Spinal Cord Flashcards
Describe the external anatomy of the spinal cord.
In adults the spinal cord extends down the vertebral canal from the medulla oblongata to the level of the L1-2 vertebrae
Spinal cord is shorter than the vertebral column
Its caudal end tapers to a point called the conus medullaris
Extending inferiorly from this point is the filum terminale, a strand of fibrous tissue that anchors the spinal cord the coccyx
The spinal cord has two regions of increased diameter:
Cervical enlargement - (C4-T1 vertebrae) gives rise to the spinal nerves that innervate the upper limbs
Lumbar enlargement - (T9-T12 vertebrae) gives rise to the spinal nerves that innervate the lower limbs
Describe the internal anatomy of the spinal cord.
Parts of internal anatomy:
- Posterior median sulcus
- Grey matter
- Posterior (doral) Horn - cell bodies of interneurons that rely sensory signals up the spinal cord
- Lateral Horn - cell bodies of autonomic motor neurons *only present in the T1-L2 and S2-S4 spinal cord segments
- Anterior (ventral) Horn - cell bodies of somatic motor neurons
- White matter
-Posterior columns, anterior column, lateral column *each of these columns contains ascending (sensory) tracts and/or descending (motor) tracts
- Central canal
- Anterior median fissure
Describe the anatomy of spinal nerves.
Anterior (lateral) Root - made up of axons of motor neurons and cell bodies are within the anterior and lateral horns of the spinal cord
Posterior (dorsal) Root - made up of axons of sensory neurons and cell bodies are within a posterior (dorsal) root ganglion
Posterior (dorsal) Ganglion
Spinal Nerve - made up of sensory and motor axons (mixed)
Describe the distribution of spinal nerves.
Spinal nerves divide almost immediately after emerging from their respective intervertebral foramina
Anterior (ventral) ramus - anterolateral trunk, limbs
Posterior (dorsal) ramus - posterior trunk
Rami communicantes - autonomic neurons
In some regions, the anterior rami of neighbouring spinal nerves branch and interconnect to form a complex network of nerves called a plexus
These plexuses give rise to the peripheral nerves that innervate many of the tissues and organs of the body
Therefore spinal nerves help to form multiple peripheral nerves and peripheral nerves are derived from various combinations of spinal nerves
*Anterior rami of T2-T12 spinal nerves do not form plexuses - they travel through intercostal spaces and supply the skin of the anterolateral trunk (sensory) and intercostal muscles (motor)
Describe the cervical principal plexus of the peripheral nervous system.
C1-C5
S: head, neck upper chest
M: anterior neck, diaphragm
Describe the brachial principal plexus of the peripheral nervous system.
C5-T1
S: upper limbs
M: upper limbs
Describe the lumbar principal plexus of the peripheral nervous system.
L1-L4
S: abdomen, genitals, lower limb
M: abdomen, lower limb
Describe the sacral principal plexus of the peripheral nervous system.
L4-S4
S: genitals, lower limb
M: perineum, lower limb
Describe the coccygeal principal plexus of the peripheral nervous system.
S4-Co1
S: coccygeal region
M: none
Which nerves arise from the brachial plexus?
Axillary nerve
Musculocutaneous nerve
Radial nerve
Median nerve
Ulnar nerve
Describe the axillary nerve that arises from the brachial plexus.
Sensory Distribution
- Skin of the upper lateral arm
- Skin of the upper posterior arm
Motor Distribution
- Deltoid
- Teres minor
Describe the musculocutaneous nerve that arises from the brachial plexus.
Sensory Distribution
- Skin of the lateral forearm
Motor Distribution
- Anterior arm muscles
Compartment
- Anterior arm
Describe the radial nerve that arises from the brachial plexus.
Sensory Distribution
- Skin of the lower lateral arm
- Skin of the lower posterior arm
- Skin of the posterior forearm
- Skin of the posterolateral hand
Motor Distribution
- Posterior arm muscles
- Posterior forearm muscles
Compartment
- Posterior arm
- Posterior forearm
Describe the median nerve that arises from the brachial plexus.
Sensory Distribution
- Skin of the anterolateral hand
Motor Distribution
- Anterior forearm muscles
- Hand muscles
Compartment
- Anterior forearm
Describe the ulnar nerve that arises from the brachial plexus.
Sensory Distribution
- Skin of the medial hand
Motor Distribution
- Anterior forearm muscles
- Hand muscles
Compartment
- Anterior forearm
Which nerves arise from the lumbar plexus?
Femoral nerve
Obturator nerve
Describe the femoral nerve that arises from the lumbar plexus.
Sensory Distribution
- Skin of the anterior thigh
- Skin of the medial thigh
- Skin of the medial leg and foot
Motor Distribution
- Anterior thigh muscles
Compartment
- Anterior thigh
Describe the obturator nerve that arises from the lumbar plexus.
Sensory Distribution
- Skin of the medial thigh
Motor Distribution
- Medial thigh muscles
Compartment
- Medial thigh
Which nerves arise from the sacral plexus?
Sciatic Nerve
Tibial Nerve
Superficial Fibular Nerve
Deep Fibular Nerve
Describe the sciatic nerve that arises from the sacral plexus.
Sensory Distribution
- None
Motor Distribution
- Posterior thigh muscles
Compartment
- Posterior thigh
Describe the tibial nerve that arises from the sacral plexus.
Sensory Distribution
- Skin of the plantar surface of the foot
Motor Distribution
- Posterior leg muscles
- Foot muscles
Compartment
- Posterior leg
Describe the superficial fibular nerve that arises from the sacral plexus.
Sensory Distribution
- Skin of the lower lateral leg
- Skin of the dorsal surface of the foot
Motor Distribution
- Lateral leg muscles
Compartment
- Lateral leg
Describe the deep fibular nerve that arises from the sacral plexus.
Sensory Distribution
- Skin between the 1st and 2nd toes
Motor Distribution
- Anterior leg muscles
Compartment
- Anterior leg
Describe the sensory and motor distributions of the nerves.
Dorsal Scapular Nerve
- Levator scapulae
- Rhomboid major
- Rhomboid minor
Long Thoracic Nerve
- Serratus anterior
Subscapular Nerve
- Supraspinatus
- Infraspinatus
Upper Subscapular Nerve
- Subscapularis
Lower Subscapular Nerve
- Subscapularis
- Teres major
Medial Pectoral Nerve
- Pectoralis major
- Pectoralis minor
Lateral Pectoral Nerve
- Pectoralis major
Thoracodorsal Nerve
- Latissimus dorsi
Medial Cutaneous Nerve (Arm)
- Skin of the medial arm
Medial Cutaneous Nerve (Forearm)
- Skin of the medial forearm
Describe the sensory and motor distributions of the lumbar nerves.
Iliohypogastric Nerve
S: Skin of the inferior abdomen and lateral buttock
M: Abdominal muscles
Ilioinguinal Nerve
S: Skin of the genitals and upper medial thigh
M: Abdominal muscles
Genitofemoral Nerve
S: Skin of the genitals and upper anterior thigh
M: Aremaster muscle
Lateral Cutaneous Nerve of the Thigh
S: Skin of the lateral thigh
M: None
Describe the sensory and motor distributions of the sacral nerves.
Superior Gluteal Nerve
- Gluteus medius
- Gluteus minimus
- TFL
Inferior Gluteal Nerve
- Gluteus maximus
Nerve to Obturator Internus
- Obturator internus
- Superior gemellus
Nerve to Quadratus Femoris
- Quadratus femoris
- Inferior gemellus
Pudendal Nerve
- Perineal muscles and skin of the genitals
Posterior Cutaneous
Nerve of the Thigh
- Skin of the posterior thigh
Which parts of the spinal cord/nerve are motor/sensory?
Motor:
Anterior (ventral) horn
Lateral horn
Anterior (ventral) root
Posterior (dorsal) root ganglion
Sensory:
Posterior (dorsal) horn
Posterior (dorsal) root
