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FORS 3331 (27)
Lecture 12

FORS 3331 Lecture 12: Dr Ferraro - FORS 3331 - Spring 2017 - Lecture 12

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Forensic Science
FORS 3331
Joseph V.Ferraro

Baker | FORS 3331 | Spring 2017 | Lecture 12 | Page 1 LECTURE 12: VERTEBRAE, SACRUM, AND STERNUM – This lecture tackles the bones of the midline thorax o Vertebrae - located posteriorly - "backbones" o Sacrum - "tail bones" o Sternum - located in the anterior mid-chest region Vertebrae Type of Vertebrae – There are five (5) types of vertebrae; 33 total – Vertebrae are serially homologous o The 5 types all have the same basic parts – There is potential for some individual variation in numbers by type o i.e. You might have 13 thoracic and 4 lumbar in some individuals – Cervical (7) o Neck o Flexible – Thoracic (12) o Chest or rib-bearing o Stable – Lumbar (5) o Lower back o Flexible – Sacral (5) o Buttocks-region o Fuse into a single sacrum during adolescence o Articulate with the ilia – Coccygeal (4) o Vestigial caudal (tail) bones Vertebral Column – Functionally, the column of vertebrae will: o Bear body weight o Anchor muscles and ligaments o Protect the spinal cord – Individual vertebrae will ossify from three (3) primary and five (5) secondary centers – There is a general trend towards decreasing size with elevation o i.e. the cervicals are relatively small, the lumbars are relatively large o This reflects basic weight-bearing principles o As a result, inferior to the sacro-iliac joint, the remaining vertebrae will decrease in size Baker | FORS 3331 | Spring 2017 | Lecture 12 | Page 2 Vertebral Curvature – Lordotic - cervical and lumbar vertebrae – Kyphotic - thoracic and sacral vertebrae Anatomy – Vertebra form by fusing a vertebral body with a vertebral arch o The enclosed hole is a vertebral foramen through which the spinal cord runs o Bony projections (processes) include: spinous (dorsal x1) and transverse (lateral x2) – Vertebral Body - forms around the notochord and replaces it o This is a weight-bearing structure o Lightweight, fragile, cancellous/spongy bone covered by a thin veneer of cortical bone – Vertebral Arch - forms around the dorsal surface of the spinal cord o The right and left halves ossify separately – Spinous Process - connects the halves of the vertebral arch in the midline o Anchors ligaments and muscles of the neck and back – Transverse Processes - grow out of the arch o They anchor muscles that move the axial skeleton o The thoracic transverse processes also articulate with ribs – Superior Articular Processes - for the articulation with other vertebrae at synovial joints o Faces superiorly in cervicals o Faces posteriorly in thoracics o Faces medially in lumbars – Inferior Articular Processes are for articulation with other vertebrae at synovial joints o Faces inferiorly in cervicals o Faces anteriorly in thoracics o Faces distally in lumbars – Pedicle - the part of arch that fuses with the body – Lamina - the flat surface that lies between the transverse and spinous processes – Vertebral Foramen - the open space between the body and the arch that the spinal cord runs through – Vertebral Canal - the long canal formed by the series of individual vertebral foramina – Intervertebral Foramen/Notch - the open space between the pedicles of adjacent vertebrae o To transmit spinal nerves – Costal Fovea - articular facets for ribs on the thoracic vertebrae o Located on both the body and transverse processes Baker | FORS 3331 | Spring 2017 | Lecture 12 | Page 3 – Intervertebral Disk - made up of rings of fibrous cartilage (annulus fibrosis) o Transmits and absorbs forces projected through the column – Nucleus Pulposus - jelly-like mass at the center of the disk o A derivative of the notochord o May herniate and "slip the desk" Movement of Vertebrae Cervical Vertebrae (7) – The most flexible of the vertebrae – Can move in all directions – Their range of motion is reflected in small bodies and thick intervertebral disks – They also have horizontal articular facets and loose joint capsules Thoracic Vertebrae – Limited ability for flexion and extension – Side to send bending is also limited by the ribs – There is some ability to twist around the vertical axis (rotation) – Their range of motion is reflected in their vertical articular facets and thinner intervertebral disks Lumbar Vertebrae – Fairly flexible vertebrae – Good capacity for flexion and extension – Some side to send bending – There is, however, no ability to twist around the vertical axis (rotation) – Their range of motion is reflected in their articular facets being parallel to the midline – They have relatively thick intervertebral disks Sacral Vertebrae – No movement – Synovial joints are lost Coccygeal Vertebrae – No movement – Synovial joints are lost Identifying Vertebrae Cervical Vertebrae (7) – Cervical bodies are smaller than the thoracic and lumbars – They have saddle-shaped superior and inferior surfaces – Also have transverse foramen lateral to the body on the arches o Transmit the vertebral arteries to the posterior part of the brain – Their spinous processes are usually bifurcated (bifid) o Shorter than those of the thoracics and less massive than those of the lumbars o Project mostly posteriorly and somewhat inferiorly – Transverse processes are very small and project laterally beyond the transverse foramina – Their articular facets are generally horizontal – C1 (Atlas) - holds up the skull o Lacks a body and intervertebral disks (above or below) o The body of C1 was "stolen" by C2 o Articulates with the skull and C2 by synovial joints Baker | FORS 3331 | Spring 2017 | Lecture 12 | Page 4
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