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Lecture 25 Part 1 Urinary and Renal Anatomy
Lecture 25 part 1
Terms in this set (36)
functions of the urinary system
maintenance of homeostasis by filtering the blood plasma
maintains homeostasis by:
blood vol, pressure, pH, & concentration
(osmolarity) of electrolytes (Na+, K+, Ca 2+, Cl-, HPO4-3, Mg2+, HCO3-)
Reabsorbing glucose & other
- Releasing of
like renin, EPO (erythropoietin), & activation of vit D
- bean-shaped organs located just above the waist btwn the peritoneum and posterior wall of abdomen (in retroperitoneal space)
- partially protected by eleventh and twelfth pairs of ribs.
- b/c of position of liver, right kidney is slightly lower than left
tough fibrous layer that surrounds kidney
filtration of the plasma
collect and concentrate the plasma filtrate and excrete urine
Consists of 8-18 conical subdivisions w/in medulla that contain the kidney's secreting apparatus and tubules
- Medullary extensions of renal cortex in btwn renal pyramids
- allows cortex to be better anchored
- Each column consists of lines of blood vessels, urinary tubes, and a fibrous material.
location where medullary pyramids empty filtrate into minor and major calyces
- Urine formed in kidney passes thru a papilla at the apex into minor calyx then into major calyx
- Once filtrate enters the calyces, it becomes urine b/c no further reabsorption can occur
btwn major calyces and ureter
- tubular structure that originates near an indented area of each kidney called the
- travels to base of bladder.
- Renal blood vessels also emerge from the hilum
Where do ureters connect to the bladder?
- ureters transport urine from renal pelvis of kidneys to bladder, using peristaltic waves, hydrostatic pressure, gravity
- no anatomical valve at opening of ureter into bladder.
How is urine prevented from flowing back into the ureter from the bladder?
- location of ureter entrance and muscular attachments help prevent urine from traveling back up into ureter.
- When bladder fills and contracts during voiding, it compresses the opening and prevents backflow
What can happen if urine flows back?
results in Vesicoureteral reflux (VUR) disease which may lead to frequent UTIs.
hollow, distensible muscular organ
act of emptying the bladder
- requires a combo of voluntary & involuntary muscle contractions
- small tube leading from internal urethral orifice in bladder floor to exterior.
- From bladder, urethra allows urine to be excreted
male vs female urethra
female: 4 cm
male: 24 cm, used to discharge semen
blood flow thru kidney starting from afferent arteriole to peritubular capillaries/vasa recta
afferent arteriole > glomerulus (capillaries) > efferent arteriole > peritubular capillaries/vasa recta
What is special about the glomerular capillary compared to others found in the body?
they're positioned btwn 2 arterioles, rather than btwn an arteriole and a venule
- main filtering unit of kidney
consists of 2 structures:
- glomerular capillaries
- glomerular capsule- a double-walled (visceral and parietal layers) epithelial cup that surrounds the glomerular capillaries
visceral layer of glomerular capsule
- made of modified simple squamous epithelial cells called
- wrap around the single layer of endothelial cells of the glomerular capillaries and form the inner wall of the capsule.
- Podocytes form a crucial component of glomerular filtration barrier
- spaces btwn foot-like projections (pedicels) contribute selectivity to what can be filtered and help maintain a massive filtration surface.
parietal layer of the glomerular capsule
simple squamous epithelium and forms the outer wall of capsule
What type of capillaries are found in the glomerulus?
the structures of the filtration membrane
pedicels of visceral layer, endothelial fenestrations (pores), and capillary basement membrane act as a filtration (dialysis) membrane.
- Allows some things to be filtered while not allowing others
- Based on molecule size and charge
What is plasma called once it enters the bowman's space?
proximal convoluted tubule
- tightly coiled tube region closest to glomerulus
- Cuboidal cells w/ dense microvilli (brush border-like => increase surface area)
- Function in reabsorption and secretion
- Confined to renal cortex
- delivers filtrate into Loop of Henle
the descending limb of the loop of Henle
- dips into the renal medulla
- returns to the renal cortex as the
- simple squamous epithelium
ascending limb of the loop of Henle
- limb delivers the filtrate to distal convoluted tubule in cortex
- may be either "thin" or "thick" portions, or both
- makes contact w/ afferent arteriole serving that renal corpuscle
known as "this" b/c the tubule cells in this region are crowded together
juxtaglomerular (JG) cells
Alongside macula densa, wall of afferent arteriole contains modified smooth muscle fibers called?
juxtaglomerular apparatus (
- important in regulating blood pressure w/in kidneys
- comprises of juxtaglomerular (JG) cells and macula densa
- cells of macula densa are sensitive to ion content and water vol of fluid passing thru this part of tubule.
- If filtrate sodium chloride concentration at macula densa is low, they'll produce molecular signals that promote renin secretion by juxtaglomerular cells
Distal Convoluted Tubule
- Cells w/ few microvilli
- Function in secretion and reabsorption
- Confined to cortex
- empty into collecting duct
- converged by collecting ducts
- drain into minor calyces, major calyces, renal pelvis, and ureters
- make up ~80-85% of >1 million microscopic nephrons that comprise each kidney.
- renal corpuscles are located in
portion of cortex
- short loops of Henle that penetrate only a small depth into medulla.
- ascending limbs consist of mostly a
, lacking little to no thin portions
- receive blood supply from
that arise from efferent arterioles
- 15-20% of nephrons
- renal corpuscles lie
in cortex, close to medulla
- long loops of Henle that extend into deepest regions of medulla; enable kidneys to create a concentration gradient in renal medulla
- ascending limbs consist of
both thin and thick
- receive blood supply from
that arise from peritubular capillaries before emptying into peritubular venules.
path of filtrate from the glomerulus to urine production to the urethra
glomerulus > PCT > descending limb > ascending limb > DCT > collecting duct > papillary duct > renal papilla > minor calyx > major calyx > renal pelvis > ureter > bladder > urethra
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