Unit 16: Urinary System Flashcards
(13 cards)
What are the structures of the urinary system?
- 2 kidneys (monitor water and ionic concentration levels)
- 2 ureters (duct work leading to urinary bladder)
- 1 urinary bladder
- 1 urethra
What are the functions of the urinary system?
Regulates:
- blood volume
- blood pressure
- pH (concentrations of H+ and HCO3-)
- concentrations of each ion in the blood (Na+, Ca++, K+, Cl-)
- section of renal hormones
Eliminates:
- wastes (e.g. urea, uric acid)
- hormones
- drugs (e.g. antibiotics)
- toxins
What is the external anatomy of the kidneys?
- retroperitoneal
- right lower than left
- supported and protected by 3 layers of CT
a) fibrous capsule - deep (inner) layer directly connected to
the kidney
b) perirenal fat capsule - middle layer
c) renal fascia - superficial (outer) layer - renal hilus (hilum):
- medial indentation (so action is in the middle, not top or
bottom) - entry point of: renal artery (superior), renal vein (inferior),
ureter, nerves
- medial indentation (so action is in the middle, not top or
What is the internal anatomy of the kidneys?
Renal cortex (superficial/outside layer)
- contains parts of nephrons
- contains afferent and efferent arterioles as well as capillary
beds called glomeruli
Renal medulla - contains:
a) renal pyramids
- apex of pyramid is called the renal papilla
- contain parts of nephrons
b) renal columns
- projections of cortex to the medulla
- separate pyramids
- contains arteries, veins and nerves that supply the cortex
Renal pelvis:
- central collecting chamber for filtrate/urine
- receives filtrate/urine from major calyces
- major calyces receive filtrate/urine from minor calyces
which are small cup-shaped structures that surround the
renal papilla
What is a nephron and what are the 2 types of nephrons?
- a functional unit of the kidney (microscopic - about 1 million per kidney)
- composed of renal corpuscle and renal tubules
Cortical
- make up majority of nephrons
- renal corpuscles near kidney surface in cortex
- short nephron loop that dips into the outer medulla
- has peritubular capillaries that branch from efferent arteriole and surround DCT and PCT
Juxtamedullary
- renal corpuscles in cortex near medulla
- long nephron loops that penetrate deep into medulla
- allow for production of dilute or concentrated urine
depending on need
- has capillaries that branch from efferent arterioles called vasa recta that run parallel to the nephron loop
Info about the renal corpuscle
In cortex - site of blood filtration (FIRST STEP IN URINE FORMATION). Parts:
i. glomerulus (looks like red ball of yarn)
- = capillary bed (endothelium formed of simple squamous
epithelium)
ii. Afferent (Arrival) arteriole - enter glomerulus
- carries blood delivered to kidney from the renal artery
iii. Efferent (Exit) arteriole - exits glomerulus
- drains into peritubular (of cortical nephrons) and vasa
recta (of juxtaglomerular nephrons)
iv. Glomerular (Bowman’s) capsule
- surrounds and collects filtrate (filtered blood plasma)
from glomerulus
- 2 layers:
a) outer layer = simple squamous epithelium
b) inner layer is made of cells called podocytes that wrap
around glomerular capillaries
Filtration membrane - consists of:
i. glomerular endothelium (capillaries) = windows
- fenestrations in the simple squamous epithelium allow
plasma through, but not formed elements and most large
proteins (they are leaky)
ii. shared basement membranes of i) and iii)
iii. podocytes (of glomerular capsule)
- have many finger-like projections that form a network of
filtration slits
Info about renal tubules
4 parts w/ specific cell types and functions:
i. Proximal Convoluted Tubule (PCT)
- in cortex
- receives filtrate from glomerular capsule
- cells are cuboidal epithelium w/ dense microvilli
- reabsorbs most useful substances (e.g. glucose, amino
acids) from the filtrate
- secretes waste products into filtrate
ii. Nephron Loop
- in the medulla
- descending limb (thin) = simple squamous epithelium,
highly water permeable
- ascending limb (thick) = simple cuboidal epithelium,
water-impermeable
iii. Distal Convoluted Tubule (DCT)
- in cortex
- cuboidal epithelium
iv. Collecting Ducts
- in cortex and medulla
- drain filtrate from numerous nephrons into minor calyces
- contain cells that regulate water and Na+ reabsorption
and acid/base balance of the blood
Info about the juxtaglomerular complex (apparatus)
- regulates the rate of filtrate formation
- point of contact btw. end of ascending limb, afferent and efferent arterioles at renal corpuscle of same nephron
- parts:
a) Tubular Portion - macula densa
- modified (tall and narrow) distal convoluted tubule cells
- monitor filtrate composition
b) Vascular (Arteriolar) Portion
- afferent and efferent arteriolar portion = granular
(juxtaglomerular cells)
- modified smooth muscle cells that monitor blood
pressure
- secrete an enzyme/hormone that helps to regulate
blood pressure and ion balance
Info about ureters
- transports urine from renal pelvis to bladder
- retroperitoneal
- histology:
a) Mucosa = transitional epithelium (stretches)
b) Muscularis externa = smooth muscle
c) Adventitia = connects ureter to body wall
Info about urinary bladder
- short term storage of urine
- retroperitoneal
- histology:
a) Mucosa = transitional epithelium w/ rugae
b) Muscularis externa
- = detrusor muscle - smooth muscle
- contraction of detrusor muscle causes urination
c) Adventitia/Serosa
- mostly adventitia
- serosa covers the superior surface
Info about the urethra
Drains urine from bladder - histology:
a) Mucosa - transitions from transitional epithelium to stratified squamous epithelium
b) Muscularis externa - is smooth muscle
c) Adventitia only
2 sphincters (both surround proximal end of urethra):
a) internal urethral sphincter (smooth muscle)
- thickening of detrusor muscle at base of bladder
b) external urethral sphincter (skeletal muscle)
- in urogenital diaphragm
Transports urine, and when testes are present, also transports semen.
*See pg. 4 of notes for flow chart on filtrate movement
Look at images too
What are 2 related medical conditions?
- Urinary Tract Infection (UTI) - bacterial infection of the mucosa of the bladder and/or urethra (most common). Can also involve ureters and kidneys (less common).
- Glomerulonephritis - inflammation of the glomeruli and structures of the filtration membrane that impairs their ability to filter blood plasma.
