Urinary System Flashcards
Functions of Urinary System
- Removal of waste products from bloodstream
- Production of urine
- Storage and excretion of urine
- Blood volume regulation
- Regulation of erythrocyte production
- Regulation of ion balance/acid-base balance
Urinary system components
- kidneys
- ureters
- urinary bladder
- urethra
Location of kidneys
- retroperitoneal on posterior abdominal wall
- superior pole of left kidney is at level of T12 - right kidney 2 cm lower due to presence of liver
- concave medial border = hilum (where vessels, nevers and ureter connect w/ kidney)
- hilum continuous w/ renal sinus (internal space)
Kidneys
- each kidney surrounded & supported by several tissue layers (deepest to most superficial);
- Fibrous capsule (direct contact w/ outer surface - maintains shape, protects)
- Perinephric fat (Provides cushioning and insultion
- Renal fascia - anchors kidney to posterior abdominal wall
- paranephric fat: outermost layer surrounding kidney between renal fascia and peritoneum
Regions of Kidney (2)
-where regions meet
- Divided into outer renal cortex and inner renal medulla
- extensions of renal cortex (renal columns) project into renal medulla and subdivide medulla into renal pyramids
- 8-15 renal pyramids per kidney
- Wide base of renal pyramid makes contact w/ cortex = CORTICOMEDULLARY JUNCTION
- apex of renal pyramid = renal papilla
Tubing w/in renal sinus
- minor & major calyx
- renal pelvis
- Each renal papilla projects into hollow funnel-shaped structure = Minor calcyx
- Several minor calyces fuse to form major calyx
- major calyces fuse to form renal pelvis (collects total urine output from one kidney and transports it to ureter)
Arterial Supply to Kidney (to cortex)
- Blood enters kidneys via renal arteries
- w/in renal sinus, renal arteries branch into interlobar arteries (b/w renal pyramids)
- interlobar branch into arcuate arteries (follow corticomedullary junction)
- arcuate arteries branch into interlobular arteries (when in cortex)
Aorta -> Renal -> Segmental -> Interlobar -> arcuate -> interlobular
Arterial supply to Kindey (from cortex)
- as interlobular arteries enter kidney cortex, extend small branches called afferent arterioles
- enter renal corpuscle (struct.) and form a tuft of capillaries called glomerulus
- remaining blood exits glomerulus and renal corpsule as efferent arteriole
- Blood filtration occurs at glomerulus
interlobular -> afferent -> glomerulus -> efferent
Capillary supply to Kidney (2)
- efferent arterioles branch into one of two capillary networks: (where exchange of gases occur)
- Peritubular capillaries: surround convoluted tubules and reside primarily in cortex
- Vasa recta - ass. mainly w/ nephron loop and primarily reside in medulla (recta = straight)
Venous Return from the Kidney
-Peritubular capillaries & vasa recta drain into network of veins;
- smallest veins are interlobular veins
- merge to form arcuate veins (corticomedullary junction)
- merge in renal sinus to form renal vein
Interlobular -> arcuate -> interlobular -> renal vein
*all this blood is deoxygenated
Nephron
- is functional filtration unit of kidney
- approx. 1.25 million nephrons in each kidney
- Form urine in 3 processes (related);
- filtration
- tubular reabsorption
- tubular secretion
*final product is formation of urine (from filtrate)
2 types of nephrons
- Cortical nephrons: approx. 85% of all nephrons
- bulk of nephron resides in cortex - small component enters medulla (nephron loop) - Juxtamedullary nephrons: renal corpuscle lies near corticomedullary junction and their long nephron loops extend deep into medulla
-long medulla in animals in dry areas - really conc. urine
4 components of a nephron
- Renal corpuscle
- Proximal convoluted tubules
- nephron loop
- Distal convoluted tubule
Renal corpuscle
-2 structures
- composed of 2 structures;
1. Glomerulus: thick tangle of fenestrated capillaries (studded by lots of holes)
2. flomerular capsule (Bowman’s capsule): epithelial covering over glomerulus - corpuscle has vascular pole where afferent arteriole enters and efferent arteriole exits
- tubular pole = proximal convoluted tubule exits
2 layers of Glomerular Capsule
-podocytes
- Visceral layer: directly overlies and comes in contact w/ glomerulus
- composed of specialised cells called PODOCYTES (have little projections that help them wrap around capillaries)
- Parietal layer: formed from simple squamous epithelium