they are capillaries that surround the loop of Henle
What is the glomerulus surrounded by
-it is surrounded by the Bowman’s capsule
What is the muscle lining the bladder referred to as? What kind of autonomic signalling causes it to contract
- it is referred to as the detrusor muscle
- >parasympathetic activity causes the detrusor muscle to contract
What are the two sphincters that regulate the urination of an individual
Internal urethral sphincter
- > consists of smooth muscle
- > contracted in normal state
- > it is under involuntary control
External urethral sphincter
- > consists of skeletal muscle
- > under voluntary control
What is the micturition reflex function
- this is when the detrusor muscles contract
- > internal sphincter then relaxes and allows an individual to urinate if they choose to relax the external sphincter
- urination itself is caused by the contraction of the abdominal musculature
- > which increases pressure within the abdominal cavity
- > resulting in compression of the bladder and increased urine flow rate
Describe filtration in terms of movement of fluid between the glomerulus and the Bowman’s capsule
- blood that passes through the glomerulus is filtered as fluid into the Bowman’s space
- > collected fluid is known as filtrate
What regulates movement of fluid into the Bowman’s capsule
-it is regulated by Starling forces
Describe the Starling forces in the Bowman’s capsule in comparison to the glomerulus
Glomerulus
- > hydrostatic pressure here is significantly higher than the Bowman’s capsule
- > which causes fluid to move into the nephron
Bowman’s
- > the osmolarity of blood is higher than that of the Bowman’s space
- > resulting in pressure oppposing the movement of fluid into the nephron
- note however, that hydrostatic pressure of the glomerulus is much larger than the oncotic pressure of the blood
- > so blood still flows into the nephron
Compare the filtrate that moves from the Bowman’s to glomerulus to that of blood
- filtrate is similar in composition to blood
- > but does not contain cells or proteins due to the filter’s ability to select based on size
-note that the filtrate is isotonic to the blood
How does the body get rid of ammonia
- the liver converts ammonia to urea
- > urea is a neutral compound
- > it travels to the kidney and is secreted into the nephron for excretion with the urine
Describe what happens in the proximal convoluted tubule
- amino acids, glucose, vitamins and majority of salts are reabsorbed along with water
- > almost 70% of filtered sodium will be reabsorbed here
-note waste like hydrogen ions, potassium ions, ammonia and urea also enter the PCT(HUNK)
Describe what happens in the descending loop of Henle
- this section dives deep into the medulla
- the descending limb is permeable only to water
- > therefore, the medulla has an ever increasing osmolarity as it travels deeper into the medulla
- note that as the descending limb goes deeper into the medulla
- > there is an increasing interstitial concentration
- > which favours the outflow of water from the descending limb
How does the countercurrent multiplier system work? What is its function
- it is created by the vasa recta and nephron
- the flow filtrate in the loop of Henle is in the opposite direction from the flow of blood through the vasa recta
- > if the two flowed in the same direction, equilibrium would be reached quickly
- by having the two flow in opposite directions, the filtrate is exposed to hypotonic blood(great amount of solutes)
- > so water flows out
Describe what happens in the ascending loop of Henle
- only salts here can leave the nephron
- > while water cannot leave(non-permeable to water)
-the filtrate becomes hypotonic compared to the interstitium
What are the characteristics of the diluting segment of the loop of Henle
- here the loop of Henle becomes thicker
- > the cells lining the tube become larger
- > these cells contain large amount of mitochondria
- > allowing for the reabsorption of sodium and chloride by active transport
What is the general characteristic of the distal convoluted tubule? What hormone does it respond to?
- site of waste production
- DCT also responds to aldosterone
- > aldosterone promotes the reabsorption of sodium
- > making water follow in the path of the sodium
What are the general characteristics of the collecting duct? What hormone does it respond to?
- it is the part of the nephron that can change its permeability
- > as permeability increases, its water reabsorption increases well
- > resulting in further concentration of the urine
- note both ADH and aldosterone interact with the collecting duct
- > allows for greater water retention and more concentrated urine output
How is aldosterone released? Describe the initial mechanisms behind this process.
- aldosterone is a hormone that responds to decreased blood pressure
- decreased blood pressure stimulates release of renin from the juxtaglomerular cells
- > renin then cleaves angiotensionogen
- > when then forms angiotensin 1
- > angiotensin 1 then is converted to angiotensin 2 using the angiotensin-converting enzyme
- > this last step promotes the release of aldosterone from the adrenal cortex
How does ADH impact the pressure in the blood
- it directly alters the permeability of the collecting duct
- >allows more water to be reabsorbed by making cell junctions of the duct leaky
What can inhibit ADH release?
-caffeine can inhibit ADH release and lead to the frequent excretion of dilute urine
How can the cardiovascular system maintain blood pressure through vasodilation or vasoconstriction
- it can constrict the afferent arterioles
- leading to lower blood pressure reaching the glomeruli
- > this vasoconstriction leads to renin release, which again helps to increase blood pressure
