Nerve Supply of the Body Wall Flashcards
What are the 4 main directional terms?
- lateral/medial
- proximal/distal
- cranial/claudal
- posterior/anterior = anterior/ventral
What are spinal nerves part of?
PNS not CNS
What is the foramen?
an opening where spinal nerves can protrude
What are the 5 major parts of a typical vertebra?
- vertebral arch
- articular processes
- pedicle
- laminae
- vertebral body
What are the 31 pairs of spinal nerves?
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
Which nerves supply the body wall?
the 12 thoracic spinal nerves and the first lumbar spinal nerve
What is within each spinal segment?
2 pairs of roots
What does the fissure determine?
the way that the spinal body is facing (dorsal or ventral)
What is white and grey matter?
- white = myelinated axon
- grey = collections of cell bodies
Where is the afferent (sensory) nerve and what does it do?
dorsal/posterior and senses the surroundings
Where is the efferent (motor) nerve and what does it do?
ventral/anterior and is the reaction to the muscle (motor function)
What does DAVE stand for?
Dorsal Afferent Ventral Efferent
What are the spinal nerves a combination of?
the anterior and posterior roots
What are the 3 layers of the meninges?
- dura mater (outer layer, most durable)
- arachnoid mater (middle layer that contains the fluid that cushions the brain)
- pia mater (innermost layer, contains blood vessels)
What does each of the 12 thoracic nerves emerge from?
an intervertebral foramen that splits to form the dorsal and ventral rami
What do the dorsal and ventral rami contain?
motor and sensory fibres
Where does a spinal nerve collect sensory information from and where does it deliver?
- collects from peripheral structures
- delivers to sensory nuclei in the thoracic or superior lumbar segments of the spinal cord
What is the area of innervation called?
the rami communicantes
Why does the spinal ganglion bulge?
it is full of cell bodies (grey matter)
What does the sympathetic nerve carry?
sensory information from the visceral organs
What does the anterior ramus contain?
sensory information from the ventrolateral body surface, structures in the body wall and the limbs
What does the posterior ramus contain?
sensory information from the skin and skeletal muscles of the back
What does the posterior root of the spinal nerve do?
carry sensory information to the spinal cord
Where do motor commands originate?
in motor nuclei of the thoracic or superior lumbar segments of the spinal cord
What do motor commands mostly execute?
muscle reflexes
What does the anterior root contain?
axons of somatic motor and visceral motor neuron
What is the white ramus communicantes?
the first branch from the spinal nerve that carries the visceral motor fibres to the nearby sympathetic ganglion
Where are white rami found?
only between T1 and L2
What does the grey ramus communicantes contain?
postganglionic fibres that innervate glands and smooth muscles in the body wall or limbs
Where are the cell bodies within the motor neuron?
the anterior horn of the spinal cord
Where is the lower motor neuron?
in the ventral horn of the spinal cord
What do the preganglionic sympathetic fibres do?
travel out of the spinal cord and connect with the sympathetic trunk via rami communicantes before synapsing
Which sympathetic fibres are myelinated and unmyelinated respectively?
- myelinated = presynaptic, white fibres
- unmeymlinated = postsynaptic, grey fibres
Where are the postganglionic sympathetic fibres distributed after rejoining the spinal nerve?
the body wall via the dorsal and ventral rami of the spinal nerve
What is the paravertebral ganglion?
the area that joins the post and presynaptic fibres
What do sympathetic fibres supply via nerves to the skin?
- blood vessels
- sweat glands
- arrectores pilorum
What do the dorsal/posterior rami supply?
muscles, bones, joints and skin of the back
What does each ventral/anterior rami supply?
the skin, muscles and serous membranes of the thoracic and abdominal walls (some ventral rami also supply the upper and lower limbs)
What is a dermatome?
a segment of skin innervated by a specific spinal nerve
What are the centre parts and boundary of dermatomes innervated by respectively?
- centre parts = single spinal nerve
- boundary = many nerves working together
Give examples of dermatome pathological conditions
- shingles
- pain in the left shoulder during a heart attack
How and where does shingles occur?
at a specific dermatome around the abdomen and travels to the skin retrogradely from the DRG
What are the ventral rami of the first 11 thoracic spinal nerves called?
intercostal nerves
What are the typical intercostal nerves?
T4, T5, T6
What do the 1st to 3rd ventral rami do?
give branches to the upper limb as well as to the thoracic wall (important for referred pain from the heart)
What are the thoracoabdominal nerves?
T7 - T11
What is the subcostal nerve?
T12
What do the typical intercostal nerves supply?
the thoracic wall including the intercostal muscles
What is the function of the intercostal muscles?
to increase thoracic diameter during inspiration
Where do the intercostal muscles lie?
on the pleura and between the innermost and internal intercostal muscles
What does each intercostal nerve give off at the angle of the rib?
a lateral cutaneous branch, which supplies the skin and subcutaneous tissue of the thorax
What is the thorax and what is it made up of?
the chest and is made up of the thoracic wall, its superficial structures (breast, muscles, and skin), and the thoracic cavity
What happens to the thorax at the end of the intercostal space medial to vessels?
it turns forward as the anterior cutaneous branch
Where are the thoracoabdominal nerves located?
between the transversus and internal oblique muscles and continue behind the rectus abdominus muscle
What are the functions of the thoracoabdominal muscles?
- flexion, lateral flexion and rotation of trunk
- forced expiration
- to increase intra-abdominal pressure during micturition, defecation and parturition
What do the thoracoabdominal nerves supply?
muscles of the thoracic and anterior abdominal walls e.g. intercostal, transverses and rectus abdominis, external and internal obliques
What would a vertical incision along the linea semilunaris do?
denervate (cut off nerve supply) the rectus abdominus
What does each thoracoabdominal nerve supply and how?
a band of skin by means of its lateral and anterior cutaneous branches
What do the thoracoabdominal nerves give sensory twigs to?
the adjacent diaphragm, pleura, and peritoneum
What are the iliohypogastric and ilioinguinal nerves derived from?
the first lumbar nerve (L1)
What do the iliohypogastric and ilioinguinal nerves innervate respectively?
- iliohypogastric = muscle and skin of abdominal region
- ilioinguinal = transverse abdominis and internal obliques
What is the inguinal region?
the lower portion of the anterior abdominal wall, located superior to the thigh, lateral to the pubic tubercle, and inferomedial to the anterior superior iliac spine
What is referred pain?
pain from the internal organs and the body wall that is felt elsewhere and shares the same subsequent pathway up to the brain i.e. cross-talk
