Back I 2025 PDF

BACK I Muscles, Spinal cord, meninges Barbara Kraszpulska, Ph.D. Neuroscience, Cell Biology, and Physiology  The back includes: 1. Skin and subcutaneous tissue 2. Muscles: a. superficial group – extrinsic muscles b. deep...

BACK I Muscles, Spinal cord, meninges Barbara Kraszpulska, Ph.D. Neuroscience, Cell Biology, and Physiology  The back includes: 1. Skin and subcutaneous tissue 2. Muscles: a. superficial group – extrinsic muscles b. deep group – intrinsic muscles 3. Vertebral column: a. vertebrae b. joints and ligaments c. intervertebral (IV) discs 4. Vertebral canal: a. spinal cord b. meninges  Superficial Back Muscles Extrinsic/not true back mm 1. Superficial group; 5 limb muscles - Latissimus dorsi m. - Trapezius m. - Rhomboid major m. - Rhomboid minor m. - Levator scapulae m. Connect the upper limb to the trunk and control limb movements. Innervation: cervical plexus, brachial plexus, spinal accessory nerve (CN XI) 2. Intermediate group; 2 accessory respiratory muscles - Serratus posterior superior m. (lies deep to rhomboid muscles) - Serratus posterior inferior m. (lies deep to latissimus dorsi) Innervation: intercostal nerves Where is and what is the meaning of the Triangle of auscultation? Le va to Trapezius r Rhomboids Latissimus dorsi  Deep Back Muscles Intrinsic/True native back muscle group 1. Superficial layer: splenius capitis and cervicis m. They cover and hold the deep neck muscles in position. 2. Intermediate layer: erector spinae, chief extensor of the trunk, divides into 3 columns: iliocostalis (lateral), longissimus (median), spinalis (medial) 3. Deep layer or transversospinalis muscles: semispinalis (extend and rotate), multifidus (stabilize), rotators (stabilize, extend and rotate) All intrinsic back muscles are innervated by dorsal rami of spinal nerves. They maintain posture, control movements of the vertebral column. They work with the muscles of the anterolateral abdominal wall to produce movements of the trunk.  Splenius capitis M. Longissimus Capitis M. ERECTOR SPINAE M. 1 Iliocostalis M. Longissimus cervicis M. Longissimus M. Spinalis M. Longissimus thoracis M. 2 1 – serratus posterior superior 2 – serratus posterior inferior  Spinal cord: Continuation of the medulla oblongata The end - conus medularis at the level of L1-L2 vertebrae (in adults). Enlargements: Cervical (C4-T1) - spinal nerves to the upper limb Lumbosacral (T11-S1) – spinal nerves to the lower limb 31 pairs of Spinal Nerves: 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal Cauda equina (horse tail) – nerve roots from the lumbosacral part of the spinal cord continue inferiorly within the lumbar cystern.  Differential growth of the vertebral column vs the spinal cord. During the initial third month of embryonic development, the spinal cord extends the entire length of the vertebral canal, and both grow at about the same rate. As development continues, the body and the vertebral column continue to grow at a much greater rate than the spinal cord proper. This results in displacement of the lower parts of the spinal cord with relation to the vertebrae column. What is the consequence of it? The outcome of this uneven growth is that the adult spinal cord extends to the level of the first or second lumbar vertebrae, and the nerves grow to exit through the same intervertebral foramina as they did during embryonic development. This growth of the nerve roots occurring within the vertebral L1 canal, results in the lumbar, sacral, and coccygeal roots extending to their L2 appropriate vertebral levels In newborns – the tip of the conus medularis is at the mean level L2-L3. (May varied from the first lumbar to the second sacral vertebra.) In Adults – conus medularis ends typically opposite the intervertebral disc between L1-L2 vertebra. Spinal nerves exit the vertebral column through the intervertebal foramina. Cervical Region – 8 pairs of spinal nerves, only 7 cervical vertebrae Cervical spinal nerves exit Above corresponding vertebrae, except spinal nerve C8. C1 – between the skull and vertebra C1 C2-C7- above their respective vertebrae C8 – between vertebrae C7 and T1 Thoracic through Sacral Regions All spinal nerves always exit Below corresponding vertebra  Inferior portion of the spinal cord and vertebral canal Cauda equina within subarachnoid space (lumbar cistern), below the level of conus medularis. Float in CSF. This is the collection of the lumbar and sacral dorsal and ventral roots. Filum terminale internum - prolongation of the pia mater extending from the conus medularis (L1-L2), to the internal aspect of the spinal dural sac. Pial part of filum terminale. Filum terminale externum – connective tissue attaching the spinal dural sac to the dorsum of the coccyx. Commonly known as the coccygeal lig. Dural part of filum terminale.  Basic plan of spinal nerve 1.Dorsal rootlets form dorsal root (sensory fibers only!) Ventral rootlets form ventral root (motor fibers only!) 2. The portion of the spinal cord giving rise to rootlets and roots form a spinal cord segment! (31 segments) 3. The dorsal root has the spinal ganglion/dorsal root ganglion DRG, large collection of the sensory cell bodies. 4. Dorsal and ventral roots unit to form the spinal nerve. It’s very short! 5. Spinal nerve immediately divides into: a. dorsal primary ramus b. ventral primary ramus How the spinal nerves exit vertebral canal? 6. Each spinal nerve is the mix What openings? nerve, carrying both motor and sensory fibers.  Basic plan of spinal nerve True back muscles Dorsal ramus Ventral ramus Body wall, extremities Spinal nerve exits via intervertebral foramen Only Ventral rami of spinal nerves form nerves networks called Plexuses! They supply the antero-lateral parts of the trunk, and upper and lower extremities. C1-C4 = Cervical plexus (Neck) C5-T1 = Brachial plexus (Upper Extremity) T1-T12 = No plexuses, segmental nerves (Thorax and Abdomen) L1-L4 = Lumbar plexus (Lower Extremity) L4-S3 = Sacral plexus (LE/pelvis) S4-Co1 = No plexuses Dorsal rami of spinal nerves supply the deep back muscles and skin of the back only!  Important information to remember! Dorsal Roots contain ONLY sensory (afferent) nerve fibers! The cell bodies of the sensory nerves are in the Dorsal Root Ganglia (DRG) which is located at the distal end of the dorsal roots. ? ? Ventral Roots contain ONLY motor (efferent) nerve fibers! ? The cell bodies?of the motor nerves are in the ventral or lateral horns of spinal cord. ? Do NOT confuse dorsal and ventral rami with dorsal and ventral roots!  Dermatomes A skin area (strip of skin) innervated by the sensory fibers of a single spinal nerve is known as a dermatome. Although slight variations do exist, dermatome patterns of distribution are relatively consistent from person to person. Important dermatomes to know. C6, 7 & 8 = hand T4 = region of the nipple on thorax T10 = region of umbilicus L1 = inguinal region L4 = knee  Spinal nerve components I SOMATIC NEURONS: 1. General somatic afferent (GSA) - transmit sensation from the body to the CNS: a. exteroceptive sensation from the skin (pain, temp., touch and pressure) b. proprioceptive sensation from muscles, joints and tendons. Usually, subconscious. Cell bodies in the dorsal root ganglion (DRG). 2. General somatic efferent (GSE) – transmit impulses from CNS to skeletal (voluntary) muscles. Cell bodies in the ventral horn of the spinal cord. II VISCERAL NEURONS : 1. General visceral afferent (GVA) - transmit pain or subconscious visceral reflexes sensation from the body organs or blood vessels to the CNS. GVA fibers are associated with chemoreception, mechanoreception and stretch reception. Cell bodies in the dorsal root ganglion (DRG). 2. General visceral efferent (GVE) – transmit impulses from CNS to smooth (involuntary) muscles, cardiac muscle and glands. Always two neurons: a. presynaptic – cell bodies in the lateral horn of spinal cord or brainstem (inside the CNS) b. postsynaptic – cell bodies in the autonomic ganglia (outside the CNS) The visceral efferent modality is more commonly referred to as the AUTONOMIC NERVOUS SYSTEM, since these functions are regulatory mechanisms generally not under conscious control.  Spinal nerve components I MOTOR (efferent) NEURONS: 1. General somatic efferent (GSE) – transmit impulses from CNS to skeletal (voluntary) muscles. Cell bodies in the ventral horn of the spinal cord. 2. General visceral efferent (GVE) – transmit impulses from CNS to smooth (involuntary) muscles, cardiac muscle and glands. Always two neurons: a. presynaptic – cell bodies in the lateral horn of spinal cord or brainstem (inside the CNS) b. postsynaptic – cell bodies in the autonomic ganglia (outside the CNS) The visceral efferent modality is more commonly referred to as the AUTONOMIC NERVOUS SYSTEM, since these functions are regulatory mechanisms generally not under conscious control. II SENSORY (afferent) NEURONS : 1. General somatic afferent (GSA) - transmit sensation from the body to the CNS: a. exteroceptive sensation from the skin (pain, temp., touch and pressure) b. proprioceptive sensation from muscles, joints and tendons. Usually, subconscious. Cell bodies in the dorsal root ganglion (DRG). 2. General visceral afferent (GVA) - transmit pain or subconscious visceral reflexes sensation from the body organs or blood vessels to the CNS. GVA fibers are associated with chemoreception, mechanoreception and stretch reception. Cell bodies in the dorsal root ganglion (DRG). Spinal nerve components Type of neurons in PNS  Spinal meninges Dura mater (Tough Mother) Composed of tough fibrous and elastic tissue. The most outer one. Form spinal dural sac, a long tubular sheath within the vertebral column. Epidural space - the space between bony wall of the vertebral canal and dura mater. This space contains internal venous plexus and epidural fat! Arachnoid mater Delicate, avascular membrane, composed also of fibrous and elastic tissue. Subdural space – its is only potential space between dura and arachnoid mater. Subarachnoid space - real space between arachnoid and pia mater, contains CSF. The enlargement of subarachnoid space between L1 and S2 is lumbar cystern. Pia mater Directly covers the spinal cord, spinal nerve roots and spinal blood vessels. The lateral extensions of pia mater, between dorsal and ventral root are called denticulate ligaments, the inferior extension is called filum terminale.  Spinal Meninges and Related Spaces in spinal cord SPACES MENINGES EPIDURAL SPACE Internal Venous Plexus DURA MATER Fat and Connective Tissue ARACHNOID SUBDURAL SPACE Spinal “Potential Space” Cord PIA MATER SUBARACHNOID SPACE BONE - Vertebral Cerebrospinal Canal Fluid = CSF Spinal cord within its meninges - posterior (dorsal) view  Spinal dura Lumbar Cervical enlargement enlargement mater  Lumbar Spinal puncture Spinal tap L3 The procedure for withdrawing CSF is called a L4 “lumbar spinal tap” and is used in suspected cases of meningitis - inflammation of the meninges that can L5 be life-threatening. It is important to do this procedure below the end the of spinal cord (conus medularis) usually at vertebral level L3. The puncture needle is inserted in the midline between the spinous process of the L3 and L4. An epidural block is an injection of pain medication (it blocks pain) into the epidural space. You can do epidurals for the neck or the low back. They are rarely done for the mid-back (thoracic spine). The injection can cause both a loss of sensation (anesthesia) and a loss of pain (analgesia). In caudal epidural anesthesia a local anesthetic agent is injected through the sacral hiatus (Important landmark sacral cornua). In transsacral epidural anesthesia a local anesthetic agent is injected through the posterior sacral foramina.  After lecture questions 1. What nerves provide innervation to the erector spinae muscles? 2. What are two most superficial muscles of the back? 3. What cell bodies can be found in the DRG? 4. What is cauda equina? 5. What spinal nerves form the brachial plexus? 6. What motor/everent nerve fibers always comprises of two neurons? 7. What is denticulate ligament? 8. What type of neurons can be found in the ventral roots? (Motor, sensory or mixed?) 9. At what vertebral level spinal cord ends in the adult person? 10. What meningeal space is potential? 11. What is filum terminale internum and externum? 12. How the spinal nerve C5 leaves the vertebral canal?