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Home , Intervertebral foramen, Suprasternal notch

Skeletal System -Axial System

Chapter 7 Part B Axial Skeleton

Axial system:

1) Skull 22 2) Bones associated with skull: Hyoid 1 Auditory ossicles 6 bones 3) : Vertebrae 24 bones 1 bone 1 bone 4) : 1 bone 24 bones 80 bones Skull – Associated Bones

Auditory ossicles: Six smallest bones…3 in each ear. Malleus, Incus and Stapes Function: amplify sound stimulus.

Auditory ossicles Hyoid: Single, U-shaped bone. Located between mandible and larynx. Often fractures during strangulation. Does not articulate with any other bone…floats. Greater Body: horizontal part. horn Greater and lesser horns/cornua: Body Lesser projections for muscle attachment. horn Function: supports tongue and attach some of the and tongue muscles. An anterior view of the hyoid bone Axial Skeleton

Axial system:

Skull 22 bones Hyoid 1 bone Auditory ossicles 6 bones Vertebral column 26 bones Thorax: Sternum 1 bone Ribs 24 bones 80 bones Vertebral Column

Strong, flexible column. Encloses the . Supports head at the superior end.

Composed of: Vertebrae - series of irregular bones – ….provide the strength.

Intervertebral disc Vertebral Column

Intervertebral disc Vertebra

Intervertebral discs: Cartilage discs inserted between the vertebrae. Provide the flexibility. Become compressed with years of pressure  reduce flexibility and shorten height!

Herniated disc: sudden pressure in the lumbar region  intervertebral discs may tear and push out posteriorly  pressure on the spinal nerves  severe pain. Complete rest or surgery. Vertebral Column – Normal Curves Four major curves: Cervical curve – neck curve. Thoracic curve – upper back curve. Lumbar curve – lower back curve. Sacral curve – hip curve.

Function: help absorb shock and provide flexibility and balance. Vertebral Column – Normal Curves New bone- a single curve with C shape-from thoracic and sacral curves-Primary curves (appear late in fetal development). Present at birth. - Also called Accommodation curves-because they accommodate visceral organs. Thoracic curve- accommodates thoracic organs Sacral curve-accommodates abdominopelvic organs

Secondary curves-cervical and lumbar curves - Appear several months after birth - Also called Compensation curves-permits upright posture/helps shift the trunk weight over the legs as the child begins to stand.

All four curves are fully developed by age 10! Vertebral Column – Abnormal Curves

Cervical curve

Thoracic curve

Lumbar curve

Sacral curve

Normal Curves Vertebral Column – Abnormal Curves-Scoliosis

Scoliosis - Abnormal lateral curvature of the spine in one or more of the movable vertebrae. - Most common distortion of the spinal curvature. Vertebral Column – Abnormal Curves-Kyphosis

Kyphosis - Kyphos-humpbacked or bent - The normal thoracic curvature becomes exaggerated posteriorly, producing a "round-back" appearance. Vertebral Column – Abnormal Curves-Lordosis

Lordosis - “Swayback“ appearance - Both the and the buttocks protrude abnormally - Caused by an anterior exaggeration of the lumbar curvature - Occur during pregnancy or the result from abnormal obesity or weakness in the muscles of the abdominal wall Vertebral Column – Typical Vertebra

Spinous Lamina Intervertebral process foramen Articular Transverse process/ process facet Vertebral Pedicle foramen Body/ Centrum Arrow passing through Vertebral canal Parts of a typical vertebra: Body/Centrum: thick disc located on the anterior side…where intervertebral disc is placed to align the vertebrae.

Pedicles: extend from the centrum  become lamina  fuse to become spinous process.

Spinous process: a projection that points out on the posterior side.

Vertebral foramen: a hole formed by fusion of pedicles/lamina  forms vertebral canal  houses spinal cord.

Transverse process: projections on the lateral sides. Vertebral Column – Typical Vertebra

Posterior

Superior - articulates with inferior articular process of the vertebra just above.

Anterior Superior view Inferior articular processes- articulates with superior articular process of the vertebra just below.

Intervertebral foramen: openings in between vertebrae for spinal nerves to exit.

* Slide 19 Vertebral Column – Typical Vertebra

Spinous Lamina process Articular Transverse process/ process facet Vertebral Pedicle foramen Body/ Centrum

Spina bifida: A congenital defect where pedicles fail to unite  vertebral foramen is open on the posterior side  meninges protrude out  spinal cord is not protected. Partial or complete paralysis, loss of urinary control, absence of reflexes. Can be detected prenatally….sonography, amniocentesis, testing mother’s blood. Vertebral Column –

7 cervical vertebrae….C1  C7. Smallest vertebrae. Extend from occipital bone of skull to thorax.

Typical cervical vertebra: - Small centrum. - Large vertebral foramen - Very short transverse processes. Bifid spinous Vertebral process Bifid spinous process. foramen Transverse foramen: next to transverse process  protect blood vessels going to or Superior coming back from the brain. articular ) facet Vertebral body

Transverse ) process Transverse foramen Vertebral Column – Cervical Vertebrae C1: . Looks like a ring. Skull rests on it. No centrum and no spinous process. Large round vertebral column foramen with anterior and posterior arch. Superior articular facet – articulates with occipital condyles  nodding movement…yes! Inferior articular facet – articulates with superior articular facet of C2. C2: . Rests on C1. C1 sits on top of C2. Dens/odontoid process - a finger-like peg in place of the centrum  fits inside vertebral foramen of C1  allows rotation movement of the head…no! C3-C6: typical cervical vertebrae.

C7: vertebra prominens. Spinous process has a rounded tip…for attachment of ligaments…support head. Vertebral Column –

12 thoracic vertebrae….T1  T12. (increase in size from superior to inferior) T2-T8-typical vertebrae T1, T9, T10, T11 and T12-atypical vertebrae

Characteristic features - Vertebral body is heart shaped. - Presence of demi-facets (superior & inferior costal facets) on the sides of each vertebral body – these articulate with the heads of the ribs (except T1, T9, T10, T11 and T12-single costal facet-atypical vertebrae). - Presence of costal facets on the transverse processes – these articulate with the tubercles of the ribs. They are present on T1-T10 only. - The spinous processes are long, pointed, and bent inferiorly. Vertebral Column – Thoracic Vertebrae Articulation of thoracic vertebrae with ribs

Thoracic vertebrae

Rib Vertebral Column – Lumbar Vertebrae

5 lumbar vertebrae….L1  L5. - Largest and the strongest vertebrae ….weight bearing. - Huge centrum, oval shaped (no costal facet) - Slender transverse process (no costal facets) - Spinous process is thick, broad, flattened and projects out posteriorly. Vertebral Column – Sacrum

Anterior view

- A triangular bone formed by fusion of 5 sacral vertebrae….S1  S5. - Fusion takes place around age 16-25 years. - Sacral apex- Narrow inferior portion of sacrum - Sacral base- Broad superior surface. - Sacral ala- Wings extending on either side at the base of the sacrum (extensive area for muscle attachment). - Sacral promontory- Prominent bulge at the anterior tip of base. - Transverse lines/ridges: represent fusion of the sacral vertebrae. VertebralAuricular Column surface – Sacrum

Sacral canal: continuation of vertebral canal…contains spinal nerves. Sacral hiatus: inferior end of the sacral canal. Sacral cornua: two small processes projecting inferiorly on either side of the sacral hiatus Median sacral crest-Ridge formed by fused spinous process. Lateral sacral crest- Ridge formed by fused transverse process. Auricular surface- Flattened area lateral and anterior to lateral crest-articulates with ilium (hip bone).

Sacral tuberosity- Roughened area between lateral sacral crest and auricular surface (site of ligament attachment that stabilizes sacroiliac joint). Sacral foramina- 4 pairs-on either side of median sacral crest. Vertebral Column – Coccyx

- At the very bottom portion of the spine- represents a vestigial tail (hence the common term "tailbone") - Small triangular shaped bone/s formed by fusion of Co1  Co4 (Happens around age 20-30).

Coccygeal cornua-Prominent laminae of first coccygeal vertebrae-curve to meet sacral cornua. Axial Skeleton

Axial system:

Skull 22 bones Hyoid 1 bone Auditory ossicles 6 bones Vertebral column 26 bones Thorax: Sternum 1 bone Ribs 24 bones 80 bones Thorax

Anterior view Posterior view

Refers to chest or thoracic cage. Composed of: Sternum….the breast bone…on anterior side. Thoracic vertebrae…on the posterior side. Ribs…connect sternum and vertebrae.

Rib cage-formed by ribs and sternum Thorax - Sternum

Sternum: the breastbone. Flat, narrow bone present on the anterior side of the thorax. Jugular notch/ Made of 3 parts: Manubrium: Widest and most superior portion of sternum-articulates with medial end of () and 1st pair of ribs.

Jugular notch/Suprasternal notch-shallow indentation on superior surface of manubrium (large, visible dip in between the neck and the collar bone).

Body: articulates directly with 2nd – 7th rib; indirectly with 8th – 10th ribs.

Xiphoid: remains cartilaginous till age 40, attaches diaphragm and abdominal muscles, often fractures during improper CPR  internal bleeding. Thorax - Ribs

11, 12

(vertebral end)

(sternal end)

Ribs: 12 pairs of flat bones. Intercostal spaces: spaces between the ribs…contain respiratory muscles. Anteriorly – sternal end of some ribs attach to the sternum. Posteriorly – vertebral end connect to two facets on thoracic vertebrae. Head of the rib to the facet on the centrum of thoracic vertebrae. Tubercle of the rib to the facet on the transverse process of thoracic vertebrae. Thorax - Ribs

11, 12

Classification of the ribs: Pairs 1  7: true ribs or vertebrosternal ribs…connect to thoracic vertebrae and directly to sternum through costal cartilage.

Pairs 8  12: false ribs…articulate indirectly or do not attach to sternum at all. Pairs 8  10 – vertebrochondral ribs…attach to thoracic vertebrae and indirectly to sternum-costal cartilages of ribs 8-10 fuse together and merge with rib 7 before they reach sternum. Pairs 11, 12 – floating/vertebral ribs…only attached to thoracic vertebrae…no connection to sternum (sternal end is free!)