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Urinary System
Anatomy & Physiology
Question | Answer |
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waste products | produced by all cells of the body and end up in the blood. The blood is filtered by the kidneys and these form the urine that is eliminated from the body by ureters, urinary bladder, and urethra |
urinary system | aka the body's "water treatment plant" and is composed of the kidneys, ureters, urinary bladder, and urethra |
kidneys | responsible for filtering blood by removing waste products and converting them into urine |
ureters | responsible for transporting urine from kidneys to urinary bladder |
bladder | expandable muscular sac that stores as much as 1 L of urine |
urethra | responsible for eliminating urine from the body |
the kidneys and their function in the formation of calcitrol | synthesize the final enzyme in calcitrol hormone formation |
the kidneys and their function in the production and release of erythropoietin | indirectly measure oxygen level of blood and secrete erythropoieten (EPO) in response to low blood oxygen |
erythropoietin functions to... | stimulate red bone marrow formation to increase rate of erythrocyte formation and the erythrocytes then transport additional oxygen from the lungs |
the kidneys and their function in regulation of ion levels and acid-base balance | help control blood's inorganic ion balance (i.e. Na+, K+, and Ca2+) and aids in maintaining acid-base balance (alters levels of H+ and HCO3-) |
the kidneys and their function in the regulation of blood pressure | alters amount of fluid lost in urine, helps regulate blood volume, and releases renin enzyme |
renin is... | required for the production of angiotensin II which is a hormone for increasing blood pressure |
kidney characteristics | two symmetrical, bean-shaped organs that have concave borders (known as the hilum) where vessels, nerves, and ureters connect to the kidney. The lateral borders are convex and the adrenal gland rests on the superior aspects of both of these |
kidney location | on posterior abdominal wall, lateral to vertebral column (L kidney b/w T12 & L3 vertebrae & R kidney is 2 cm inferior to L to accommodate liver), both partially protected by rib cage (vulnerable to forceful blows to inferior region of back) |
several tissue layers surrounding the kidney | fibrous capsule, perinephric fat, renal fascia, and paranephric fat |
fibrous capsule | directly adhered to external surface of the kidney, dense irregular connective tissue, maintains kidney's shape and protects it from trauma, and prevents pathogen penetration |
perinephric fat | adipose connective tissue external to fibrous capsule that provides cushioning and support for the kidney |
renal fascia | external to perinephric fat and is made of dense irregular connective tissue and functions to anchor kidney to surrounding structures |
paranephric fat | outermost layer surrounding kidney that is composed of adipose connective tissue and provides cushioning and support for kidney |
two regions of function tissue in the kidney | outer renal cortex and inner renal medulla |
renal columns | extension of cortex projecting into the medulla |
renal pyramids | portion of medulla divided by renal columns that has a wide base at external edge of medulla meeting cortex and the medial apex is termed the renal papilla |
renal lobe components... | renal pyramid and portion of adjacent renal columns and renal cortex external to base |
renal sinus | medially located urine drainage area that is organized into minor calyces, major calyces, and the renal pelvis |
minor calyses | funnel-shaped structures associated with renal pyramids that merge to form the major calyx |
renal pelvis | formed from merged major calyces and merges and medial edge of kidney with ureter and is surrounded by renal arteries, veins, lymph vessels, nerves, and fat |
nephron | microscopic functional filtration unit of kidney that consists of renal corpuscle and renal tubule (all corpuscles and most tubules reside in the cortex) |
renal corpuscle | enlarged bulbous region of nephron within the renal cortex that is composed of glomerulus and glomerular capsule |
glomerulus | tangle of capillary loops (glomerular capillaries) with blood entering by afferent arterioles and exiting by efferent arterioles |
renal tubule | portion located off of the glomerulus that has three continuous parts |
three continuous parts of the renal tubule | proximal convoluted tubule, nephron loop (descending limb and ascending limb, and distal convoluted tubule |
nephrons are classified based on | relative position of nephron to cortex and length of loop |
two types of nephrons | cortical nephrons and justamedullary nephrons |
cortical nephrons | oriented with renal corpuscles near peripheral cortex, have short nephron loop just penetrating medulla, bulk residing within cortex, and 85% of nephrons |
justamedullary nephrons | renal corpuscles adjacent to corticomedullary juction, long nephron loops extending deep into medulla, and help establish salt concentration gradient in interstitial space |
nephron drainage | each nephron drains into a collecting tubule which empties into larger collecting ducts with empty into papillary ducts |
filtrate | formed when blood flows through the glomerulus (as blood moves across wall of glomerulus capillaries and into capullar space) and water and solutes are filtered from the blood plasma |
tubular fluid | filtrate renamed as it enters proximal convoluted tubule, and it flows through PCT, nephron loop, and DCT, and enters collecting tubules to collecting ducts |
urine | name given to tubular fluid as it leaves collecting ducts and enters papillary ducts located within renal papilla and flows within renal sinus of kidney from minor to major calyx to renal pelvis which connects to ureter which connects to urinary bladder |
urinary bladder | stores and excretes urine from the body through the urethra |
three processes of urine formation | filtration, tubular reabsorption, and tubular secretion |
filtration | in glomerular capillaries, water and dissolved solutes are separated from blood plasma to yield a separated fluid termed the filtrate |
tubular reabsorption | movement of components within tubular fluid, move by diffusion, osmosis, or active transport, return blood to capillaries, and all vital solutes and most water is reabsorbed, but excess solutes, waste products, and some water remains in tubular fluid |
tubular secretion | movement of solutes, usually by active transport, move into tubular fluid, and materials moved selectively into tubules to be excreted |
the urinary system | prevents the accumulation of cellular waste, various hormones and metabolites, and foreign substances by filtering some at the glomerulus and secreting other along the tubule pathway |
nitrogenous waste | metabolic waste containing nitrogen |
main nitrogenous waste products | urea, uric acid, and creatinine |
urea | molecule produced from protein breakdown that is both reabsorbed and secreted |
uric acid | produced from nucleic acid breakdown in liver that is both reabsorbed and secreted |
creatinine | produced from creatinine metabolisim in muscle (only secreted) |
urine | product of filtered and processed blood plasma and is sterile unless contaminated with microbes in kidney or urinary tract. It is mainly water (95%) and 5% solutes |
solutes in urine | Na+, Cl-, K+, etc., some hormones and drugs, small amounts of ketone bodies |
abnormal components of urine | glucose, ketones, protein (in more than trace amounts) and bile, erythrocytes, hemoglobin, leukocytes, and nitrites (may indicate disease states) |
daily volume of urine | usually 1-2 L, but can be a minimum of 0.5 L, but variation occurs due to fluid intake, blood pressure, temperature, diuretics, diabetes, and other fluid excretion |
ureters | conduct urine from kidneys to urinary bladder, originate from renal pelvis as they exit the hilum of kidney, enter posterolateral wall of base of urinary bladder, and have a wall composed of three tunics |
three tunics of the ureters | mucosa, muscularis, adventitia |
mucosa | distensible and impermeable to urine, folds to fill lumen when no urine present |
muscularis | inner longitudinal and outer circular layer of smooth muscle cells, contract rhythmically with presence of urine, propel urine through ureters into bladder |
adventitia | external layer of ureter wall, compressed as bladder distends, and decreases likelihood of urine backflowing while emptying |
urinary bladder | expandable, muscular container that serves as a reservoir for urine, and is positioned immediately posterior to pubic symphysis |
shape changes of bladder | inverted pyramidal shape when empty and oval shaped when full |
trigone | posteroinferior triangular area of bladder wall that is formed by imaginary lines connecting ureters opening and the urethra. Remains immobile as bladder fills and empties and serves as a funnel to direct urine into urethra during contraction |
mucosa | innermost layer lining that bladder that accommodates shape changes with distension and has mucosal folds allowing for greater distension |
muscularis | three layers of smooth muscle (collectively termed detrusor muscle) and part is the involuntary internal urethral sphincter |
involuntary urethral sphincter | formed by smooth muscle encircling urethral opening |
adventitia | outer layer of areolar connective tissue |
urethra | exits urinary bladder thru urethral opening, conducts urine to exterior of body, luminal lining is protective mucous membrane, houses mucin-producing cells (urethral glands), & smooth muscle fibers surrounding mucosa contracts, propelling urine to outside |
urethra sphincters | restrict release of urine until signaled to release |
internal urethral sphincter | involuntary, superior sphincter, composed of smooth muscle, surrounds the neck of the bladder, and is controlled by autonomic nervous system |
external urethral sphincter | inferior to internal urethral sphincter, formed by skeletal muscles of urogenital diaphragm, voluntary sphincter controlled by somatic nervous system, and learn to control muscle during "toilet training" |
female urethra | single function is to transport urine from urinary bladder to exterior |
male urethra | passageway for urine and semen |
micturition | expulsion of urine from bladder |
two reflexes associated with micturition | storage reflex (regulated by sympathetic division) and micturition reflex (regulated by parasympathetic divisions) |
storage reflex | continuous sympathetic stimulation causes relaxation of detrusor to accommodate urine and stimulates contraction of internal urethral sphincter (so urine retained in bladder) and contraction of external urethral sphincter |
micturition reflex (1) | 1) volume of urine in bladder is between 200 and 300 mL (bladder distended and baroreceptors activated in bladder wall and the sensation is relayed along sensory axons to cerebral cortex) |
micturition reflex (2-3) | 2) visceral sensory neurons signaled by baroreceptors (stimulate micturition reflex center in pons) and 3) mictuition center (alters nerve signals down spinal nerve through pelvic splanchnic nerves |
micturition reflex (4) | contraction of detrusor and relaxation of internal urethral sphincter (stimulated by parasympathetic system and urination if voluntary control of external urethral sphincter undeveloped) |