Anatomy Exam 2 (Module 6)

Bones in the skull

- 28 bones
- most are "flat" bones formed via intramembranous ossification
- bones united by sutures (interlocking, immovable joints)

Major sutures of the skull

- coronal suture
- squamous suture
- lambdoid suture
- sagittal suture

1) sagittal suture
2) coronal suture
3) squamous suture
4) lambdoid suture

Fetal/Infant skulls

- connect by flexible CT to allow head to deform during birth & rapid brain growth
- area between bone = fontanelles (soft spots), will fuse over time

1) fontanelles

Craniosynostosis

premature fusion of the skull bones, leading to unusual cranial vault shape

Subdivisions of the skull

1) cranial division
2) facial division

Cranial bone functions

- protect brain
- provide attachment sites for some neck/head muscles

Facial bone functions

- form the framework of face openings for passage of air and food
- hold the teeth
- anchor muscles of the face

Cranium subdivisions

1) vault = superior, lateral, and posterior bones of the skull (forehead included)
2) base = inferior part of the cranium

How many bones are in the cranium?

8 bones

Bones of the cranium

- frontal (forehead)
- occipital
- sphenoid
- ethmoid
- 2 parietals (left & right)
- 2 temporals (left & right)

1) frontal bone
2) parietal bone
3) temporal bone
4) occipital bone
5) sphenoid bone
6) ethmoid bone

Parietal bones

- make up most of the superior part of the skull, extend posteriorly and laterally
- sagittal suture between two parietal bones
- lambdoid suture between parietal and occipital bones

1) sagittal suture
2) lambdoid suture

Occipital bone

- posterior part of the cranium and cranial base
- contain foramen magnum and occipital condyles

Foramen magnum

large opening in the occipital bone that allows the spinal cord to pass & connect w/ the brain

Occipital condyles

region where the skull articulates w/ the vertebral column (atlas or C1 vertebra)

1) occipital
2) occipital condyles
3) foramen magnum

Temporal bones

paired bones (left & right side) that house the openings to the ear, forming the base of the cheekbone

Main regions of temporal bones

1) petrous
2) tympanic
3) squamous

Petrous region of temporal bones

- best seen internally
- contains middle & inner ear cavities
- hard

Tympanic region of temporal bones

contains external acoustic meatus (EAM) opening, leading to the middle & inner ear

Squamous region of temporal bones

vertical portion (part of cranial vault)

1) squamous part
2) mastoid process
3) tympanic part
4) styloid process

Temporomandibular joint (jaw joint)

condyle of the mandible articulates w/ temporal bone at the mandibular fossa

1) mandibular fossa
2) condyle
3) temporomandibular joint

Middle ear cavity (inside temporal bone)

- 3 ear ossicles: malleus, incus, and stapes (small bones)
- sound waves cause vibrations of these bones that are transmitted to the inner ear (cochlea)

1) middle ear

1) malleus (hammer)
2) incus (anvil)
3) stapes (stirrup)

Sphenoid

- large and wing-shaped
- sella turcica = bony depression that holds the pituitary gland
- only cranial bone that articulates with every other cranial bone

1) sphenoid
2) sella turcica

Ethmoid bone

- just anterior to sphenoid
- takes up most of the area between the nasal cavity and the orbits
- forms some boundaries of the nasal cavity and separates the nasal cavity from the brain
- contains crista galli and cribriform plate

1) ethmoid bone

Crista galli

- attaches to cribriform plate
- separates nasal cavity from brain
- site of attachment for dura mater (membrane covering brain)

Cribriform plate

- help form the roof of nasal cavities
- foramina allow passage of olfactory nerves into brain

1) crista galli
2) cribriform plate

How many bones are in the facial skeleton?

14 bones

Bones of the facial skeleton

1) mandible (unpaired)
2) vomer (unpaired)
3) 2 nasals (form bridge of nose)
4) 2 lacrimals (allows tears to drain into nasal cavity)
5) 2 maxillae
6) 2 zygomatics (form cheekbones)
7) 2 palatine bones
8) 2 inferior nasal conchae

1) lacrimal bones
2) inferior nasal concha
3) vomer
4) nasal bones
5) zygomatic bones
6) maxillae
7) mandible

Maxilla(e)

- form upper jaw
- articulate w/ all other facial bones except mandible
- contain alveolar processes (contains teeth), frontal processes (extend upward to reach frontal bone), and zygomatic processes (articulate w/ zygomatic bone)

1) orbital surface
2) zygomatic process
3) frontal process
4) alveolar processes

The orbit

- supports the eyes and muscles that move the eyes, contain fat and lacrimal glands (tear-producing glands)
- walls formed by frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid bones

1) frontal
2) ethmoid
3) lacrimal
4) palatine
5) maxilla
6) zygomatic
7) sphenoid

Nasal cavity in sagittal section

- lateral walls: nasal bones, nasal conchae (superior, middle, inferior), maxillae, palatines
- floor = hard palate, formed by palatine process of maxillae, horizontal plate of palatine

1) frontal sinus
2) ethmoid (superior & middle nasal conchae)
3) nasal bone
4) maxilla
5) inferior nasal concha
6) maxilla
7) palatine bone
8) sphenoidal sinus
9) cribriform plate

Palate and inferior nasal septum

- hard palate composed of maxillary bones and palatine bone
- vomer forms inferior portion of nasal septum

1) maxilla
2) palatine
3) vomer

Cleft palate

- failure of the 2 sides of the palate to join
- opening between mouth and nasal cavity makes effective nursing difficult
- can be repaired surgically w/ good outcomes

Mandible

- largest, strongest bone in the face
- body contains lower teeth
- alveolar processes = tooth sockets on superior border
- mandibular symphysis = 2 halves of the body join to form chin (mental protuberance)
- vessels and nerves enter via mandibular foramen and exit via mental foramen inferior to teeth
- condyle articulates w/ the temporal bone to form the temporomandibular joint (TMJ)
- coronoid process serves as an attachment site for the temporalis muscle (major chewing muscle)

1) ramus of mandible
2) body of mandible
3) mandibular foramen
4) alveolar process
5) mental foramen

1) condyle
2) coronoid process

Fetal/infant face

- cranium huge relative to face
- skull is 3/4 adult size by age 2
- age 6-13: face grows outward and develops more "adult" proportions, body size begins to catch up w/ head

Hyoid

- "free floating" bone in neck inferior to mandible
- only bone in the skeleton that does not articulate w/ any other bone
- acts as base for tongue, site of muscle attachments for muscles that move the larynx

1) hyoid

Thoracic cage

- includes thoracic vertebrae, ribs, sternum, and costal cartilages
- protects heart, lungs, and other organs
- supports pectoral girdle and provides attachment points
- intercostal spaces hold muscles that aid in breathing

Sternum

- 3 bones: manubrium, body, xiphoid process
- articulates w/ clavicles & ribs and costal cartilage
- sternal angle is an important landmark for thoracic anatomy

1) jugular notch
2) sternal angle
3) manubrium
4) body
5) xiphisternal joint
6) xiphoid process

Rib cage

- protects internal organs & aids in respiration
- all ribs attach posteriorly to thoracic vertebrae

How many pairs of ribs are there?

12 pairs

First 7 ribs (true ribs)

attach to sternum by costal artilages

Ribs 8-10 (false ribs)

do not have a direct attachment to the sternum; attach via a shared costal cartilage

Rib 11-12 (floating ribs)

do not attach anteriorly to the sternum

Rib structure

- main part of rib = shaft (body)
- rib articulates w/ the vertebra at the head and tubercle
- "neck" = thinner region between head and tubercle
- head has 2 "facets"= one articulates w/ the body of its vertebra and one articulates on the body of the vertebra superior to it
- tubercle articulates w/ a facet on the transvers process of the vertebrae

1) tubercle
2) head
3) shaft

1) transverse process
2) tubercle
3) head
4) transverse costal facet (for tubercle)
5) costal facet

How many vertebrae in the vertebral column?

26 vertebrae
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral (will fuse into 1)
- 4 coccyx (will fuse into 1)

Vertebral column functions

- protect spinal cord
- supports body axis
- attachment points for ribs and muscles of neck and back
- anchor pectoral and pelvic girdles

1) cervical
2) thoracic
3) lumbar
4) sacral
5) coccygeal

Curves of the spine

- vertebrae become larger as they move inferiorly to support weight
- sacrum articulates w/ hip bones of pelvis, passes weight to appendicular skeleton
- curves increase flexibility; also position center of gravity of axis of body

Scoliosis

lateral curvature of the spine, usually treated w/ body braces or surgery when young

Kyphosis (Dowager's Hump)

excessive curvature of the thoracic spine, typically the result of vertebral body factures caused by osteoporosis

Osteoporosis

- results from imbalance in normal bone building and degradation cycle
- usually after menopause, women don't absorb as much calcium so osteoclasts break bone down to release the calcium into the bloodstream

Lordosis

- excessive curvature of the lumbar spine
- usually temporary and resulting from shift for a larger front load (belly in men, pregnant women)

Basic vertebral anatomy

- body located anteriorly
- vertebral arch made of lamina and pedicles: creates vertebral foramen (surrounds spinal cord) and stacked vertebrae result in vertebral canal
- spinous processes & transverse process are ligament & muscle attachment sites
- vertebrae articulate at superior and inferior articular processes and facets: each articular process has an articular facet, individual vertebrae articulate w/ the vertebrae just superior and inferior to it, articulation also makes intervertebral foramina between 2 vertebrae

Vertebral column and spinal cord

- spinal cord passes through, and is protected within, the vertebral (spinal) canal
- spinal nerves exit between the body of the vertebra and the vertebral arch via intervertebral foramina

1) spinal cord within spinal canal
2) nerve root
3) intervertebral disc
4) spinous process
5) lamina

Seven cervical vertebrae (C1-C7)

- have transverse foramina
- articular facets face superior/inferior
- bifid (split) spinous processes

1) transverse foramen
2) articular facets
3) bifid spinous process
4) transverse foramen

Atlas (C1)

- no body or spinous process
- articulates w/ occipital condyles, allows flexion/extension of head (nodding "yes")

Axis (C2)

- dens articulates w/ atlas, allows rotational movement (shaking head "no")
- dens used to be the body of the atlas, but not part of axis

Twelve thoracic vertebrae (T1-T12)

- coastal facets for ribs, located on each body of the thoracic vertebrae
- articular facets face anterior/posterior
- spinous processes are long & project inferiorly

Five lumbar vertebrae (L1-L5)

- large bodies
- articular facets face medial/lateral
- short, flat spinous processes

Sacrum

- 5 fused vertebrae
- forms posterior wall of pelvis
- ala on lateral sacrum articulate w/ hip bones to form sacroiliac joints

Coccyx

- 3-5 fused vertebrae
- "tail bones"

1) sacrum
2) coccyx

Thoracic vertebra

Lumbar vertebra

Cervical vertebra