Skeletal System Outline (Chapter 6) AP&P
I.
Components
A. Cartilage
B. Bone
C. Joints
D. Ligaments and Tendons
II.
Functions
A. Support
B. Movement
C. Protection
D. Mineral storage
E. Blood cell synthesis - hematopoiesis
III.
Cartilage
A. Hyaline cartilage – most abundant; spherical chondrocytes with thin collagen fibers
1. Articular cartilage – covers ends of bones and moveable joints
2. Costal cartilage – attach ribs to the sternum
3. Respiratory cartilage – forms respiratory passages and larynx
4. Nasal cartilage – forms external nose
B. Elastic cartilage
1. Forms external ear
2. Forms epiglottis
C. Fibrocartilage – withstands heavy pressure and tensile forces
1. Intervertebral disks
2. Knees and elbows
IV.
Bone (Cell, tissue, organ)
A. Skeleton – Greek for dried up body; composed of 206 bones
1. Axial skeleton – 80 bones
2. Appendicular skeleton – 126 bones
B. Classification of bone
1. Long bones
a. Diaphysis – shaft
b. Epiphysis – ends of bone; contain red marrow
c. Medullary cavity – contains yellow marrow
d. Epiphyseal plate – found between diaphysis and epiphysis; long bone growth
2. Short bones – roughly cuboidal in shape
3. Sesamoid bones – form within a tendon e.g. patella
4. Flat bones – Thin, flattened, and slightly curved
a. Diploe – spongy bone found between compact bone layers
5. Irregular bones – complicated shapes e.g. vertebrae, pelvis
C. Bone cells
1. Osteoclast – cells which dissolve bone (puts calcium into the blood for muscular
contraction, nerve transmission, blood clotting, etc…)
2. Osteoblast – cells which build bone by removing calcium and phosphates from the
blood in the presence of the enzyme alkaline phosphatase secreted by osteoblasts
3. Osteocyte – mature cells found within compact bone (living bone)
4. Bone remodeling occurs under the periosteum (White, double layered membrane)
which is held to bone by Sharpey’s fibers
D. Osseous tissue
1. Compact bone (Lamellar bone) – Dense and hard; found on the external surfaces of
bones
a. Osteon or Haversian System – structural unit of compact bone (cylindrical in
shape) which bear weight
b. Lamella – each ring of an osteon
c. Haversian canal – contains blood vessels and nerve fibers which travel vertically
in bone
d. Volkmann’s canal – contain blood vessels and nerve fibers which travel
horizontally in bone
e. Lacuna – spaces found in compact bone occupied by osteocytes
f. Canaliculi – lateral canals which connect lacunae which allow osteocytes to
diffuse nutrients and wastes into or out of bone tissue through gap junctions
2. Spongy bone - contain trabeculae (little beams) which align along lines of stress; and
open spaces filled with red or yellow marrow
E. Chemical composition
1. Hydroxyapatites – mineral
salts; mainly calcium
phosphates
2. Glycoproteins which make
up collagen fibers
F. Bone markings
1. Sites of muscle and ligament attachment
a. Tuberosity – large rounded projection
b. Crest – narrow prominent ridge
c. Trochanter – large, blunt, irregularly shaped process (Only found on the femur)
d. Tubercle – small rounded projection or process
e. Epicondyle – raised area above a condyle
f. Spine – sharp, slender, often pointed projection
g. Process – any bony prominence
2. Projections that help form joints
a. Head – bony expansion carried on a narrow neck
b. Condyle – rounded articular projection
c. Ramus – arm like bar of bone
3. Depressions and openings allowing blood vessels and nerve fibers to pass
a. Meatus – canal like passage way
b. Sinus – Cavity within bone filled with air and lined with mucous membrane
c. Fossa – shallow basin like depression in bone
d. Fissure – narrow, slit like opening
e. Foramen – round or oval opening through a bone
G. Hormone Control of Bone Remodeling
1. Osteoblast and osteoclast activity is regulated by two hormones; PTH and Calcitonin
A. PTH (Parathyroid hormone) is released by parathyroid glands when serum calcium
levels are low which increase osteoclast activity.
B. Calcitonin is released by the thyroid gland when serum calcium levels are to high
which stimulate osteoblast activity
H. Homeostatic Imbalance
1. Fracture – a break in the bone
a. Comminuted – bone broken into 3 or more pieces
b. Spiral – ragged break due to twisting forces
c. Depressed – broken bone is pressed inward
d. Compression – bone is crushed
e. Epiphyseal – epiphysis separates from diaphysis
f. Greenstick – incomplete break where only one side of bone is fractured; like
when you break a branch from a live tree
g. Open fracture – bone penetrates through the skin
h. Closed fracture – bone does not penetrate skin
2. Fracture treatment
a. Closed reduction – When a physician pulls on bone to realign bone ends
b. Open reduction – When a physician surgically inserts pins or wires to realign
bones
3. Fracture healing
a. Hematoma formation
b. Fibrocartilaginous callus formation
c. Bony callus formation
d. Bone remodeling