Anatomy and Physiology

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Anatomy and Physiology

• Respiratory, Liver
• and Bladder
• Melanie Shale

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Beginners guide to the Liver and gall bladder
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• The largest gland in the body
• The hepatic blood vessels enter the liver at the
  porta hepatis

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The gallbladder

• Bile leaves the liver via
• Bile ducts, which fuse into the common hepatic
  duct
• The common hepatic duct, which fuses with the
  cystic duct
• These two ducts form the bile duct

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Liver Microscopic Anatomy

• Hexagonal-shaped liver lobules are the structural
  and functional units of the liver
• Composed of hepatocyte (liver cell) plates
  radiating outward from a central vein
• Portal triads are found at each of the six
  corners of each liver lobule
• Portal triads consist of a bile duct and
• Hepatic artery supplies oxygen-rich blood to
  the liver
• Hepatic portal vein carries venous blood with
  nutrients from digestive viscera

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Liver lobes, liver lobules, hepatocytes and
portal triads
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What do hepatocytes do?

• Hepatocytes functions include
• Production of bile
• Processing blood borne nutrients
• Storage of fat-soluble vitamins
• Detoxification
• Secreted bile flows in canaliculi between
  hepatocytes toward the bile ducts in the portal
  triads
• Liver sinusoids enlarged, leaky capillaries
  located between hepatic plates
• Kupffer cells hepatic macrophages found in
  liver sinusoids

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Composition of bile

• A yellow-green, alkaline solution containing bile
  salts, bile pigments, cholesterol, fats,
  phospholipids, and electrolytes
• Bile salts are cholesterol derivatives that
• Emulsify fat
• Facilitate fat and cholesterol absorption
• Help solubilise fat and cholesterol
• Enterohepatic circulation recycles bile salts
• The chief bile pigment is bilirubin, a waste
  product of haem

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The gall bladder

• Thin-walled, green muscular sac
• Stores and concentrates bile by absorbing its
  water and ions
• Releases bile via the cystic duct, which flows
  into the bile duct

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Regulation of bile secretion

• Acidic, fatty chyme causes the duodenum to
  release
• Cholecystokinin (CCK) and secretin into the
  bloodstream
• Bile salts and secretin transported in blood
  stimulate the liver to produce bile
• Vagal stimulation causes weak contractions of the
  gallbladder
• Cholecystokinin causes
• The gallbladder to contract
• The hepatopancreatic sphincter to relax
• As a result, bile enters the duodenum
• http//www.execulink.com/ekimmel/cck_0.htm

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Production of bilirubin

• The bilirubin in blood plasma is derived from the
  breakdown of haemoglobin.
• At the end of their 120 day life span, red cells
  are removed from the circulation by the spleen
  and the hb contained within them is broken down
  to its constituent parts haem and globin.
• The haem part is converted
• to bilirubin.

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Handling of bilirubin

• As a waste product of haemoglobin breakdown and
  with no physiological functions, bilirubin must
  be removed from the body by the liver, in bile.
• The first phase in the process of bilirubin
  excretion is transport in blood plasma (bound to
  albumin) from the spleen, where it is produced,
  to the liver.

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Conjugation

• Bilirubin arriving at the liver is lipid soluble
  for excretion in bile it must first be made water
  soluble.
• This is accomplished in the hepatocytes by
  joining (conjugation) with glucuronide acid
• The process of conjugation within hepatocytes is
  dependent on a key enzyme, uridine
  diphosphate-glucuronosyltransferase (UPD-GT).

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Bile excretion

• Conjugated bilirubin is secreted from hepatocytes
  to the bile canaliculi of the liver and outwards
  in bile
• Bacterial action within the ileum and colon
  converts bilirubin to stercobilinogen.
• Finally stercobilin, the product of
  stercobilinogen oxidation, is excreted in faeces.
• A small amount of stercobilinogen is reabsorbed
  from the gastrointestinal tract back into the
  blood system and subsequently excreted in urine
  as urobilinogen.

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The Bilirubin Pathway
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The Urinary System
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Ureters

• Slender tubes that convey urine from the kidneys
  to the bladder
• Ureters enter the base of the bladder through
  the posterior wall
• This closes their distal ends as bladder pressure
  increases and prevents backflow of urine into the
  ureters

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Ureters

• Ureters actively propel urine to the bladder via
  response to smooth muscle stretch
• Ureters have a trilayered wall
• Transitional epithelial mucosa
• Smooth muscle muscularis
• Fibrous connective tissue adventitia

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Cross-sectional view of the ureter wall
Lumen
Adventitia
Circular layer
Muscularis
Longitudinal layer
Transitional epithelium
Mucosa
Lamina propria
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Urinary Bladder

• Smooth, muscular sac that stores urine
• The bladder is distensible and collapses when
  empty
• As urine accumulates, the bladder expands without
  significant rise in internal pressure
• It lies retroperitoneally on the pelvic floor
  posterior to the pubic symphysis
• Males prostate gland surrounds the neck
  inferiorly
• Females anterior to the vagina and uterus

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Position and shape of a distended and an empty
urinary bladder in an adult male
Umbilicus
Superior wall of distended bladder
Superior wall of empty bladder
Pubic symphysis
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Urinary Bladder

• The bladder wall has three layers
• Transitional epithelial mucosa
• A thick muscular layer
• A fibrous adventitia
• Trigone triangular area outlined by the
  openings for the ureters and the urethra
• Clinically important because infections tend to
  persist in this region

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Urinary Bladder
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Urethra

• Muscular tube that
• Drains urine from the bladder
• Sphincters keep the urethra closed when urine is
  not being passed
• Internal urethral sphincter involuntary
  sphincter at the bladder-urethra junction
• External urethral sphincter voluntary sphincter
  surrounding the urethra as it passes through the
  urogenital diaphragm
• Levator ani muscle voluntary urethral sphincter

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Urethra

• The female urethra is tightly bound to the
  anterior vaginal wall
• Its external opening lies anterior to the vaginal
  opening and posterior to the clitoris
• The male urethra has three named regions
• Prostatic urethra runs within the prostate
  gland
• Membranous urethra runs through the urogenital
  diaphragm
• Spongy (penile) urethra passes through the
  penis and opens via the external urethral orifice

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Urethra
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Micturition (Voiding or Urination)

• The act of emptying the bladder
• Distension of bladder walls initiates spinal
  reflexes that
• Stimulate contraction of the external urethral
  sphincter
• Inhibit the detrusor muscle and internal
  sphincter (temporarily)
• Voiding reflexes
• Stimulate the detrusor muscle to contract
• Inhibit the internal and external sphincters

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Neural Circuits Controlling Urine Storage
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Neural Circuits Controlling Micturition
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The Process of respiration
Drive from the CNS
Neuromuscular Function
Mechanics of chest wall pressure changes in
lungs
Ventilation
Transfer between alveolus and pulmonary capillary
Carriage in blood stream
Transfer from systemic capillary to tissue cell
Use in tissue cells
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Overview of the Respiratory System

• Respiration
• ventilation of lungs
• exchange of gases between
• air and blood
• blood and tissue fluid
• use of O2 in cellular metabolism

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Organs of Respiratory System

• Nose, pharynx, larynx, trachea, bronchi, lungs

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Regions of Pharynx
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Lower Respiratory Tract
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Alveolar Blood Supply