Download The Axial Skeleton

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Scapula wikipedia, lookup

Autopsy wikipedia, lookup

Anatomical terms of location wikipedia, lookup

Body snatching wikipedia, lookup

Anatomical terminology wikipedia, lookup

Skull wikipedia, lookup

Vertebra wikipedia, lookup

Transcript
Copy and Return to Teacher
The Axial Skeleton
The Axial Skeleton

Forms the longitudinal part of the body

Divided into three parts

Skull

Vertebral column

Bony thorax
The Skull

Two sets of bones
o
Cranium – encloses & protects brain
o Facial bones – holds eyes in anterior position & allows the facial muscles to show
emotions.

All but 1 of the bones are joined by sutures (interlocking, immovable joints)

Only the mandible is attached by a freely movable joint
The Cranium

Frontal – forms forehead, brow bone, superior eye orbit

Parietal (2) – form most of the superior & lateral walls of the cranium

o
Meet in midline = sagittal suture
o
Meet frontal = coronal suture
Temporal (2) – inferior to parietals & join to them at the squamous sutures
o
Important bone markings found here

External acoustic (auditory) meatus – canal leading to eardrum

Styloid process – sharp needle-like projection inferior to external auditory
meatus (attachment point for many neck muscles

Zygomatic process – thin bridge of bone that joins w/ the zygomatic
(cheek) bone

Mastoid process – rough projection posterior & inferior to the external
auditory meatus



Full of air cavities (sinuses)

Attachment for some neck muscles

Close to middle ear & leads to ear infections
Jugular foramen – junction of occipital & temporal

Allows for passage of jugular vein

Largest vein of the head – drains the brain
Internal auditory meatus – anterior to jugular foramen


Carotid canal - anterior to jugular foramen


Transmits cranial nerves 7 & 8 (facial & vestibulocochlear)
Carotid artery runs through it to brain
Occipital – most posterior bone of cranium forming back wall & floor of the skull
o
Joins parietals anteriorly at lambdoid suture
o
Foramen magnum = large opening in base of the occipitals (spinal cord connects
with the brain)

Lateral to the foramen magnum are rockerlike occipital condyles which
rest on the 1st vertebra

Sphenoid – butterfly-shaped – spans the width of the skull and forms part of cranial
cavity floor
o
Sella turcica “Turk’s saddle” = small depression on the midline of the sphenoid,
holds the pituitary gland
o
Foramen ovale = large oval opening in line w/ the posterior end of the sella
turcica (allows cranial nerve 5 (trigeminal) to pass to chewing muscles of
mandible
o
Parts of the sphenoid form part of the eye orbits

2 important openings:
1. Optic canal (optic nerve)
2. Superior orbital fissure (cranial nerves 3, 4 & 6 – eye movements)
o Central part of the sphenoid riddled w/ air cavities = sphenoid sinuses

Ethmoid – irregularly shaped, anterior to sphenoid – forms roof of nasal cavity and
medial walls of the orbits.
o
Crista galli “cock’s comb” = superior ethmoid surface projection – outermost brain
covering attaches
o
Cribriform plates – holey areas on sides of crista galli= nerve fibers for smell pass
through from nose
o
Superior & middle nasal conchae – extensions of the ethmoid – form part of
lateral walls of nasal cavity & increase turbulence of air flowing
Facial Bones
*14 bones
*12 paired, only the mandible and vomer are single

Maxillae (2) / maxillary bones – fused to form upper jaw
o
Upper teeth carried in the alveolar margin
o
Palatine processes- extensions that form the anterior part of the hard palate
o
Paranasal Sinuses – drain the nasal passages, lighten the skull bones, amplify
sounds as we speak


Hollow portions of bones surrounding the nasal cavity

Sinusitis (infection of sinuses) – can result in headache or upper jaw pain
Palatine (2) – posterior to palatine processes of maxillae – form posterior part of hard
palate
o
Cleft palate= failure of these to fuse

Zygomatic (2) – cheek bones – form portion of lateral walls of orbits

Lacrimal (2) – fingernail sized bones forming part of medial walls of orbits
o

Groove serves as passageway for tears
Nasal (2)– small rectangular bones – form bridge of nose – lower part of nose made of
cartilage

Vomer “plow” (1) – median line of nasal cavity – forms most of the nasal septum

Inferior nasal conchae (2) – thin, curve bones projecting from lateral walls of the nasal
cavity

Mandible (lower jaw) – largest, strongest bone of the face – joins temporal bones on
each side of face, forming the only freely movable joints in the skull (find them!)
o
Horizontal part (body) forms the chin
o
2 upright bars of bone (rami) extend from the body to connect the mandible with
the temporal bone.
o
Lower teeth lie in alveolar margin
The Hyoid Bone

Not really part of the skull

Horseshoe shaped w/ a body and 2 pair of
horns (cornua)

Closely related to mandible and temporal
bones

Unique b/c it’s the only bone that does not
articulate w/ any other bone

Suspended in mid–neck region 2 cm above
the larynx, anchored by ligaments to the
styloid processes of the temporal bones

Serves as a movable base for the tongue &
attachment point for neck muscles (lower and
raise larynx when we swallow & speak)
The Fetal Skull

Face small compared to size of cranium (skull is large
compared to body length)

Adult skull is 1/8 total body length; newborn is 1/4

Fontanels – fibrous membranes connecting the cranial
bones
o
Baby’s pulse can be felt in these soft spots
(explains their name “little fountain”)
o
Allow fetal skull to be compressed in birth
process
o
Allow infants brain to grow
o
Largest fontanels are diamond shaped anterior
shaped fontanel and smaller triangular shaped
posterior
o
Convert to bone within 24 months after birth
The Vertebral Column

Serves as axial support of the body

Extends from the skull, which it supports, to the
pelvis, where it transmits the weight of the body to
the legs.

26 irregular bones connected & reinforced by
ligaments creating a flexible, curved structure.

Spinal cord runs through central cavity, protected
by vertebrae

Before birth = 33 separate vertebrae but 9 later
fuse to form 2 composite bones – the sacrum (5
fused) & the coccyx (4 fused).

Each vertebrae is given a name according to its
location


24 single vertebrae
o
7 cervical vertebrae
o
12 thoracic vertebrae
o
5 lumbar vertebrae
Vertebrae separated by pads of flexible
fibrocartilage – intervertebral discs –cushion &
absorb shocks while allowing flexibility.

o
Young person – discs = 90% water content – spongy & compressible.
o
As you age – water content decreases – harder & less compressible.
Can lead to herniated (“slipped”) discs.

Can also occur from exceptional twisting forces.

If disc presses on spinal cord or nerves = numbness & excruciating pain.
Disks & S-shaped curvature of spine prevent shock to head when we walk or run.
o
o


Primary curvatures

Thoracic & sacral regions

Present at birth
Secondary curvatures

Cervical curvature appears when baby begins to raise its head.

Lumbar curvature when baby begins to walk.
Abnormal spinal curvatures
o
Scoliosis - abnormal lateral curvature of the spine.
o
Kyphosis - Abnormal rearward curvature of the spine, resulting in hunchback.
o
Lordosis - Abnormal forward curvature of the spine in the lumbar region.
Vertebrae

All vertebrae have a similar structural
pattern.
o
Body: disclike, weight bearing
part facing anteriorly.
o
Vertebral arch: formed from the
joining of all posterior
extensions, the laminae &
pedicles.
o
Vertebral foramen: canal through
which the spinal cord passes.
o
Transverse processes: 2 lateral projections
from the vertebral arch.
o
Spinous process: single projection arising from
the posterior aspect of the vertebral arch (fused
laminae).
o Superior & inferior articular processes: paired
projections lateral to the vertebral foramen
allowing a vertebra to form joints w/ adjacent
vertebrae.
Cervical Vertebrae

7 (C1 to C7) – form the neck region.

First 2 – atlas & axis – are different because they
perform functions not shared by any other cervical
vertebrae.

Atlas (C1) has no body; the superior surfaces of its
transverse processes contain large depressions
that receive the occipital condyles of the skull;
allows you to nod “yes.”

Axis (C2) has a large upright process (dens or
odontoid process), which acts as a pivot point;
allows you to indicate “no.”

C3 through C7 are the smallest, lightest vertebrae

All transverse processes of cervical vertebrae only contain foramina through which
vertebral arteries pass to the brain.
Thoracic Vertebrae

12 with body somewhat heart shaped w/ 2 costal
facets on each side, which receive the heads of the
ribs.

Spinous process is long & hooks sharply downward
(from the side looks like a giraffe’s head).
Lumbar Vertebrae

5 w/ massive blocklike bodies & short hatchetshaped spinous processes (looks like moose head
from side).

Sturdiest vertebrae – most stress here.
Sacrum

Formed by the fusion of 5 vertebrae.

Winglike alae articulate laterally w/ the hipbones
forming the sacroiliac joints.

Forms the posterior wall of the pelvis.

Median sacral crest roughens the posterior midline & are flanked by sacral foramina.

Vertebral canal continues inside the sacrum as the sacral canal – terminates in large
inferior opening called the sacral hiatus.
Coccyx

Formed by fusion of 3 to 5 tiny, irregularly shaped vertebrae

This is the human “tailbone” – a remnant of the tail other vertebrate animals have.
Bony Thorax


Made-up of three parts
o
Sternum
o
Ribs
o
Thoracic vertebrae
Often called the “thoracic cage” b/c it forms a cone-shaped cage of slender bones to
protect the major organs of the thoracic cavity.

Sternum – “breastbone”
o
Flat bone that is a result of the fusion of 3 bones – the manubrium, body and
xiphoid process
o
Attached to the first 7 pairs of ribs
o
Three important bony landmarks:
1. .jugular notch (concave upper border of the manubrium) – can be felt easily –
generally at level of T3
2. .sternal angle - where manubrium & body meet - formed at level of 2nd ribs
(reference to locate 2nd intercostal space for listening to heart valves)
3. .xiphisternal joint – body and xiphoid process fuse (level of T9)
o
Sternal puncture used to get bone marrow tissue to diagnose certain blood
diseases

Ribs – 12 pair – form walls of bony thorax
o
Articulate w/ vertebral column posteriorly & curve downward toward anterior body
surface.
o
True ribs = first 7 pair – attach directly to sternum by costal cartilage
o False ribs = next 5 pair – attach indirectly to sternum or not at all (last 2 pair are
called “floating ribs” b/c they are
the ones not attached at all)
o Contrary to popular myth – men &
women have the same number of
ribs!! 