A&p Ii: Chapter 25

Front 1

FUNCTIONS OF THE URINARY SYSTEM

Back 1

A. MAINTAIN VOLUME, COMPOSITION, pH OF BODY FLUIDS
B. EXCRETION: of toxins, wastes, excesses
C. SECRETE ERYTHROPOIETIN: needed to increase the speed of RBC formation
D. CONTROL BLOOD PRESSURE: through production of RENIN
E. CONVERT VITAMIN D TO ACTIVE FORM

Front 2

KIDNEYS

Back 2

: retroperitoneal, located below diaphragm, surrounded by perirenal fat

1. EXTERNAL ANATOMY
a. ADRENAL (SUPRARENAL) GLANDS: superior to kidneys
b. RENAL CAPSULE: connective tissue covering
c. RENAL HILUS: where renal aa, vv, nerves, lymphatics & ureter enter/exit
d. PERIRENAL FAT

Front 3

KIDNEYS

Back 3

. INTERNAL ANATOMY: two tissue divisions filtering blood to produce urine
a. RENAL MEDULLA: internal tissue layer consists of
RENAL PYRAMIDS (8/kidney), each with a BASE: flat portion nearer
to exterior of kidney, and an APEX (PAPILLA): pointed region nearer to
center of kidney

b. RENAL CORTEX: outer tissue surrounding pyramids

1) RENAL COLUMNS: cortex running between renal pyramids
2) RENAL ARCHES: cortex curving around base of each renal pyramid

c. RENAL LOBE: consists of one renal pyramid with surrounding renal cortex

d. cavities that collect urine (lined with smooth m.)
1) MINOR CALYCES (calyx = s.): collect urine from each renal
pyramid
2) MAJOR CALYCES: collect urine from one or more minor calyx
3) RENAL PELVIS: collects urine from major calyces-> URETER

Front 4

URETERS

Back 4

: carry urine from kidneys to bladder. Lined with smooth m. & transitional
epithelium

Front 5

URINARY BLADDER

Back 5

sm. muscular bag (DETRUSOR m.) lined with transitional
epithelium

1. TRIGONE: triangular region in floor of bladder where urine enters from the two
URETERS and exits from the URETHRA

2. RUGAE: folds in mucosa when bladder is empty (may hold upwards of 1000 ml)

Front 6

URETHRA

Back 6

exit from bladder to outside of body.

1. FEMALE URETHRA: short, opens to exterior close to anus, prone to infections

2. MALE URETHRA: courses through penis, shared passageway for urinary and
reproductive systems, long, opens to exterior far from anus, not prone to infections;
three regions

a. PROSTATIC URETHRA: first part of urethra passes through PROSTATE
GLAND inferior to bladder.

1) EJACULATORY DUCTS: from reproductive tract empty into
prostatic urethrea

b. MEMBRANOUS URETHRA: second part of urethra, short: between prostate
and penis

c. CAVERNOUS (SPONGY OR PENILE) URETHRA: last part of urethra,
longest portion, runs through penis

Front 7

PASSAGEWAYS, OPENINGS AND SPHINCTERS OF URETHRA

Back 7

a. INTERNAL URETHRAL ORIFICE: opening to urethra from bladder

b. INTERNAL URETHRAL (URINARY) SPHINCTER: surrounds internal
urethral orifice = thickening of detrusor muscle (smooth muscle) of bladder

c. UROGENITAL DIAPHRAGM: skeletal muscle acts as an EXTERNAL
URETHRAL (URINARY) sphincter around urethra as it passes through
pelvic floor

d. EXTERNAL URETHRAL ORIFICE: opening to exterior
1) females: located anterior to vaginal orifice
2) males: located at the tip of the penis

e. LEVATOR ANI MUSCLES: skeletal muscles running between pubic bones
and external anal sphincter. When contracted, they draw the anus anteriorly
and close off the external urethral orifice, aid in preventing urination.

Front 8

MICROSCOPIC ANATOMY - NEPHRON

Back 8

* functional urine forming unit of kidney
* millions in each kidney
* not replaced after birth
* two main parts of nephron: glomerulus and renal tubule

Front 9

GLOMERULUS OF NEPHRON

Back 9

in kidney cortex (granular appearance)
1. cluster of capillaries bringing blood to nephron
2. FENESTRATED capillaries to allow hi filtration of blood
3. FILTRATE = RAW URINE

Front 10

. RENAL TUBULE

Back 10

: in cortex and medulla
1. series of tubes. Concentrate and sort through filtrate to make urine

2. BOWMAN'S (GLOMERULAR) CAPSULE: 2-layered cup surrounding glomerulus,
receives filtrate from glomerulus. First part of renal tubule.

* RENAL CORPUSCLE=BOWMAN'S CAP + GLOMERULUS

Front 11

REST OF RENAL TUBULE

Back 11

processes raw urine (filtrate) into urine. Will return
99% of filtrate back to blood.

a. PROXIMAL CONVOLUTED TUBULE (PCT): next to Bowman's.
1) primarily in cortex
2) designed for absorption from filtrate and secretion into filtrate
3) highly coiled, then dips toward medulla

b. LOOP OF HENLE: next portion of renal tubule
1) dips in and out of medulla = hairpin

2) DESCENDING LIMB (THIN SEGMENT): allows free movement of
water only

3) ASCENDING LIMB (THICK SEGMENT): allows easy movement of
solutes, no water movement.

Front 12

REST OF RENAL TUBULE

Back 12

c. DISTAL CONVOLUTED TUBULE (DCT): last nephron part
1) in cortex, highly coiled
2) designed for secretion
3) has specialized cells -> MACULA DENSA that contain
chemoreceptors responding to changes in filtrate [solute].
* MD cells influence RENIN release
* if filtrate flows fast, or if has hi [solute], secrete
vasoconstrictors -> constrict afferent arterioles decreases rate of
filtration, decreases rate of flow, increases water in filtrate

*not part of renal *d. COLLECTING DUCTS (CD): long tubes extending from cortex into
tubule medulla, receive urine from DCT's of many nephrons

*e. PAPILLARY DUCTS: terminal portion of CD's, carry urine into minor
calyces

*urine from minor calyx -> major calyx -> renal pelvis ->ureter

Front 13

. TYPES OF NEPHRONS

Back 13

1. CORTICAL NEPHRONS: (85%) mainly in cortex, short loops of Henle
2. JUXTAMEDULLARY NEPHRONS: (15%) long loops of Henle invade medulla.
Important for concentrated urine production

Front 14

. BLOOD FLOW THROUGH KIDNEY

Back 14

1. RENAL A. bring blood to kidney, profusely branch into smaller arteries then into
arterioles that form afferent arterioles

2. AFFERENT ARTERIOLES: carry blood to glomerulus
has specialized smooth m. cells -> JUXTAGLOMERULAR CELLS (JG cells)
that secrete RENIN. Also act as BARRORECEPTORS to sense changes in BP.

3. GLOMERULUS: capillary bed under high pressure: filtrate from blood enters
Bowman's capsule due to hi pressure in glommerular capillary bed

Front 15

. BLOOD FLOW THROUGH KIDNEY

Back 15

4. EFFERENT ARTERIOLES: leave glomerulus carry blood into two types of capillary
beds surrounding the nephron

a. PERITUBULAR CAPILLARIES: surround tubular nephron, absorb materials
back out of filtrate (urine)

b. VASA RECTA: capillaries following loop of Henle: in juxtamedullary
nephrons, important for keeping a concentration gradient in the kidney tissue

5. RENAL VENULES - > RENAL VEINS

Front 16

. URINE FORMATION: KIDNEYS WORK TO CONSERVE WATER/ELECTROLYTES

Back 16

*for homeostasis: maintain blood volume, concentration & pH, ensure excretion of
waste, toxins & excess materials

1. GLOMERULAR FILTRATION: non-selective (except for size), passive process

a. occurs at junction of glomerulus & Bowman's capsule

b. FILTRATE = fluid like plasma except no proteins

c. Two types of pressures drive filtration:

Front 17

NET FILTRATION PRESSURE

Back 17

difference in pressure between glomerulus
and Bowman’s capsule. Based on HYDROSTATIC PRESSURE: caused by
fluid pushing on a wall and on OSMOTIC PRESSURE: caused by large
particles in a fluid pulling water toward them

NFP = pressures out of glomerulus - pressures into glomerulus
NFP = HPg - (OPg + HPc) = 55- (30 + 15) = 10mmHg

1) glomerular hydrostatic pr: HPg = 55mmHg out
2) glomerular osmotic pr: OPg = 30mmHg in
3) capsular hydrostatic pr: HPc = 15mmHg in
4) capsular osmotic pr: OPc = 0mmHg (no prot.)

Front 18

GLOMERULAR FILTRATION RATE (GFR):

Back 18

): filtrate formed/min
1) normal = 120ml/min = 180 L/day
2) depends on
a) surface area for filtration
b) permeability of glomerulus, Bowman's capsule c) NFP (which depends on BP)

Front 19

GLOMERULAR FILTRATION RATE (GFR):

Back 19

3) maintain proper GFR to produce urine properly
a) RENAL AUTO REGULATION: MD cells release
vasoconstrictors to keep kidney BP (HPg) constant despite
changes in BP

b) RENIN-ANGIOTENSIN-ALDOSTERONE
JG cells release renin: angtiotensinogen in plasma is converted
to angiotensin II which acts as a vasoconstrictor. This increases
HPg, NFP and thus slight increase to GFR . Angiotensin II
also stimulates the adrenal cortex to release aldosterone to inc.
Na+ retention, inc. water retention, inc. blood vol & pr)

c) SYMPATHETIC NS: epinephrine stimulates vasocontsrticton
to decrease renal flow causing a slight decrease in GFR, but it
also stimulates JG cells to secrete renin to inc. HPg, NFP, and
thus slight increase in GFR

Front 20

. TUBULAR REABSORPTION

Back 20

reclaim water/useful stuff from filtrate, dec. filtrate
volume, decrease filtrate conc.

Front 21

FUNCTIONS OF RENAL TUBULE & CD IN REABSORPTION

Back 21

a. PCT: 65% of filtrate reabsorbed here
*reabsorb all glucose, uric acid, most amino acids, K+, Phosphates, Ca+,
Mg+, HCO3-
*osmosis of water (passive)
*NET RESULT: decreased volume, same conc.

Front 22

MOVEMENT IN LOOP OF HENLE DUE TO COUNTER CURRENT MECHANISM

Back 22

-involves loop of Henle and vasa recta in medulla
-loop creates concentration gradient increasing from cortex into medulla (loosely, an
increase in osmolarity is the same as and increase in concentration of solutes)
-vasa recta maintain gradient

b. DESCENDING LIMB OF LOOP OF HENLE
*HIGHLY PERMEABLE TO WATER - water leaves tubules
*NET RESULT: more concentrated, less vol.

c. ASCENDING LIMB OF LOOP OF HENLE
*IMPERMEABLE TO WATER
*ACTIVE TRANSPORT OF Na+, Cl-, PO3- to blood
*NET RESULT: same volume, less concentrated urine

d. DCT AND CD (80% of filtrate has been reabsorbed)
*filtrate entering: 20% of initial water 10% of initial NaCl
*reabsorption regulated by hormones. No hormones, no reabsorption,
DCT & CD impermeable to Na+ & H2O: urine Dilute

Front 23

*HORMONES and DRUGS AFFECTING [URINE]

Back 23

1) ADH => more conc. urine inc. water reabs., inc. active transport of
Na+ out of tubules

2) RENIN-ANGIOTENSIN-ALDOSTERONE
LO BP stim JG cells to produce RENIN stimulates formation of
ANGIOTENSIN II in blood which inc. vasoconst. to inc. BP,
stimulates adrenal cortex to release ALDOSTERONE which
stimulates Na+ and H2O reab. causing a conc. urine, inc. BP

3) ANF in response to HI BP, atria release ANF which inhibits RENIN
release, inhib. aldosterone, dilute urine, dec. BP

4) DIURETICS increase urine production
*caffeine inc. GFR
*alcohol inhibits ADH
*high glucose in urine causes water to stay there

Front 24

TUBULAR SECRETION

Back 24

: transp. of molecules/ions into urine
a. important for:
1) disposing of drugs: penicillin, phenobarbital
2) eliminating undesirable substances that have been reabsorbed (uric
acid)
3) eliminating excess K+, creatine, histamine
4) control of pH by excretion of H+
b. occurs in PCT, but mostly in DCT and CD
c. urine = filtrate - reabsorbed + secreted substances

Front 25

URINATION = MICTURITION = VOIDING = ELIMINATION

Back 25

* MICTURITION REFLEX controls urination
1. urine stretches bladder
2. stretch receptors in bladder send signals to spinal cord
3. parasymp.NS sends signals to relax internal urinary sphincter and to contract bladder
4. higher brain centers are alerted "feel the urge" and can override keeping external
sphincter closed
5. urge will subside until receptors are stimulated again

Front 26

. PHYSIOLOGICAL CHARACTERISTICS OF NORMAL URINE

Back 26

1. COLOR: clear to yellow tinged (due to bile pigments)

2. pH: slightly acidic 4.5 - 8.0
*changes with diet, inc. prot, inc. acidity (uric acid) inc. veggies, dec. acidity


3. VOLUME: 1-2 L/day more if inc. fluid intake

Front 27

. PHYSIOLOGICAL CHARACTERISTICS OF NORMAL URINE

Back 27

4. ODOR: slightly aromatic when fresh, ammonia smell when stale

5. SPECIFIC GRAVITY: how many solutes in urine (Inc. SG if inc. solutes)

SG of pure water is low = 1.0
dilute urine has low SG, is hi in H2O, lo in solutes
conc. urine has hi SG, is lo in H2O, hi in solutes
normal range = 1.001 -> 1.035

6. CONTENT: 95% water, 5% solutes, mostly urea

if have hi conc. of Ca+, Mg+, or Uric Acid, may have crystals form: RENAL
CALCULI = KIDNEY STONES

Front 28

BLOOD SCREENING TESTS FOR KIDNEY FUNCTION

Back 28

1. BUN: blood - urea - N test: nitrogen is byproduct of protein catabolism
-measures urea in plasma
-if kidneys are not filtering well have hi bun

2. PLASMA CREATINE: byproduct of skeletal muscle ATP formation
-hi [creatine] poorly working kidneys

3. RENAL PLASMA CLEARANCE (C): how fast a substance is removed from blood
by kidneys
a. hi C = efficient removal
b. lo C = inefficient removal by kidneys
*glucose clearance normally = 0, because kidneys reabsorb all glucose
and save it for body
c. C depends on: GFR, tubular secretion, tubular reabsorption