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40.Autonomic innervation of the abdominal and pelvic organs. The cartilage tissue. Fetal membranes. Umbilical cord. Amniotic fluid. Fetal circulation.

10 Jan

Autonomic innervation of the abdominal and pelvic organs. The cartilage tissue. Fetal membranes. Umbilical cord. Amniotic fluid. Fetal circulation.

Anatomy: Autonomic innervation of the abdominal and pelvic organs.

Autonomic Nervous Supply (Ashwell)

  • The sympathetic supply includes:
  1. Greater splanchnic nerve (T5-9)
  2. Lesser splanchnic nerve (T9-10)
  3. Lowest (least) splanchnic nerve (T12)
  4. Lumbar splanchnic nerves (L1-3)
  5. Sacral splanchnic nerves
    • primarily pre-ggl SNS fibers that come off the chain, synapse in inf hypogastric plexus
  • The parasympathetic supply includes:
  1. Vagus nerve
  2. Pelvic splanchnic nerve (S2-4)
    • only splanchnic n that carry PNS fibers
    • all others have SNS fibers
    • contribute to formation of pelvic (inf hypogastric) plexus, supply => desc colon, sigmoid colon, other viscera in pelvis and perineum
  • These project to the paravertebral plexuses, which are situated anterior to the aorta and vertebral column.

Paravertebral Plexuses



Coeliac Plexus

  • This contains the paired coeliac ganglia and is located at the level of the last thoracic and 1st lumbar vertebra.
  • It surrounds the root of the coeliac trunk and the superior mesenteric artery.
  • The coeliac ganglia are paired structures, which lie between the suprarenal glands and the coeliac trunk origin.
  • The lower part is partially detached and is sometimes referred to as the aorticorenal ganglion as it forms most of the renal plexus.
  • Secondary plexuses derived from or connected to the coeliac are the phrenic, splenic, left gastric, intermesenteric (aortic), suprarenal, renal, gonadal, superior mesenteric and inferior mesenteric.

Phrenic Plexus

  • This accompanies the inferior phrenic artery to the diaphragm and suprarenal gland.

Hepatic Plexus

  • This is the largest coeliac derivative and receives filaments from both the right and left vagus as well as from the phrenic nerves.
  • It accompanies the hepatic artery and the portal vein and their branches and also supplies the cystic plexus to the gallbladder.
  • Branches may also supply the pylorus, greater curvature of stomach as well as the lower bile duct, pancreatic head and 1st and 2nd part of duodenum.

Left Gastric Plexus

  • This goes to the lesser curvature of the stomach.

Splenic Plexus

  • This is formed by branches of the coeliac plexus, left coeliac ganglion and the right vagus.
  • It supplies the blood vessels and smooth muscles of the splenic capsule and trabeculae.

Suprarenal Plexus

  • This supplies the medulla of the suprarenal gland.

Renal Plexus

  • This is formed by fibres from the coeliac ganglion and plexus, aorticorenal ganglion, lowest thoracic splanchnic nerves, 1st lumbar splanchnic nerve and the aortic plexus.
  • It gives off the ureter and gonadal plexuses (ovarian or testicular).
  • The ureteric plexus accompanies the ureter and the gonadal plexuses accompany the appropriate artery to the respective organs.

Superior Mesenteric Plexus

  • This is a downward extension of the coeliac plexus.
  • It accompanies the superior mesenteric artery to the pancreas, small intestine (duodenum, jejunum and ileum), and large intestine as far as the left trisection of the transverse colon.

Abdominal Aortic Plexus (intermesenteric)

  • This supplies the IVC, and testicular plexuses as well as connecting the superior and inferior mesenteric plexuses.

Inferior Mesenteric Plexus

  • This receives supply from the aortic plexus and 2nd and 3rd lumbar splanchnic nerves.
  • It supplies the colon from the left trisection of the transverse colon to the rectum.

Superior Hypogastric Plexus

  • This is situated anterior to the aortic bifurcation, L5 and the sacral promontory.
  • This plexus is formed from branches of the aortic plexus, 3rd and 4th lumbar splanchnic nerves.
  • It divides into the left and right hypogastric nerves, which descend to the 2 inferior hypogastric plexuses, which lie anterior to the sacrum.
    • lies in extraperitoneal CT lat to rectum
    • sends br to sigmoid, desc colon
  • located retroperitoneally
  • has preggl/post ggl SNS fibers, visc aff fibers + PNS fibers (few), which may run a recurrent course thru inf hypogastric plexus

Inferior Hypogastric Plexus

  • This is formed from the pelvic splanchnic nerves (from the sacral plexus, S2-4) and also receives the sacral splanchnic nerves., and hypogastric n
  • lies against post/lat pelvic wall
  • lat to rectum, vagina, base of bladder
  • contains pelvic ggl = where SNS, PNS preggl fibers synapse
  • Several plexuses arise from the inferior hypogastric plexuses, including:
  1. Middle rectal plexus
  2. Vesical plexus
  3. Prostatic plexus
  4. Uterovaginal plexus
  5. Deferential plexus



Histology: The cartilage tissue.

Embryology: Fetal membranes. Umbilical cord. Amniotic fluid. Fetal circulation.

Fetal Membranes

Around the beg of 2nd month, villi system in trophoblast layer consists mostly of sendary & tertiary villi

consists mostly of secondary/tertiary villi
As development continues – more primitive villi will grow as extensions of exisitng ones
some of the cytotrophoblast cells /CT  will disappear – leave just syncyticum, endothelium lining of capillaries as barrier b/w fetal and maternal circulations = syncytial knots

Villi system covers the entire span of chorion @ early stages of development
However, w/ time changes will occur on diff poles of the embryo
1. villi on embryonic pole will continue to grow creating = chorion frondosum –> fetal portion of placenta
2. villi on abembryonic pole will degenerate leaving a smooth side = chorion laeve

From maternal side, b/w 3 deciduas which are functional layers of endometrium
1. Decidua basalis – in contact w/ chorion frondosum, decidual cells w/ lipids, glycogen
2. Decidua capsularis – covering abembryonic pole, will later degenerate when embryo grows
3. Decidua parietalis – covering opp side of uterine wall, will fuse w/ amnion & chorion laeve

Once amnion/chorion laeve unite – they form amniochroionic membrane which destroys chorionic cavity

Amnion & Umbilical Cord

Umbilical Cord
@ 5th week, opening can be found connecting amnion & ectoderm = primitive umbilical ring
a) Yolk sac stalk (= vitelline duct) along w/ vitelline vessels
b) Canal connecting intra/extra embryonic cavities
c) Connecting stalk: allantois, umbilical vessels (2 arteries, v)

Amniotic cavity will expand, eventually getting rid of chorionic cavity
this pushes vitelline duct & connecting stalk until they join = primitive umbilical cord
Prox = allantois *urachus*, intestinal loops
Distal = vitelline duct, umbilical a/v

During growth of abdominal organs, abdominal cavity isn’t big enough for organs, so intestinal loops push into umbilical cords = umbilical herniation
Come out again @ end of 3rd month
vitelline vessels are obliterated

Only umbilical vessels, and Wharton’s jelly left inside – jelly has many PGs, and protects the a/v

Amniotic fluid

formed by amnioblasts (cells from epiblast that line amniotic cavity) & maternal blood
replaced every 3 hours – sterile because waste products are filtered out

  • shock absorbance
  • prevents adhesion of embryo to amnion
  • allows fetal movement

@ fifth month, organ systems begins to function, fetus swallows the amniotic fluid, also produces urine into it (which is mostly water – as mentioned b4 placenta filiters it out)

Fetal Circulation

Anim = Fetal Circulation and Baby’s First Breath

Anim2 = The Wonders of Fetal Circulation

  • Introduction
  • Throughout the fetal stage of development, the maternal blood supplies the fetus with O2 and nutrients and carries away its wastes.
    • These substances diffuse between the maternal and fetal blood through the placental membrane.
    • They are carried to and from the fetal body by the umbilical blood vessels.
  • Adaptations of fetal blood and vascular system.
  • The concentration of hemoglobin in fetal blood is about 50 % greater than in maternal blood.
  • Fetal hemoglobin is slightly different chemically and has a greater affinity for O2 than maternal hemoglobin.
    • At a particular oxygen partial pressure, fetal hemoglobin can carry 20-30% more O2 than maternal hemoglobin.
  • Fetal Circulation OH-98
  • In the fetal circulatory system, the umbilical vein transports blood rich in O2 and nutrients from the placenta to the fetal body.
    • The umbilical vein enters the body through the umbilical ring and travels along the anterior abdominal wall to the liver.
      • About 1/2 the blood it carries passes into the liver.
      • The other 1/2 of the blood enters a vessel called the ductus venosus which bypasses the liver.
    • The ductus venosus travels a short distance and joins the inferior vena cava.
      • There, the oxygenated blood from the placenta is mixed with the deoxygenated blood from the lower parts of the body.
      • This mixture continues through the vena cava to the right atrium.
    • In the adult heart, blood flows from the right atrium to the right ventricle then through the pulmonary arteries to the lungs.
      • In the fetus however, the lungs are nonfunctional and the blood largely bypasses them.
    • As the blood from the inferior vena cava enters the right atrium, a large proportion of it is shunted directly into the left atrium through an opening called the foramen ovale.
      • A small valve, septum primum is located on the left side of the atrial septum overlies the foramen ovale and helps prevent blood from moving in the reverse direction.
    • The rest of the fetal blood entering the right atrium, including a large proportion of the deoxygenated blood entering from the superior vena cava passes into the right ventricle and out through the pulmonary trunk.
      • Only a small volume of blood enters the pulmonary circuit, because the lungs are collapsed, and their blood vessels have a high resistance to flow.
        • Enough blood reaches the lung tissue to sustain them.
    • Most of the blood in the pulmonary trunk bypasses the lungs by entering a fetal vessel called the ductus arteriosus which connects the pulmonary trunk to the descending portion of the aortic arch.
      • As a result of this connection, the blood with a relatively low O2 concentration which is returning to the heart through the superior vena cava, bypasses the lungs.
      • At the same time, the blood is prevented from entering the portion of the aorta that provides branches leading to the brain.
    • The more highly oxygenated blood that enters the left atrium through the foramen ovale is mixed with a small amount of deoxygenated blood returning from the pulmonary veins.
      • This mixture moves into the left ventricle and is pumped into the aorta.
        • Some of it reaches the myocardium through the coronary arteries and some reaches the brain through the carotid arteries.
    • The blood carried by the descending aorta is partially oxygenated and partially deoxygenated.
      • Some of it is carries into the branches of the aorta that lead to various parts of the lower regions of the body.
      • The rest passes into the umbilical arteries, which branch from the internal iliac arteries and lead to the placenta.
        • There the blood is reoxygenated.
  • The Newborn
  • The initial inflation of the lungs causes important changes in the circulatory system.
  • Inflation of the lungs reduces the resistance to blood flow through the lungs resulting in increases blood flow from the pulmonary arteries.
    • Consequently, an increased amount of blood flows from the right atrium to the right ventricle and into the pulmonary arteries and less blood flows through the foramen ovale to the left atrium.
  • In addition, an increased volume of blood returns from the lungs through the pulmonary veins to the left atrium, which increases the pressure in the left atrium.
    • The increased left atrial pressure and decreased right atrial pressure (due to pulmonary resistance) forces blood against the septum primum causing the foramen ovale to close.
    • This action functionally completes the separation of the heart into two pumps–right and left sides of the heart.

  • The closed foramen ovale becomes the fossa ovalis.
    • The ductus arteriosis, which connects the pulmonary trunk to the systemic circulation, closes off within 1-2 days after birth.
      • Once closed, the ductus arteriosus is replaced by connective tissue and is known as the ligamentum arteriosum.

  • If the ductus arteriosus does not completely close it is said to be patent.
    • This is a serious birth defect resulting in marked elevation in pulmonary pressure because blood flows from the left ventricle to the aorta, through the ductus arteriosus to the pulmonary arteries.
    • If not corrected, it can lead to irreversible degenerative changes in the.heart and lungs.
    • The fetal blood supply passes to the placenta through two (2) umbilical arteries from the internal iliac arteries and returns through an umbilical vein which passes through the liver, ductus venosus, and joins the inferior vena cava.
      • When the umbilical cord is cut, no more blood flows through the umbilical arteries and vein and they degenerate.

  • The remnant of the umbilical vein becomes the round ligament of the liver and the ductus venosum becomes the ligamentum venosum.