Flashcards in urinary system Deck (59):
what are the major components of the urinary system & what are their primary functions?
2 kidneys: (8 primary functions)
1. regulation of blood ionic composition
2. regulation of blood pH
3. regulation of blood volume
4. regulation of blood pressure (through the secretion of renin)
5. maintenance of blood osmolarity
6. production of hormones (namely calcitriol and erythropoietin)
7. regulation of blood glucose level
8. excretion of wastes and foreign substances
2 ureters: paired tubes that transport urine from the kidneys to the urinary bladder
1 urinary bladder: a temporary storage reservoir for urine
1 urethra: a tube that carries urine from the bladder to the body exterior
what is the location of the kidneys?
· Located above the waist and attached to the posterior wall of the abdomen (retroperitoneal).
· They are positioned between the levels of the last thoracic and the third lumbar vertebrae.
· They are partially protected by the eleventh and twelfth pairs of ribs.
· The right kidney is slightly lower than the left becuase of the presence of the liver on the right side
Near the center of the kidney's concave medial border is a depression called the _____ _____, through which travel:
2. blood vessels and lymphatic vessels
what are the three layers of supportive tissue that surround each kidney (from superficial to deep)?
- renal fascia (superficial layer) - anchors the kidney and adrenal gland to surrounding structures and to the abdominal wall
- adipose capsule - (mass of fatty tissue) which protects the kidney from trauma and holds it in place
- renal capsule (deep layer) - smooth transparent sheet of dense irregular connective tissue which maintains the shape of the kidney and prevents infections in surrounding regions from spreading to the kidney
the functional portion of the kidney's tissue is called ______.
what are the two layers of the parenchyma?
- an outer layer called the renal cortex
- an inner region called the renal medulla
the renal medulla contains 8-18 cone-shaped _____ _____, whose apexes are called _____ _____
renal pyramids, renal papillae
what is the name of the portions of the renal cortex that extend between renal pyramids?
what makes up a renal lobe?
a renal pyramid, its overlying area of renal cortex, and half of each adjacent renal column
what are the functional units of the kidney's parenchyma that filters blood, returns useful substances to blood, and removes unwanted substances from the blood, thereby producing urine?
what is the pathway in which urine flows once it is produced by nephrons?
· urine from the nephrons drains into the papillary dicts and onwards into minor calyces, which merge from major calyces, which deliver the urine into a large cavity called the renal pelvis
· urine then exits the kidney by flowing into a uterer
blood flows through the kidneys via the following sequence:
1. the right and left renal arteries supply the kidneys
2. they branch into segmental arteries, which branch into interlobar arteries
3. the interlobar arteries arch between the renal medulla and cortex, and are referred to as arcuate arteries here.
4. afferent arteriole branches come off the interlobar arteries and supply each nephron
5. the afferent arteriole divides into a ball of capillaries called a glomerulus
6. the glomerular capillaries reunite to form the efferent arteriole
7. the efferent arteriole divides to form the peritubular capillaries
8. these reunite to form peritubular venules, then interlobar veins and eventually the renal vein.
renal nerves are part of the _____ division of the autonomic nervous system
a nephron consists of what two portions?
- the renal corpuscle, where plasma is filtered
- the renal tubule, into which the filtered fluid passes
what are the two components of the renal corpuscle?
- glomerulus: a capillary network (recieves blood from afferent arterioles & drains blood into efferent arterioles)
- glomerular (bowman's) capsule: a double walled epithelial cup that surrounds the glomerular capillaries; this is where blood plasma is filtered before being passed into the renal tubule
as filtered fluid travels through the renal tubule, it passes through these three segments:
- proximal convoluted tubule (PCT)
- loop of henle (nephron loop)
- distal convoluted tubule (DCT)
distal convoluted tubules of several nephrons empty into a single _____ _____.
collecting ducts merge to form what kind of ducts?
papillary ducts (which drain into a minor calyx)
which kind of nephron consists of about 80-85% of all nephrons and usually has its glomerulus in the outer part of the cortex, and its short loop of henle penetrating into the outer region of the medulla?
which kind of nephron consists of about 15-20% of all nephrons and usually has its glomerulus deep in the cortex, and its long loop of henle penetrating deep into the medulla?
which kind of nephron has a thin ascending limb followed by a thick ascending limb and permits the excretion of very dilute to very concentrated urine?
what are the three major processes involved in urine formation?
1. glomerular filtration: water and most solutes in blood plasma move across the wall of glomerular capillaries into the glomerular capsule and into the renal tubule
2. tubular reabsorption: tubule cells reabsorb about 99% of the filtered water and many useful solutes into the peritubular capillaries and vasa recta (reabsorption refers to the return of substances to the bloodstream)
3. tubular secretion: tubule cells and collecting duct cells secrete wastes, drugs, and excess ions into the fluid as it moves through the tubule and collecting duct (secretion here means removing substances from blood)
* excreted substances remain in the urine and subsequently leave the body *
pores in the glomerular epithelial cells that cause them to be quite leaky are called ______. what is their role?
fenestrations - permits filtration of water and small solutes but prevents filtration of most plasma protein, blood cells & platelets
what are the spaces between the pedicels which allow passage of molecules smaller than 6-7nm? Ie: water, glucose, vitamins, amino acids, very small plsma proteins, ammonia, urea, and ions?
Each of the two ureters transport urine from the _____ _____ of one kidney to the _____ _____
renal pelvis, urinary bladder
In what three ways is the transport of urine from the ureters to the UB made possible?
- peristaltic waves
- hydrostatic pressure
what is meant by there is no anatomical valve existing between the uterers and bladder, but there is a functional one?
each ureter passes obliquely through the wall of the UB to create an effective physiological valve that prevents the backflow of urine, since filling of the UB with urine compresses the oblique openings to the ureters
what is the location of the urinary bladder?
it resides in the pelvic cavity poosterior to the pubic symphysis:
- in males it is directly anterior to the rectum
- in females it is anterior to the vagina and inferior to the uterus, and it usually as a smaller capacity
the floor of the urinary bladder has a small triangular area called the ______.
around the opening to the urethra, the circular fibers form an ______.
internal urethral sphincter
what is micturition?
discharge of urine from the urinary bladder. Aka: urination or voiding
describe the female urethra
- it lies directly posterior to the pubic symphysis and is embedded in the anterior wall of the vagina
- it is about 4 cm long
- It leads to the external urethral orifice, which is located between the clitoris and vaginal opening
describe the male urethra
- it is about 20 cm long
- it consists of the prostatic urethra, the membranous (intermediate) urethra, and the spongy urethra (which passes through the body of the penis)
the renal corpuscle and both convoluted tubules lie within the renal _____; the loop of Henle extends into the renal _____, makes a hairpin turn, and then returns to the renal _____.
one kidney has about how many nephrons?
in a nephron, the loop of Henle connects the ____ and ____ convoluted tubules.
T or F: a single layer of epithelial cells forms the entire wall of the glomerular capsule, renal tubule, and ducts
describe the visceral and parietal layers of the glomerular (Bowman's) capsule:
· the visceral layer consists of modified simple squamous epithelial cells called podocytes, which have foot-like projections called pedicels
· the parietal layer consists of simple squamous epithelium and forms the outer wall of the capsule
· fluid filtered from the glomerular capillaries enters the capsular (Bowman's) space, the space between the visceral and parietal layers of the capsule
T or F: the number of nephrons is constant from birth
True -- any increase in kidney size is due solely to the growth of individual nephrons; if nephrons are injured or become diseased, new one do not form.
(signs of kidney dysfunction do not become apparent until function declines to less than 25% of normal bc the remaining functional nephrons adapt to handle a larger-than-normal load)
what are the three main pressures involved with glomerular filtration? does these promote or oppose filtration?
· glomerular blood hydrostatic pressure (GBHP) - the blood pressure in glomerular capillaries, which promotes filtration by forcing water & solutes in blood plasma through the filtration membrane
· capsular hydrostatic pressure (CHP) - the hydrostatic pressure exerted agains the filtration membrane by fluid already in the capsular space & renal tubule, which opposes filtration ("back pressure")
· blood colloid osmotic pressure (BCOP) - is due to the presence of proteins such as albumin, globulins & fibrinogen in blood plasma, which also opposes filtration
how do you calculate net filtration pressure (NFP), or the total pressure that promotes filtration? what are the normal values?
NFP = GBHP - CHP - BCOP
NFP = 55 mmHg - 15 mmHG - 30 mmHG = 10 mmHg
Thus a pressure of only 10 mmHg causes a normal amount of blood plasma (minus plasma proteins) to filter from the glomerulus into the capsular space
the glomerular filtration rate (GFR) is the amount of filtrate formed in all the renal corpuscles of both kidneys each minute. what is the average GFR in males and females?
males: 125 mL / minute
females: 105 mL / minute
normally, what percentage of filtered water is reabsorbed during tubular reabsorption?
epithelial cells all along the renal tubule & duct carry out reabsorption, but ______ ______ tubule cells make the largest contribution.
name some solutes that are reabsorbed during tubular reabsorption (the second step in urine formation):
sodium, potassium, calcium, chloride, bicarbonate, and phosphate ions
name some substances that are secreted during tubular secretion (the third step in urine formation):
· hydrogen, potassium, ammonium ions
· certain drugs such as penicillin
the proximal convoluted tubules reabsorb what percent of filtered water before fluid enters the loop of Henle?
the loop of Henle reabsorbs what percent of filtered water before fluid enters the distal convoluted tubules?
(all reabsorption occurs in the DESCENDING limb of the loop of Henle bc the ascending limb is virtually impermeable to water)
by the time fluid reaches the end of the distal convoluted tubule, what ___ to ___% of filtered solutes and water have returned to the bloodstream
90 to 95%
which hormone controls whether dilute urine or concentrated urine is formed?
· in the absence of ADH, urine is very dilute
· a high level of ADH stimulates reabsorption of more water into blood, producing a concentrated urine
what is normal urine volume?
1 or 2 liters in 24 hours, but varies considerably
what is the normal pH of urine?
· ranges between 4.6 and 8.0 (average 6.0)
· varies considerably with diet (high-protein diets increase acidity, while vegetarian diets increase alkalinity)
what is urinalysis? how is it useful in revealing info about the state of the body?
· an analysis of the volume and physical, chemical, and microscopic properties of urine
· if disease alters body metabolism or kidney function, traces of substances not normally present may appear int he urine, or normal constituents may appear in abnormal amounts
water constitutes ___% of the total volme of urine; the remaining ___% consists of electrolytes, solutes derived from cellular metabolism, and exogenous substances such as drugs
typical solutes normally present in urine include:
· filtered & secreted electrolytes that are not reabsorbed
· urea (from breakdown of proteins)
· creatinine (from breakdown of creatine phosphate in muscle fibers)
· uric acid (from breakdown of nucleic acids
· urobilinogen (from breakdown of hemoglobin)
· small quantities of other substances like fatty acids, pigments, enzymes, and hormones
describe the anatomy of the ureters:
· the ureters are about 25-30 cm long, and are retroperitoneal like the kidneys
· at the base of the UB, the paired ureters curve medially and pass obliquely through the wall of the posterior aspect of the UB
describe the three layers that make up the wall of the ureters:
1. mucosa (deepest) - a mucous membrane with transitional epithelium that is able to stretch, and an underlying lamina propria
2. muscularis (intermediate) - smooth muscle fiber responsible for peristalsis
3. adventitia (superficial) - areolar connective tissue which contains blood vessels, lymphatic vessels, and nerves; blends with surrounding connective tissue; and anchors ureters in place
which is voluntary and which is involuntary?
· internal urethral sphincter
· external urethral sphincter
· internal urethral sphincter is involuntary
· external urethral sphincter (in the deep muscles of the perineum) is voluntary