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sacral plexus - Coggle Diagram
sacral plexus
branches
- the anterior rami of S1-S4 spinal roots
( & the lumbosacral trunk) divide into several cords
- these cords then combine together to form the 5 major peripheral nerves of the sacral plexus
- these nerves then descend down the posterior pelvic wall
-they have 2 main destinations:
- leave pelvis via
the greater sciatic foramen
- these nerves enter the
gluteal region & innervate the
structures here
- these nerves innervate the
pelvic muscles,organs
& perineum
inferior gluteal nerve
course
- leaves the pelvis via the
greater sciatic foramen
-entering the gluteal region
inferiorly to the piriformis
-is accompanied by the
suoerior gluteal artery & vein
for much of it's course
-
-
-
superior gluteal nerve
course
- leaves the pelvis via the
greater sciatic foramen
-entering the gluteal region
superiorly to the piriformis
-is accompanied by the
suoerior gluteal artery & vein
for much of it's course
-
motor functions
innervates
- gluteus minimus
- gluteus medius
- tensor fascia lata
-
Sciatic nerve
course
As the largest branch of the sacral plexus,
-the sciatic nerve is formed from both anterior and posterior divisions of the
-anterior rami of spinal nerves L4 to S3.
-The nerve can be functionally divided into two divisions:
-a common fibular (peroneal) component that is formed by the posterior divisions of the anterior rami of spinal nerves L4 -S2, and a -tibial component that is formed by anterior divisions of the anterior rami of spinal nerves L4 – S3.
- The nerve exits the pelvic cavity by way of the greater sciatic foramen.
-In the gluteal region, it travels deep to gluteus maximus and the inferior gluteal artery.
-It courses over the posterior surface of the gemelli, piriformis, quadratus femoris and the ischial fibers of adductor femoris.
-The sciatic nerve begins branching at about the midpoint between the ischial tuberosity and the greater trochanter
-to supply the hamstring muscles and the ischial fibers of adductor magnus.
-At the apex of the popliteal fossa,
the nerve typically divides into
-the common peroneal and tibial nerves proper.
-These two nerves are responsible for innervating the muscles and joints of the leg and foot.
-It is noteworthy that the sciatic nerve receives a vasa nervorum (small artery providing arterial blood to peripheral nerves) from the inferior gluteal artery.
-
motor functions
- hamstrings
-biceps femoris
-semitendinosus
-semimembranosus
- adductor magnus
- indirectly innervates:
(via peroneal & tibial nerves)
the muscles of the leg & foot
sensory functions
indirectly innervates:
(via tibial & peroneal)
the skin of the
- lateral leg
- heel
- & both the dorsal & plantar
surfaces of the foot
branches
- tibial nerve
- common peroneal/fibular nerve
common fibular nerve
-
course
- begins @ the apex of the popliteal fossa
where the sciatic nerve bifurcates into the
tibial & common fibular nerves
- the common fibular nerve follows the
-*medial border of the biceps femoris
-running in a lateral & inferior direction
-over the lateral head of gastrocnemius.*
- at this point the nerve gives rise to
-2 cutaneous branches
-which contribute to the innervation of the
skin of the leg
- to enter the lateral compartment of the leg,
-the nerve wraps around the neck of fibula,
-passing between the attachments of the
fibularis longus muscle.
- here the common fibular nerve terminates
-by dividing into the
- superficial fibular nerve &
- the deep fibular nerve
motor functions
innervates
- short head of biceps femoris
(part of hamstring muscles which flex the knee)
- Also supplies (via branches) the
muscles in the lateral and anterior
compartments of the leg
-
-
deep fibular nerve
- is a terminal division of the
common fibular nerve
course
- arises within the lateral compartment of the leg,
betw the fibularis longus & neck of fibula
- with the anterior tibial artery
-it descends in a plane initially between
the tibialis anterior & extensor digitorum longus
-& then distally betw the tibialis anterior &
-finally medial to the anterior tibial artery
tibial nerve
course
- Here, the tibial nerve also gives rise to
branches that contribute towards
-the sural nerve,
which innervates the
posterolateral aspect of the leg.
- it its course down the leg,
posterior to the tibia.
- During its descent,
it supplies the deep muscles of
the posterior leg.
- is a branch of the sciatic nerve
- arises at the apex of the popliteal fossa.
- It travels through the popliteal fossa
giving off branches to
-muscles in the superficial
posterior compartment of the leg.
- At the foot, the nerve passes
posteriorly and inferiorly to the medial malleolus, through a structure known as the tarsal tunnel.
- This tunnel is covered superiorly
by the flexor retinaculum.
- Within this tunnel, branches arise
from the tibial nerve
to supply cutaneous innervation to
the heel.
- Immediately distal to the tarsal tunnel,
the tibial nerve terminates
by dividing into sensory branches,
which innervate the sole of the foot.
-
pudendal nerve
course
- leaves the pelvis
via the greater sciatic foramen
-then re-enters
via the lesser sciatic foramen
-
motor functions
innervates:
- the skeletal muscles of the perineum
- the external urethral spincter
- the external anal spincter
- levator ani
sensory function
innervates:
- the penis
- clitoris
- & most of the skin of perineum
-
other branches
- nerve to piriformis
- nerve to obturator internus
- nerve to quadratus femoris
- nerves that directly supply muscles
- except the:
-perforating cutaneous nerve
supplies the skin over the inferior gluteal region
&
- pelvic splanchnic nerves
innervates the abdominal viscera
- is a network of nerve fibers
that supply the skin & muscles
of the pelvis & lower limb
- is located on the posterior pelvic wall
-anterior to the piriformis muscle
- is formed by the anterior rami of sacral spinal nerves S1,S2,S3 & S4.
- also recieves contributions from L4 & L5