Chapter 5 the skeletal system - Faculty Pages | MSU

Human Biology
Chapter 5
The Skeletal
System
Functions of Skeleton
1. Supports the body
2. Protects soft body parts
3. Produces blood cells
4. Stores minerals and fat
a. Matrix- stores mineral
b. Medullary cavity of adults - fats
5. Permits flexible body movements
(working with muscular system)
Sum „09
Tissues of Skeletal System
The skeletal system consists of 3 types of
connective tissue:
1. Bone
a. 2 types
i. Compact bone
ii. Spongy bone
2. Cartilage
3. Fibrous connective tissue - forms
ligaments (Ligaments are NOT a type of
tissue! as implied by text)

Compact Bone
1.Highly organized in tubular units
called osteons
2.Osteocytes
3.Lacunae
4.Canaliculi
5.Lamellae
6.Central canal
Spongy Bone
1. Appears unorganized vs. compact bone
2. Trabeculae – thin plates of bone
3. Designed for strength & lightweight
4. Spaces
a. Varying sizes – “sponge-like”
appearance
b. Contain red marrow
5. No osteons, all cells are close to blood
supply

Tissues of Skeletal System
2. Cartilage
a. Gel-like matrix is flexible
b. Chondrocytes in lacunae
c. Avascular – slow to heal
d. 3 types based on fiber types
i. Hyaline
ii. Fibrocartilage – strongest
a) “Shock absorbers” – discs
iii. Elastic

Tissues of Skeletal System
3. Fibrous connective tissue
a. Contains dense collagen fibers
b. Make up tendons and ligaments
Ligaments attach
bone to bone
Cells of Bone
1. Osteoblasts – Young cells that secrete
protein fibers to help form matrix
2. Osteocytes – Mature cells that reside in
lacunae and function to detect stress
3. Osteoclasts – Bone-dissolving cells that
secrete HCl and enzymes
4. Osteogenic cells – Stem cells that divide
to replace osteoblasts

Anatomy of a Long Bone
1. Epiphysis
2. Articular cartilage
3. Diaphysis
4. Medullary cavity
5. Endosteum
6. Periosteum

Bone Development and Growth
1. Ossification = formation of bone
2. Bones of skeleton form in 2 ways
a. Intramembranous ossification –
i. “Between sheets” of connective tissue
ii. Many flat bones develop this way
b. Endochondral ossification
a. Cartilage models developed in fetus are
replaced with bone
b. Most bones of body develop this way
c. Articular surface and epiphyseal growth
plate retain hyaline cartilage
Bone Growth
1. Long bones continue to grow in length
until after puberty
2. Testosterone and estrogen stimulate
growth
3. Once hyaline cartilage of growth plate
gone (closed), bones cannot grow
lengthwise

Growth at Epiphyseal Plate
Remodeling of Bone
Bones constantly remodeling in response to:
1. Physical use – mechanical stress
2. Hormones
a.Parathyroid hormone – stimulates
osteoclasts
b.Calcitonin – stimulates osteoblasts

Fracture Repair
1. Hematoma forms
2. Fibrocartilaginous callus
3. Bony callus
4. Remodeling – spongy bone into
compact bone

Classification of Bones
By shape: By location:
1. Long bones 1. Axial Skeleton
2. Flat bones a. Midline of body
3. Round bones
4. Short bones
5. Irregular bones
b. Skull, vertebrae
c. Ribs, sternum
2. Appendicular
a. Limbs
b. Attachments
(Girdles)
Axial & Appendicular Skeleton
The Skull
1. Axial skeleton in
yellow
– skull, vertebrae,
sternum, ribs,
sacrum & hyoid
2. Appendicular
skeleton in blue
– pectoral girdle
– upper extremity
– pelvic girdle
– lower extremity
1. Cranium
a. Cranial bones enclose and
protects the brain
b. 8 flat bones
c. Fontanels in babies
d. Sinuses
2. Facial bones

8 Cranial Bones
1. Frontal – 1
2. Parietal – 2
3. Occipital -1
4. Temporal - 2
5. Sphenoid – 1
6. Ethmoid - 1

The Facial Bones
Most prominent:
1. Mandible – lower jaw
a. Only moveable portion of skull
b. Tooth sockets
2. Maxillae (2) – upper jaw
a. Anterior portion of hard palate
3. Palatine (2)
a. Posterior portion of hard palate
b. Floor of nasal cavity
4. Zygomatic – (2) Cheekbone prominence
5. Nasal bones (2)
6. Temporal & Frontal bones contribute to face

The Hyoid Bone
1. Not part of skull
2. Is axial skeleton
3. Sits above larynx
4. *Only bone in body
that doesn’t articulate
with another bone
5. Anchors tongue &
muscles for swallowing

The Vertebral Column
Functions:
1. Supports head and trunk
2. Protects spinal cord
3. Site for muscle attachment
5 Anatomical regions of vertebral column:
1. Cervical
2. Thoracic
3. Lumbar
4. Sacral
5. Coccyx
Total =
33 vertebrae
Vertebra and Intervertebral Disk

The Rib Cage
1. 12 Thoracic vertebrae
2. 12 pairs of ribs
3. Sternum
a. 3 fused bones:
i. Manubrium
ii. Body
iii. Xiphoid process
4. Protects heart and lungs
a. Yet flexible for breathing
Classification of Ribs
1. True ribs - upper 7 pair
a. Each connects directly to sternum
by costal cartilage
2. Rib pairs 8 - 10
a. Connect indirectly to sternum by
joining cartilage of 7 th rib
3. Floating ribs - # 11 and #12
a. No connection to sternum at all

Vertebrae and Rib Articulation
The Pectoral Girdle
1. Specialized for flexibility and wide
range of motion, compromises strength
2. Consists of:
a. Clavicle = collarbone
b. Scapula = Shoulder blades
a.Held to axial skeleton only by muscle

The Arm
1. Humerus – upper arm
a. Head – fits into socket of scapula
b. Distal end articulates with ulna
and radius
2. Radius & Ulna – 2 bones of forearm
3. Carpal bones – 8 bones of wrist,
remember carpal “clapping”
The Hand
1. Metacarpal bones – 5 bones in palm
a. Knuckles – heads of metacarpals
2. Phalanges – long slender bones of
fingers and thumb
a. 14 phalanges in each hand
b. Fingers have 3 each
c. Thumb has only 2 phalanges

Metacarpals and Phalanges
Metacarpals
V
IV
III
II
Middle phalanx II
I
Distal
phalanx I
Proximal
phalanx I
The Pelvic Girdle
1. Specialized for strength and stability
2. Coxal bones (2) -each is fusion of 3 bones
a. Ilium – largest, palpate as hips
b. Ischium – “sit bone”
c. Pubis – meet at symphysis
3. Female pelvis adapted for childbirth
a. Ilium more flared
b. Pelvis is broader and shallower
c. Pelvic opening is wider

Sacrum
Coccyx
The Leg
1. Femur – Longest and strongest bone
a. Head of femur fits in socket of coxal bone
2. Patella – knee cap
3. Tibia - shin bone of lower leg
a. Articulates with femur and tarsal bones
b. Medial malleolus – inner bulge of ankle
4. Fibula – slender bone of lower leg
a. Lateral malleolus – outer bulge of ankle
5. 7 Tarsal bones of ankle, including calcaneus (heel)
a. Tarsal = “tapping”
6. 5 Metatarsals and 14 phalanges as in hand

Articulations
1. Fibrous joints – immoveable
2. Cartilaginous – slightly moveable
a. Connected by hyaline cartilage
b. Costal cartilages of ribs
3. Synovial joints
a. Freely moveable
b. 2 bones separated by cavity
c. Ligaments form joint capsule
d. Tendons stabilize joint
e. Synovial membrane – synovial fluid

Some Types of Synovial Joints
1. Hinge Joints
2. Ball and socket joints
3. Pivot joints
4. Saddle joint

The End.