APHY 101, Lecture 8 – Skeletal System & Joints
Growth At Epiphyseal Plates
A. Plate Remains same width during bone growth
1. New cartilage near epiphysis is added to plate
2. Cartilage facing diaphysis is removed
B. 4 Zones of Cartilage
1. Zone of Resting Cartilage = no growth
2. Zone of Proliferating Cartilage = New cartilage is formed by mitosis
3. Zone of Hypertrophic Cartilage = Cartilage enlarges & thickens
4. Zone of Calcified Cartilage = Dead cells & calcified matrix
New Bone = Osteoclast remove calcified matrix & osteoblasts deposit bone
Homeostasis of Bone
A. Constant exchange of Calcium & Phosphate between blood & bone
 Bone resorption = osteoclast breakdown bone
 Bone deposition = osteoblast deposit new bone
Factors affecting bone growth
1. Nutrients
a. Vitamin D
 Promotes Ca2+ absorption in small intestine
 Lack of vitamin D = soft & deformed bones
1. Rickets in children
2. Osteomalacia in adults
b. Vitamin A
 Balances bone resorption & bone deposition
c. Vitamin C
 Required for collagen synthesis
 Lack of vitamin C inhibits bone development
2. Sunlight
a. Dehydrocholesterol is stored in skin
b. UV rays from sunlight convert dehydrocholesterol to Vitamin D
3. Hormones
a. Growth Hormone (GH)
 Secreted from pituitary gland
 Stimulates cell division at epiphyseal plate
1. Pituitary Gigantism = excess GH during development
2. Pituitary Dwarfism = Lack of GH during development
3. Acromegaly = excess GH in adulthood
o Hands, feet, jaw enlarge
b. Testosterone & Estrogen (Sex Hormones)
 Promote bone formation, especially beginning at puberty
c. Calcitonin
 Hormone from Thyroid gland
 Bone Deposition
d. Parathyroid Hormone
 Hormone from Parathyroid gland
 Bone resorption
4. Exercise
a. Muscle contractions pull on bones
b. Stress from pulling promotes bone thickening
Fractures Repair
1. Hematoma Formation
o Severe bleeding from broken blood vessels forms blood clot
2. Osteoblasts Invade
o Osteoblasts from Periosteum deposit temporary spongy bone in hematoma
3. Formation of Cartilaginous Callus
o Fibroblasts deposit fibrocartilage “callus”
o Phagocytes remove hematoma
4. Callus ossification
o Cartilaginous callus is broken down
o Osteoblasts deposit new bone = bony callus
5. Bone Remodeling
o Osteoclasts remove excess bone & debris
Types of Fractures
I.
Incomplete
1. Greenstick fracture = One side of bone breaks, the other side bends
o Common in children – pliable bones
2. Fissured fracture = Longitudinal break along bone
II.
Complete Fracture
1. Transverse fracture = Break at right angle to diaphysis
2. Oblique fracture = Angle other than right angle to diaphysis
3. Comminuted fracture = Bone fragments formed
4. Spiral fracture = Twisting break
Bone Disorders
1. Osteopenia = weak bone
a. Progresses to osteoporosis
2. Osteoporosis = porous bone
a. Bones develop spaces & canals = fragile bone
b. Most common in women after menopause; Lack of estrogen weakens bone
c. Ways to prevent osteoporosis
 Exercise
 Calcium
 Vitamin D
JOINTS
I.
Overview
a. Arthrology = science of joints
b. Articulation = joint
II.
Classifications
a. Degree of movement
i. Synarthrotic = immovable
ii. Amphiarthrotic = slightly movable
iii. Diarthrotic = freely movable
b. Structure
i. Fibrous Joints
ii. Cartilaginous Joints
iii. Synovial Joints
Fibrous Joints = bones joined by dense connective tissue (C.T.) with collagenous fibers
I.
Syndesmosis
a. Bones joined by bundle or sheet of dense C.T.
b. Amphiarthrotic
c. Example = Tibia + Fibula
 Interosseous membrane
 Interosseous ligament
II.
Suture
a. Connects flat bones of skull
b. Bones supported by sutural ligaments
c. Synarthrotic
III.
Gomphosis
a. Cone-shaped process inserted into socket
b. Tooth anchored by periodontal ligament into socket
c. Synarthrotic
Cartilaginous Joints = bones joined by cartilage
I.
Synchondrosis
a. Band of hyaline cartilage joins bone
b. Synarthrotic
c. Examples:
 Diaphysis & Epiphysis joined by epiphyseal plate in childhood
 1st rib & Manubrium
II.
Symphysis
a. Pad of springy fibrocartilage
b. Amphiarthrotic
c. Examples
i. Pubic Symphysis
ii. Intervertebral Disc
1. Annulus fibrosis = ring of fibrocartilage
2. Nucleus Pulposis = gelatinous core of Intervertebral disc
3. Herniated disc = nucleus pulposis “slips” out of disc
Synovial Joints
I.
Structure
a. Articular cartilage = covers ends of bones
b. Synovial Membrane
 Secretes synovial fluid
1. Lubricates joint
2. Nourishes cartilage
c. Joint capsule = dense C.T.
 Stabilizes & protects joint
 Anchored into Periosteum
b. Bursa
 Sac of synovial fluid
 Bursitis = inflammation of bursa
Types of Synovial Joints
1. Ball & Socket
a. Rounded head & cup-shaped socket
b. Movements in all planes & rotation
c. Includes hip & shoulder joints
2. Condylar joint
a. Oval head + elliptical socket
b. Movement in all planes, but no rotation
c. Joints of metacarpals + phalanges
3. Plane “gliding” joint
a. Flat bones glide across
b. Joints of carpals, and joints of tarsals
c. Ribs 2-7 + Manubrium
4. Hinge joints
a. Increase/Decrease angles
b. Joint of ulnar + Humerus
c. Phalanges
5. Pivot joints
a. Rotation around a central axis
b. Joint of Radius & ulna
c. Joint of Atlas & Axis
6. Saddle joint
a. 2 concaved bones at right angles of each other
b. Joint of Metacarpal & carpal of thumb
Movements
1. Flexion – decrease angle of joint (bend elbow)
2. Extension – increase angle of joint (straighten elbow)
3. Hyperextension – increase angle of joint beyond anatomical position (tilt head back)
4. Abduction – movement away from midline (lift arm horizontally away from body)
5. Adduction – movement towards midline (move arms downward towards side of body)
6. Rotation – movement around an axis (twisting arm)
7. Circumduction – movement in a circular motion (make circles with fingers)
8. Dorsiflexion – move foot to point toes towards sky
9. Plantar flexion – move foot to point toes towards ground
10. Pronation – turn hand so palm is facing downward or posteriorly
11. Supination – turn hand so palm is facing upward or anteriorly
Joint Disorders
I.
Arthritis = inflamed, swollen, and painful joints
a. Osteoarthritis
i. Most common arthritis = 21million people each year
ii. Induced by injury
1. Begins with Breakdown of articular cartilage
2. Bone rubs against bone
3. Painful & Stiff joints
4. May result in gnarled fingers & bulging knees
b. Rheumatoid Arthritis
i. Autoimmune disorder
1. Immune system attacks tissue
2. Synovial membrane thickens & becomes inflamed
3. Mass of fibrous C.T. forms = Pannus
4. Pannus invades synovial space + destroys articular cartilage
5. Joints may ossify
Knee Joint
I.
Largest & Most complex joint
II.
Modified Hinge Joint
III.
Structure
a. Bones
i. Femur
ii. Patella
iii. Tibia (medial bone) & Fibula (lateral bone)
b. Tendons & Ligaments
i. Quadriceps tendon – surrounds patella
ii. Patellar ligament = extends from patella to tibial tuberosity
iii. Tibial Collateral ligament
1. Joins Medial tibia + medial condyle of femur
2. May tear with blow to lateral leg, such as a football tackle
iv. Fibular Collateral ligament
1. Joins Lateral fibula + Lateral condyle of femur
v. Anterior Cruciate Ligament
1. Joins Anterior Tibia + Lateral condyle of femur
vi. Posterior Cruciate Ligament
1. Joins posterior tibia + medial condyle of femur
c. Bursa
i. Prepatellar Bursa
1. Anterior to patella
2. Prepatellar bursitis = housemaid’s knee
ii. Suprapatellar Bursa
1. Largest Bursa, superior to patella
d. Menisci
i. Pad of fibrocartilage
ii. Separates femur + tibia