Biology Ch 10. Homeostasis Flashcards
(83 cards)
Excretory system
Serves many functions including the regulation of blood pressure, blood osmolarity, acid base balance, and removal of nitrogenous wastes, consists of the kidneys, ureters, bladder, and urethra
Kidney
Two bean shaped structures located behind the digestive organs, produced urine, contains a cortex and a medulla, each has a hilium and portal system, participates in solute movement through filtration, secretion, and reabsorption, under hormonal control, can regulate pH by increasing or decreasing secretion of hydrogen ions and bicarbonate , functional unit is the nephron
Urine path
Kidney, ureter, bladder, urethra
Ureter
Transports urine from the kidney to the bladder to be stored, at the renal pelvis
Renal pelvis
Where all nephrons empty into that narrows into the ureter (ie the widest part of the ureter)
Bladder
Stores urine, has detrusor muscle and two sphincters
Urethra
Where urine is excreted
Hilium
Part of a kidney, deep slit in the center of the kidney’s medial surface, contains renal artery, renal vein, and ureter
Kidney portal system
Two capillary beds in series, the renal artery branches into afferent arterioles which then form glomeruli, after the glomeruli, blood passes to efferent arterioles
Bowmans capsule
Cuplike structurearound the glomerulus, in the first capillary bed blood from the renal artery in the medulla flows into afferent arterioles in the cortex which form glomeruli, leads to long tubule of the PCT, loop of henle, DCT and collecting duct
Vasa recta
Second capillary bed in the kidney, blood from efferent arterioles, surrounds the nephron, leave kidney in renal vein, surround the loop of henle
Detrusor muscle
Muscular lining in bladder, under parasympathetic control
Internal urethral sphincter
Consists of smooth muscle and is under involuntary/parasympathetic control
External urethral sphincter
Consists of skeletal muscle and is under voluntary control
Kidney filtration
The movement of solutes from blood to filtrate at Bowmans capsule, the direction and rate of filtration is determined by starling forces, hydrostatic pressure higher in the glomerulus so fluid moves into nephron, osmolarity higher in the glomerulus which opposes the movement of fluid into the nephron, net flow still from blood into nephron but rate will vary
Starling forces kidneys
Account for the hydrostatic and oncotic pressure differentials between the blood and Bowmans space
Kidney secretion
The movement of solutes from blood to filtrate anywhere other than Bowmans capsule by either active or passive transport, quantity and identify of substances secreted directly related to the needs of the body at that time, also a mechanism for excreting wastes that are simply too large to pass through glomerular pores
Kidney reabsorption
Movement of solutes from filtrate to blood, typically glucose, amino acids, and vitamins always reabsorbed, amount of water reabsorbed depends on ADH or aldosterone levels
Nephron segments
Proximal convoluted tubule, descending limb of the loop of Henle, ascending limb of the loop of Henle, distal convoluted tubule, collecting duct
Proximal convoluted tubule
PCT - The site of book reabsorption of glucose, amino acids, soluble vitamins, salt, and water (picked up by vasa recta and returned to blood stream), it is also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea, filtrate remains isotonic, in the kidney cortex
Descending limb of the loop of Henle
Permeable to water but not salt, therefore as filtrate moves into the more osmotically concentrated renal medulla, water is reabsorbed from the filtrate. the vasa recta and nephron flow in opposite directions creating a countercurrent multiplier system that allows maximal reabsorption of water, dives from cortex to inner medulla
Countercurrent multiplier system
System that allows the maximal reabsorption of water such as how the vasa recta and nephron flow in opposite directions, flow of the filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta, therefore, filtrate constantly exposed to hypertonic blood
Ascending limb of the loop of Henle
Permeable to salt but not water, therefore salt is reabsorbed both passively and actively, the diluting segment is in the outer medulla; because salt is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to the blood
Diluting segment
Transition from inner to outer medulla where the loop of Henle gets thicker, cells in the lining are larger because they contain large amounts of mitochondria, allows for maximum reabsorption of sodium and chloride by active transport, filtrate becomes hypotonic, only part of nephron capable of producing urine more dilute than the blood (important for overhydration)
