BIO 210 CHAPTER 8 THE SKELETAL SYSTEM
I.
II.
DIVISIONS OF THE SKELETAL SYSTEM
A.
AXIAL SKELETON (80 BONES)
- Bones of the Head, Neck, and Torso
B.
APPENDICULAR SKELETON (126 BONES)
- Bones of the Upper and Lower Extremeties
* Total Number of Major Bones in the Body = 206
NAMES AND NUMBERS OF BONES THAT COMPOSE THE AXIAL SKELETON
Bones of the Axial Skeleton Are Organized into 4 Major Groups
A. BONES OF THE SKULL (28)
1.
CRANIAL BONES (8)
Form the Cranium (Surrounds the Brain)
a. FRONTAL - 1
- Anterior:
1) Forms Anterior Portion of Cranium (Forehead)
2) Forms Anterior Cranial Floor
- Forms Roofs of Orbits (Eye Sockets)
b. PARIETAL - 2
- Superior: Forms Superior Portion of Cranium
c. TEMPORAL - 2
- Lateral:
1) Forms Lateral Portion of Cranium
2) Forms Lateral Cranial Floor
d. OCCIPITAL - 1
- Posterior:
1)
Forms Posterior Portion of Cranium
2)
Forms Posterior Cranial Floor
e. SPHENOID - 1
- Central:
1)
Forms Central Portion of Cranial Floor (Shape
Resembles Bat)
2)
Known as the “Keystone of the Cranium” B/C the
Sphenoid Bone Anchors All the Other Cranial Bones
- Lateral:
1)
Forms Lateral Walls of Cranium (Lies in Front of
Temporal Bone)
2) Forms Lateral Walls of Orbits
f.
ETHMOID - 1
- Complex, Irregularly Shaped Bone
- General Location: Between Nasal and Sphenoid Bones
- Where the Ethmoid Bone Can Be Seen in an Articulated
Skull:
1) Medial Walls of Orbits
2) Upper Portion of Nasal Septum
3)
Upper "Ledges" Projecting into the Nasal Cavities
4)
Anterior Cranial Floor
FACIAL BONES (14)
Primarily Form the Face
a. NASAL - 2
- Form Bridge of Nose
b. MAXILLARY (MAXILLA) - 2
- Upper Jawbones
- Form the central portion of the face; (Known as the
"Keystone of the Face" Because Anchors All the Other
Facial Bones Except For the Mandible)
- Also Forms:
B.
1) Floor of Orbits
2) Anterior Portion (Most) of Hard Palate
c. ZYGOMATIC - 2
- Cheekbones
- Also Form Lateral Walls of Orbits
d. MANDIBLE - 1
- Lower Jawbone
- Largest, Strongest Bone of the Face
e. LACRIMAL - 2
- Forms Medial Walls of Orbits (B/T the Maxillary and
Ethmoid Bones)
- Paper Thin Bones (Usually Broken in Real Bone Skulls)
f.
PALATINE - 2
- Shaped like 2 L's facing one another ( )
1) Horizontal Portion of L's Forms Posterior Portion
of Hard Palate
2) Vertical Portion of L's Forms Lateral, Posterior
Walls of Nasal Cavities
g. INFERIOR TURBINATES (CONCHAE) - 2
- Form Lower "Ledges" That Project into Nasal Cavities
(Scroll-Shaped)
h. VOMER - 1
- Forms Lower Portion of Nasal Septum
3.
BONES OF THE EAR (6)
Tiny Bones Located Within Temporal Bones (In Middle Ear)
3/Ear
a.
MALLEUS (2)
b.
INCUS (2)
c.
STAPES (2)
HYOID BONE
U Shaped Bone That Lies in the Neck B/T Mandible and Larynx
The Only Bone in the Body That Doesn’t Form a Joint With
Another Bone
Held in Place By Ligaments and Muscles
Supports and Provides Muscle Attachment For Muscles That Form
Floor of Mouth and Tongue
C.
BONES OF THE SPINAL (VERTEBRAL) COLUMN (Backbone) (26)
1. CERVICAL VERTEBRAE - 7
a. ATLAS: 1st Cervical Vertebra, Named For Atlas in Greek
Mythology
b. AXIS: 2nd Cervical Vertebra, Named B/C Atlas Pivots Around
Axis
2.
THORACIC VERTEBRAE – 12
3.
LUMBAR VERTEBRAE – 5
4.
SACRUM – 5 FUSED INTO 1
- Wedge-Shaped Bone, Consists of 5 Separate Vertebrae
(Childhood) That Fuse Into 1 After Bones Mature
5.
COCCYX – 4 OR 5 FUSED INTO 1
- Tailbone, Consists of Separate Veterbrae That Fuse (Like
Sacrum)
D.
STERNUM AND RIBS (25)
1. STERNUM - 1
- Breastbone, Dagger-Shaped, Flat Bone
2. RIBS – 12 PAIR
a.
TRUE RIBS – 7 PAIR
Called True Ribs B/C They Attach Directly to the Sternum
By Costal Cartilage
b.
FALSE RIBS – 5 PAIR
-
Called False Ribs B/C:
1) They Attach Indirectly to the Sternum By the Costal
Cartilage of Rib 7 (1st 3 Pair of False Ribs,
#’s 8,9,10 Counting From the 1st True Rib) or
2) They Don’t Attach to the Sternum At All (Last 2 Pair
Of False Ribs, #’s 11,12 Counting From the 1st True
Rib), These Are Also Known as Floating Ribs
*Note: Posteriorly, ALL Ribs Are Attached to the Thoracic
Vertebrae
*Thorax (Thoracic Cage) = Sternum + Ribs + Vertebral Column,
(Creates a Complete Boney Cage)
III. NAMES AND NUMBERS OF BONES THAT COMPOSE THE APPENDICULAR
SKELETON
A. BONES OF THE UPPER EXTREMETIES (64)
1.
CLAVICLE – 2
- Collarbone
2.
SCAPULA – 2 (SHOULDER GIRDLE)
- Shoulder Blade
- Shoulder Girdle = Clavicle + Scapula
3.
HUMERUS – 2
- Long Bone of the Upper Arm
4.
RADIUS – 2
5.
ULNA – 2
- Radius and Ulna Are Bones of the Forearm
- Radius: Thumb Side, Ulna: Little Finger Side
6.
CARPALS – 16
- Bones of the Anatomical Wrist (Proximal End of Hand)
7.
METACARPALS – 10
- Bones That Form the Palm of the Hand (Knuckles = Heads of
Metacarpals)
8.
PHALANGES – 28
- Bones of the Fingers; 3 in Each Finger, 2 in Each Thumb
B. BONES OF THE LOWER EXTREMETIES (62)
1.
OS COXAE (COXAL/INNOMINATE) – 2 (PELVIC GIRDLE)
- Pelvic/Hip Bones, Broadest Bone in the Body
- Os Coxae (2) + Sacrum + Coccyx, Forms Complete Boney Ring
2.
FEMUR – 2
- Thigh Bone; Longest, Largest, Strongest Bone
3.
PATELLA – 2
- Kneecap
4.
TIBIA – 2
5.
FIBULA – 2
- Tibia and Fibula Are Bones of the Lower Leg
- Tibia: Shin Bone; Larger, More Medial and More Superficial
Compared to Fibula
6.
TARSALS – 14
- Bones That Form the Heel and the Posterior Portion of the
Foot
7.
METATARSALS – 10
- Bones That Form the Long Portion of the Foot
8.
PHALANGES – 28
- Bones of the Toes; 3 in Each Toe Except Big Toes, 2 in Each
Big Toe
IV. TERMS USED TO DESCRIBE BONE MARKINGS
- Bone Markings: Identifying Features on Bones; “Marks”
Bone as Unique
A. DEPRESSIONS AND OPENINGS
1.
FORAMEN
- Round Hole in Bone for Blood Vessels and Nerves
- Example: Supraorbital Foramen
2. FOSSA
- Depression in Bone into Which Another Bone Fits
(Forms Joint)
- Example: Mandibular Fossa
3. MEATUS
- Tubelike Canal in Bone
- Example: External Auditory Meatus
4. NOTCH
- V-like Depression in Bone
- Example: Supraorbital Notch
B. PROCESSES
- Extensions of Bone
- 2 Groups
1. THOSE THAT FIT INTO JOINTS (Form Joints)
a. CONDYLE
- Rounded Bump That Usually Fits into a Fossa on Another Bone Forming a Joint
- Example: Mandibular Condyle
b.
HEAD
- Large, Rounded Distinct End of a Long Bone That Fits into a Depression on Another
Bone Forming A Joint
- Example: Head of Femur
2.
THOSE TO WHICH MUSCLES ATTACH
a. EPICONDYLE
- Bump Above a Condyle for Muscle Attachment
- Example: Epicondyles of Femur
b. SPINE (SPINOUS PROCESS)
- Sharp, Pointed Process for Muscle Attachment
- Example: Spine of Vertebra
c.
TROCHANTER
- Large Bump for Muscle Attachment
- Example: Trochanters of Femur
d.
TUBEROSITY
- Small Bump for Muscle Attachment
- Example: Tibial Tuberosity
3.
OTHERS
1.
BODY
- Main Portion of a Bone
- Example: Body of Vertebra
2.
SINUS
- Cavity Within Bone
- Example: Frontal Sinuses
V.
BONE MARKINGS OF INDIVIDUAL BONES
A. BONE MARKINGS OF THE SKULL
1. FRONTAL BONE
a. SUPRAORBITAL FORAMEN (NOTCH)
- "Hole/Notch Above Orbit"
-2
- May Be a Foramen/May Be a Notch (Varies)
b. FRONTAL SINUSES
- Cavities Within Frontal Bone (Above Orbits)
- Usually 2 (One Above Each Orbit) But Varies
2. TEMPORAL BONE
*Note: 2 Temporal Bones Means 2 Each of These Bone Markings
a. MASTOID PROCESS
- Projection of Bone Just Behind Ear
- Contains Mastoid Air Cells (Small Sinuses That
Communicate With Middle Ear Rather Than Nose)
b. EXTERNAL AUDITORY MEATUS
- "External Ear Canal"
- Tube That Extends into the Temporal Bone From the
External to Middle Ear
c. STYLOID PROCESS
- Slender Spike of Bone That Extends Downward From the
Temporal Bone
d. MANDIBULAR FOSSA
- Depressed Area in the Temporal Bone into Which the
Mandible Fits
e. ZYGOMATIC PROCESS
- The Portion of the Temporal Bone That Joins the
Zygomatic Bone
- Zygomatic Arch = Zygomatic Process (Temporal Bone) +
Zygomatic Bone
3. OCCIPITAL BONE
a. FORAMEN MAGNUM
- "Large Hole"
- The Hole Through Which the Spinal Cord Enters the
Cranial Cavity
b. OCCIPITAL CONDYLES
- 2 Oval Shaped Bumps on Either Side of the Foramen Magnum (Where Skull Joins
Vertebral Column)
4. SPHENOID BONE
a. OPTIC FORAMEN
- "Hole in Eye"
-2
- Transmits the Optic Nerve (Vision) From Eye to Brain
b. SELLA TURCICA
- Depression in the Center of the Sphenoid Bone (Houses
the Pituitary Gland)
c. SPHENOID SINUSES
- Cavities Within the Sphenoid Bone
- Number Varies
5. ETHMOID BONE
a. CRISTA GALLI
- Upward Projection of Ethmoid Bone (Lies in Anterior Cranial Floor)
- Point of Attachment for the Meninges (Protective Coverings for Brain and Spinal Cord)
b. CRIBIFORM PLATE
- Thin Plate (Anterior Cranial Floor) That Crista Galli Sets On
- Separates the Cranial and Nasal Cavities
- Contains Numerous Holes for Branches of the Olfactory Nerve (Smell) (Branches of This
Nerve Pass From Nose to Brain Through These Holes)
c. PERPENDICULAR PLATE
- Upper Portion of Nasal Septum (Nasal Septum is the
Midline Wall in Internal Nose)
d. SUPERIOR AND MIDDLE CHONCHAE (TURBINATES)
- Upper and Middle "Ledges" in Nasal Cavities
- 2 Superior and 2 Middle Conchae
e. ETHMOID SINUSES
- Small, Spongy Cavities That Lie Within the Lateral portions of the Ethmoid Bone
6. MAXILLARY BONE
a. ALVEOLAR PROCESS
- Arch That Contains the Teeth
b. INFRAORBITAL FORAMEN
- "Hole Below Orbit"
-2
PALATINE PROCESS
- The Portion of the Maxillary Bones That Forms the Anterior (and Most) of Hard Palate
(Hard Palate is the Hard Portion of the Roof of the Mouth)
d. MAXILLARY SINUSES
- Cavities Within the Maxillary Bones (Below Orbits)
- Usually 2 (One Below Each Orbit) But Varies
- The Largest of the Sinuses
7. MANDIBLE BONE
a. MANDIBULAR CONDYLE
- Rounded Portion of Mandible That Fits Into Mandibular Fossa of Temporal Bone to Form
the Jaw Joint
-2
b. ALVEOLAR PROCESS
- Arch That Contains the Teeth
c. MENTAL FORAMEN
- "Hole in Chin" (Outer Surface of Mandible)
-2
d. MANDIBULAR FORAMEN
- "Hole in Mandible" (Inner Surface of Mandible)
-2
8. PALATINE BONE (HORIZONTAL PLATE)
- Posterior portion of the hard palate
B. SPECIAL FEATURES OF THE SKULL
1. SUTURES
- Immovable Joints Between Skull Bones
a. SQUAMOUS
- Lies Along the Top Curved Edge of the Temporal Bone
(Joint Between Temporal, Parietal, and Part of the Sphenoid Bones)
b. CORONAL (FRONTAL)
- The Joint Between Parietal and Frontal Bones
c. LAMBDOIDAL
- The Joint Between Parietal and Occipital Bones
d. SAGITTAL
- The Joint Between the 2 Parietal Bones
2. FONTANELS
a. DEFINITION
- "Soft Spots" in an Infant's Skull: Areas Where ossification is Incomplete at Birth
b. PURPOSE
- Allows Compression of the Skull During Childbirth
c. NAMES
1) Frontal (Anterior)
- Largest, Diamond-Shaped
- Located Between Parietal and Frontal Bones
- Closes (Ossifies) By 1 and a Half Years of Age
2) Occipital (Posterior)
- Located Between Parietal and Occipital Bones
3) Sphenoid (Anteriolateral)
- Located Between Frontal, Parietal, Temporal, and Sphenoid Bones
4) Mastoid (Posteriolateral)
- Located Between Parietal, Occipital, and Temporal Bones
3. SINUSES
a. PARANASAL SINUSES (PREVIOUSLY LISTED WITH SKULL BONES)
- "Sinuses Around Nose" (Communicate Directly (Open
Into) Internal Nose)
1. FRONTAL
2. SPHENOID
3. ETHMOID
c.
4. MAXILLARY
MASTOID SINUSES (AIR CELLS)
- Located in the Mastoid Processes of the Temporal Bones
- Small Sinuses That Communicate With the Middle Ear Rather Than the Nose
4. ORBITS
- Eye Sockets
- Formed By Many Cranial and Facial Bones: Frontal,
Sphenoid, Zygomatic, Ethmoid, Lacrimal, Maxillary (See Previous Info)
5. NASAL SEPTUM
- Midline Wall in the Internal Nose (Divides the Internal Nose Into 2 Cavities)
- Formed By:
1) Bone
a) Perpendicular Plate of Ethmoid Bone: Forms Upper Portion
b) Vomer: Forms Lower Portion
2) Cartilage (Hyaline): Forms Anterior Portion
6. WORMIAN BONES
- Small Islands of Bone Located Within Sutures
- Highly Individual So the Number Varies
VERTEBRAE
*Note: These are markings that are common to most vertebrae
1. BODY
- Flat, rounded portion
- Anterior and medial
2. SPINOUS PROCESS (also called spine)
- Sharp, pointed, posterior, and medial projection
- Can be felt through the skin of the back
3. TRANSVERSE PROCESSES
- Sharp, pointed, and lateral projections
- 2 (left and right)
4. SUPERIOR ARTICULAR PROCESSES
5. INFERIOR ARTICULAR PROCESSES
- "Joining Processes"; One Way That the Vertebrae Join
Together (They Also Join By Their Bodies)
- Superior Articular (Articulating) Processes: 2; Uppermost (Project Up)
- Inferior Articular (Articulating) Processes: 2; Lowermost (Project Down)
- The Superior Articular Processes of One Vertebra Join to
the Inferior Articular Processes of the Above Vertebra
6. SPINAL (VERTEBRAL) FORAMEN
- Hole in the Center of Each Vertebra
- When All the Vertebrae are Joined, These Holes Create the Spinal Cavity
(Houses the Spinal Cord)
STERNUM
1. MANUBRIUM: Upper Portion of the Sternum
2. BODY: Middle (Main) Portion of the Sternum
3. XIPHOID PROCESS:
- Blunt, Lower Tip of Sternum
- Composed of Cartilage That Ossifies As One Ages
RIBS: COSTAL CARTILAGES
- Cartilage (Hyaline) That Joins Ribs to Sternum
SCAPULA
1. SPINE
- Sharp Ridge on the Posterior Surface of the Scapula
2. GLENOID CAVITY
- Arm Socket: A Shallow Depression That Holds the Head of the Humerus to Form the Shoulder
Joint
HUMERUS
1. HEAD
- Large, Rounded, Proximal Epiphysis
b.
C.
D.
E.
F.
G.
2.
- Medial (Fits Into Glenoid Cavity)
* Numbers 2-5 Are All Distal
MEDIAL EPICONDYLE
3. LATERAL EPICONDYLE
4. CAPITULUM
- Rounded, Lateral Knob
5. TROCHLEA
Rounded, Medial Knob That Contains a Depression in the Center
H. RADIUS
1. HEAD: Proximal; Disk-Shaped
2. STYLOID PROCESS: Distal, Pointed Projection (Lateral in Anatomical Position)
I.
ULNA
1. OLECRANON PROCESS: Proximal, Upward Projection of the Ulna (Elbow)
2. SEMILUNAR NOTCH
- Curved Depression
- Proximal
3. STYLOID PROCESS
- Distal, Pointed Projection (Medial in Anatomical
Position)
- Can Be Felt Through the Skin in the Wrist Area
J. OS COXAE (COXAL/INNOMINATE)
- Each Os Coxa Bone is Composed of 3 Separate Bones That Fuse
1. ILIUM: Uppermost, Flaring Portion (Largest)
2. ISCHIUM: Lowermost Portion (Strongest)
3. PUBIS: Anterior, Medial Portion
4. ACETABULUM
- Hip Socket: A Deep Depression that Holds the Head of the Femur to Form the Hip Joint
5. SYMPHYSIS PUBIS
- Joint Between the Pelvic Bones (Pubis Portion)
- Anterior and Medial
- Composed of Cartilage (Fibrocartilage)
6. TRUE PELVIS
- Space Between Pelvic Inlet and Pelvic Outlet
- "Basin" Portion of Pelvis (Houses Pelvic Organs)
7. PELVIC INLET
- Boundary That Leads Into True Pelvis
8. PELVIC OUTLET
- Boundary That Leads Out of True Pelvis
9. FALSE PELVIS
- Broad, Shallow Space Above Pelvic Inlet
- Called False Pelvis Because It's Actually Located in the Abdominal Cavity Rather Than the
Pelvic Cavity
K. FEMUR * Numbers 1-4 Are All Proximal, Numbers 5-8 Are Distal
1. HEAD
- Large, Rounded, Proximal Epiphysis
- Medial (Fits Into Acetabulum)
2. NECK: Narrow Portion Just Below the Head
3. GREATER TROCHANTER: Lateral
4. LESSER TROCHANTER: Medial
5. MEDIAL EPICONDYLE
6. LATERAL EPICONDYLE
7. MEDIAL CONDYLE
8. LATERAL CONDYLE
L. TIBIA * Numbers 1-3 Are All Proximal
1. MEDIAL CONDYLE
2. LATERAL CONDYLE
3. TIBIAL TUBEROSITY: Anterior, Medial, Rounded Bump
4. MEDIAL MALLEOLUS
- Distal, Medial Process
- Can be Felt on the Inner Surface of the Ankle
M. FIBULA
1.
HEAD: Proximal and Rounded
2. LATERAL MALLEOLUS
- Distal, Lateral Process
- Can be Felt on the Outer Surface of the Ankle
N. TARSALS
1. CALCANEUS: Heel Bone
2.
TALUS: Uppermost Tarsal