Download New The Human Skeleton

The Human Skeleton
Divisions of the Skeleton
• Axial skeleton – skull,
vertebrae, and bony
thorax
• Appendicular skeleton
– bones of the arms
and legs, including
their associated
girdles
The Skull
• Consists of 22 bones
interlocked along sutures
(all except the mandible)
– 8 bones make up the
cranium
– 13 bones make up the
facial skeleton
– Mandible = lower jawbone;
only movable bone held to
the cranium by ligaments
• Orbit of the eye is formed
by cranial and facial
bones
The Cranium
• Encloses and protects
the brain
• Surface provides
attachments for
muscles involved in
chewing and head
movements
Sinuses
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Air-filled cavities of the cranium
Lined with mucous membranes
All connected by passageways to the nasal cavity
Function to reduce the weight of the skull and increase
voice intensity and resonance
Cranial Bones
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Frontal bone
Parietal bones (2)
Occipital bone
Temporal bones (2)
Sphenoid bone
Ethmoid bone
Frontal Bone Features
• Supraorbital foramen
• Frontal sinuses
• Develops in 2 parts that grow together by 5-6
years old
Parietal Bone Features
• Sagittal suture
• Coronal suture
Occipital Bone Features
• Lambdoidal suture
• Foramen magnum
• Occipital condyles
Temporal Bone Features
• Squamosal suture –
temporal to parietal
• External auditory meatus
• Mandibular fossae – joint
with mandible
• Mastoid process – neck
muscle attachment
• Styloid process – below
EAM, anchors muscles of
tongue and pharynx
• Zygomatic process –
helps form cheek
prominence
Sphenoid Bone Features
• Wedged between several
other bones in anterior
portion of the cranium
• 2 winglike structures
extend laterally toward
each side of the skull
• Sella turcica – houses
pituitary gland
• Sphenoidal sinuses
Ethmoid Bone Features
• Located in front of the sphenoid
bone
• Consists of 2 masses on each
side of the nasal cavity
• Cribriform plates – join the 2
parts of the ethmoid bone
• Perpendicular plate – form most
of nasal septum
• Superior and middle nasal
conchae – support mucous
membranes of the nose
• Ethmoid sinuses
• Crista galli – triangular process
that projects upward from the
cribriform plates; place of
attachment for membranes
around the brain
Facial Skeleton
• 13 immovable bones
+ the mandible
• Provides attachments
for muscles for facial
expressions and jaw
movements
Bones of the Facial Skeleton
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Maxillary bones (2)
Palatine bones (2)
Zygomatic bones (2)
Lacrimal bones (2)
Nasal bones (2)
Vomer bone
Inferior nasal conchae
(2)
• Mandible
Maxillary Bone Features
• Form upper jaw
• All other immovable facial
bones articulate with
them
• Hard palate
• Sockets of upper teeth
• Maxillary sinuses
• Palatine processes –
where the maxillary
bones meet
Palatine Bone Features
• L-shaped bones
behind the maxillae
• Posterior hard palate
Zygomatic Bone Processes
• Prominences of the
cheeks
• Temporal processes
Lacrimal Bone Features
• Thin, scalelike bones
between the ethmoid
bone and maxillae in
the medial walls of
the orbits
• Groove in anterior
portion provides
pathway for tears to
the nasal cavity
Nasal Bone Features
• Form the bridge of the
nose
Vomer Bone Features
• Joins perpendicular
plate of ethmoid bone
to form the nasal
septum
Inferior Nasal Conchae Features
• Scroll-shaped bones
attached to lateral
walls of the nasal
cavity
• Support mucous
membranes of the
nose
Mandible Features
• Ramus – attachment for large
chewing muscles
• Mandibular condyle –
articulates with mandibular
fossae of temporal bones
• Alveolar border – houses lower
tooth sockets
• Mandibular foramen – carries
nerves and blood vessels to
the lower teeth; dental injection
site
• Mental foramen – carries
branches of nerves and blood
vessels of the mandibular
foramen
Review of Fontanels
• Fontanels = membranous
areas where the skull is
incompletely developed;
soft spots
• Permit some movement
during childbirth
• Eventually close as
bones grow together
– Posterior fontanel – closes
at 2 months
– Sphenoid fontanel – closes
at 3 months
– Mastoid fontanel – closes
near end of 1st year
– Anterior fontanel – closes
near end of 2nd year
Other Infantile Skull Features
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Relatively small face
Prominent forehead
Large orbits
Small jaw
Small nasal cavity
Sinuses are incompletely
formed
• Frontal bone is in 2 parts
• Thin skull bones, but not
easily fractured
The Vertebral Column
• Extends from the skull
to the pelvis
• Forms the vertical
axis of the skeleton
• Composed of
vertebrae,
intervertebral disks,
and ligaments
Functions of the Vertebral Column
• Supports the head and trunk
• Permits movement
• Protects the spinal cord which passes
through the vertebral canal
Development of the Vertebral
Column
• Consists of 33 bones
at infancy
– 5 fuse to form the
sacrum
– 4 fuse to form the
coccyx
• 26 bones are found in
the adult vertebral
column
Curvatures of the Vertebral Column
• Primary curvatures are
anteriorly concave
– Thoracic curvature
– Pelvic curvature
• Secondary curvatures are
anteriorly convex
– Cervical curvature
– Lumbar curvature
• Cervical curvature
develops when a baby
begins to hold up its head
• Lumbar curvature
develops when a child
begins to stand
Typical Vertebra
• Body – thick, drum-shaped,
anterior portion of bone
• Intervertebral disks – cushion
and soften forces caused by
movements
• Pedicles – 2 short stalks that
project posteriorly from each
vertebral body
• Laminae – 2 plates that arise
from pedicles to fuse and form
the spinous process
• Transverse processes –
between the pedicles and
laminae; project laterally and
posteriorly
Typical Vertebra continued…
• Vertebral arch – formed
by the pedicles, laminae,
and spinous process;
around the vertebral
foramen
• Vertebral foramen –
opening through which
the spinal cord passes
• Intervertebral foramina –
passageways for spinal
nerves; between adjacent
vertebrae
Cervical Vertebrae
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7 vertebrae
Make up the neck region
Smallest vertebrae
Denser bone tissues than the
other regions
• Distinctive because they have
transverse foramina
(passageways for arteries
leading to the brain)
• Spinous processes are uniquely
forked (C2-C6)
• C7 = vertebrae prominens;
spinous process is longer and
protrudes beyond the other
cervical vertebrae
Atlas
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C1
Supports the head
Has no body or spine
Consists of a bony ring
with 2 transverse
processes
• Facets – kidney-shaped
areas on the superior
surface that articulate
with the occipital
condyles
Axis
• C2
• Dens – toothlike
process that projects
upward and lies in the
ring of the atlas
• As the head is turned
from side to side, the
atlas pivots around
the dens.
Thoracic Vertebrae
• 12 in number
• Larger than cervical
vertebrae
• Long, pointed spinous
process which slopes
downward
• Facets on sides of
vertebral body articulate
with the ribs
• Bodies of the vertebrae
increase in size from T3
down  can bear an
increasing load of body
weight
Lumbar Vertebrae
• 5 in number
• Located in the small of
the back
• Larger, stronger, and
support more weight than
the others
• Transverse processes
project posteriorly at
sharp angles
• Short, thick spinous
processes are nearly
horizontal
Sacrum
• Triangular structure at the
base of the vertebral column
• 5 vertebrae fuse to form the
sacrum between 18-30 years
of age
– Fused spinous processes form
a ridge of tubercles called the
median sacral crest
• Dorsal sacral foramina –
openings to the sides of the
tubercles through which
nerves and blood vessels
pass
• Sacral canal – formed from
vertebral foramina and opens
at the sacral hiatus
Coccyx
• Tailbone
• Lowest part of the
vertebral column
• Made of 4 vertebrae
that fuse by the 25th
year
• Acts as a shock
absorber when sitting
Vertebral Column Disorders
• Ruptured/herniated disk –
outer layers of the
intervertebral disk are
broken and the central
mass of the disk is
squeezed out from extra
pressure, pressing on the
spinal cord and spinal
nerves  pain,
numbness, loss of
muscular function
Curvature Disorders of the Spine
• Kyphosis –
hunchback;
exaggerated thoracic
curvature
• Scoliosis – abnormal
lateral curvature
• Lordosis – swayback;
exaggerated lumbar
curvature
Thoracic Cage
• Includes ribs,
thoracic
vertebrae,
sternum, and
costal cartilages
• Supports the
shoulder girdle
and upper limbs
• Protects viscera
• Plays a role in
breathing
Ribs
• 12 pair – one pair for
each vertebra
• True ribs – 1st 7 rib pairs;
join the sternum directly
by costal cartilages
• False ribs – bottom 5 rib
pairs; do not join the
sternum directly
– Cartilages of the upper 3
false ribs join the cartilage
of the 7th rib
– Floating ribs – last 2 rib
pairs; no attachment to the
sternum
Rib Structure
• Long, slender shaft which
curves around the chest and
slopes downward
• Head – enlarged area on
posterior end that articulates
with own vertebra and next
higher vertebra
• Tubercle – small knoblike
process that articulates with
transverse process of
vertebra
• Costal cartilages – hyaline
cartilage
Sternum
• Breastbone
• Develops in 3 parts:
– Manubrium –
articulates with
clavicles at clavicular
notches
– Body – fuses to
manubrium at middle
age at the sternal
angle
– Xiphoid process –
begins as cartilage,
slowly ossifies, and
fuses to the body at
middle age
• Red bone marrow in
sternum produces
RBCs into adulthood
Pectoral Girdle
• Made of 2
clavicles and 2
scapulae
• Supports upper
limbs
• Provides
attachment for
muscles that
move the upper
limbs
Clavicles
• Slender, rodlike bones with
elongated S shapes
• Located at base of the neck
and run horizontally between
the sternum and the shoulders
• Sternal ends – articulate with
the manubrium
• Acromial ends – articulate with
the scapulae
• Brace the scapulae, holding
the shoulders in place
• Structurally weak
Scapulae
• Broad, triangular bones located
on either side of the upper back
• Spine – divides posterior surface
• Supraspinous fossa – area above
the spine
• Infraspinous fossa – area below
the spine
• 2 processes at the head:
– Acromion process – forms tip of
the shoulder and articulates with
the clavicle
– Coracoid process – curves
anteriorly and inferiorly to the
clavicle
• Glenoid cavity – between the
acromion and coracoid
processes; articulates with the
head of the humerus
Upper Limb Bones
• Bones form the
framework of the arm,
forearm, and hand
• Bones function as levers
for muscle contraction
• Includes:
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Humerus (2)
Radius (2)
Ulna (2)
Carpals (16)
Metacarpals (10)
Phalanges (28)
Humerus
• Long bone that extends from
scapula to the elbow
• Head fits into glenoid cavity of
scapula
• Greater tubercle – on leteral
side
• Lesser tubercle – on anterior
side
• Surgical neck – tapering region
below head and tubercles
(common fracture site)
• Deltoid tuberosity – V shaped
rough area near the middle of
the shaft on the lateral side 
attachment for the deltoid
muscle
Humerus Bone Features
continued…
• Coronoid fossa – process
where the elbow bends:
receives the ulna
• Capitulum – articulates with
the radius
• Olecranon fossa – on posterior
surface, receives the
olecranon process of the ulna
when the elbow straightens
• Trochlea – articulates with the
ulna
• Epicondyles – attachments for
elbow muscles and ligaments
Radius
• On thumb side of forearm
• Shorter than the ulna
• Extends from the elbow to the
wrist and crosses over the ulna
when hand is turned over at
the wrist
• Head is thick and disk-like;
articulates with the capitulum
of the humerus and radial
notch of the ulna
• Radial tuberosity – process
just below the head;
attachment for the biceps
• Styloid process – attachment
for wrist ligaments at the distal
end
Ulna
• Longer than the radius
• Overlaps end of humerus
posteriorly
• Trochlear notch – at proximal
end, wrench-like opening that
articulates with the trochlea of
the humerus
• Olecranon process – above the
trochlear notch; attachment for
triceps that straightens the upper
limb at the elbow; fits into
olecranon fossa
• Coronoid process – below
trochlear notch, fits into coronoid
fossa when elbow bends
• Styloid process – at distal end
provides attachment for wrist
ligaments
Wrist
• Wrist consists of carpals
bound in 2 rows of 4
bones each
• Articulate with radius and
ulna proximally and
metacarpals distally
• Carpal bones are:
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Pisiform
Triquetrum
Lunate
Scaphoid
Hamate
Capitate
Trapezoid
Trapezium
Metacarpals
• Form the palm of the
hand
• 5 per hand
• Long bones with rounded
distal ends (knuckles)
• Articulate with carpals
and phalanges
• Lateral metacarpal is the
most freely moveable
• Numbered 1-5, starting at
the thumb
Phalanges
• Finger bones
• 3 per finger (proximal,
middle, and distal)
• 2 in thumb – no
middle phalanx
Pelvic Girdle
• Consists of 2 coxae
• Coxae articulate with each
other anteriorly and the
sacrum posteriorly
• Pelvis – formed by the
sacrum, coccyx, and pelvic
girdle
• Girdle supports the trunk of
the body, provides
attachments for lower limb
muscles, protects the
bladder, distal end of the
large intestine, and internal
reproductive organs
• Body weight is transmitted
through the pelvic girdle to
the lower limbs
Os Coxae
• Each coxa develops from 3 parts:
– Ilium
– Ishium
– Pubis
• Acetabulum – cup-shaped cavity where the 3 parts of
coxa fuse
• Largest and most superior
portion of the coxa
• Flares outward and forms the
prominence of the hip
• Iliac crest – margin of the ilium
• Iliac fossa – smooth, concave
surface on anterior aspect of
the ilium
• Sacroiliac joint – where ilium
and sacrum join
• Anterior superior iliac spine –
found lateral to the groin,
provides attachments for
ligaments and muscles
• Posterior superior iliac spine –
on posterior border
Ilium
Ischium
• Forms lowest portion of the
coxa
• L-shaped
• Ischial tuberosity – rough
surface that points down
and back; supports body
weight when sitting
• Ischial spine – sharp
projection above ischial
tuberosity, near the junction
between the ilium and the
ischium
– Area between ischial spines is
the shortest diameter of the
pelvic outlet; felt during
vaginal exams
Pubis
• Anterior portion of coxa
• Symphysis pubis –
fibrocartilage joint
between the 2 pubic
bones
• Pubic arch – angle
between pubic bones
• Obturator foramen –
largest opening in the
body
– Formed between ischium
and pubis
– Covered and nearly closed
by obturator membrane
Male vs. Female Pelvis
• Male Pelvis:
– Heavier bone
– More evidence of
muscle attachments
• Female Pelvis
– Iliac bones are more
flared
– Broader hips
– Greater angle of pubic
arch
– Greater distance
between ischial spines
and tuberosities
– Shorter, flatter sacral
curvature
– More delicate bones
Lower Limb Bones
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Femur (2)
Patella (2)
Tibia (2)
Fibula (2)
Tarsals (7/foot)
Metatarsals (5/foot)
Phalanges (14/foot)
Femur Bone Features
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Thigh bone
Longest bone in body
Extends from hip to knee
Head of femur – large and
rounded; projects medially
into acetabulum of coxal bone
Fovea capitis – pit on head of
femur that marks ligament
attachment
Greater trochanter and lesser
trochanter – attachments for
muscles of buttocks and lower
limbs
Linea aspera – longitudinal
crest on posterior surface in
middle third of shaft
Lateral and medial condyles –
articulate with tibia
Patella
• Articulates with the femur
on distal anterior surface
• Kneecap
• Flat sesamoid bone
located in a tendon that
passes anteriorly over the
knee
• Controls the angle at
which the tendon
continues toward the tibia
 functions in lever
actions
Tibia Bone Features
• Shin bone
• Larger of 2 leg bones; located
on the medial side
• Medial and lateral condyles –
on proximal end, articulate with
condyles of femur
• Tibial tuberosity – below
condyles on anterior surface;
attachment of patellar ligament
• Anterior crest – extends
downward from tuberosity; site
of CT attachments
• Medial malleolus – inner ankle
• Articulates with fibula and talus
on distal end
Fibula Bone Features
• Long, slender bone
located on the lateral
side of the tibia
• Articulates with the
tibia just below the
lateral condyle
• Lateral malleolus –
distal end that forms
the outer ankle
Bones of the Foot
• Tarsus – consists of 7
tarsal bones
• Talus – tarsal bone that
can move freely where it
joins the tibia and fibula
 ankle
• Other tarsals are bound
firmly together to support
the talus
• Calcaneus – largest
tarsal bone; heel bone
– Located below the talus
and projects backward
– Helps support weight of the
body
Metatarsals
• Numbered 1-5 beginning
on the medial side
• Ball of the foot formed by
the distal ends
• Longitudinal arch extends
from the heel to the toe;
provides a stable, springy
base for the body
• Transverse arch
stretches across the foot
• If tissues that bind the
metatarsals weaken 
fallen arches (flat feet)
Phalanges
• Shorter, but otherwise
similar to fingers
• 3 bones per toe,
except 2 in the great
toe