LECTURE OUTLINE CHAPTER 24 Marieb
The Urinary System
Lecture Outline
I. Functions of the urinary system
A. Regulate fluid balance of the body
B. Regulate ion concentrations in the blood
C. Stabilize pH
D. Conservation of nutrients, etc.
II. Structures
A. pair of kidneys
B. pair of ureters
C. urinary bladder
D. urethra
III. Kidney structure
A. Size of bar of soap - high on body wall, under floating ribs
B. Retroperitoneal - between the body wall and peritoneum
C. Bean shaped
D. Hilus - indentation
E. Renal capsule - fibrous tunic
F. Adipose capsule -protects kidney
G. Renal fascia - anchors kidney to body wall, continuous with
peritoneum
H. Cortex - outer layer, granular appearing
I. Medulla
1. renal pyramids - terminate with a papilla, make up lobes
2. columns between pyramids
J. Pelvis
1. minor calyx - papilla empty into these which in turn drain into
2. major calyx - which empty into the pelvis
IV. Nephron – functional unit of kidney
A. Types of nephrons
1. cortical nephron - shorter, mostly in cortex of kidney, produce
"standard" urine
2. juxtamedullary nephron - "juxta-next-to" the medulla responsive to ADH, can concentrate urine
B. Microscopic structure
1. renal tubule
a. renal corpuscle = Bowman’s capsule (contains
glomerulus) - receives filtrate
i. capsular epithelium - simple squamous epithelium,
forms capsule wall and is continuous with
ii. glomerular epithelium - covers glomerulus
III. podocyte cells with pedicels- forming
iv. filtration slits
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b. proximal convoluted tubule (PCT) - primarily
reabsorptive
c. loop of Henle (nephron loop) - contains thick (near
cortex) and thin (near medulla) segments , water
absorption and ion regulation
i. descending limb
ii.. loop of g Henle
iii. ascending loop of Henle
d. distal convoluted tubule (DCT)
e. collecting tubule drains into minor calyx by way of papilla
f. juxtaglomerular apparatus - specialized cells i. macula densa - part of DCT
ii. juxtaglomerular cells - part of afferent arteriole
iii. entire apparatus secretes hormones - renin and
erythropoietin
2. vascular portion of nephron
a. afferent arteriole - larger diameter, enters
b. glomerulus i. fenestrated capillaries
ii. lamina densa - thicker than normal basement
membrane and may cover more than one capillary. If
this happens,
iii. mesangial cells - support capillary walls
iv. glomerular epithelium - formed by podocytes and
pedicels ( See above)
c. efferent arteriole - smaller diameter - leaves glomerulus
d. peritubular capillary - surrounds convoluted tubules for
reabsorption and secretion
e. vasa recta - capillaries "straight vessels" parallel the
nephron loop
B. Blood flow pattern in kidney
1. renal artery - from abdominal aorta
2. lobar ( segmental) artery to each segment of kidney
3. interlobar artery - in columns between pyramids
4. arcuate artery - at boundary between cortex and medulla
5. interlobular artery - in cortex, form afferent arterioles
6. afferent arteriole
7. glomerulus - see previous description
8. efferent arteriole
9. peritubular capillary
10. interlobular vein - as above artery
11. arcuate vein - as above artery
12. interlobar vein - as above artery
13. lobar (segmental) vein - as above artery
14. renal vein -as above artery
V. Control of kidneys
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A. Renal nerves - carry ANS
B. Hormonal
C. Autoregulation
VI. Ureters–
A. Paired muscular tubes also retroperitoneal, enter bladder at base with a
flap valve
B. Histology
1. mucosa - transitional epithelium
2. muscularis layer -inner is longitudinal, outer - circular
3. adventitia - continuous with renal capsule and peritoneum
VII. Urinary bladder
A. Behind pubis
B. Retroperitoneal
C. Structure
1. median umbilical ligament - remnants of umbilical arteries,
stabilize form superior border to umbilicus
2. internal folds - rugae - permit expansion
3. trigone - area at base bounded by openings of ureters and
urethra - without muscle - stabilized from contraction
4. neck
5. internal urethral sphincter - involuntary sphincter
D.. Histology
1. transitional epithelium
2. detrusor muscle – smooth muscle
3. rugae – folds internally
4. trigone – smooth area delineated by two ureters and urethra
(See above)
VIII. Urethra
A. External urethral sphincters
1. involuntary at base of urethra
2. voluntary at pelvic floor
B. Female - short – from base of bladder to vestibule
C.. Male
1. prostatic urethra – from base of bladder through prostate gland
2. membranous urethra – between prostate gland & base of penis
3. penile (spongy) urethra – traverses penis to orifice
D. Histology
1. male - epithelial type varies along length - transitional to
pseudostratified columnar to stratified columnar to stratified
squamous
2. female - stratified squamous epithelium
IX. Micturition reflex and urination
A. Stretch receptors (baroreceptors) in the urinary bladder - sense
distension
B. Initiate the desire to urinate
C. Combination of ANS and cerebral cortical orders coordinate
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Micturition
D. Voluntarily assisted by abdominal compression
X. Aging and the Urinary System
A. Elasticity of the urinary tract is slowly lost with age
B. Bladder requires more frequent emptying
C. Micturition is less efficient and coordinated so the bladder does not
empty completely.
D. Nephrons die and become less efficient
E. In the male problems arise from enlargement of the prostate gland
encircling and constricting the urethra.
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