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Yr 3 Sem 1 > Week 6 > Flashcards

Week 6 Flashcards

1
Q

What is the urinary system made up of?

A

kidneys, ureters, bladder & urethra.

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2
Q

What is the upper urinary tract made up of?

A

Kidneys & Ureters

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3
Q

What is the lower urinary tract made up of?

A

Bladder & urethra

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4
Q

What are the functions of the kidney? (2)

A

URINE FORMATION
Filter ~1,200 mL of blood/minute

Regulates levels of fluids and electrolytes
Removes metabolic wastes, drugs and toxins

Maintains acid-base balance: H+, HCO3-

ENDOCRINE & METABOLIC FUNCTIONS
Erythropoietin: blood cell production

Renin: blood pressure regulation

Vitamin D: converts inactive form (cholecalciferol) to active form (calcitriol)

Gluconeogenesis: formation of glucose from non-carbohydrate sources

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5
Q

What are the kidneys?

A

Paired, bean-shaped structures
Reddish-brown colour

10cm (l) x 5cm (w) x 2.5 cm (d)
~130g in weight

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6
Q

What is the gross external structure of the kidneys? (2)

A

Kidney poles & surfaces:
Lateral border - convex
Medial border - concave, has a vertical cleft (renal hilum) which extends into an internal cavity (renal sinus)

Structures entering hilum: (ant. to post.)
Renal vein
Renal artery accompanied by autonomic nerves and capsular lymphatics
Renal pelvis (funnel-shaped beginning of the ureter)

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7
Q

What are the supporting tissues of the kidneys? (3)

A

Surrounding each kidney (superficial to deep):

Renal fascia
Anchors the kidney and adrenal gland to surrounding structures

Perinephric fat
Variable amount
Cushions the kidney
Helps retain its position

Fibrous capsule
Strong, transparent sheath composed chiefly by collagen & elastin

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8
Q

What is the location of the kidneys?

A

Kidneys extend approximately from T12 to L3
Lie obliquely in the paravertebral gutters

Rt kidney is crowned by the liver and sits lower than the Lt
Rib 12 overlies the upper pole of Rt kidney

Rib 11 overlies the upper pole of Lt kidney

Vertical range of movement: ~2cm (during full respiratory excursion of the diaphragm)

Retroperitoneal: the kidneys lie on the posterior abdominal wall (anterior aspect covered by parietal peritoneum)

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9
Q

What is the gross internal structure of the kidneys? (3)

A

CORTEX
Lies beneath the capsule

MEDULLA
Arranged as pyramids (cone-shaped masses), that have a papilla and base
Pyramids: striped appearance due parallel bundles of urine collecting tubules

Renal columns: inward extensions of cortical tissue that separate the pyramids
Pyramid + surrounding cortical tissue = kidney lobe (~8 per kidney)

RENAL PELVIS
Urine drains from the papillae of the renal pyramids into several minor calyces
Minor calyces converge to form 2-3 major calyces

Major calyces empty into the renal pelvis
A funnel-shaped expansion continuous with the ureter leaving the hilum

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10
Q

What is the arterial supply to the kidneys?

A

Renal arteries

Arise from aorta at the level of L1/2 IVD
Rt renal a. slightly longer than Lt

Upon entering the renal sinus, each artery divides into smaller branches:

Segmental aa –>interlobar aa –>arcuate aa –>cortical radiate aa –>afferent arterioles –>glomerular capillaries

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11
Q

What is the venous drainage of the kidneys?

A

Renal veins

Each renal vein is formed by 5-6 interlobar veins that unite at the hilum

Lt renal v. is longer than Rt
Runs over ant. surface of aorta to the IVC

Lt renal v. is joined by the Lt suprarenal v. & Lt gonadal v. before draining into the IVC

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12
Q

What is the lymphatic drainage of the kidneys?

A

Para-aortic nodes near the origin of the renal arteries

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13
Q

What is the nerve supply of the kidneys?

A

Parasympathetic: CN X Vagus
Sympathetic: T10 - 12 splanchnic nn
Visceral afferents

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14
Q

What is the basic functional unit of the kidneys?

A

Nephron

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15
Q

What is the function of a nephron?

A

Blood filtration and urine formation

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16
Q

What are the key components of the microscopic structure of the kidney? (2)

A

Renal corpuscle

Glomerulus
Glomerular (Bowman’s) capsule

Renal tubule & collecting duct

Proximal convoluted tubule
Nephron loop (loop of Henle)
Distal convoluted tubule
Collecting duct

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17
Q

What is the glomerulus?

A

A ‘knot’ of capillaries
Receives blood from an afferent arteriole and drained by an efferent arteriole

Fenestrations (capillary pores) allow for the easy formation of filtrate

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18
Q

What is the Glomerular (Bowman’s) capsule?

A

A cup-shaped hollow structure that surrounds the glomerulus, continuous with the renal tubule

Features podocytes (specialised epithelial cells with foot processes) that cling to the capillaries
Foot processes of podocytes contain filtration slits
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19
Q

What is the renal tubule composed of? (3)

A

~3cm in length

PROXIMAL CONVOLUTED TUBULE
Receives filtrate from Bowman’s capsule

Cuboidal cells lining the wall of PCT possess microvilli & abundant mitochondria
Large capacity for the reabsorption of substances

LOOP OF HENLE
Descending limb – squamous cells (THIN segment)
Ascending limb – cuboidal/columnar cells (THICK segment)

DISTAL CONVOLUTED TUBULE
Cuboidal cells lack microvilli
Conveys urine to the collecting ducts

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20
Q

What is the collecting duct?

A

Each collecting duct receives filtrate from many nephrons

Collecting ducts give the pyramids their striated appearance

Passage through the medulla allows for final adjustments to urine concentration & content

The ducts fuse together and deliver urine to the minor calyces via the renal papilla

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21
Q

What are the types of nephrons? (2)

A

Cortical

Juxtamedullary

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22
Q

What is a cortical nephron?

A

85% of nephrons
Located predominantly in the cortex

Efferent arterioles of cortical nephrons feed into a network of peritubular capillaries that cling to adjacent renal tubules

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23
Q

What is a juxtamedullary nephron?

A

Originate close to the cortex-medulla junction
Posses long nephron loops that extend deep into the medulla

These nephrons create an osmotic gradient in the medulla that allows the kidneys to create concentrated urine (more on this later!)

Efferent arterioles of juxtaglomerular nephrons feed into vasa recta – long bundles of vessels

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24
Q

What is the juxtaglomerular apparatus (complex)?

A

A region where the most distal portion of the loop of Henle lies against the afferent (and sometimes efferent) arteriole of its glomerulus

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25
Q

What are the specialised cells of the juxtaglomerular apparatus (complex)? (3)

A

Macula densa cells
Located in the wall of the tubule, act as chemoreceptors
Monitor the NaCl content of filtrate entering the DCT

Juxtaglomerular cells
Located in the arteriolar walls, act as mechanoreceptors
Contains granules of renin

Extraglomerular mesangial cells
Lie in between the tubule & arteriole
Help to regulate MD & JG cells

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26
Q

What is urine composed of?

A

95% water and 5% solutes

Normal solutes (in order of decreasing concentration): 
Urea, Na+, K+, PO43-, SO42-, creatinine, uric acid

Variable amounts: Ca2+, Mg2+, HCO3-

NITROGENOUS WASTES
Urea (breakdown of amino acids)
Uric acid (breakdown of nucleic acids)
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27
Q

What are some abnormal urinary constituents?

A

blood proteins, WBCs (pus), bile pigments, glucose, ketones

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28
Q

What are the major processes of urine formation? (3)

A

Involves three major processes:

GLOMERULAR FILTRATION
Occurs in the renal corpuscle
Produces a cell-free and protein-free filtrate

TUBULAR REABSORPTION
Selective reabsorption of substances that the body needs to keep
Healthy kidneys: 99% of water & salt; all glucose, amino acids

Anything that is not reabsorbed becomes urine
Each day: ~180L of filtrate is formed, but only ~1.5L leaves the body as urine

TUBULAR SECRETION
Selective addition of substances from blood into the filtrate

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29
Q

What is filtrate formation?

A

a passive process that relies on net outwards pressure from the glomerular capillaries into the capsular space

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30
Q

What are the filtration membrane components?

A

Endothelium of glomerular capillaries (fenestrated)
Podocytes of Bowman’s capsule (foot processes have filtration slits)
Basement membrane

Filtration membrane permits passage of molecules < 3nm in diameter
Water, electrolytes, glucose, amino acids, nitrogenous wastes

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31
Q

What is the glomerular filtration rate (GFR)?

A

volume of filtrate formed each minute by the kidneys

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32
Q

What are factors affecting GFR? (3)

A

NET FILTRATION PRESSURE (NFP)
Key determinant of NFP is the hydrostatic pressure of the glomerular capillaries (HPGC)

HPGC is the main controllable factor in the body

Most homeostatic mechanisms act on this one variable – usually by altering blood volume or changing the diameter of the afferent arteriole

TOTAL SURFACE AREA AVAILABLE*

FILTRATION MEMBRANE PERMEABILITY*
*These two factors can be impacted by disease states

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33
Q

What is normal GFR?

A

180L of filtrate per day ~ GFR of 120-125mL/min

Clinically, GFR is estimated by an equation that takes into factors including age, sex and serum creatinine
Estimated GFR (eGFR)

Normal GFR: >90 mL/min

Mild loss of kidney function: 60-89 mL/min

Kidney failure: <15mL/min

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34
Q

What are consequences of inadequate GFR?

A

Excess fluid, solutes, waste

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35
Q

How does the body maintain GFR?

A

Body possesses intrinsic and extrinsic mechanisms that maintain GFR

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36
Q

What is the intrinsic regulation of GFR? (3)

A

Autoregulation: maintenance of GFR due to mechanisms local to the kidney

Myogenic mechanism
Vascular smooth m. contracts when placed on stretch (and relaxes when not)

High systemic BP: afferent arterioles constrict to limit NFP and prevent glomerular damage
Low systemic BP: afferent arterioles dilate

Tubuloglomerular mechanism
Initiated by macula densa cells (chemoreceptors sensitive to NaCl concentration of filtrate)

High GFR: not enough time for reabsorption of NaCl from filtrate
MD cells detect the high NaCl and release adenosine (induces vasoconstriction of afferent arterioles)

Prostaglandin E2 (PGE2)
Produced by renal cells (tubules &amp; medulla) and has a paracrine function 
Maintains GFR by inducing vasodilation of afferent arterioles
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37
Q

What is the extrinsic regulation of GFR? (2)

A

Hormonal mechanism
Activation of the RAAS occurs when systemic BP (and consequently GFR) is low

Juxtaglomerular cells release renin
Renin catalyses a cascade that increases systemic BP, renal perfusion and GFR

Neural controls
Sympathetic nervous system acts upon kidneys when systemic BP is low (baroreceptor reflex)

Renal sympathetic nerves activate B1-adrenergic receptors on juxtaglomerular cells
Renin release catalyses a cascade that increases systemic BP, renal perfusion and GFR

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38
Q

What is the exception of extrinsic regulation of GFR?

A

Occurs when ECF volume is extremely low i.e. circulatory shock
Cerebral & cardiac perfusion prioritised over renal (shunting of blood)

Prolonged reduction in perfusion can result in renal damage

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39
Q

What is reabsorption?

A

Selective reclaiming of filtrate components (return from tubule back to the blood)

40
Q

Where does reabsorption occur?

A

Occurs through or between tubule cells

41
Q

Is the process of reabsorption active or passive?

A

Depending on the substance reabsorbed, the process is active (requires ATP) or passive

Active processes: primary & secondary active transport
Passive processes: osmosis, diffusion, facilitated diffusion

42
Q

What is the transport maximum (Tm)?

A

a limited amount of transport proteins are available for the reabsorption of a particular substance

43
Q

Which cells are most specialised for reabsorption?

A

Tubule cells of the PCT are most specialised for reabsorption

44
Q

What is the passive transport of reabsorption at the PCT?

A

Passive transport:
Water (65% of filtrate volume)

Ions: Cl-, K +, Ca2+

Urea (reabsorbed here, but later secreted back into filtrate)

45
Q

What is the active transport of reabsorption at the PCT?

A

Active transport:
Na +, HCO3-

Glucose, amino acids, vitamins

46
Q

What is the passive transport of reabsorption at the Loop of Henle?

A

Passive transport:
Water
Ions: Ca2+

47
Q

What is the active transport of reabsorption at the Loop of Henle?

A

Active transport:

Ions: Na+, Cl-, K+

48
Q

What is the mechanism of loop diuretics?

A

(e.g. frusemide) inhibit the transport protein for Na+/Cl-/K+ in the ascending limb
This interferes with the medullary osmotic gradient (kidneys unable to produce concentrated urine)

49
Q

Where does hormone-regulated reabsorption of water & electrolytes occur?

A

the DCT & CD

50
Q

Where is antidiuretic hormone released and what is its function?

A

Released by the posterior pituitary in response to increased ECF osmolarity (dehydrated state)

Increases the permeability of the DCT & CD to water, by inserting aquaporins (water channels) into the apical membrane of tubule cells

ADH release is reduced in the overhydrated state

Caffeine and alcohol inhibit the release of ADH

51
Q

Where is aldosterone released and what is its function?

A

Released by the cortex of the adrenal gland as part of the RAAS (initial stimulus: low blood pressure)

Aldosterone is also released in response to hyperkalaemia

Aldosterone enhances the (active) reabsorption of Na+ at the DCT & CD
Reabsorption of Na+ is coupled to K+ secretion

52
Q

Where is atrial natiuretic peptide released and what is its function?

A

ANP is produced by cardiac atrial cells and released when blood volume/pressure is elevated

Directly inhibits the reabsorption of Na+ at the DCT & CD

53
Q

What is the function of parathyroid hormone?

A

Increases the (passive) reabsorption of Ca2+ at the DCT

54
Q

What is secretion?

A

Movement of selected substances from the peritubular capillaries through the tubule cells into the filtrate

Some substances (e.g. HCO3-) are synthesised by tubule cells and secreted directly

55
Q

What are secreted substances? (4)

A

Certain drugs

Undesirable metabolites reabsorbed by passive processes
Urea, uric acid

Excess K+
Driven by aldosterone at the DCT & CD

Acids and bases (depending on blood pH)
H +, NH4+
HCO3-

56
Q

What are ureters?

A

Paired, narrow tubes with a thick muscular wall
~25 cm long

Convey urine from the kidneys to the bladder
~1,200ml per day

Upper half is in the abdomen, lower half in pelvis

Abdominal part extends from the kidney to the bifurcation of the common iliac artery

Urine is propelled by the peristaltic contractions of smooth m. as well as the filtration pressure of the glomeruli

57
Q

What is the pathway of the ureters?

A

Retroperitoneal: covered anteriorly by parietal peritoneum

They run inferiorly along the psoas m. and cross the front of the genitofemoral nerve (L1-2)

The ureters leave the psoas m. near the bifurcation of the common iliac a. and pass over the SIJ to enter the pelvis

Terminal parts pierce the posterior lateral angle of the bladder

In males, the ureters are crossed by the vas deferens before they enter the bladder.

58
Q

What is the arterial supply to the ureters?

A

Upper part: ureteric branch of the renal artery
Middle part: branches from the abdominal aorta; gonadal, common iliac & internal iliac aa
Lower part: branches from the superior and inferior vesical aa, uterine aa

59
Q

What is the venous drainage of the ureters?

A

Veins that have the same names and serve the same areas as the arteries above

60
Q

What is the lymphatic drainage of the ureters?

A

Abdominal portion: para-aortic lymph nodes,

Pelvic portion: common iliac & internal iliac lymph nodes

61
Q

What is the nerve supply of the ureters?

A

Sympathetic: T10 – L2 via renal, coeliac and hypogastric plexuses
Parasympathetic: Pelvic splanchnic nn, S2 - S4
Visceral afferents

62
Q

What is the histology of the ureters? (3)

A

MUCOSA
Transitional epithelium – continuous with the mucosae of the renal pelvis and bladder

MUSCULARIS
Internal longitudinal layer
External circular layer

An additional external longitudinal layer is present in the lower 1/3

SEROSA/ADVENTITIA
Serosa seen in aspects of the ureter in contact with peritoneum

63
Q

What is transitional epithelium and where is it found?

A

Found in the renal pelvis, ureters and bladder

Cells of the basal layer are cuboidal or columnar

Apical cells vary in appearance, depending on the degree of distension

i.e. their appearance transitions between stratified cuboidal and stratified squamous epithelia

In the relaxed state, this type of epithelium appears ~6 cell layers thick

In the stretched state (distended with urine), it appears only 2 or 3 cells thick (although the actual number of cells remains constant)

64
Q

What is the bladder?

A

A hollow organ with strong muscular walls

Serves as a temporary reservoir for urine:

Moderately full bladder holds 500mL
Max. capacity 800-1000 mL

65
Q

Where is the bladder located?

A

The size, shape and position of the bladder depends on the volume of its contents:

When empty it is situated within the entire pelvic cavity

As it distends it domes up into the abdominal cavity (a full bladder may even reach the level of the umbilicus)

Lies in front of the rectum (M) or vagina (W)

66
Q

What is the gross structure/regions of the bladder? (5)

A

APEX
Points anteriorly to the top of the pubic symphysis
Separated from the pubic bones by the potential retropubic space

Median umbilical ligament (remnant of urachus)

BASE/FUNDUS
Formed by the posterior wall and is convex

BODY
Part between the apex and the fundus

NECK
Formed where the base and two inferolateral surfaces meet

It is pierced by the urethra at the internal urethral orifice

TRIGONE (L. ‘triangle’)
A triangular region at the base of the bladder

Area between the two ureteral orifices* and the internal urethral orifice

The trigone lacks rugae (it has a smooth appearance)

*Flaps of bladder mucosa act as valves and prevent vesicoureteric reflux

67
Q

What are the 4 surfaces of the bladder?

A

1x inferoposterior (base), 2x inferolateral and 1x superior surface

68
Q

What are the bladder relations? (2)

A

Peritoneum:
The superior surface and 1 cm of the base of the bladder are the only parts covered with peritoneum

The rest of the bladder is subperitoneal and sits above the pelvic floor

Fascia:
The entire organ is surrounded by fascia known as the vesical fascia (L. ‘little blister’)

The vesical venous plexus, lies within this fascia on the side of the bladder

69
Q

Discuss the male bladder

A

Prostate gland: located below the bladder

Between the posterior surface and rectum: seminal vesicles, vas deferens, rectovesical pouch

70
Q

Discuss the female bladder

A

In females the bladder is in contact with uterus and the vagina

Uterovesical pouch: separates the bladder from the uterus in females (shallow, empty pouch).

71
Q

What is the histology of the bladder? (3)

A

MUCOSA
Bladder is lined with transitional epithelium that is thrown into numerous folds (rugae) in the relaxed state

MUSCULARIS
The smooth muscle of the bladder is referred to as detrusor muscle (L. ‘to thrust’)

Three layers of smooth muscle
Inner and outer layers of longitudinally arranged mm fibres
Middle layer of circular arranged mm fibres

These layers may be difficult to identify in the cadaver

ADVENTITIA
Variable amounts of perivesical fat

72
Q

What is the arterial supply of the bladder?

A

Branches of the internal iliac aa:

Superior vesical aa - supply the anterosuperior parts of the bladder

Supply to fundus & neck: inferior vesical aa (M) or vaginal aa (F)

73
Q

What is the venous drainage fo the bladder?

A

The names of the veins correspond to the names of the arteries

They are tributaries of the internal iliac vein

74
Q

What is the lymphatic drainage of the bladder?

A

Superior surface of the bladder drained by external iliac lymph nodes

Fundus –> internal iliac lymph nodes

75
Q

What is the nerve supply of the bladder?

A

Nerves from the vesical plexus, which is continuous with the hypogastric plexus

Parasympathetics: pelvic splanchnic n (S2-S4)
Motor supply to detruser mm and inhibitory to the internal urethral sphincter

Sympathetics (T10 - L2)
Visceral afferents

76
Q

Describe the male urethra:

A

Serves both urinary & reproductive function

~20 cm long (much longer than the female urethra)

Extends from the bladder neck to the urethral orifice at the tip of the penis
Passes through the prostate and the entire corpus spongiosum

Consists of 3/4 parts:
Preprostatic & Prostatic

Intermediate (membranous)

Spongy (penile)

77
Q

What is the prostatic urethra?

A

~2-4 cm in length

The urethra runs closer to the anterior surface of the prostate

Receives the openings of the ejaculatory ducts (the union of the vas deferens and ducts of the seminal vesicles bilaterally)

78
Q

What is the Intermediate (membranous) urethra?

A

~1-2 cm in length

Runs from the apex of the prostate to the bulb the penis, where it is continuous with the spongy urethra

Bulb of penis: expanded proximal portion of the corpus spongiosum

Surrounded by the external urethral sphincter and the perineal membrane

Located posterolaterally: the paired bulbourethral glands and their ducts (these open into the beginning of the spongy urethra)

79
Q

What is the spongy (penile) urethra?

A

Longest region ~15 cm

Passes though the bulb and corpus spongiosum of the penis

Bulbourethral ducts open into its dilated, proximal region

Many mucous-secreting glands are located along its length

Ends at external urethral orifice (narrowest part of the urethra)

Just proximal to the EUO is a short dilated region called the navicular fossa

80
Q

What is the internal urethral sphincter?

A

Formed by thickening of the detrusor smooth m. at the neck of the bladder

Involuntary sphincter (autonomic control)

SNS keeps the IUS tonically contracted
Prevents leaking between voiding, retrograde ejaculation

PNS causes the IUS to relax

81
Q

What is the external urethral sphincter?

A

Composed of striated muscle and is under voluntary control

Innervated by the perineal branch of the pudendal nerve (S2-S4)

Maintains constant muscular tone and only relaxes during micturition

It surrounds the membranous urethra where it passes through the striated muscle of the pelvic floor

The levator ani mm (voluntary m.) also contributes to urinary continence

82
Q

What is the histology of the urethra?

A

MUCOSA
Most of the male urethra is lined by transitional epithelium (typical of the urinary tract)

An exception is the navicular fossa where the epithelium is stratified squamous epithelium

This is continuous with the stratified squamous epithelium of the glans penis

Mucous-secreting glands produce a protective mucous layer.

MUSCULARIS
The urethral smooth muscle is a continuation of the involuntary smooth muscle of the bladder

83
Q

What is the arterial supply to the urethra?

A

Internal pudendal a. (from internal iliac a)

84
Q

What is the venous drainage of the urethra?

A

Internal pudendal veins

85
Q

What is the lymphatic drainage of the urethra?

A

Internal iliac, deep inguinal and external iliac nodes

86
Q

What is the nerve supply go the urethra?

A

Spongy urethra & EUS: pudendal n. (S2-S4)

Intermediate & prostatic urethra: autonomic fibres from the inferior hypogastric plexus

Sympathetic: T10-L2
Parasympathetic: Pelvic splanchnic n (S2-4)
Visceral afferents

87
Q

Describe the female urethra:

A

Serves a urinary function only
Is relatively short ~4cm (greater incidence of urinary tract infections in females)

A straight muscular tube which passes in an anteroinferior direction from the bladder neck to the external urethral orifice (EUO is anterior to the vaginal orifice and posterior to the clitoris)

Most of the urethra is embedded within the anterior vaginal wall

The walls of the urethra are in contact except during urination

88
Q

What are the 2 urethral sphincters?

A

Internal urethral sphincter

External urethral sphincter

89
Q

Describe the internal urethral sphincter

A

Located at the bladder-urethra junction, formed by the continuation of detrusor m.

Under involuntary control (autonomic nervous system)

90
Q

Describe the external urethral sphincter

A

Formed by circular, striated muscle

Surrounds the urethra where it passes through the pelvic floor

It is supplied by the pudendal nerve (S2-S4) and is under voluntary control

Levator ani mm also contribute to urinary continence

91
Q

Describe the histology of the urethral sphincters (2)

A

MUCOSA
Lined by non-keratinized stratified squamous epithelium

Mucous glands are also situated in the wall of the urethra

The largest of these are the paired paraurethral glands

PARAURETHRAL GLANDS
Are histologically homologous to the prostate gland

These glands are drained by a common duct (one on each side) just inside the external meatus or orifice

92
Q

What is the arterial supply of the urethral sphincters?

A

Upper part: Vaginal arteries

Lower part: Internal pudendal arteries

93
Q

What is the venous drainage of the urethral sphincters?

A

Into the vesical plexus  internal pudendal veins

94
Q

What is the lymphatic drainage of the urethral sphincters?

A

Drain mainly into the internal iliac lymph nodes

Some into the external iliac lymph nodes

95
Q

What is the nerve supply of the urethral sphincters?

A

IUS: autonomic nerves from inferior hypogastric plexus
Sympathetic & Parasympathetic

EUS: pudendal nerve S2-S4

96
Q

What is micturition?

A

Also referred to as urination or voiding

In infants, urination is mediated by a simple spinal reflex (involuntary control)

By age 2-3, descending circuits from higher brain centres mature enough to override reflexive urination (involves the SNS, PNS & somatic nervous system)

The micturition and storage centres are located in the pons

97
Q

What are the 3 events of micturition?

A

Contraction of the detrusor muscle
Relaxation of the IUS
Relaxation of the EUS

Yr 3 Sem 1 (7 decks)

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