BSC2085L Practical 2

The axial skeleton

skull, vertebral column, bony thorax

Skull is composed of the

cranium and facial bones

2 Major areas in the cranium

cranial vault and cranial floor

cranial vault

superior, lateral, and posterior walls of skull

cranial floor

3 concavities; anterior, middle, and posterior cranial fossae

Cranium major sutures

coronal, lambdoid, sagittal, squamous

Coronal suture

connects the frontal bone to the parietal bone

Lambdoid suture

connects the parietal bone to the occipital bone

Sagittal suture

connects the left and right parietal bones

Squamous suture

connects the parietal bone to the temporal bone

Frontal bone structures

Glabella, Supraorbital foramen (notch)

Glabella

located between the orbital cavities

Supraorbital foramen (notch)

opening above each orbit, passageway for blood vessels and nerves

Parietal bone structures

sagittal suture, coronal suture

Temporal bone structures

Squamous region, tympanic region

Squamous region

Zygomatic process

Tympanic region

External acoustic meatus, styloid process, mastoid region, petrous region

External acoustic meatus

ear canal

Styloid process

muscle/ligament attachment site

Mastoid region

muscle attachment site (mastoid process)

Petrous region

jugular foramen, carotid canal, internal acoustic meatus

Jugular foramen

passage for internal jugular vein, cranial nerves IX (glossopharyngeal), X (vagus), XI (accessory)

Carotid canal

passage for internal carotid artery

Internal acoustic meatus

passage for cranial nerves VII (facial) & VIII (vestibulocochlear)

Occipital bone structures

Foramen magnum, occipital condyles, hypoglossal canal

Foramen magnum

where the spinal cord enters the cranium to connect to the brain

Occipital condyles

articulation site with 1st cervical vertebra (atlas)

Hypoglossal canal

passage for cranial nerve XII (hypoglossal nerve)

Sphenoid bone structures

Greater wings, lesser wings, sella turcica, optic canals

Greater wings of sphenoid

part of orbital cavity

Lesser wings of sphenoid

-anchors dura mater (covering that encloses the brain)

Sella turcica

midline of sphenoid bone, hypophyseal fossa here

Hypophyseal fossa

houses the pituitary gland

Optic canals

openings at base of lesser wings for cranial nerve II (optic nerve)

Ethmoid bone structures

Cribriform Plate, crista Galli

Crista galli

anchors dura mater (leathery connective tissue membrane that surrounds and protects the brain and spinal cord)

Cribriform plate

allows olfactory fibers (cranial nerve I) from nasal mucosa to enter the brain

Mandible structures

Body of mandible, Mandibular ramus, Mandibular angle, Coronoid process, Mandibular notch, Condylar process

Maxilla structures

Palatine process (anterior part of the hard palate)

Facial bones

mandible, maxilla, palatine, zygomatic, lacrimal, nasal, vomer, inferior nasal conchae

The hard palate is composed of...

BOTH the palatine process of the maxilla AND the palatine bone.

Hyoid bone

serves as a point of attachment

for many tongue and neck muscles.

Paranasal Sinuses

Four skull bones (maxillary, sphenoid, ethmoid, frontal) contain sinuses (mucosa-lined air cavities); lighten the skull; may act as resonance chambers for speech

Sinusitis

inflammation of sinuses (from bacterial infection or allergy); as air in sinus cavity is absorbed, partial vacuum forms causing sinus headache; severe infections may require surgery to drain

Fetal Skull

contain fontanelles to allow the skull to compress slightly during birth; allows for brain growth during late fetal life

Fontanelles

Areas of fibrous membranes; completely ossify (become bone) by the time the child is 1.5-2 years old

Craniosynostosis

birth defect that causes one or more of the sutures on a baby's head to close earlier than usual; cause: unknown, may be genetic; symptoms: abnormally shaped head, no fontanelles, slow or no increase in head size as baby grows

Vertebral column

24 vertebrae, sacrum, coccyx

24 vertebrae

7 cervical, 12 thoracic, 5 lumbar

Cervical vertebrae

C1-C7

Cervical 1 (C1/atlas)

lacks body and spinous process, allows head to nod

Cervical 2 (C2/axis)

has dens (odontoid process) for head rotation

Cervical 1-7 (C1-C7) distinguishing features

triangular vertebral foramen, transverse processes contain foramen/foramina for vertebral arteries traveling to brain, C7 (vertebra prominens) is a landmark for counting vertebrae

Thoracic Vertebrae (T1-T12) distinguishing features

heart shaped body, small articulating surfaces/costal facets (superior and inferior) articulates with head of rib, round/oval vertebral foramen, transverse costal facets (on transverse process) articulate with rib tubercles

Lumbar Vertebrae (L1-L5) distinguishing features

block-like body & short thick spinous process, superior articular process pointing posteromedial, inferior articular process pointing anterolateral, spinal cord ends at superior area of L2

Spinal/lumbar 'tap' performed between...

between L3 and L4 or L4 and L5 to minimize injury to spinal cord. Administration of anesthesia for childbirth also performs in these regions

Intervertebral Foramen

A foramen exists between the inferior notch of a superior vertebra and the superior notch of an inferior vertebra; for nerves to enter or exit the spinal cord

Sacrum

Formed by fusion of 5 bones

Sacrum prominent features

Sacral promontory, median sacral crest, ala, transverse ridges, anterior/posterior sacral formina

Sacral promontory of sacrum

at anterior border of S1

Median sacral crest of sacrum

remnant of fused spinous processes

Ala of sacrum

formed by fusion of transverse processes

Transverse ridges of sacrum

site of vertebral fusion

Anterior/Posterior sacral foramina of sacrum

passage for blood vessels and nerves

Coccyx

Commonly known as the "tailbone"; It is formed by fusion of 3-5 irregularly shaped vertebrae; Attached to sacrum by ligaments

Spinal Curvatures

Primary and secondary curvatures

Primary curvatures

present at birth (thoracic & sacral curvatures)

Secondary curvatures

develop after birth (cervical & lumbar curvatures)

Cervical curvature allows...

baby to hold head up

Lumbar curvature allows...

baby to walk

Abnormal curvatures

scoliosis, kyphosis, lordosis

Scoliosis

lateral thoracic spine curvature

Kyphosis

excessive posterior thoracic curvature

Lordosis

excessive lumbar curvature

Bony Thorax Composed of...

sternum, ribs, thoracic vertebrae

Sternum

Attaches to 1st seven pairs of ribs. The sternum is formed by fusion of 3 bones

Three bones of the sternum

manubrium, gladiolus, xiphoid process

Manubrium of sternum

articulates with clavicle

Gladiolus (body) of sternum

bulk of sternum

Xiphoid process of sternum

located at the inferior end

(made of hyaline cartilage in children,

usually ossified in adults)

Landmarks of the sternum

jugular notch, sternal angle, xiphisternal joint

Jugular notch of sternum

at the level of the 3rd thoracic vertebra

Sternal angle of sternum

at the level of the 2nd ribs and 5th thoracic vertebra

Xiphisternal joint of sternum

at the level of the diaphragm and 9th thoracic vertebra

Ribs

We have 12 pairs of ribs; Ribs interact with the thoracic vertebrae. The facets on the head of the rib interacts with the inferior costal facet AND superior costal facet of adjacent thoracic vertebrae. The facet on the tubercle of the rib interacts with the transverse costal facet

Vertebrosternal ribs (1-7)

true ribs, attach to the sternum thru their own costal cartilage

Vertebrochondral ribs (8-12)

false ribs; ribs 8-10 attach to sternum thru costal cartilage of rib 7; ribs 11-12: floating/vertebral ribs do not attach to sternum

The Appendicular Skeleton

Pectoral girdle, pelvic girdle, appendages/limbs

Pectoral Girdle

clavicle and scapula

Clavicle (anterior)

convex forward & concave lateral

Clavicle important structures

acromial end, sternal end, conoid tubercle

Acromial end of clavicle

articulates with scapula

Sternal end of clavicle

attaches to sternum

Conoid tubercle of clavicle

ligament attachment site

Scapula (posterior)

acromion superior & lateral

Scapula important structures

spine, acromion, coracoid process, glenoid cavity, suprascapular notch, superior/lateral/medial borders, supraspinous fossa, superior angle, inferior angle

Spine of scapula

extends into the acromion

Acromion of scapula

connects with clavicle

Coracoid process of scapula

muscle attachment

Glenoid cavity of scapula

socket for humerus