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Urinary%20System

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The kidneys perform the following functions: excretion of urea (from amino acid ... site is the glomerulus, it has afferent and efferent capillaries (no venuoles) ... – PowerPoint PPT presentation

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Title: Urinary%20System


1
Urinary System
  • Human Anatomy
  • Chapter 23

2
  • I. Kidneys
  • The kidneys perform the following functions
    excretion of urea (from amino acid breakdown),
    uric acid (nucleic acid turnover), and creatine
    (from creatine phosphate breakdown). It also
    disposes of waste and excess ions, it regulates
    blood volume and its chemical make up, it affects
    blood pressure and red blood cell formation
    (erythropoetin- hormone to stimulate blood
    production). People can survive with just one
    kidney.

3
  • A. Gross anatomy
  • 1. Location and external anatomy - The kidneys
    appear to be bean shape, both the left and right
    kidney lie against the posterior abdominal wall
    above the ilium and are protected by the lower
    two ribs. The renal hilus is the location where
    blood vessels and nerves enter the kidney.
    Superior to each kidney is the adrenal gland.

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  • The kidneys are surrounded by the renal capsule
    (dense connective tissue), the adipose capsule
    (contains perirenal fat), and the most external
    membrane is renal fascia. There is some fat that
    lies close to the kidneys called pararenal fat,
    both fat layers cushion and support the kidneys.

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  • 2. Internal gross anatomy- The following features
    can be seen with the naked eye in dissection.
    The most superficial region is the renal cortex
    which is lighter in color than the deeper region
    called the renal medulla. The renal medulla is
    divided into sections called renal pyramids, the
    renal columns (extensions of the cortex) lie in
    between the renal pyramids. The minor calices
    collect urine and merge into major calices which
    are branches that converge to form the renal
    pelvis (superior part of the ureter). The renal
    pelvis joins the ureter.

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Microscopic View of Renal Cortex (Shows
nephron)
8
Microscopic view of Renal Medulla
9
  • 3. Gross vasculature and nerve supply- The
    kidneys have a rich blood supply (see figure
    23.3, 23.9, 23.10 for summary). The largest
    blood vessels are the renal arteries and veins.
    They eventually become segmental arteries, then
    lobar, then interlobar. They narrow more and
    become arcuate, they are called interlobular
    ateries again and finally reach the nephron as
    affarent and efferent arterioles. They then wrap
    around the nephron as pritubular capillaries and
    vasa recta. As this point they are veins and
    have the same names as the ateries interlobular,
    arcuate, and renal vein. The renal plexus serves
    the nerves supply of the kidney carrying
    autonomic NS fibers. The sympathetic fibers
    control the diameters of the kidney arteries and
    influence uriniferous tubules.

10
  • 3. Gross vasculature and nerve supply- The
    kidneys have a rich blood supply (see figure 23.9
    for summary). The largest blood vessels are the
    renal arteries and veins. They eventually become
    segmental arteries, then lobar, then interlobar.
    They narrow more and become arcuate, they are
    called interlobular ateries again and finally
    reach teh nephron as affarent adn efferent
    arterioles. They then wrap aroudn the nephron as
    pritubular capillaries and vasa recta. As this
    point they are veins and have the amse as teh
    ateries interlobular, arcuate, and renal vein.
    The renal plexus serves the nerves supply of the
    kidney carrying autonomic NS fibers. The
    sympathetic fibers control the diameters of the
    kidney arteries and influence uriniferous
    tubules.

11
  • B. Microscopic anatomy of the kidneys-This
    section examines the uriniferous tubules composed
    of the nephron and the collecting tubule.
  • We will also look at urine production.
  • 1. Mechanisms of urine production- urine
    production has three stages
  • a. Filtration- blood filtrate enters the nephron,
    it resembles blood plasma and it is further
    processed to create urine. Note that normally NO
    blood cells or large proteins enter as part of
    filtrate.
  • b. Reabsorption- along the nephron beneficial
    molecules such as nutrients, water, and essential
    ions are reclaimed. These are returned into the
    blood.
  • c. Secretion- Undesired molecules are actively
    removed and passed along the tubules of the
    nephron on their way to become urine.

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  • 2. The nephron- the filtering unit of the kidney
    contain various sections that perform different
    functions.
  • a. Nephron types- cortical nephrons are the most
    abundant type. Most of the nephron is located
    within the cortex and only a small portion of the
    loop of Henle enters into the medulla. About 15
    of the nephrons are juxtamedullary nephrons
    because the Loop of Henle extends well into the
    renal medulla, these are used to produce highly
    concentrated urine.

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  • b. Renal corpuscle- this is the site of
    filtration. The network of capillaries at this
    site is the glomerulus, it has afferent and
    efferent capillaries (no venuoles). These are
    surrounded by the glomerular capsule (Bowmans
    capsule). The cells of the glomerular capsule are
    called podocytes. This site has fenestrations on
    the capillaries and filtration slits within
    podocytes, making it highly permeable.

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  • c. Tubular section-connecting to the renal
    corpuscle are the tubules responsible for
    reabsorption and secretion. First is the
    proximal convoluted tubule (cortical nephron) it
    is surrounded by peritubular capillaries. The
    proximal convoluted tubule goes into a long loop
    called the Loop of Henle. There is a descending
    and ascending limb. The ascending limb connects
    to the distal convoluted tubule which connects to
    the collecting tubules. Blood vessels in the Loop
    of Henle are called vasa recta, they are involved
    in concentrating urine.

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  • 3. Collecting tubules- these collect urine from
    several nephrons and run into the medulla where
    they merge with other collecting tubules to form
    papillary ducts that empty into minor calyces.
    When the body dehydrates the collecting tubules
    become more permeable and allow water to be
    reabsorbed, reducing urine volume and increasing
    its concentration.
  • .

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  • 4. Juxtaglomerular apparatus- a structure that
    regulates blood pressure by releasing a hormone
    called rennin as a response to falling blood
    pressure. This causes an increase in blood solute
    concentration which leads to an increase blood
    volume and thus increased blood pressure.
  • 5. Interstitial connective tissue- layers of
    connective tissue that surround the uriniferous
    tubules and contain cells that release hormones
    to influence blood pressure and red blood cell
    production

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II. Ureters Tubules that carry urine from the
kidney to the bladder. A. Gross Anatomy- about
10 inches long, runs from the renal pelvis and
reaches the bladder medially on its posterior
wall. It enters at an oblique angle to prevent
back flow. Forma two points of the trigone. B.
Microscopic anatomy- this tube has three layers
mucosa, muscularis, and adventitia. Urine reaches
the bladder through peristalsis. The muscle
contractions seem to be guided by a reflex
response.
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  • III. Urinary bladder- a muscular sac that stores
    urine. It can collapse when empty and expand
    enough to enter into the abdominal cavity. In
    males it lies anterior to the rectum and in
    females it lies anterior to the uterus and
    vagina. It also has three layers the mucosa,
    muscularis, and adventitia

30
  • IV. Urethra- a thin tube that drains the urine
    out of the body from the bladder. It is short in
    females and long in males. In females the opening
    of the urethra lies posterior to the clitoris and
    anterior to the anus. The male urethra opens at
    the tip of the penis and carries both urine and
    semen. An involuntary sphincter muscle keeps the
    urethra closed when there is no urine, a
    voluntary sphincter constricts urine flow until
    the appropriate time to void.

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  • V. Micturition- Urination or voiding occurs when
    pressure in the bladder is increased either by
    bladder muscle and/or abdominal muscle
    contraction. This action is controlled by the
    brain, the parasympathetic neurons stimulate
    contraction of the muscle to induce voiding and
    the sympathetic branch stimulates the sphincter
    to prevent micturition.

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  • VI. Disorders of the urinary system
  • A. Urinary tract infections- these are more
    common in women than in men. In women they most
    often result from intercourse because it brings
    bacteria into the urethra and spermacides kill
    the natural living bacteria in the vagina. In men
    it can arise from long-term catheterization. The
    infection can spread from the bladder up the
    ureters and to the kidneys. The symptoms include
    frequent micturition accompanied by a burning
    sensation and fever. These infections are treated
    with antibiotics.
  • B. Renal Calculi- commonly known as kidney
    stones, they form when calcium, magnesium, or
    uric acid salt precipitate and accumulate. They
    cause pain when they obstruct a ureter. Kidney
    stones are caused by different factors but one of
    them is dehydration. Treatment includes
    ultrasonic shock wave therapy.
  • C. Cancer of Urinary Organs
  • 1. Bladder cancer- five times more common in men
    than in women, the cancer arises from the
    transitional epithelial cells of the mucosa. It
    can arise from exposure to tar in tobacco smoke,
    chemicals, and artificial sweetners. Blood in
    urine is a sign of bladder cancer.
  • 2. Kidney cancer- arises from epithelial cells of
    the uriniferous tubules or renal pelvis. It is
    more common in men than in women. Risk factors
    include obesity, high blood pressure, and a high
    protein diet. By the time it is detected the
    tumor has metastasized and since it is resistant
    to cancer treatment, the person only has months
    to live.

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