Lecture 3 Flashcards
Costal Facets
Rib head articulates ENTIRELY with surface T11-T12
Typical Thoracic Vertebra: Vertebral Body
- Heart Shaped
- Convex anterior surface, concave posterior
- Have costal facets or demifacets for rib articulation
Demifacets
Half of rib head articulated with facet of vertebra above and half with facet of vertebra below T1-T10
Typical Thoracic Vertebra: Pedicles
- Space posteriorly
- Small vertebral canal
- Short with inferior vertebral notch
Typical Thoracic Vertebra: Laminae
Short, broad & thick
Typical Thoracic Vertebra: Spinous Process
- Long, slender with triangular shape in cross-section
- Point obliquely downward overlapping the vertebrae below
Typical Thoracic Vertebra: Transverse Process
- Large, thick, strong & long
- Thickened ends, point laterally, posteriorly and superiorly
- T1-T10 have large costal facets on anterior aspect
Typical Thoracic Vertebra: Intervertebral foramen
- Circular and relatively smaller compared to lumbar and cervical
Typical Thoracic Vertebra: Articular Facet
- Form angle 60 degree to sagittal plane
- Superior facet orientated superolateral & posterior
- Inferior facet orientated inferomedial & anterior
Typical Thoracic Vertebra: Intervertebral Disc
- Slightly wedge shaped
- Anterior height less then posterior making a kyphotic curve
Thoracic: Intervertebral Joints
- Connects body of vertebrae
- Secondary cartilaginous joints composed of fibrocartilage
- Amphiarthroses (allow only slight movements)
Thoracic: Zygapophyseal Joints
- Joints of vertebral arches
- Between superior and inferior articular processes
- Enclosed by a thin & loose fibrous capsule
Atypical Thoracic Vertebrae
T1:
- Resembles C7 and has 1 facet on the first rib
T9-T12:
- Rib articulations vary
T11 & T12:
- Resembles Lumbar vertebrae
Thoracic Curve
- 20-50 degress, average 45
- Present from birth (primary curve)
- Curve is partially due to posterior vertebral body 2mm higher
Thoracic Ligaments
- Anterior longitudinal ligament
- Posterior longitudinal ligament
- Ligamentum flavum
- Interspinous ligament
- Supraspinous ligament
- Joint capsule
Superior Costotransverse Ligament
- Neck of rib to TP of vertebra above it
Radiate Ligaments
- Fan-shaped ligament
- Arises from the anterior aspect of the head of rib
- Extends to the bodies of two adjacent thoracic vertebrae
Biomechanics of Thoracic Spine
Shape and orientation of zygapophyseal/facet joint:
- Allows for large rotational and lateral flexion movements
- Limit flexion & Extension
Limitation of flexion & extension due to:
- Thin intervertebral discs relative to vertebral body height
- Inferiorly projecting SP
- Projection of ribs anteriorly
Functions of rib cage
- Protect organs
- Increase stability of thoracic spine
- Ventilation
Borders of Rib Cage
Anterior: Sternum
Posterior: Thoracic Spine
Lateral: Ribs
Superior: Jugular notch of the sternum first costocartilage and first ribs
Inferior: Xiphoid process, costocartilage of Rib 7 & 10, inferior portions of Rib 11-12 and T12
Parts of sternum
- Manubrium
- Body
- Xiphoid Process
Manubrium
Articulates with clavicles and the costal cartilage of first pair of ribs
Sternum Body
- Individual costal cartilages from rib pairs 2-7 are also attached to body
- Rib pairs 8-10 are also attached to body, but by a single pair of cartilages shared with rib pair 7.
Xiphoid Process
- Angles dorsally from sternum
- Muscular diaphragm & rectus abdominis muscle sttach at xiphoid process
Ossificatioon of Sternum
- Ossification begins in 6-10 different articulation centres & fusion is completed by age 25
- Before 25, sternal body consists of 4 separate bones
- Xiphoid process is the last component of sternum to undergo fusion & ossification
Rib Classification
1-7:
- True ribs = attach directly to sternum
8-10:
- False ribs = articulated by costal cartilage indirectly with sternum
11-12:
- Floating ribs = no articulation or attachment to sternum
Typical Ribs Parts
- Head
- Neck
- Body
Typical Rib: Head
- Wedge shaped
- 2 articular facets separated by a wedge of bone
- 1 facet articulates with numercally corresponding vertebra, the other articulates with vertebra above
Typical Rib: Neck
*Fix this
- Connects head with body
- Neck meets the vertebral body there is a roughed tubercle, with a facet for articulation with TP of corresponding vertebra
Typical Rib: Body/Shaft
- Flat & curved
- Has a groove for neurovascular supply of thorax
Rib 1
- Atypical
- Shorter and wider
- 1 facet on its head for articulation
- Superior surface is marked by 2 grooves for subclavian vessels
Atypical Ribs
1, 2, 10, 11 & 12
Rib 2
- Atypical
- Thinner and longer then rib 1
- 2 articular facets on head (normal)
- Roughened area on upper surface, from which serratus anterior muscles originates
Rib 10
- Atypical
- 1 facet
- Shorter and wider
Ribs 11 & 12
- Atypical
- 1 facet
- No neck
Posterior Rib Articulations
- Articulates with vertebral column posteriorly & sternum anteriorly
- 2 types of articulation with vertebrae:
1. Costovertebral Joint
2. Costotransverse Joint
Costovertebral Joint
- Between head of rib, superior costal facet of corresponding vertebrs & inferior costal facet of vertebra above
- Costovertebral joints of ribs 1, 10-12 articulate with single vertebral body
Ligaments of costovertebral joint
Single capsular ligaments surrounding demifacets strengthened by radiate ligament
Costotransverse Joint
Connecting necks and tubercles of rib with transverse process
Ligaments of Costotransverse Joint
Surrounded by joint capsule, lateral costrotransverse ligament and superior costotransverse ligament
Biomechanics of Rib Cage
- Rib cage increase stability of spine
- Ribs can influence movements of individual thoracic vertebra
- Influences movement of thoracic
- Primary motion occurs during inspiration and expiration
Rib Cage in Inspirations
- AP diameter of thorax increases when ribs are raised
- Elevation of ribs lifts sternum at the manubriosternal joint
- Movement of costovertebral joints raises & lowers the sternal ends of ribs 1-6 (pump handle)
- 7-10 swing outward, increase transverse diameter (bucket handle)
Rib Cage in Expiration
- Elastic recoil of the lungs and the weight of thoracic walls cause lateral and anteroposterior diamteres of thorax to return to the relaxed position
Serratus Anterior
- Fan shaped at lateral wall of thoracic
- Serrated appearance
Origin: 1st - 8th or 9th ribs
Insertion: Anterior superior of scapula
Action: Draws scapula anterolateral, suspends scapula on thoracic wall, rotates scapula
Intrinsic Muscles of the Chest Wall
- Serratus Posterior
- Intercostal
- Levatores Costarum
- Transverse Thoracis
Sarratus posterior
- Intermediate layer of intrinsic back muscles
Serratus Posterior Superior:
- Elevates ribs
Serratus Posterior Inferior:
- Depresses Ribs
Intercostal Muscles
- Presents within rib cage
Includes: - External intercostal muscles
- Internal intercostal muscles
- Innermost intercostal muscles
External Intercostal Muscles
- Most superficial set of muscles that occupy intercostal space
Functions:
- Elevated ribs during FORCED inhalation
- Maintain stability of thoracic cage
Internal Intercostal Muscles
Origin: Inferior margin of costal cartilage & inner lip of costal groove
- Fibres course posteroinferiorly and medially insert to the superior border of the immediate rib
Functions:
- Enables FORCED exhalation by depressing ribs
- Maintain stability of thoracic cage
Innermost Intercostal Muscles
Origin: Inner surface of costal groove of the ribs
- Fibres course posteroinferiorly and medially insert to the superior border of scapula
Functions:
- Forced expiration by depressing the ribs
- Maintain stability of thoracic cage
Levatores Costarum Muscles
- Deep muscles of the back
- parts of intrinsic muscles of chest wall
- C7-T12
- 12 smaller triangular muscles that connect thoracic vertebrae and the rib
Origin: TP with adjacent ribs
Insertion: External surface of rib 1 level below
Function: Elevate the ribs
Transverse Thoracis Muscles
Triangular Sternae & Sternocostalis
- Found inner surface of anterior chest wall
- Several slips that radiate from body and xiphoid process to costal cartilages of ribs 2-6
Functions:
- Support thoracic cage
- Helps to move the ribs during forced breathing
Subcostales Muscles
- Thin muscles on the inner surface of the posterior thoracic wall bridging 2 or 3 intercostal spaces
Functions:
- Pull ribs inferiorly during forced exhalation
- Support intercostal spaces and thoracic cage
