Anatomy of the External Sphincter
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Questions and Answers

What role does the external sphincter play in urination?

  • It is contracted to enable urination.
  • It inhibits urination when relaxed.
  • It allows urine to pass through when contracted.
  • It must be inhibited to allow urination. (correct)

    • Which nerve is important for the control of the external sphincter during urination?

  • Lumbar nerve
  • Vagus nerve
  • Spinal nerve
  • Pedendal nerve (correct)

    • What happens when the inhibition from the brain becomes more potent than voluntary contraction signals?

  • The external sphincter remains contracted.
  • The bladder becomes overly distended.
  • Urination is prevented.
  • Urination occurs. (correct)

    • What is the role of the micturition reflex in urination control?

    <p>It facilitates the inhibition of the external sphincter.</p> Signup and view all the answers

    How does potty training affect the control over urination?

    <p>It increases inhibition from higher brain centers.</p> Signup and view all the answers

    What is primarily affected when a child's bladder becomes too full?

    <p>The spinal cord reflexes.</p> Signup and view all the answers

    Which part of the brain contains areas that can inhibit the micturition reflex?

    <p>Cerebral cortex</p> Signup and view all the answers

    What does the contraction of the external sphincter during potty training signify?

    <p>Control over the micturition reflex.</p> Signup and view all the answers

    What does voluntary urination primarily involve?

    <p>Contracting the abdominal muscles</p> Signup and view all the answers

    Urination typically results in emptying the bladder with over 20 milliliters still remaining.

    <p>False</p> Signup and view all the answers

    What kind of reflex is stimulated by stretching the walls of the bladder?

    <p>Micturition reflex</p> Signup and view all the answers

    The process of filtering liquid through the nephron is referred to as __________.

    <p>filtration</p> Signup and view all the answers

    How much urine does an average person urinate daily?

    <p>About 1 liter</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Micturition Reflex = Response to bladder wall stretching Urination = The act of expelling urine from the body Filtration = Process of removing waste from blood External Sphincter = Muscle controlling urine release</p> Signup and view all the answers

    The external sphincter facilitates urination by relaxing.

    <p>True</p> Signup and view all the answers

    The nephron is responsible for the __________ of urine.

    <p>formation</p> Signup and view all the answers

    What is primarily reabsorbed in the nephron?

    <p>Sodium and chloride</p> Signup and view all the answers

    Secretion of substances in the renal tubules is primarily done through passive transport.

    <p>False</p> Signup and view all the answers

    What happens to dangerous substances in the kidneys?

    <p>They are filtered and can be secreted into the urine.</p> Signup and view all the answers

    The process of moving substances from the blood into the renal tubules is called __________.

    <p>secretion</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Filtration = The process of removing waste from the blood Reabsorption = The process of retaining essential substances in the bloodstream Secretion = The active transport of substances into the renal tubules Glomerulus = The filtration unit of the kidney</p> Signup and view all the answers

    Which of the following substances is known to be actively secreted in excess to eliminate toxicity?

    <p>Salicylic acid</p> Signup and view all the answers

    Reabsorption occurs at a higher rate than excretion for most electrolytes in the nephron.

    <p>True</p> Signup and view all the answers

    What is the main reason for increased permeability of the glomeruli to plasma proteins?

    <p>T cell secretion of cytokines</p> Signup and view all the answers

    The __________ tubule is primarily responsible for reabsorption of many substances.

    <p>proximal convoluted</p> Signup and view all the answers

    The presence of albumin in the urine is normal and indicates healthy kidney function.

    <p>False</p> Signup and view all the answers

    What type of microscopy shows flattened podocytes in cases of increased permeability?

    <p>electron microscopy</p> Signup and view all the answers

    The podocytes are normally ______ charged, which provides a barrier to protein filtration.

    <p>negatively</p> Signup and view all the answers

    What is the most common demographic affected by glomerular permeability issues?

    <p>Young children</p> Signup and view all the answers

    Match the following forces with their correct descriptions:

    <p>Glomerular hydrostatic pressure = Pressure pushing fluid into the Bowman's capsule Colloid osmotic pressure = Pressure that pulls fluid back into the capillaries Bowman's capsule pressure = Pressure exerted by fluid in the Bowman's capsule Filtration coefficient = Measure of the efficiency of glomerular filtration</p> Signup and view all the answers

    In pathological conditions, there can be a Bowman's capsule osmotic pressure due to protein filtration.

    <p>True</p> Signup and view all the answers

    What specific protein is primarily filtered in the case of increased albumin in urine?

    <p>albumin</p> Signup and view all the answers

    What effect does an increase in Bowman's capsule pressure have on glomerular filtration?

    <p>It decreases glomerular filtration.</p> Signup and view all the answers

    The normal colloid osmotic pressure of plasma entering the glomerular capillaries is 36.

    <p>False</p> Signup and view all the answers

    What happens to the plasma protein concentration when water is filtered out?

    <p>It increases.</p> Signup and view all the answers

    In postrenal disease, such as a kidney stone, Bowman's capsule pressure can increase from ___ to ___.

    <p>18, 72</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Bowman's capsule pressure = Pressure that can affect glomerular filtration Colloid osmotic pressure = Pressure exerted by plasma proteins in the blood Hydronephrosis = Swelling of a kidney due to a build-up of urine Gonorrhea infiltration = Not typically affected by Bowman's pressure</p> Signup and view all the answers

    What is the average colloid osmotic pressure as blood exits the glomerular capillaries?

    <p>32</p> Signup and view all the answers

    Plasma proteins are found in Bowman's capsule.

    <p>False</p> Signup and view all the answers

    What is a potential cause of increased Bowman's capsule pressure?

    <p>Kidney stone</p> Signup and view all the answers

    What effect does an increase in arterial resistance have on renal blood flow?

    <p>Decreases renal blood flow</p> Signup and view all the answers

    Increasing efferent arterial resistance affects renal blood flow similar to increasing afferent arterial resistance.

    <p>True</p> Signup and view all the answers

    How does low dose dopamine affect renal perfusion?

    <p>It increases renal perfusion.</p> Signup and view all the answers

    When glomerular filtration decreases due to increased arterial resistance, this also leads to increased concentration of __________ in the plasma.

    <p>proteins</p> Signup and view all the answers

    Match the following mechanisms with their effects:

    <p>Increased arterial resistance = Decreased renal blood flow Low dose dopamine = Increased glomerular filtration rate High dose dopamine = Decreased renal perfusion Efferent resistance increase = Similar effect to afferent resistance increase</p> Signup and view all the answers

    What is the primary reason for the decrease in glomerular filtration when efferent arterial resistance is increased?

    <p>It raises plasma protein concentration</p> Signup and view all the answers

    High doses of dopamine are beneficial for renal function throughout the entire dosing range.

    <p>False</p> Signup and view all the answers

    What happens when too much resistance is applied on the arterial side of the kidneys?

    <p>Renal blood flow and glomerular filtration rate decrease.</p> Signup and view all the answers

    Study Notes

    Micturition Reflex and External Sphincter Control

    • The micturition reflex triggers urination when the bladder stretches due to filling.
    • Pedendal nerves control the external sphincter, which contracts to inhibit urination.
    • Strong inhibition from the brain can lead to urination despite voluntary contractions of the external sphincter.
    • Potty training involves teaching toddlers to control their external sphincters to avoid accidental urination.

    Brain Centers and Urination

    • Specific brain regions can inhibit or facilitate the micturition reflex.
    • The pons in the brainstem and cerebral cortex play key roles in controlling urination.
    • Potty-trained individuals rely on higher brain control over spinal reflexes for urination.

    Glomerular Filtration and Proteinuria

    • Glomeruli are typically impermeable to plasma proteins; damage can lead to increased protein excretion (proteinuria).
    • Podocytes, negatively charged cells in the glomerulus, are crucial for filtering proteins, and their damage increases albumin filtration.
    • Cytokine secretion from T-cells may cause injury to podocytes, leading to heightened glomerular permeability.

    Filtration Dynamics

    • Renal filtration is driven by the balance of hydrostatic and colloid osmotic pressures in glomeruli.
    • Increased Bowman's capsule pressure (due to obstructions like kidney stones) can reduce glomerular filtration rates.
    • Colloid osmotic pressure increases as plasma proteins concentrate, opposing filtration flow.

    Mediation of Urination and Muscle Contraction

    • Voluntary urination involves abdominal muscle contraction, increasing bladder pressure and extending walls to stimulate micturition reflex.
    • Stretch receptors in the bladder trigger further micturition reflexes and inhibit the external sphincter relaxation.

    Tubular Handling of Substances

    • The kidneys filter significant amounts of substances daily, reabsorbing most of what is filtered.
    • Some substances are neither reabsorbed nor secreted, while harmful compounds may be filtered and additionally secreted into the renal tubules.

    Importance of Secretion and Reabsorption

    • Active transport mainly mediates secretion, impacting elements like potassium and hydrogen ions.
    • Certain drugs and toxins are poorly reabsorbed, necessitating renal secretion to maintain homeostasis.

    Influence of Arteriolar Resistance

    • Increased resistance in afferent arterioles decreases renal blood flow and glomerular filtration rates.
    • Locally squeezing efferent arterioles can enhance filtration pressures initially but may lower rates due to higher colloid osmotic pressures.

    Dopaminergic Effects on Urine Output

    • Low-dose dopamine can enhance renal blood flow and filtration, while high doses may cause vasoconstriction and decrease urine output due to differing receptor effects.

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    Description

    This quiz explores the anatomy and physiology of the external sphincter, focusing on its control mechanisms and the role of the pedendal nerves. Understanding how the inhibition of vitreousion reflux impacts bladder function is crucial for grasping the overall functionality of these systems.

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