THE
SKELETAL
SYSTEM
I. BONE STRUCTURE & FUNCTION
A. There are 206 bones in
the body.
A. FUNCTION
1. Support
2. Protection
3. Movement due to muscles
4. Blood formation
5. Electrolyte Balance
6. Acid Base Balance
aka hematopoesis
stores and releases calcium and phosphate
Buffers blood by storing and releasing alkaline salts
Skeletal system is divided Into 2
parts:
Axial Skeleton
Appendicular Skeleton
Parts of the skeletal
system include:
bones (skeleton);
joints,
cartilage,
& ligaments
A.
blood by storing and releasing alkaline salts
IV. The Skeleton
A. Organization
1. Axial Skeleton
– Skull
– Vertebral Column
– Vertebrae
– Ribs
2. Appendicular Skeleton
– limbs
– girdles
Two types of Bone
Spongy
(cancellous)
Compact
Bone
B. Microscopic Anatomy
3. Mature Bone
Osseous
Tissue
3. Mature Bone
• Called
Lamellar
bone
•Two kinds of
bone
 Compact
 Spongy
(cancellous)
• Spongy (cancellous)
• contains trabeculae
• contains spaces
3. Mature Bone
Compact
Bone
• Dense, few spaces
• Haversian canals
• Concentric Lamellae
Osseous Vocabulary & Anatomy
• Osteon (Haversian System) is a unit of bone.
• Central (Haversian) Canal is an opening in the
center of an osteon that carries bloodvessels &
nerves.
Osseous Vocabulary & Anatomy
• Perforating (Volkman’s) Canal runs perpendicular to
the central canal & carries blood vessels & nerves.
Osseous Vocabulary & Anatomy
• Lacunae are cavities
holding the mature bone
cells (osteocytes).
Arranged in concentric
rings..
• Lamella are the
concentric rings around
the central canal that
holds the lacunae
Osseous Vocabulary & Anatomy
• Canaliculi are the tiny
canals radiating
perpendicularly from the
central canal through the
lamella creating a
transport system from
nutrients.
Osseous Vocabulary & Anatomy
• Osteoblasts are young
bone forming cells that
cause the hard
extracellular matrix to
form.
• Osteoclasts are bone
dissolving cells
• Osteocytes are mature
bone cells.
Osteoblasts
Osteocytes
Osteoclasts
Osteoclasts
Osteoblasts
Osteocytes
Name C, D & E
C = Osteoclast
D = Osteoblast
E = Osteocytes
I. BONE STRUCTURE & FUNCTION
4 Shapes of Bone:
–Long bones Have a shaft with
heads at both ends & Contain mostly
compact bone.
–Short bones Generally cubeshape & contains mostly spongy bone.
–Flat bones thin, flattened, usually
curved & has thin layer of compact bone
surrounding spongy bone.
–Irregular bones Do not fit
into other bone classification categories
Long bones
Short bones
Flat bones
Irregular
bones
Classify the
bone types
to the left
B. Structure
Parts of Long Bone
– Epiphyses
AKA: head
• Contains red
bone marrow
• Spongy bone
and compact
bone
B. Parts of a Long Bone
Diaphysis:
• Shaft of bone
• Contains
yellow bone
marrow w/in
medullary cavity
• Spongy and
compact bone
Diaphysis of Long
Bone
• Medullary
cavity contains
yellow marrow
(fat & minerals)
in adults.
B. Parts of a long bone
Epiphyseal plate
 Allows for growth in
bone
 Found only in children
Articular Cartilage:
Covers the epiphyses
Made of hyaline
cartilage
Decreases Friction @
joint surfaces
B. Parts of a long bone
Periosteum: outer
covering of diaphysis
Fibrous connective
tissue membrane
Sharpey’s Fibers:
Secure periosteum
to underlying bone
Arteries:
Supply bone cells
w/nutrients
D. Membranes
1. Periosteum:
a. The external
covering of bone
2. endosteum:
a. Found on internal
bone surface
b. covers trabeculae
of spongy bone
c. in marrow cavities
II. BONE GROWTH & DEVELOPMENT
A. Two Patterns of Bone Formation
1. Intramembranous
bones
– originate
between
sheet-like
layers of
connective
tissues
II. BONE GROWTH & DEVELOPMENT
A. Two Patterns of Bone Formation
2. Endochondral
bones
– begin as masses
of hyaline
cartilage that
bone tissue later
replaces.
II. BONE GROWTH & DEVELOPMENT
B. Growth in Long Bones
1. grow by interstitial growth at
epiphyseal plates
a. rate of cartilage growth is
balanced by replacement with
bone
b. end of growth as cartilage
cells slow down division
Bone Growth in Long Bones
II. BONE GROWTH & DEVELOPMENT
B. Growth in Long Bones
2. bones grow in width by
appositional growth
a. Osteoblasts in periosteum:
secretes bone matrix
b. Osteoclasts in endosteum:
removes bone matrix (a little
slower)
Appositional Growth
– New bone forms at ridges around
blood vessels
– Periosteum becomes endosteum
Appositional Growth
– New lamella formed
– More bone added forming osteon
II. BONE GROWTH & DEVELOPMENT
C. Hormones
1. growth hormone from pituitary:
stimulates growth in childhood
a. Gigantism: excessive growth
hormone
b. dwarfism: not enough growth
hormone or thyroid hormones
II. BONE GROWTH & DEVELOPMENT
C. Hormones
2. thyroid: regulates activity of
growth hormone
3. sex hormones: promote growth
spurt, induce epiphyseal plate
closure
estrogen: maintains bone
density
III. Bone Maintenance & Repair
A.Bone remodeling:
1. Life long process
2. Local areas of bone are destroyed
and rebuilt
3. Repairs microdamage caused by
normal wear and tear
B.Fractures
1. Simple
bone breaks
cleanly, does
not break
through skin
B.Fractures
2. Compound
broken ends
protrude
through the
skin, risk of
bone infection
B.Fractures
3. Greenstick
Does not
break
completely
Greenstick:
(children)
Impact Fx of distal radius & ulna @ Epiphyseal Line
Facial Comminuted Fx
Tibial Oblique Fx
III. Remodeling and Repair
C. Repair
1. Hematoma forms
2. Spongy bone forms in area of
hematoma forming a soft callus
C. Repair
3. Osteoblasts lay down new bone
matrix converting the soft callus into a
hard callus of spongy bone
4. The boney callus is remodeled to
form a permanent patch
III. Types of Bone Repair
• Bone healing occurs
in stages:
–fracture
–granulation
–callus
–lamellar bone
–normal contour
III. Calcium Homeostasis
A. Blood Ca2+ Level
1. Has a very narrow range
2. Ca2+ Required for
– For normal muscle contraction
– Nerve impuses
III. Calcium Homeostasis
A. Blood Ca2+ Level
3. Abnormal levels
– Hypocalcemia
causes marked jitteriness and
convulsive seizures
III. Calcium Homeostasis
A. Blood Ca2+ Level
3. Abnormal levels
– Hypercalcemia
the most common lifethreatening metabolic disorder
associated with cancer
III. Calcium Homeostasis
B. Bone’s Role
1. Major storage site for calcium
2. Calcium moves
– Into bone as osteoblasts build
new bone
– Out of bone as osteoclasts
break down bone
III. Calcium Homeostasis
C. Bone, Calcium and Hormones
1.Parathyroid Hormone –
Increases blood Ca2+ levels
2. Calcitonin
Decreases blood Ca2+ levels
III. Calcium Homeostasis
D. Homeostatic Imbalances
• Osteopenia
– Inadequate ossification
• Osteoporosis
– Bone absorption outpaces
deposition
– Fractures common
– More common in elderly women
D. Homeostatic Imbalances
• Rickets
– Lack of vitamin D or
calcium during
growth
– Bowed legs
– Deformed pelvis
Rickets
D. Homeostatic Imbalances
• Osteosarcoma
– Bone cancer
– Usually between ages 10-25
– Survival rate is about 50% with
amputation
D. Homeostatic Imbalances
• Bone spur
– Abnormal
projection at one
site of bone due to
overgrowth
– Common in aging
bones
Bone Markings
• Bony markings are the surface features of a bone.
• They are sites of attachments for muscles, tendons &
ligaments.
• They can serve as passage ways for nerves & blood
vessels.
• There are 2 Categories of Bony Markings
– Projections & processes – outward growths on
the bone surface.
– Depressions or cavities – indentations on the
surface of the bone.
C.Bone Markings –
1. Kinds
1. Kinds
• Articulating
Surfaces
For
formation
of a joint
•Openings
• Depressions &
Enlargements
For muscle
attachment
To allow blood vessels or
nerves to pass through
C.Bone Markings –
2. Articulating surfaces
Head
A rounded projection
set off from the body
of a bone by a
constriction (the
neck) ex. head of
femur
C.Bone Markings –
2. Articulating
surfaces
Any large articulating
surface, may be concave or
convex
Condyle
C.Bone Markings –
2. Articulating
surfaces
A smooth, flat surface,
generally small
Facet
C.Bone Markings –
2. Articulating
surfaces
Fossa
A shallow depression
C.Bone Markings –
3. Enlargements & Processes
Process
generic term for bone projection
that serves as a point for
attachment of other structures
C.Bone Markings –
3. Enlargements
Epicondyle
projection or swelling to the side
of or above a condyle
C.Bone Markings –
3. Enlargements
a sharp, slender
projecting process
Spine
C.Bone Markings –
3. Enlargements
a small
rounded
projection
Tubercle
C.Bone Markings –
3. Enlargements
Turberosity
a large
rounded
roughened
projection
C.Bone Markings –
3. Enlargements
a large blunt
projection
Trochanter
C.Bone Markings –
3. Enlargements
a prominent
border or
ridge
Crest
C.Bone Markings –
A
major
3. Enlargements
branch or
division off
of the main
body of a
bone
Ramus
C.Bone Markings –
4. Openings
C.Bone Markings –
4. Openings
Meatus
Canal
like
opening
C.Bone Markings –
5. Depressions
Sulcus
A
shallow
groove
C.Bone Markings –
5. Depressions
Fovea
A very
shallow
groove
C.Bone Markings –
5. Depressions
Fissure
A deep
groove
Axial Skeleton
•
•
•
•
•
Forms the longitudinal part of the skeleton.
Divided into 3 parts:
Skull
Vertebral Column
Bony Thorax
The Skull
•
•
•
•
•
The skull is divided into 2 parts:
Cranium
Facial Bones
The cranial bone joints are called sutures.
Only the mandible is attached by a freely
movable joint.
Lateral view of the Skull
Frontal view of the Skull
Transvers section of Inferior, Internal Skull
Inferior, External view of Skull
Sinuses
The sinuses are hollow portions of bone within the skull surrounding the
nasal cavity. They lighten the face/skull, act as resonance chambers &
amplify the voice.
The Hyoid Bone
The only bone
in the body that
does not
articulate
w/another
bone.
It serves as a
moveable base
for the tongue.
The Fetal Skull
• The fetal skull is large
compared to the
infant’s total body
length.
• Fontanels are fibrous
membranes connecting
the cranial bones
• The fontanels allows
the brain to grow.
• The fontanels converts
to bone within 24
months after birth.
The Vertebral Column
The Vertebrae are
separated by
intervertebral discs made
of fibrocartilage,
connective tissue.
The spine has a normal
“S” curvature.
Each vertebrae is given a
name according to its
location.
Bony Thorax
Made of 3 parts:
Sternum
Ribs
Thoracic vertebrae
The bony thorax forms the
rib cage that protects the
thoracic internal organs.
The Appendicular Skeleton
Includes
the:
Appendages
(limbs)
Pectoral
Girdle
Pelvic
Girdle
Pectoral – Shoulder Girdle
Made of 2
bones:
Clavicle aka
collarbone
Scapula aka
shoulder blade
The pectoral
girdle allows
the upper limb
to have free
range of
movement
Pectoral – Shoulder Girdle
Pectoral Girdle – Posterior View
Upper Extremity Bones
Includes the:
Humerus (upper
arm bone)
Radius (thumb
side of forearm)
Ulna (pinki side of
forearm)
& the Hand
Anterior
Humerus
Posterior
Humerus
Upper Extremity Bones
The distal head
of the radius is
larger than the
proximal
The proximal
head of the Ulna
is larger than the
distal.
Upper Extremity Bones
The Hand includes:
Carpals – short
bones of the wrist.
Metacarpals – long
bones of the palm
of the hand.
Phalanges (Digits)
– Proximal, Middle,
Distal fingers.
Upper Extremity Bones - Carpals
1.The Trapezium is the lateral carpal
bone that is proximal to the 1st
metacarpal.
2.The Schaphoid is the proximal carpal
bone that is distal to the radius.
3.The Lunate is a proximal carpal bone
that articulates w/the ulna.
4.The Trapezoid is a carpal bone that is
proximal to the 2nd metacarpal.
5.The Capitate is the largest distal carpal
bone that is proximal to the 3rd
metacarpal.
6.The Hamate is a distal carpal bone
that articulates w/the 4th & 5th
metacarpals.
7.The Triquetral bone is a triangular
shaped carpal bone later to the hamate.
8.The Pisiform is the smallest carpal
bone lateral to the triquetral bone &
feels like a hard bump at the base of the
wrist.
Pelvic Girdle
Made of the
Coxal Bone (hip)
which is 3 bones
fused together:
Ilium
Ischium
Pubic Bone
The total weight of the upper body sits on the pelvis.
The pelvis protects the reproductive organs, urinary
bladder, & part of the large intestine
Lateral View of Pelvis
B. Male vs. Female Skeleton - Pelvis
a. spines farther
apart in male
b. hole in ischium:
smaller and
triangular in
female
c. angle across
pubic
symphysis =
pubic arch: less d. distance between
than 90° and
ischia larger in
more sharply
female
angled in male
Male & Female Pelvic Differences
Lower Extremity
The lower
extremity is
made of:
Pelvis
Femur (thigh)
Tibia (shin)
Fibula
Foot
Anterior
Femur View
Posterior Femur
View
Lower Extremity
The flat superior
portion of the tibia
is called the Tibial
Plateau.
The distal head of
the tibia is called
the medial
malleolus while the
distal head of the
fibula is called the
lateral malleolus
Lower Extremity
The Foot is made
up of the :
Tarsals – short
bones of foot
Metatarsals – long
bones of foot
Phalanges (Digits)long bones of the
toes
Lower Extremity - Tarsals
1. The Medial Cuneiform(1) is proximal to
the 1st metatarsal.
2. The Intermediate Cuneiform(2) is
proximal to the 2nd metatarsal.
3. The Lateral Cuneiform(3) articulates
w/the 3rd & 4th metatarsals.
4. The Talus is superior to the
calcaneus & articulates w/the
Navicular/Schaphoid bone.
5. The Calcaneus is the largest
tarsal bone also known as the heel
bone.
6. The Navicular/Schaphoid is a
medial tarsal bone that is proximal
to the cuneiform bones.
7. The Cuboid is the most lateral
tarsal bone that articulates w/the
4th & 5th metatarsals.
The Arches
The bones of the
foot make up 3
arches. The 2
long arches are
the lateral &
medial
longitudinal
arches. The arch
across the foot is
the transverse
arch.
Joints
Joints are where 2
or more bones come
together.
Joint Functions:
Holds bones
together.
Allows for
mobility.
Classified either
Functionally or
Structurally.
Joint Functional Classification
Synarthrosis – immovable joints These joints permit
no movement. Certain fibrous joints fall into this
category.
Amphiarthrosis – slightly moveable joints. These
joints permit only a little bit of movement. Some
cartilaginous and fibrous joints are in this category.
Diarthroses – freely movable joints. These joints
permit a variety of movements. Synovial joints fall
into this category.
Joint Structural Classification
Fibrous Joints – immovable
joints. Formed by dense fibrous
connective tissue
Cartilaginous Joints – slightly
moveable joints. Formed by
cartilage
Synovial Joints – freely
movable joints. Formed by a
synovial capsule
Joint Structural Classification
Fibrous Joints
Exaples:
Sutures of Skull
Syndemoses – Allows
slightly more movement
than sutures
Medial Mallelous
Lateral Mallelous
Joint Structural Classification
Cartilaginous Joints
Examples:
Pubic Symphysis
Intervertbral joints
Joint Structural Classification
Synovial Joints:
Bones are separated by
a joint cavity &
surrounded by a fibrous
capsule.
Synovial fluid fills the
joint cavity/capsule.
Ends of bones covered
w/hyaline cartilage.
Ligaments reinforce
these joints.
Structures associated w/ Synovial Joints
Bursa – flattened
fibrous sacs filled
w/synovial fluid.
Tendon Sheath –
Elongated
bursa/membrane
that wraps around
a tendon to hold it
together &
protection.
Types of Synovial Joints
Ball-and-socket joint
Hinge joint
Pivot joint
Gliding or Plane joint
Saddle joint
Condyloid or Ellipsoid joint
Types of Synovial Joints
Gliding or Plane joint –allows a wide range of side-to-side movements. Ex. Carpals & Tarsals
Hinge joint - permit an angular motion along one plane, which is similar to the opening and
closing of a door. Ex. Knee, elbow, PIP, MIP, DIP joints.
Pivot joint – This allows a rotation similar to the turning of a dial. Ex. Radius pivots w/ulna.
Types of Synovial Joints
Ball-and-socket joint –produce a wide array of movements. Ex. Hip & shoulder
Saddle joint – joints resemble a saddle in which one bone’s articular surface rocks back and
forth upon another. Ex. Metacarpal & carpal or Metattarsal & tarsal.
Condyloid or ellipsoid joint –a ball-like articular surface rests against the curve-shaped end of
another articular surface. This articulation allows a circular or elliptical pattern of motion. EX.
Metacarpal & phalange
Joint Homeostatic Imbalances
Bursitis – inflammation of the bursa usually due to trauma or
friction
Tendonitis – inflammation of the tendon usually due to overuse.
Joint Homeostatic Imbalances
Arthritis – inflammation or degeneration of a joint. It’s the most
widespread & crippling disease in the US. There are over 100 different
types.
Osteoarthritis - Most common type, due mostly to aging.
Joint Homeostatic Imbalances
Rheumatoid Arthritis – an autoimmune disease where the body sees it’s
joints as a foreign threat & will try to destroy them. Symptoms are
bilateral joint pain & can lead to deformities.
Gouty Arthritis – inflammation caused by deposits of uric crystals from
the blood. Typically occurs in big toe. Usually due to diet.
That’s All Folks!