Week 8: Regional Anatomy: The Trunk Flashcards
What is regional Anatomy?
- Study by regions (as opposed to body systems) e.g. region of the head and neck, trunk, limbs
- You will see parts of multiple body systems in a given region
- Regional anatomy is important to understand the interactions of different systems in a given anatomical location
Clinically it is important to differentially diagnose conditions when symptoms are localized to a particular region
Region of the trunk:
- Can be divided into:
- The back (posterior/dorsal) trunk
- The anterior/ventral body cavities
- Thoracic cavity
Abdominopelvic cavity
Main body systems of the posterior trunk:
- Integumentary: Protection and sensation, skin and subcutaneous tissue
- Muscular: Stabilizes body position and produces movement, moving and maintaining the position of the axial skeleton, muscles of ventilation e.g. intercostals
- Skeletal: Protection of organs, facilitates movement. Vertebral column, vertebrae, intervertebral discs and associated ligaments, sternum and ribs
Nervous: Receives, interprets and elicits response to information, spinal cord and meninges, nerves
The vertebral column:
Functions:
- Provides a framework for the body as part of the axial skeleton
- Facilitates weight transfer
- Protects the spinal cord and organs
- Provides a location for muscle attachment
General bone functions: Blood cell formation, calcium store
Vertebral column structure:
- Made up of bone and connective tissue
- Thirty-three vertebrae in a child and 26 in an adult
- 7x cervical
- 12 x thoracic
- 5 x lumbar (fused in adults to form one)
- 4x coccygeal (fused in adults to form one)
Intravertebral discs made of fibrocartilage that are between vertebrae
Components of typical vertebrae:
Vertebral body, vertebral arch, processes
Vertebral body:
- Disc shaped anterior portion
- Weight baring part of the vertebrae
Superior and inferior surfaces attached to intravertebral discs
- Weight baring part of the vertebrae
Vertebral arch:
- The pedicles project posteriorly from the vertebral body and unite with the lamina to form the arch
Houses the spinal cord and its protective tissues
Processes:
- Transverse processes: Projects laterally from lamina- serve as muscle attachment sites
- Spinous process: Projects posteriorly from lamina - serve as muscle attachment sites
Superior and inferior articular processes (x2 of each) - serve as articulation sites of vertebrae above and below
- Spinous process: Projects posteriorly from lamina - serve as muscle attachment sites
Structure of Cervical vertebrae:
Small, one vertebral two transverse foramina, often slender build C2-C6, no articular facet for ribs, articular facets are posterosuperior and anteroinferior, thick intervertebral discs relative to size of vertebral bodies
Structure of thoracic vertebrae:
Larger, one vertebral foramina, long thick spinous processes, fairly large transverse process, articular faces for ribs present, articular facets are posterolateral, anteromedial, intervertebral discs are thin relative to the size of vertebral bodies,
Structure of lumbar vertebrae:
Largest, one vertebral foramina, short blunt (posterior rather than inferior) spinous processes, large and blunt transverse process, articular facets for ribs are absent, direction of articular facets are medial and lateral, thickest size of intervertebral discs
Vertebral column regions:
The neck region: Cervical vertebrae
- First two vertebrae (C1 and C2, known as the atlas and axis respectively) are specialised in structure to facilitate side-to-side movement of the head
The chest region: Thoracic vertebrae
- Articulate with the ribs
Lumbar region:
- Largest and strongest unfused vertebrae as the amount of body weight supported increases toward the inferior end of the vertebral column
Sacral and coccygeal region:
Serves as a strong foundation for the pelvic girdle
Vertebral column curvatures
- When viewed in a sagittal plane, the four normal curves of the vertebral column are visible
- Relative to the anterior (front) surface of the body
- Cervical and lumbar curves are convex (bulge out)
Thoracic and sacral curves are concave (cup inward)
Functions of the vertebral curves:
- Increase vertebral column strength
- Helps to maintain balance in an upright position
- Shock absorption during walking
- Protect vertebrae against fracture
Cervical and lumbar curves may be progressively lost in old age
Vertebral column joints:
There are 2 main types of joints in the vertebral column:
- Intervertebral discs and vertebral bodies form cartilagenous joints
- These joints limit the range of intervertebral motion
- Superior/inferior articular processes on adjoining vertebrae form facet/zygapophyseal joints
- These are synovial joints
The size, shape and positioning of the articulating surfaces and the resulting joint planes depend on the vertebral region. The orientation of the articular surfaces determine the type and range of movements possible at each region
Vertebral column ligaments:
- Ligaments are dense fibrous connective tissue
- They attach bone to bone
- Serve to limit joint movement
- Anterior longitudinal ligament (most anterior element) - limits extension
- Posterior longitudinal ligament - limits flexion
- Intertransverse ligament - limits lateral flexion
Supraspinous (on top of spinous) ligaments - limit flexion
Recall: Muscles and movement
- Muscles must cross a joint to make movement
- Muscle attachment sites are:
- Origin: muscle beginning, does not move during contraction, usually proximal end of bone/joint
- Insertion: Muscle end - is pulled towards the origin during contraction. Usually distal end of bone/joint
Flexion of the vertebral column:
- Flexion occurs in the sagittal plane
- Muscles involved in flexion are positioned anterior ro intervertebral joints
Rectus abdominus
- Muscles involved in flexion are positioned anterior ro intervertebral joints
Extension of the vertebral column:
- Extension occurs in the sagittal plane
- Muscles involved in extension are positioned posterior to the intervertebral joints
Erector spinae muscle group
- Muscles involved in extension are positioned posterior to the intervertebral joints
Rotation of the vertebral column:
- Rotation occurs in the transverse/horizontal plane
- Muscles involved in rotation are positioned in an oblique direction
- Sternocleidomastoid, internal and external obliques
Lateral flexion of the vertebral column:
- Lateral flexion occurs in the coronal/frontal plane
- Muscles involved in lateral flexion are positioned lateral to the intervertebral joint
- Erector spinae muscle group
- Internal and external obliques
Development of the vertebral column:
Embryonic development:
- During the third week of embryonic development, three distinct germ layers develop and form different structures of the body
- Endoderm: Gives rise to epithelial linings and glands of digestive and respiratory systems, abdominal organs and urinary bladder
- Mesoderm: Gives rise to all connective tissue, muscular tissue, the dermis, the vascular system and the urogenital system (except the urinary bladder)
- Ectoderm: Gives rise to epidermis, nails, hair and nervous tissue
Differentiation of the Mesoderm:
- Recall that the mesoderm gives rise to all connective tissue, muscular tissue, the dermis and the vascular system and the urogenital system (except the urinary bladder)
- During embryonic development, there are modifications that occur to the mesoderm on either side of the notochord
These modifications are called somite’s (number of somite pairs increases as embryo develops/lengthens
- During embryonic development, there are modifications that occur to the mesoderm on either side of the notochord
Differentiation of Somite’s:
Differentiate into three possible structures:
- Sclerotome: Forms the vertebrae and ribs
- Dermatome: Forms dermis of the skin
- Myotome: Forms skeletal muscle of the neck, trunk and limbs) that further differentiates into
- Epimere: Muscles on the posterior/dorsal surface
- Hypomere: Muscles on the anterior/ventral surface
Innervation and blood supply of the trunk
Recall: Structure of spinal nerves:
- Anterior/ventral roots contain motor neurons (motor info out) and posterior/dorsal roots contain sensory neurons (sensory info in)
- Spinal nerves form where the anterior and posterior root comes together as they exit the spinal cord through the intervertebral foramina
- Spinal nerves branch into anterior and posterior rami
Trunk region supplied by rami from spinal nerves T1-T12
Anterior and posterior rami:
- Posterior ramus supplies the structures of the back
- Anterior ramus supplies the entire anterior surface of the body and the limbs (hence large diameter)
- Any given ramus may have the following branches
- Muscular branch: Innervating muscle
- Cutaneous branch: Innervating skin
- Articular branch: Innervating the joint
Vascular branch: Innervating blood vessels
Arterial supply of the trunk:
- The major artery supplying the trunk (thoracic and abdominopelvic regions) is the aorta
The aorta has 4 distinct regions:
- Ascending aorta
- Aortic arch
- Thoracic (descending aorta)
- Spans from approx T4-T12 vertebral level
- Has many branches to supply structures of the thoracic region
- Passes through the diaphragm (aortic hiatus) - Abdominal aorta
- Continuation of thoracic aorta and spans from approx. T12-L4 vertebral level
Has many branches to supply structures of the abdominopelvic region
- Descending thoracic aorta: Aorta that rises from the heart, ascending aorta and then it will continue down as the descending aorta. Branches of the descending thoracic aorta will supply the tissues of the thoracic part of the trunk. Descending thoracic aorta will Peirce the diaphragm and continue to the abdominal region and will be called the abdominal aorta
Abdominal aorta: Branches will supply abdominal and pelvic part of the trunk
Venous drainage of the trunk:
- Recall: Wherever there is an artery, you will find a vein
The major veins that drain the trunk (thoracic and abdominopelvic regions) are the superior and inferior vena cava- Inferior vena cava: drain lower part
- Superior vena cava: Drain upper half of the body
- Nerves arteries, veins and lymphatics will travel together and form neurovascular bundles
Superior vena cava:
- Located in the thoracic region
Has many branches that allow it to drain deoxygenated from the upper half of the body (head, neck, upper limbs and upper thoracic) back to the heart
Inferior vena cava
- Located in the abdominopelvic region
Has many branched that allow it to drain deoxygenated from the lower half of the body (lower thoracic, abdominopelvic and lower limbs) back to the heart
Muscle placement and movement:
- Application of knowledge: A muscle must cross a joint to act on that joint, the position of a muscle relative to a joint determines the plane and direction of movement it can produce
- Flexion: Muscle to lie anterior to the joint at which the movement occurs e.g. intervertebral joints. Muscle would need to lie anterior to the intervertebral joints
- Extension: Muscle would need to lie posterior to intervertebral joints, support extension of VC
- Rotation: Direction of muscle fibers. For rotation, direction would need to be oblique, primary muscles are internal and external obliques
- Lateral flexion: Position of muscle needs to be lateral to intervertebral joints. Erectus spinae, internal and external obliques
Innervation of the trunk:
- Ventral ramus = front
- Dorsal ramus = back
- Supplies muscles along the surface and will also have a dorsal ramus towards the dorsal aspect of the trunk
- Supplies muscle along dorsal surface of the trunk
Spinal nerves: Thoracic spinal nerves - Other tissues around the wall that need to be innervated
- Tissue innervation: The nerve that supplies the muscle acting a joint also supplies tissues of that joint and the skin over the muscles and/or the joint
- e.g. dorsal ramus will supply joint and skin over the muscle
The ventral ramus supplies anterior/lateral abdominal wall
Structures innervated by branches (dorsal/ventral rami) of spinal nerves
- Muscular branches: Innervating muscle
- Cutaneous branches: Innervating skin
- Articular branches: Innervating the joint
- Vascular branches: Innervating blood vessels
Spine and structure of segments:
- Most vertebrae share a similar shape with the following features:
- Body: The major part of the bone e.g. vertebral body
- Protuberances (bumps) for attachment sites for muscles or ligaments e.g. transverse processes
- Articular surfaces for articulation (joint) with another bone e.g. superior and inferior facets
Depression/holes for passage of other structures e.g. foramen
What are the functions of these features of a vertebra:
The vertebral body
Transverse processes
Intervertebral foramen
Superior portion of the foramen
The vertebral body is a weight bearing surface, allowing the transmission of load through the spine. It is also part of the cartilaginous joint formed with the intervertebral disc and the adjacent vertebral body.
Transverse processes provide a site for muscle and ligament attachment.
The vertebral foramen provides a passage for the spinal cord and cauda equina.
The intervertebral foramen provides a passage for the spinal nerves.
The superior portion of the foramen is formed by the inferior notch of the superior vertebra and the inferior portion in formed by the superior notch of the inferior vertebra
Vertebral column curvatures
- Primary curvatures concave anteriorly and develop before birth in all regions
- Secondary curvatures are concave posteriorly and develop during childhood as a result of changes in shape of vertebrae and intervertebral discs
- Secondary curvatures facilitate upright postures
Joints of the vertebral column
- There are 2 main types of joints
- Intervertebral discs and vertebral bodies form cartilaginous joints. These joints limit the range of intervertebral motion
Facet joints (zygapophyseal joints) are synovial joints which limit the direction of intervertebral motion based on the orientation of the articular facets
- Intervertebral discs and vertebral bodies form cartilaginous joints. These joints limit the range of intervertebral motion
Ligaments of the spinal joints:
- Ligaments are made up of dense fibrous connective tissue, the major fiber type is collage with is inelastic
- Ligament attaches bone to bone
- The role of a ligament is to limit joint movements
Ligaments of the spinal joints can be continuous across the whole spine rather than specific to a specific joint at a particular level of the spine
Spinal nerves:
- In the cervical region a spinal nerve leaves the vertebral canal through the intervertebral foramen immediately proximal to the vertebra for which it is named
- e.g. C5 spinal nerve leaves through the intervertebral foramen between C5 and C4
In the thoracic and lumbar region, the spinal nerve leaves the vertebral canal through the intervertebral foramen immediately distal to the vertebra for which it is named. Therefore the T8 spinal nerve leaves through the intervertebral foramen between T8 and T9
- e.g. C5 spinal nerve leaves through the intervertebral foramen between C5 and C4
Patient A wants to know what the major difference is in function of the vertebrae of the thoracic region compared to the vertebrae of the other regions.
They anchor the rib cage
Patient A wants to know which of the normal vertebral curvatures are primary curvatures.
Thoracic and Sacral
Patient A wants to know about movements permitted by the vertebral column. Which of the following statements matches (A) The spinal movement, and (B) the plane in which the movement occurs in.
(A) Rotation (B) Transverse/Horizontal plane
Which of the following muscles would NOT be innervated by branches of the posterior ramus
Rectus abdominus
