CRANIOVERTEBRAL
JOINTS
©
2005 zillmusom
I. CRANIOVERTEBRAL
JOINTS
A. Atlanto‑occipital
joint: joint between atlas (vertebra C1)
and occipital bone; movements ‑ flexion ‑ extension of the neck
(nodding the head in "yes" movement).
B. Atlanto‑axial joint: joint
between atlas (C1) and axis (C2); movement: rotation of atlas on axis (shaking
head in "no" movement)
C. Ligaments of joint ‑
stabilize joints and protect medulla and spinal cord; some prevent excessive
movement; some are extensions of ligaments of spinal column (Atlas Figs. 4.38,
4.39; Snell Fig. 12‑4)
2. Membrana Tectoria =
extension of posterior longitudinal ligament of spinal column ‑ extends
from axis to occipital bone, posterior to cruciate ligament.
3. Posterior atlanto‑occipital membrane = extension
of ligamenta flava ‑ extends from atlas to occipital bone
4. Cruciate (cross)
ligament ‑ composed of 1) Transverse ligament of atlas ‑ transverse
band within vertebral canal which is attached to inner side of atlas; holds dens of axis against inner aspect of
anterior arch of atlas; 2) Superior and inferior bands ‑ upper and lower extensions from transverse
ligament of atlas to occipital bone superiorly and to body of the axis
inferiorly.
Clinical
note: Tear of cruciate ligament of atlas
can allow dens to be driven into spinal cord (resulting in quadriplegia) or
medulla (resulting in death).
Morbid
note: Hanging someone: most cervical vertebrae have articular facets that
permit extension‑flexion and rotational movements; the joint between the
atlas and axis however is specialized and permits only rotational movement; in
accurate hanging, a large knot is placed posterior to the joint between the
atlas and the axis and the weight of the body forcibly flexes the joint,
driving the dens into the medulla, resulting in instantaneous death; in
inaccurate hanging, the knot is placed behind other cervical joints, resulting
in flexion of the neck, prolonged agony and death by strangulation; amateurs
should not attempt hanging people.
5. Alar ligament ‑
"check" ligament extending laterally from dens to occipital bone;
prevents excessive rotation of head.
II.
PREVERTEBRAL MUSCLES (Atlas Fig. 8.24) ‑ located anterior to
cervical vertebrae.
|
MUSCLE |
ORIGIN |
INSERTION |
ACTION |
NERVE |
|
Longus colli |
Vertebra – transverse
processes lower cervical |
Vertebra - bodies of
upper cervical |
Flex neck |
Cervical
ventral rami |
|
Longus
capitis |
Vertebra – transverse
processes C3-C6 |
Occipital
bone |
Flex head |
Cervical
ventral rami |
|
Rectus
capitis anterior |
Atlas |
Occipital
bone |
Flex head |
Cervical
ventral rami |
|
Rectus
capitis lateralis |
Atlas – transverse
process |
Occipital
bone |
Flex head |
Cervical
ventral rami |
Note:
Colli means neck in Latin.
III.
PHARYNX ‑ a fibromuscular tube which forms superior end of both
respiratory and digestive tubes continuous inferiorly with trachea and
esophagus, anteriorly with oral and nasal cavities. (Atlas Figs. 8.28. page 767)
A. Layers (from internal to
external): correspond to layers of GI tract:
1. mucosa = epithelial lining; 2. submucosa = connective tissue layer;
3. muscular layer composed of inner circular and outer longitudinal layers,
muscles listed below ; 4. adventitia =
Buccopharyngeal fascia = part of Pretracheal fascia of neck.
B. Location ‑ Extends from
base of skull superiorly to level of cricoid cartilage inferiorly; posterior to
nasal cavity, oral cavity, and larynx;
anterior to vertebrae C1 to C6; medial to carotid sheath and cranial
nerves 9‑12.
C. Circular muscles of pharynx ‑
(Snell Figs. 11‑76) overlap each other somewhat; Function; constrict
pharynx during swallowing to propel food inferiorly into esophagus and aid in
closing off nasal from oral pharynx by contacting soft palate; All constrictors
insert to Pharyngeal raphe which is a median fibrous band on posterior aspect
of pharynx.
Circular Muscles of Pharynx
|
MUSCLE |
ORIGIN |
INSERTION |
ACTION |
NERVE |
|
Superior
Constrictor |
Pterygomandibular
raphe - continuous anteriorly with buccinator muscle |
Pharyngeal
raphe |
Constrict
pharynx |
X |
|
Middle
Constrictor |
Hyoid bone |
Pharyngeal
raphe |
Constrict
pharynx |
X |
|
Inferior
Constrictor |
Thyroid and
cricoid cartilages |
Pharyngeal
raphe |
Constrict
pharynx |
X |
D. Gaps between constrictor muscles ‑
allow vessels, nerves, and muscles to pass into the interior of the pharynx.
(Snell Figs. 11‑76, 11-77)
1. Gap between superior
constrictor and base of skull ‑ passage of auditory tube into pharynx and
levator veli palatini muscle.
2. Gap between superior
and middle constrictors: passage of stylopharyngeus muscle and glossopharyngeal
nerve.
3. Gap between middle
and inferior constrictor muscles: for passage of Internal laryngeal nerve and
E. Longitudinal muscles of pharynx ‑
three muscles located mostly internal to pharynx which fuse with circular
muscles when they insert. (Atlas Figs. 8.28, 8.29)
Longitudinal Muscles of Pharynx
|
MUSCLE |
ORIGIN |
INSERTION |
ACTION |
NERVE |
|
Stylopharyngeus |
Temporal bone - styloid
process |
Thyroid
cartilage |
Raises
pharynx and pulls wall laterally |
IX |
|
Palatopharyngeus |
Soft palate - palatine
aponeurosis |
Thyroid
cartilage |
Raises
pharynx and pulls down soft palate |
X |
|
Salpingopharyngeus |
Auditory tube |
Thyroid
cartilage |
Raises
pharynx |
X |
F. Divisions of pharynx ‑
location relative to nasal and oral cavities and larynx.
1. Nasopharynx ‑
a. Location ‑ superior to soft palate and
posterior to nasal cavity, anterior to occipital bone ; superior border is body
of sphenoid;
b. Contents ‑ 1) pharyngeal tonsil (lymphoid tissue in
submucosa of roof and posterior wall of nasopharynx); 2) opening of auditory
tube
Note:
Adenoids: enlargement of pharyngeal tonsil common in children; enlarged
pharyngeal tonsils can interfere with breathing.
2. Oropharynx ‑
(Snell Fig. 11‑78)
a. Location ‑
Note:
palatoglossal arch is mucosal fold covering palatoglossus muscle; forms
boundary between oral cavity and oropharynx
b. Contents ‑
1) Palatine tonsils ;2) Glossoepiglottic folds ‑ folds of mucosa from
posterior tongue to epiglottis; there is one Medial glossoepiglottic fold and two Lateral folds
Note:
Valleculae (L. for little ditches) are two depressions of mucous membrane
between Medial and Lateral Glossoepiglottic folds; food or foreign objects can
lodge in valleculae (Snell Fig. 11-78)
3. Laryngopharynx
a. Location ‑ between upper border of
epiglottis superiorly and lower border of cricoid cartilage inferiorly;
communicates inferiorly with esophagus
and anteriorly with larynx.
b. Contents ‑ 1) Piriform recess ‑
deep trench in mucous membrane in anterolateral wall of laryngopharynx, lateral
to laryngeal inlet.(Atlas Fig. 8.29A)
Note:
Foreign bodies can lodge in piriform recesses.
G. Innervation ‑ Motor (SVE) ‑ all muscles of pharynx are
innervated by the Pharyngeal branch of Vagus (X) except stylopharyngeus
which is innervated by the Glossopharyngeal nerve (IX); Sensory (GVA) ‑ nasopharynx is
mostly innervated by Facial nerve (VII); oropharynx by Glossopharyngeal
(IX) and laryngopharynx by Vagus (X).
H. Blood supply and lymphatics ‑
Arteries from Ascending Pharyngeal, Facial, Maxillary and Lingual arteries;
Veins drain to pharyngeal plexus which drains to Internal Jugular; Lymphatics
to Deep Cervical nodes.