Urinary system Flashcards
Kidneys
lower thoracic and upper lumbar region
Fat surrounding kidneys (3)
- Paranephric fat (pararenal fat body): located external to the renal fascia,
extraperitoneal fat of the L region, P to kidney. - Renal fascia: a membranous layer that encloses the kidneys, suprarenal glands,
and perinephric fat, sends collagen bundles through the - Perinephric fat (perirenal fat capsule): surrounds the kidneys and their vessels
Cortex and Medulla
Cortex - outermost layer of an organ
Medulla - internal portion of an organ
Both can function differently and could derive from very different embryological precursors
Organs with a defined cortex
Brain (Cerebral cortex), Kidneys, Adrenal glands, Ovaries and the Thymus gland
Organs with a defined medulla
Brain (Medulla oblongata), Kidneys, Adrenal
glands, Ovaries, Thymus gland and Hair
Adrenal medulla
- derived from neural crest
- modified ganglion
- Medullary chromaffin cells are
modified post-synaptic S neurons that secrete amine hormones: epinephrine, norepinephrine, for flight or fight response
Adrenal cortex: secretes lipid-based
steroid hormones
Derived from somatic lateral plate
mesoderm
- Zona glomerulosa – spherical clusters of
cells
- Zona fasciculata – parallel cords of cells
that contain many lipid droplets
- Zona reticularis – branching cells
Hormones
hormones secreted by the cortex are corticosteroids, which are the body’s primary steroid hormones
Hormones: Mineralocorticoids and Glucocorticoids
Mineralocorticoids: Aldosterone – related to blood volume (and thus blood pressure)
- Secreted by the Zona glomerulosa
Glucocorticoids: Cortisol – secreted by the cortex to help the body deal with stress (fasting, anxiety, trauma, infection, etc.)
- Secreted by Zona fasciculata and Zona reticularis
- Synthetic cortisol examples include cortisone and prednisone
Surface anatomy
lateral to T12-L3 vertebrae
- deep to 11th and 12th ribs
- Kidney levels change during respiration and posture alteration by 2~3 cm
vertically
Hilium
the concave surface of the kidney where vessels and nerves enter and exit
Medulla of kidneys
consists of 6+ renal pyramids which contain urine- collecting tubules (concentration
of urine by removing water)
Cortex of kidneys
composed of nephrons (responsible for urine production through filtration, resorption, and secretion)
Other internal kidney structures
Minor and major calices along with
the renal pelvis drain urine into the
ureters.
- In living persons, the renal pelvis
and calices are usually collapsed
Renal arteries and veins
- Renal arteries: arise at the IV disk level between L1 and L2; P to the renal veins.
- Renal veins: the longer left renal vein passes A to the aorta; drain into IVC
Renal Arteries (again)
divide close to the hilum into 5 segmental end arteries – vessels that do not anastomose with other segmental arteries, so the area supplied by each segmental artery is an independent, surgically resectable unit called a renal segment
Urine production
Occurs at nephrons: nephrons have two parts corpuscles and tubules
Corpuscle is the site of filtration
Tubules are responsible for resorption and secretion
kidneys usually have +1,000,000 nephrons: are lined with simple epithelium
Urine excretion
Urine leaves the collecting system.
- Enters the renal pelvis.
- The remainder of the urinary system transports, stores, and eliminates urine
Ureters
muscular ducts extending from the renal pelvis to the bladder (~25-30 cm), runs IM along transverse processes of L vertebrae, cross external iliac artery, runs along L wall of pelvis, -> bladder, Oblique entry into bladder prevents backflow of urine, any increase in pressure within bladder
compresses wall and closes distal ureters
Ureter constriction site
- at the junction with the renal pelvis
- site of crossing the pelvic brim
- passage through the bladder wall
Bladder
hollow collapsible organ with strong muscular walls composed of the detrusor
muscle, retroperitoneal, enveloped by
loose CT, S surface covered by peritoneum, apex (anterior end), fundus, body (lies between the apex and fundus), and neck
More about the bladder
empty bladder lies entirely within the lesser pelvis, has the shape of inverted pyramid, when filled, it ascends S in extraperitoneal tissue of AAW -> GP. Male: mf form involuntary internal urethra sphincter
Female urethra
3-4 cm length, 6 mm. diameter, passes from the IUO of the bladder to the EUO in vestibule of vagina; musculature surround IUO not organized into internal sphincter.
- Trigone: smooth triangular region defined by the ureteric orifices and IUO
Male urethra
18-22 cm. length, (4) regions:
1. Intramural (preprostatic) – surrounded by an IUS composed of S innervated SM
2. Prostatic urethra - passes through prostate gland.
3. Intermediate (membranous) urethra – surrounded by somatic innervated EUS
4. Spongy (penile) urethra - passes through length of penis
