Plexus x...

Question 1

Lumbar plexus

Answer 1

iliohypogastric
ilioinguinal
genitofemoral
lateral cutaneous
obturator
femoral

Question 2

Illiohypogastric

Answer 2

(T12)-L1
It runs to the iliac crest, across the quadratus lumborum muscle of the posterior abdominal wall. It then perforates the transversus abdominis, and divides into its terminal branches.

Motor Functions: Innervates the internal oblique and transversus abdominis.

Sensory Functions: Innervates the posterolateral gluteal skin in the pubic region.

Question 3

Ilioinguinal

Answer 3

L1
The ilioinguinal nerve follows the same anatomical course as the larger iliohypogastric nerve. After innervating the muscles of the anterior abdominal wall, it passes through the superficial inguinal ring to innervate the skin of the genitalia and middle thigh.

Motor Functions: Innervates the internal oblique and transversus abdominis.

Sensory Functions: Innervates the skin on the upper middle thigh. In males, it also supplies the skin over the root of the penis and anterior scrotum. In females, it supplies the skin over mons pubis and labia majora.

Question 4

Genitofemoral

Answer 4

L1-L3
After leaving the psoas major muscle, the genitofemoral nerve quickly divides into a genital branch, and a femoral branch.

Motor Functions: The genital branch innervates the cremasteric muscle.

Sensory Functions: The genital branch innervates the skin of the anterior scrotum (in males) or the skin over mons pubis and labia majora (in females). The femoral branch innervates the skin on the upper anterior thigh.

Question 5

Lateral cutaneous

Answer 5

Roots: L2, L3
This nerve has a purely sensory function. It enters the thigh at the lateral aspect of the inguinal ligament, where it provides cutaneous innervation to the skin there.

Motor Functions: None.
Sensory Functions: Innervates the anterior and lateral thigh down to the level of the knee.

Question 6

Obturator

Answer 6

Roots: L2, L3, L4.

Motor Functions: Innervates the muscles: obturator externus, pectineus, adductor longus, adductor brevis, adductor magnus, gracilis.

Sensory Functions: Innervates the skin over the medial thigh.

Question 7

Femoral

Answer 7

Roots: L2, L3, L4.

Motor Functions: Innervates the muscles: Illiacus, pectineus, sartorius, all the muscles of quadriceps femoris.

Sensory Functions: Innervates the skin on the anterior thigh and the medial leg.

Question 8

Sacral plexus desitinatiions

Answer 8

Leave the pelvis via the greater sciatic foramen – these nerves enter the gluteal region of the lower limb, innervating the structures there.
Remain in the pelvis – these nerves innervate the pelvic muscles, organs and perineum.

Question 9

Sacral plexus-mnemonic

Answer 9

A useful memory aid for the major branches of the sacral plexus is ‘Some Irish Sailor Pesters Polly’. This stands for Superior Gluteal, Inferior Gluteal, Sciatic, Posterior (FEMORAL)cutaneous nerve of thigh, Pudendal.

Question 10

Lumbosacral plexus

Answer 10

L4-S4

Question 11

superior gluteal

Answer 11

he superior gluteal nerve leaves the pelvis via the greater sciatic foramen, entering the gluteal region superiorly to the piriformis muscle. It is accompanied by the superior gluteal artery and vein for much of its course.

Roots: L4, L5, S1.
Motor Functions: Innervates the gluteus minimus, gluteus medius and tensor fascia lata.
Sensory Functions: None.

Question 12

inferior gluteal

Answer 12

leaves the pelvis via the greater sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle.
It is accompanied by the inferior gluteal artery and vein for much of its course.

Roots: L5, S1, S2.
Motor Functions: Innervates gluteus maximus.
Sensory Functions: None.

Question 13

sciatic

Answer 13

Roots: L4, L5, S1, S2, S3
Motor Functions:
Tibial portion – Innervates the muscles in the posterior compartment of the thigh (apart from the short head of the biceps femoris), and the hamstring component of adductor magnus. Innervates all the muscles in the posterior compartment of the leg and sole of the foot.
Common fibular portion – Short head of biceps femoris, all muscles in the anterior and lateral compartments of the leg and extensor digitorum brevis.
Sensory Functions:
Tibial portion: Innervates the skin on the posterolateral and medial surfaces of the foot as well as the sole of the foot.
Common fibular portion: Innervates the skin on the anterolateral surface of the leg and the dorsal aspect of the foot.

(Tibial nerve, Common Fibular nerves_???

Question 14

posterior (femoral) cutaneous… of thigh?

Answer 14

The posterior cutaneous nerve of thigh leaves the pelvis via the greater sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle. It descends deep to the gluteus maximus and runs down the back of the thigh to the knee.

Roots: S1, S2, S3
Motor Functions: None
Sensory Functions: Innervates the skin on the posterior surface of the thigh and leg. Also innervates the skin of the perineum.

Question 15

pudendal

Answer 15

leaves pelvis via greater sciatic foramen, then re-enters via lesser sciatic foramen. It moves anterosuperiorly along lateral wall of schiorectal fossa, and terminates by dividing into several branches.

Roots: S2, S3, S4
Motor Functions: Innervates the skeletal muscles in the perineum, the external urethral sphincter, the external anal sphincter, levator ani.
Sensory Functions: Innervates the penis and the clitoris and most of the skin of the perineum.
(Tip – an easy way to remember the functions of the pudendal nerve is S2, S3, S4 keeps poo off the floor!)

Question 16

Pudenal mnemonic

Answer 16

(Tip – an easy way to remember the functions of the pudendal nerve is S2, S3, S4 keeps poo off the floor!)

Question 17

Brachial plexus general info

Answer 17

brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb. It begins in the root of the neck, passes through the axilla, and runs through the entire upper extremity.

The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C5, C6, C7 and C8, and the first thoracic spinal nerve, T1.

Question 18

Brachial plexus mnuemonic

Answer 18

a good mnemonic for this is Read That Damn Cadaver Book

roots, trunks, divisions, cords and branches

Question 19

anterior rami of spinal nerves

Answer 19

C5, C6, C7, C8, and T1.

At each vertebral level, paired spinal nerves arise. They leave the spinal cord via the intervertebral foramina of the vertebral column.
Each spinal nerve then divides into an anterior and a posterior ramus. The roots of the brachial plexus are formed by the anterior rami of spinal nerves C5-T1 (the posterior divisions innervate the skin and musculature of the intrinsic back muscles).
After their formation, these nerves pass between the anterior and medial scalene muscles to enter the base of the neck.

Question 20

Trucnks of brachial plexus

Answer 20

roots of the brachial plexus converge to form three trunks. These structures are named by their relative anatomical location:

Superior trunk – a combination of C5 and C6 roots.
Middle trunk – continuation of C7.
Inferior trunk – combination of C8 and T1 roots.

The trunks traverse laterally, crossing the posterior triangle of the neck.

Question 21

Divisions of the brachial plexus

Answer 21

Each trunk divides into two branches within the posterior triangle of the neck. moves anteriorly and other posteriorly :known as the anterior and posterior divisions.
3 anterior and 3 posterior nerve fibres. These divisions leave the posterior triangle and pass into the axilla. They recombine into the cords of the brachial plexus.

Question 22

Cords of the brachial plexus

Answer 22

the anterior and posterior divisions have entered the axilla, they combine together to form three cords, named by their position relative to the axillary artery.

The lateral cord is formed by:
The anterior division of the superior trunk
The anterior division of the middle trunk

The posterior cord is formed by:
The posterior division of the superior trunk
The posterior division of the middle trunk
The posterior division of the inferior trunk

The medial cord is formed by:
The anterior division of the inferior trunk.

cords give rise to major branches of brachial plexus.

Question 23

Roots of brachial plexus

Answer 23

refer the anterior rami of the spinal nerves anterior rami of spinal nerves C5, C6, C7, C8, and T1.

Question 24

Musculocutaneous Nerve

Answer 24

Roots: C5, C6, C7.
Motor Functions: Innervates the brachialis, biceps brachii and coracobrachialis muscles.
Sensory Functions: Gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm, and a small lateral portion of the posterior forearm.

Question 25

Axillary Nerve

Answer 25

Roots: C5 and C6.
Motor Functions: Innervates the teres minor and deltoid muscles.
Sensory Functions: Gives off the superior lateral cutaneous nerve of arm, which innervates the inferior region of the deltoid (“regimental badge area”).

Question 26

Median nerve

Answer 26

Roots: C6 – T1. (Also contains fibres from C5 in some individuals).
Motor Functions: Innervates most of the flexor muscles in the forearm, the thenar muscles, and the two lateral lumbricals associated with the index and middle fingers.
Sensory Functions: Gives off the palmar cutaneous branch, which innervates the lateral part of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.

Question 27

Radial nerve

Answer 27

Roots: C5 – T1.
Motor Functions: Innervates the triceps brachii, and the muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist and fingers).
Sensory Functions: Innervates the posterior aspect of the arm and forearm, and the posterolateral aspect of the hand.

Question 28

Ulnar nerve

Answer 28

Roots: C8 and T1.
Motor Functions: Innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus.
Sensory Functions: Innervates the anterior and posterior surfaces of the medial one and half fingers, and associated palm area.