The Lower Urinary Tract Flashcards
Once urine leaves the medulla and enters the minor calyx is it modified anymore?
- no
Once urine leaves the medulla and enters the minor calyx it does not get modified anymore, which means that the epithelial tract are impermeable to H2O and electrolyes. What type of epithelial cells line the walls of the urinary tract?
- transitional epithelium
- a type of stratified epithelium
- these cells contract and expand in order to adapt to the degree of distension needed
Once urine leaves the medulla and enters the minor calyx it does not get modified anymore, which means that the epithelial tract are impermeable to H2O and electrolyes. Transitional epithelium, a type of stratified epithelium line the urinary tract and are able to contract and expand in order to adapt to the degree of distension needed. Why are these cells also good if there is a blockage in the kidney?
- they are able to distent and dilate
- accomadates the back up of urne
Once urine leaves the medulla and enters the minor calyx it does not get modified anymore, which means that the epithelial tract are impermeable to H2O and electrolyes. Transitional epithelium, a type of stratified epithelium line the urinary tract and are able to contract and expand in order to adapt to the degree of distension needed. The cells in the renal pelvis then stretch causing dilation and distention to accomadates the back up of urne. This stretch then causes what?
- triggers peristaltic contractions starting at the hilum
- aims to move out of renal pelvic, down ureter and towards the bladder
When urine needs to move down the ureters, there are peristaltic contractions, also known as (vermiculation) similar to GI tract. What are the orientations of smooth muscle that facilitate the process of peristaltic contractions in the ureters?
-
- longitudinal and circular smooth muscle
- create successive peristaltic waves
When urine needs to move down the ureters, there are peristaltic contractions, also known as (vermiculation) similar to GI tract. SUccessive peristaltic waves from longitudinal and circular smooth muscle faciliate the movement of urine. How do curcular and longitudinal muscles work together?
- longitudinal muscle contracts first followed by circular muscle relaxation
- longitudinal muscle then starts to relax allowing a bolus to form followed by circular muscle contraction which pushes against the bolus
In ureters there is a mucosal layer that is lined by transitional epithelium, which impermeable to H2O and electrolytes. What is this mucosa supported by?
- inner longitudinal muscles (L)
- outer circular/spiral muscle (C)
- extra outer layer of longitudinal muscle
When urine needs to be moved through the ureters to the bladder dilation of renal pelvis generates action potential from hilar pacemaker cells. The number of action potentials can be acted on by the autonomic nervous system. What do the parasympathetic and sympathetic nervous system do to the number of action potentials for peristalsis?
- parasympathetic = enhances action potentials
- sympathetic = inhibits action potentials
Does the bladder attach to the anterior or posterior abdominal wall?
- posterior
What is the name of where the ureters enter the bladder and is this a two way junction or one way junction for urine direction?
- vesico-ureteric junction
- small flaps of mucosa cover these openings and act as valves that allow urine to enter the bladder but prevent it from leaving
Where is the fundus and neck of the bladder?
- fundus = the body of the bladder
- neck = where the urether leaves the bladder
What is the name of the outer muscle layer of the bladder and does it have the same muscle origentation all the way around?
- called Detrusor Muscle layer
- composed of longitudinal and circular muscles
What type of cell lines the inner mucosa of the bladder and why?
- transitional epithelial cells
- these cells can be folder up to reduce the bladder size, creating rugae
- allow for dilation and stretching
There is a triangle shape that is formed from the openings of ureters and entrance to urethra. What is this called?
- trigone
There is a triangle shape that is formed from the openings of ureters and entrance to urethra called the trigone. What are the 2 main functions of the trigone?
1 - acts as a funnel
2 - contains stretch receptors. Once stretched past a certain degress they signal the need to pass urine
What is the rough capacity of the bladder and how is it activated to release?
- 1L
- parasympatheitc activity stiumlates contraction of the bladder to release urine
To ensure control of the bladder and its urine content there are 2 urethal sphincters. What are these called working from inside to outside the bladder?
1 -internal urethral sphincter
2 - external uretheral sphincter
To ensure control of the bladder and its urine content there are 2 urethal sphincters, the internal and external uretheral sphincters. What is the composition and role of the internal uretheral sphincter?
- band of smooth muscle (detrusor) muscle
- normal tone keeps neck of bladder and urethra free of urine
To ensure control of the bladder and its urine content there are 2 urethal sphincters, the internal and external uretheral sphincters. What is the composition and role of the external uretheral sphincter?
- composed of circular band of skeletal muscle where urethra passes through urogenital diaphragm
- acts as a valve with resting muscle tone
- voluntary relaxation permits micturition (action of urinating)
To ensure control of the bladder and its urine content there are 2 urethal sphincters, the internal and external uretheral sphincters. Out of the internal and external uretheral sphincter, which is under voluntary and involuntary control?
- internal uretheral sphincters = involuntary
- external uretheral sphincters = voluntary
In females, the urethra is located where?
- between clitoris and vagina
In females, the urethra is located where between the clitoris and the vagina. It is much shorter than the urethra in males, making females more susceptibel to what?
- UTIs
In females, the urethra is located between the clitoris and the vagina. It is much shorter than the urethra in males, making females more susceptibel to UTIs. In addition the external sphincter is not as well developed in females. What can this cause following pregnancy or trauma?
- incontinence (loss of bladder control)
In males the urethra has to pass through what gland and another site?
- passes through the prostate
- then passes through the uro-genital diaphragm and into the penis
Why are men less likley to contract a UTI than women
- longer urethra
In 50% of men over 60 years what can happen to the prostate?
- prostate gland enlarges
- hypertrophy of detrusor muscle
- may require surgical or hormone treatment
In 50% of men over 60 years the prostate gland enlarges due to hypertrophy of detrusor muscles, which may require surgical or hormone treatment. What else is, in relation to the prostate is common in older men?
- prostate cancer
one of the commonest cancers with mortality rate of 3%
Micturation (passing of urine) is a 2 stage process. What are the 2 stages?
1 - bladder fills until pressure within bladder reaches a threshold
2 - “micturition reflex” occurs presenting as a conscious desire to urinate
Micturation (passing of urine) is a 2 stage process. Where the micturation reflex triggers the need to urinate. This is an autonomic reflex controlled by higher centres in the brain, but what 2 things can happeb following this higher centre stimulation in the brain?
1 - inhibited by higher centres in the brain, causing contraction of external sphincters
2- facilitated by cortical centres in the brain that initiate the micturition reflex and relax the external sphincter, causing the internal sphincter to relax at the same time and urination occurs
In the figure belowe the dashed lines denote pressure peaks (micturition contractions) that are periodic reflex contractions of short duration which occur as the bladder is filling. At this point does micturation have to occur?
- no
- contractions tell you bladder is filling
In the figure belowe the red solid line denotes the normal intrinsic tone of the detrusor muscles of the bladder. As the red solid line increases the pressure inside the bladder increases and the number and intensity of the micturation contrations increases, what then follows?
- micturation (passing of urine)
The intravesicle pressure increases in the bladder as it fills with urine. During normal hydratiom, how quickly does the bladder fill?
- 1ml/min
The bladder is innervated by the sympathetic nerves. Which nerve provides this innervation, and where does this originate from in the sympathetic trunk?
- hypogastric nerve
- T12-L3
The bladder is innervated by the sympathetic nerves, specifically the hypogastric nerve which originates from the sympathetic chain at T12-L3. Does this provide voluntary or involuntary control and what effect does this have on micturation?
- involuntary control
- inhibits micturation (dont need to urinate in fight or flight)
The bladder is innervated by the para-sympathetic nervces. Which nerve provides this innervation, and where does this originate from in the spine?
- pelvic nerve
- S2-S4
Once the bladder stretch receptors are activated with filling of the bladder, what do they innervate, and what does this do to the bladder?
- pelvic nerve (afferent and efferent signals)
- periodic contractions of the detrusor muscle of the bladder
- relaxation of the internal sphincter
Once the bladder stretch receptors are activated with filling of the bladder, they innervate the pelvic nerve (afferent and efferent signals) which then starts periodic contractions of the detrusor muscle of the bladder and relaxation of the internal sphincter. When the bladder fills to a certain limit, the bladder stretch receptors ensure that bladder contractions supersede the micturation contractions. This then provides a full bladder sensation. Where does this signal in the brain and what does this cause?
- full bladder sensation
- message recieved by the thalamus in the brain stem and onto the cerebral cortex
- desire to urinate starts to increase
In a normal bladder, the stretch receptors are activated by filling of the bladder which innervates the pelvic nerve and initiate micturation contractions. In patients who are incontinent the hypogastric nerve and pudendal nerve is also innervated, what 3 things does this do to the bladder?
1 - bladder contractions are inhibited
2 - internal urethra sphincter contracts and remains closed
3 - external urethra sphincter contract and remains closed
Paraplegia is when the nerves are completely severed from the cerebral cortex. What does this do to bladder control?
- cortical control (voluntary control) is lost
- micturition reflexes return
- patients have periodic but unannounced bladder emptying – “Automatic bladder” = patients have no control over this
Partial spinal cord damage can cause problems with bladder control. The pelvic nerve and hypogastric nerve continue to send signals from the bladder. What is a common dysfunction that can occur?
- micturation signals sent that bladder is filling
- loss of inhibitory descending signals from medulla
- frequent urination as excitatory impulses from cerebral cortex remain unopposed
- known as “Overactive/Uninhibited bladder” (lots of passage of urine even when bladder not full)
In spinal crush injuries, the dorsal root of the nerve can be damaged. If the pelvic afferent nerves are damaged, what can this cause?
- loss of afferent nerves (telling body bladder is filling with micturation contractions)
- bladder fills to capacity and overflows referred to as “overflow incontinence” or “Atonic bladder” with no warning
When stretch receptors are stimulated the send signals via the pelvic nerve. This inturns via efferent neurons initiates micturation contraction through acetycholine (ACh) release. This release of ACh triggers detrusor muscle contraction and involuntary internal sphincter relaxation. If a patient is suffering with incontinance how can this be treated?
- use a drug to block ACh
- cuases retention
What is reflux nephropathy?
- kidney damage (nephropathy)
- bladder contracts and urine flows backward (reflux) from the bladder
Obstructive uropathy refers to a blockage in the urinary tract. This can occur anywhere in the urinary tract. Bladder outflow obstruction can also occur, what are the three most common causes of bladder outflow obstruction?
1 - enlarged prostrate (older men)
2 - posterior urethral valve = external valve overgrows and needs operating on
3 - urethral stricture can be caused by inflammation (narrowing)
What are the two common methods to treat acute urinary retention?
1 - catheterisation
2 - surgery
What are sacral nerve stimulators?
- stimulators are implanted into patient
- send stimulation to sacral nerves for innervation
When the bladder has some urine in it, the stretch receptors are stimulated. They send a signal to the S2-S4 spinal nerves to initiate mictuation contractions of the bladder. The sympathetic system innervates what in the detrusor muscles and what does this do?
- the same stretch receptors signal the hypogastric nerve
- hypogastric nerve innervates the B3 receptor on detrusor muscles signalling to relax
When the bladder has some urine in it, the stretch receptors are stimulated. They send a signal via the pelvic nerve to the S2-S4 spinal nerves to initiate mictuation contractions of the bladder. The same stretch receptors signal the sympathetic innervation via the hypogastric nerve at T12-L3, which innervates the B3 receptors on the detrusor muscles signalling the bladder to relax. What else does the hypogastric nerve stimulate in the bladder at the same time to stop urination?
- hypogastric nerve innervates the a1 receptors located on the internal urethra sphincter
- internal urethra sphincter contracts and urine cannot pass
When the bladder has some urine in it, the stretch receptors are stimulated. They send a signal to the S2-S4 spinal nerves to initiate mictuation contractions of the bladder. The same stretch receptors signal the sympathetic innervation, which innervates the B3 receptors on the detrusor muscles signalling the bladder to relax. The hypogastric nerve also innervates the a1 receptors located on the internal urethra sphincter causing the internal urethra sphincter to contract and urine cannot pass. In addition the micturinic centre located in the pons is able to send innervation to the S2-S4 nerves to innervate something that comes under voluntary control, what is this?
- pudendal nerve at S2-S4 is innervated
- innervates the nicotinic receptors at the external urethra sphincter
- allows us to have voluntary control over if we pass urine
If we have a full bladder the stretch receptors in the bladder will begin firing at a much faster rate than when we have a partially full bladder. Where will these signals be sent?
- sent to the pons micturation centre and bypass the thoracic nerves which stimulate the hypogastric nerves
If we have a full bladder the stretch receptors in the bladder will begin firing at a much faster rate than when we have a partially full bladder. This signal is sent to the pons micturation centre and bypass the thoracic nerves which stimulate the hypogastric nerves. What does the pons micturation centre then do to the sympathetic control of the bladder, specifically the B3 receptors on the detrusor muscles and the a1 receptors on the internal urethera sphincter?
- inhibits these receptors
- detrusor muscles relax and sphincter opens
If we have a full bladder the stretch receptors in the bladder will begin firing at a much faster rate than when we have a partially full bladder. This signal is sent to the pons micturation centre and bypass the thoracic nerves which stimulate the hypogastric nerves. The pons micturation centre then inhibits the B3 receptors on the detrusor muscles and the a1 receptors on the internal urethera sphincter causing them to relax and open, respectively. What do the same signals from the pons micturition centre do to the M3 receptors on the destrusor muscles and nicotinic receptors on the external urethra sphincter?
- activate M3 receptors causing detrusor muscle contractions
- inhibition of nicotinic receptors causing the external urethra sphincter to open
