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Urinary System
Chapter 20 Hole's Anatomy and Physiology
| Question | Answer | |||
|---|---|---|---|---|
| What does the Urinary System do? | maintains homeostasis by regulating the composition, pH, and volume of body fluids | |||
| How does the Urinary System maintain homeostasis? | regulating the composition, pH, and volume of body fluids by producing urine | |||
| What is included in the Urinary System? | KD, ureters, UB, and urethra | |||
| Where are the KDs? | either side of the vertebral column high on the posterior wall of the abdominal cavity | |||
| What are the KDs located posterior to? | parietal peritoneum | |||
| What encloses the KDs? How is it anchored? | a renal capsule anchored by adipose and connective tissue | |||
| What is the structure of a KD? | has a hollow "renal sinus" the KD tissue is divided into a renal medulla and a renal cortex | |||
| What projects from the apex of the renal pyramids into the minor calyces? | renal papillae | |||
| Where does each ureter originate from? | an expansion called the "renal pelvis" | |||
| How is the "renal pelvis" formed? | the convergence of major and minor calyces | |||
| What are the functions of the KDs? | they remove metabolic wastes from the Blood and excrete them they also help regulate red blood cell production, blood pressure, calcium ion absorption, and the volume, composition, and pH of the blood | |||
| What are the structures which arterial blood flows through in the KDs? | renal artery, segmental arteries, interlobar arteries, arcuate arteries, cortical radiate arteries, afferent arterioles, glomerular capillaries, efferent arterioles, and peritubular capillaries | |||
| Where does venous blood flow in the KDs? | returns through a series of vessels that correspond to those of the arterial pathways (except there are no segmental veins) | |||
| What is a nephron? | the functional unit of the KD | |||
| What makes up a nephron? | a renal corpuscle and a renal tubule | |||
| What happens at the renal corpuscle? | filtration | |||
| What does a renal corpuscle consist of? | glomerulus and a glomerular capsule | |||
| The renal tubule of the nephron includes what? | the proximal tubule, the nephron loop (ascending and descending limbs), and the distal tubule | |||
| The nephron joins a collecting duct which empties where? | into a minor calyx | |||
| What are the types of nephrons? | 1) cortical nephrons 2) juxtamedullary nephrons | |||
| What are cortical nephrons ? | the most numerous they have corpuscles near the surface of the KD | |||
| What is a juxtamedullary nephron? | they have corpuscles near the medulla and long nephron loops deep in the medulla w/ surrounding vasa recta | |||
| What is the juxtaglomerular apparatus? | it is between the ascending limb of the nephron loops and the afferent and efferent arterioles it consists of the macula densa and the justaglomerular cells | |||
| What do nephrons do? | they remove wastes from the blood and regulate water and electrolyte concentrations | |||
| What is urine the product of? | glomerular filtration, tubular reabsorption, and tubular secretion | |||
| What is the first step of glomerular filtration? | urine formation begins when water and dissolved materials are filtered out of the glomerular capillaries which are much more permeable than other capillaries | |||
| Other than extra permeable membranes of the capillaries what affects filtration? | osmotic pressure of the blood plasma and hydrostatic pressure in the glomerular capsule | |||
| What is filtration pressure? | the net force moving material out of the glomerulus and into the glomerular capsule | |||
| The composition of the filtrate from the glomerulus to the glomerular capsule is similar to what? | tissue fluid | |||
| How much glomerular fluid do the KDs produce per minute? | 125 milliliters; most is reabsorbed | |||
| Filtration pressure variation causes changes in what? | the rate of filtration | |||
| When does filtration pressure change | with the diameters of the afferent and efferent arterioles | |||
| as the osmotic pressure in the glomerulus increases, filtration | decreases, and as the hydrostatic pressure in the glomerular capsule increases, the filtration rate | decreases | ||
| the volume of filtrate varies with the surface area of what? | the glomerular capillaries | |||
| What causes the GFR (glomerular filtration rate) to increase or decrease? | need | |||
| What is autoregulation? | the ability of an organ or tissue to maintain a constant blood flow under certain conditions when the arterial blood pressure is changing | |||
| The myogenic mechanism regulates what? | GFR which is? | glomerular filtration rate the myogenic mechanism involes what? | the response of stretched smooth muscle in the walls of arterioles to regulate GFR | |
| tubularglomerular feedback happens when? | GFR increases what happens? | macula densa cells detect increased NaCl concentration which leads to constriction of afferent arteriole to do what? | bring GFR back to normal | |
| Neural control of GFR comes from where? | sympathetic nervous system | |||
| What happens when tubular fluid NaCl concentration decreases? | the macula densa causes the juxtaglomerular cells to release renin what happens then? | it triggers a series of changes leading angiotensis II formation and vasoconstriction (maybe affecting GFR) and secretion of aldosterone which does what? | stimulates tubular sodium reabsoption | |
| Tubular reabsorption is when substances are selectively reabsorbed from where? | the glomerular filtrate and then returned to what? | the internal environment | ||
| The peritubular capillary is adapted for reabsorption in what 3 ways? | 1)it carries low pressure blood 2) it is permeable 3)it has a high concentration of plasma proteins Where does most reabsorption occur? | in the proximal tubule | ||
| Different modes of transport reabsorb various substances in particular segments of what? | the renal tubule how are glucose and amino acids reabsorbed? | active transport mechanisms how is water reabsorbed? | osmosis how are smaller proteins reabsorbed? | by electrolytes |
| The transport maximum means that | active transport mechanisms have limited capacities if the concentration of a substance in the filtrate exceeds its renal plasma theshold, what happens to the excess? | it is excreted in the urine how are sodium ion reabsorbed? | active transport | |
| Reabsorption of other ions than sodium is linked to what? | sodium ion reabsorption by a number of mechanisms water is passively reabsorbed by what? | osmosis as sodium ions are what? | actively reabsorbed what happens to subs that remain in the filtrate as water is reabsorbed? | they are concentrated |
| Aldosterone and ADH can cahnge sodium and water reabsorption to do what? | keep conditions in blody fluids constant | |||
| Tubular secretion does what? | transports certain subs from the plasma to the tubular fluid which substances are actively secreted? | various organic compounds and hydrogen ions which tubes secrete hydrogen ions? | the proximal and distal tubes where are potassium ions secreted? | the distal tubule and the collecting duct |
| where does ADH come from? | posterior pituitary gland where does it increase permeability? | the last part of the distal tubule and the collecting duct what does this do? | promotes water reabsorption what is the countercurrent mechanism? | concentrates sodium ions in the renal medulla |
| in the countercurrent mechanism where are sodium and chloride ions actively reabsorbed? | the ascending limb what happens then? | tubular fluid in ascending limb becomes hypotonic as it loses solutes the descending limbs loses water via? | osmosis and tubular fluid in the descending limb becomes | hypertonic as it loses water |
| As the process of the descending limb becoming hypertonic continues what happens? | the NaCl concentration in the medulla increases what is accomplished? | the vasa recta countercurrent mechanism helps maintain NaCl concentration in the medulla in the absence of ADH, both the last part of the distal tubule and the collecting duct are essentially what? | impermeable to water which results in what? | more water excreted in urine |
| What is urea a byproduct of? | amino acid metabolism it is reabsorbed and secrete by different portions of what? | the renal tubule about how much urea is reabsorbed? | 40-60% | |
| uric acid results from the metabolism of what? | nucleic acids most uric acid is reabsorbed by what mechanism? | active transport some is secreted where? | in the renal tubule | |
| What is the composition of urine? | 95% water and usually contains urea, uric acid, and creatinine it may also contain what? | traces of amino acids and varying amounts of electrolytes depending on diet the volume of urine varies w/ fluid intake, certain environmental factors and a person's what? | emotional condition, respiratory rate and body temperature | |
| what is renal clearance? | the rate at which a chemical is removed from the plasma which tests calculate GFR? | inulin clearance test creatinine clearance test para-aminohippuric acid test | ||
| what is the ureter? | a tubular organ that extends from each KD to the UB its wall has what layers? | mucous, muscular, and fibrous what forces urine to UB? | peristaltic waves what does obstruction in the ureter cause? | strong peristaltic waves and a reflex that decreases urine production |
| the UB is a distensible organ that stores what? | urine and forces it into the urethra the ureters and urethra open at 3 angles of the what? in the floor of the UB? | trigone the UB has what layers? | mucosa, muscularis, and serosa what is formed by smooth muscle fibers in the wall of the UB muscularis layer? | detrusor muscle |
| A portion of the detrusor muscles forms an internal what? | urethral sphincter | |||
| What does the urethra do? | conveys urine from teh UB to the outside how does the mucosa layer of the urethra change? | progressively changes from nearest the bladder to the external urethral orifice what is the difference in the urethra for females? | it is short and empties between the labia minora what does it do in males? | its long and conveys products of reproductive organs as well as urine |
| What are the 3 portions of the male urethra? | prostatic urethra membranous urethra spongy urethra where does the male urethra empty? | tip of penis | ||
| What is micturition? | the process of expelling urine what does the detrusor muscle do during micturition? | contracts what relaxes then? | the external urethral sphincter where is the micturition reflex center? | sacral portion of spinal cord |
| how does the micturition reflex start? | as the UB fills w/ urine, distention stimulates stretch receptors in UB wall then what? | micturition reflex center sends parasympathetic impulses which stimulate contraction of what? | detrusor muscle the external urethral sphincter is under what? | voluntary control |
| what does the voluntary contraction of the external urethral sphincter do? | inhibits/delays micturition reflex where do these signals come from? | brainstem and cerebral cortex what happens following the decision to urinate? | the detrusor muscle contracts, the external urethral sphincter relaxes and urine is expelled through the urethra Impulses from which part of the brain facilitate the micturition reflex? | hypothalamus and pons |
Created by:
Goldbellie
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