م يحرلا نمحرلا الله مسب

﴾لايلق لاإ ملعلا نم متيتوأ ام و﴿

ميظعلا الله قدص 58 ةيا ءارسلاا

By

Dr. Abdel Aziz M. Hussein

Lecturer of Medical Physiology

Member of American Society of Physiology

Def.,

• It is the periodic evacuation of the urinary bladder through the urethra .

Site:

The urinary bladder is a

hollow, muscular

and

distensible

or

elastic organ

that sits on the

pelvic floor

(superior to the prostate in males).

Urinary Bladder in Male



Shape and Size:

 The

size

and

shape

of the urinary bladder

varies

with the

amount

of urine it contains and with pressure it receives from surrounding organs.

Parts:

 We can divide

1) Body: urinary bladder

into: which is the major part in which the urine collects

2) Neck (posterior urethra):

connects to urethra funnel-shaped that

A) Body of Bladder: Inner cavity:

•The posterior wall of the body, immediately above the bladder neck , shows a triangular zone, called

trigone

•The apex of

trigone

joins the base marks the opening of the

bladder neck two ureters

, and its

Wall :

•3 layers 1. Mucosa and submucosa 2. Muscle layer (detrusor muscle) 3. Adventia

• Its base is

bounded

by the

opening of the 2 ureters

, while its

apex

forms the

bladder neck

. • The

two ureters

course obliquely through the detrusor muscle for

1-2 cm

underneath the mucosa before emptying into the bladder.

• When the bladder is

filled by urine

, it compresses the 2 ureters (intravesical portion of the ureters) preventing reflux of urine into the ureter.

• The

urine flow

from the kidney by

peristaltic

movement of the

ureter

one

every 6 seconds

.

1) Submucosa:

 The wall of UB is lined by a

transitional epithelium

that is continuous with that in the ureters.

 When the bladder is empty, the mucosa has numerous folds called

rugae

.

 As the bladder fills with urine these

rugae flatten out

and distend with little change in  This results in

intravesical pressure high compliance

of the bladder, so the volume of the bladder can

↑ from 10 ml

to

400 ml

with a pressure change of only

10 cm H2O

2) Submucosa:

• It supports the mucous membrane.

• It is composed of connective tissue with elastic fibers.

3) Muscle layer (Detrusor muscle):

• It is composed of smooth muscle.

• The smooth muscle fibers are interwoven in all directions and collectively these are called the

detrusor muscle

.

• It consist of a mixture of spiral and longitudinal muscle fibers • It can

increase the pressure

in the bladder to

40 – 60 mmHg

.

Bladder Neck :

• It is a

funnel shaped extension

of the body toward the urogenital triangle, to join the anterior urethra (external urethra). • The lower

2-3 cm

of the bladder neck is called the

posterior or internal urethra .

• The ms fibers in the bladder neck are arranged in

3 layers

: inner

longitudinal

,

middle circular

, and

outer longitudinal

. • The

inherent tone

of the bladder neck ms, specially the

middle layer

, prevents emptying of the bladder until the

appropriate time

for micturition .

Bladder Neck :

• The

urethra

passes through the

urogenital diaphragm

where it is surrounded by the

external urethral sphincter

(under voluntary control) used to

prevent

interrupt urination, specially in

males

, it is poorly developed in females .

or

Parasympathetic Supply Sympathetic Supply Nerve Efferents: Origin: Supply: Functions Afferents:

Pelvic nerve Hypogastric Nerve -LHCs of the S 2,3, and 4.

-Body and neck of the bladder.

a) Contraction of bladder wall.

b) Relaxation of the bladder neck → stimulation of the detrusor ms of the body causes longitudinal layers to open the bladder neck .

a) Carry input from stretch receptors in the bladder neck..

b) Detect bladder fullness.

c) Carry pain and temperature sensation.

- L1,2, and 3.

- Bladder neck.

a) Contraction of bladder neck, specially the middle layer→ facilitate the storage of urine.

b) Relaxation of the bladder wall by inhibiting the parasympathetic ganglia.

a) Transmit pain sensation b) Detect bladder fullness

The Pudendal nerves (AHCs of S 2,3,and 4)

 Its efferent fibers arise as the

nerves

from the 2 nd , 3 rd and 4 th

parasympathetic

sacral segments of the spinal cord but from the AHCs.

 They supply and control the activity of the external urethral sphincter

In healthy individuals, the bladder has two discrete phases of activity: 1. The storage phase

, when urine is stored in the bladder; and

2. The voiding phase

, when urine is released through the urethra.

• During storage, bladder pressure stays low, because nature.

of the bladder's

highly compliant

• • This property is helped by the presence of the

transitional epithelium

.

This function

is studied by a curve or plot between bladder (intravesical) pressure against the volume of fluid in the bladder (called a

cystometrogram

)

Def.

• It is a curve which studies the relationship between

intravesical pressure (IVP)

and

volume

.

Method:

•It is done by inserting a

catheter

into the bladder to fill and empty the bladder by water, and through special

transducer

, the

intravesical pressure

is recorded.

•First, the bladder is

empted

from urine and the

pressure is recorded

, then the bladder is

filled

with

50 ml water

and

the pressure

is recorded for every

↑ in the volume

.

II Ib Ia

0 100 200 300 400 500

Intravesical Volume (ml)

Ia Ib II

Long flat Initial slight rise segment Produced by the Produced Sharp rapid rise by Produced by 1 st increment of further increase further increase volume by about in volume up to in volume above 50 ml.

400 ml.

400 ml.

•

Segment I

b

of Laplace

,

pressure

which states in a spherical viscus is that the

equal to twice radius

.

is a manifestation of the the wall

tension law

divided by the • In the case of the bladder, the

increases tension

as the organ fills, but so

does the radius

.

• Therefore, the

pressure

increase is until the organ is relatively full.

slight

Micturition

Def:

It is the periodic evacuation of urinary bladder through urethra

Mechanism:

• Micturition is fundamentally a

reflex spinobulbospinal

facilitated and inhibited by

higher brain centers

and, like defecation, subject to

voluntary facilitation and inhibition

.

• •

Center

: sacral segments 2, 3 & 4.

Receptors

: stretch (receptor) in the wall of bladder.

• •

Afferent & efferent

: pelvic nerve.

Response

: 1. Contraction of detrusor muscle (body).

2. Relaxation of

internal sphincter of urethra.

3. Relaxation of

external urethral sphincter

pudendal nerve which is somatic nerve via the originating from AHC of sacral segment 2, 3, & 4.

Center

S2,3,4,

Afferents

Pelvic Nerve

Stretch receptors ↑ IVP Contraction of wall Relaxation of int. sphincter Efferent

Pelvic Nerve

Relaxation of ext. sphincter

• • • •

1) Cerebral cortex:

Motor cortex exerts a voluntary control of micturition either stimulation or inhibition.

2) Hypothalamus:

There is facilitatory area in the hypothalamus.

3) Midbrain:

Inhibition.

4) Pons:

facilitation

1. Keeping the micturition reflex partially

inhibited

all the time except when there is a desire for micturition.

2. Prevent the micturition

even when the reflex is initiated until appropriate time allows.

Voluntary Initiation of Micturition

Voluntary initiation of micturition

• Relaxation of perineal ms causing traction on the bladder • Contraction of anterior abdominal wall and diaphragm to increase intra-abdominal pressure  compressing bladder.

• • Relaxation of external urethral sphincter.

• Flow of urine in urethra  intensification of the reflex.

If the condition unfavourable,

the higher center will

delay micturition

until convenient time by: • 1) Inhibition of sacral segment of micturition.

• 2) Stimulation of external urethral sphincter.

• 3) Contractions of perineal muscle  intravesical pressure. decrease

• If the bladder fluid content exceeds 700 ml, urine starts to dribble in spite of the voluntary control

1) Tabetic bladder:

• Due to interruption of the afferent fibers  sensory atonic bladder  over flow incontinence. • Occurs in tabes dorsalis.

2- Denervated or decentralized bladder:

• There is interruption of the afferent and efferent fibers as in cauda equine lesion  shrunken and hypertrophied bladder, it can expel dripples 25-50 ml at a time.

•

3- Injury to superior frontal gyrus:

• Causes reduction in the desire to micturition, but once started it's difficult to interrupt. •

4- Transection of spinal cord:

• • • Complete transection of spinal cord affects micturition as such:

During the spinal shock

 over flow incontinence.

After recovery

 automatic bladder the U.B fill with urine, till certain volume and pressure capable of micturition reflex to be carried out in the spinal sacral centers without supraspinal influence and with conscious feeling of micturition as infants and children below 2 years.

THANKS