What is the enteric NS?
'Brain of the gut', consisting of more than 100m intrinsic neurones that extend most of the GIT
How is the ENS arranged?
In ganglionated plexuses with interconnecting bundles of unmyelinated nerve fibres
What does the ENS allow the GIT to do?
Perform basic reflex functions of secretion, absorption, mixing and gut movements without the influence of CNS or ANS
How does the CNS communicate with the ENS?
Via para/sympathetic nerves with intrinsic neurones of ENS to bring about modulation GIT functions
Where do axons of intrinsic neurones of ENS project to?
Sympathetic ganglia, pancreas, gall bladder, trachea, spinal cord and brain stem
What is the general plan of the GIT? FITB
Where is the ENS distributed?
Intrinsic network of neurones is in the tissues of the gut wall from oesophagus to anus
Where does the ANS innervate?
It has 2 divisions which innervate organs of abdomen and pelvis
Where does the ANS arise from?
Different anatomical regions of CNS -> sympathetic arising from spinal cord segments T1-L2 and the parasympathetic system arising from cranial nerves III, VII, IX and X and spinal cord segments S2-4
What is the function of the efferent autonomic nerves in the abdomen?
Motor to smooth muscle and secretomotor to glands
What is the function of the afferent autonomic nerves in the abdomen?
Sympathetic: pain Parasympathetic: specific functional sensation (stretch)
What are the sympathetic nerves to the abdomen? FITB
At what spinal level does the greater splanchnic nerve emerge?
At what spinal level does the Lesser splanchnic nerve emerge?
At what spinal level does the least splanchnic nerve emerge?
Where does the parasympathetic supply come from in the organs of the abdomen and pelvis?
Vagus nerve (CNX) and sacral outflow (S2-4)
How are the sympathetic autonomic nerves to peripheral vessels and skin distributed?
Sympathetic nerves run with somatic nerves to the same region
How are the autonomic nerves to organs lacking somatic innervation distributed?
Most nerves run with arteries to same organs, with few cases where autonomic nerves run seperately
What is a nerve plexus?
Interconnecting network of nerves
How are the autonomic nerves to the abdomen routed?
Via plexuses surrounding the aorta and its branches
Where do the sympathetic nerves synapse?
At the ganglia associated with these plexuses
How are plexuses and ganglia named?
According to associated blood vessels
What are the 9 main plexuses/ganglia in the abdomen?
Anterior vagal trunk, superior mesenteric ganglion, coeliac trunk and ganglion, renal plexus and ganglion, inferior mesenteric ganglion, sympathetic trunk and ganglion, superior hypogastric plexus and inferior hypogastric plexus
Where are the 9 important plexuses/ganglia located? FITB
Which nerve plexuses and ganglia surround the aorta and where do they innervate?
Why is referred pain caused?
The cerebral cortex of the brain hasn't got a sensory map for visceral organs and diaphragm, so can't localise the pain from these, hence the pain is referred
Where is the pain from visceral organs referred to?
Regions of skin supplied by nerves with the same segmental supply (dermatomes)
What is a dermatome?
An area of skin supplied by a single spinal nerve (i.e. single segment of the spinal cord)
How do dermatomes prevent complete anaesthesia in a region?
Adjacent dermatomes overlap so that on the trunk at least 3 spinal nerves would have to be blocked to produce a region of complete anaesthesia
What does the dermatomal map of the body look like?
What are the 9 abdominal regions and how are they formed (which lines)?
In which of the 9 regions is the appendix?
Top right of the suprapubic region, nearly part of right inguinal region (main)
What pain is referred to the epigastric region?
T7/8 - pain from foregut structures -> including stomach, proximal duodenum, pancreas, liver, gall bladder
What are the dermatomes of the abdominal wall?
What pain is referred to the umbilical region?
From midgut structures (duodenal papilla to splenic flexure) including inflamed appendix referred to periumbilical region -> usually colicky
Where do the afferent pain fibres from the midgut enter the spinal cord?
Afferent pain fibres from midgut enters spinal cord at T10 and skin of umbilical region is also supplied by T10
How does the pain in appendicitis progress?
Inflammation of appendix spreads to surrounding peritoneum, becoming localised and constant at right inguinal region -> movement of hip joint, coughing eliciting pain
What structures refer pain to the suprapubic region?
Pain from hindgut structures (descending colon to anal canal) -> T12/L1-2)
Fill in the blanks of the visceral referred pain map
Fill in the blanks of the pelvic girdle structures
Fill in the structures of the right hip bone
What are the main structures of the pelvic wall?
Sacrum and coccyx, pelvic bones and sacrospinous and sacrotuberous ligaments
Fill in the structures of the right hip bone and sacrum
What is the difference in the axis of the pelvic and abdominal cavity?
45 degrees further backwards from the abdominal cavity
Where is the pelvic inlet and outlet located?
What does the iliac fossae form?
Shallow basin containing lower abdominal viscera
How is the axis of the pelvic cavity inclined?
What shape is the pelvic cavity?
Conical or cylindrical
What lines the pelvic cavity?
Muscles and nerves
Fill in the blanks of the pelvic wall structures
What covers most of the pelvic bone facing the pelvic cavity?
Obturator internus muscle and its fascia
Fill in the blanks of the pelvic wall muscles and ligaments
What are the names of the ligaments and muscles in the pelvic wall?
Piriformis muscle, obturator internus muscle, sacrospinous ligament and sacrotuberous ligament
Fill in the muscles forming the pelvic diaphragm in a medial aspect
What muscles does the levator ani muscle consist of - from the pelvic diaphragm muscles?
Iliococcygeus, pubococcygeus, puborectalis
What is the tendinous arch formed from?
Obturator internus fascia
What does the pelvic diaphragm consist of?
Bowl-like pair of skeletal muscles -> levator ani which are slung from the pelvis and sacrum
What is the function of the levator ani?
Support the main pelvic organs
What are the pelvic organs?
Bladder, cervix/uterus and rectum
What is the nerve supply to the pelvic diaphragm?
Pudendal S2-4 and directly by S4
Fill in the blanks of the pelvic diaphragm in a sagittal plane
Fill in the blanks of the pelvic diaphragm inferior view
What are the openings in the levator ani muscle for?
Urethra, vagina (female) and anal canal
What is the perineal membrane?
Inferior layer of the fascia of the urogenital part of the pelvic diaphragm
What is underneath the pelvic diaphragm?
Perineum which contains voluntary sphincters and external genitalia
Where is the urinary apparatus located?
Lower part is located in the pelvic cavity
Fill in the blanks of the male pelvis in sagittal section
Fill in the blanks of the male pelvis in a coronal section
What is the fat filled space in the male pelvis called?
Fill in the blanks of the urethral sphincters in males
What kind of muscle makes up the internal and eternal urethral sphincter?
Internal: Smooth External: skeletal
Fill in the blanks of the female pelvis
How are the internal urethral sphincter in the female organised?
The internal sphincter isn't well organised
What are the urethral sphincters present in the female?
Internal/external urethral sphincter, sphincter urethrovaginalis and compressor urethrae
What is the external urethral sphincter made of?
Skeletal muscle surrounding the urethra in the deep perineal pouch
Fill in the blanks of the urethral sphincters in the female
What is the shape of the bladder?
Tetrahedral (when empty), with a structure at each corner of the tetrahedron
Fill in the blanks of the urinary bladder
What structures enter at each corner?
Ureters at supero-posterior angles. Urethra leaves through inferior angle
What covers the superior surface of the bladder?
Where does the bladder expand to?
Between transversalis fascia and lining peritoneum
Where is the location of the 2 sphincters?
Smooth muscle (vesicae) sphincter at neck and skeletal muscle (urethrae) sphincter in perineum
What is the shape of the rectum?
Double-S bend -> probably acting as an anti-gravity device keeping the load off the sphicter
Fill in the blanks of the rectum
What is the rectum innervated with and what is it mainly sensitive to?
By autonomic NS and mainly sensitive to filling
What is the anal canal innervated with and what is it mainly sensitive to?
By somatic nerves and extremely sensitive to injury
Which muscles are important for faecal continence?
Sphincter ani is less important (surrounds anal canal) and puborectalis part of levator ani, which puts a sharp angle into the recto-anal junction
How can the puborectalis be injured?
In a badly performed episiotomy
How does the rectum become the anal canal?
Rectum descends within the concavity of sacrum, showing 3 lateral curvatures, with right angle bend back at recto-anal junction
What types of muscles form the external and internal sphincters of the rectum?
Smooth muscle - internal and skeletal muscle - external
What is the main functional sphincter?
Pubo-rectalis sling of levator ani
What type of nerves supply the rectum and anal canal?
Rectum -> visceral Anal canal -> somatic
What artery supplies the pelvic organs?
Internal iliac artery supplies pelvic organs (all but the ovaries), pelvic walls and much of the gluteal region
Fill in the blanks of the arterial supply of the pelvic organs