Use It or Lose It
,Case 1 – Anatomy muscles
‘What is the anatomy of muscles and bones?’
1) What types of joint exist?
Joints are the sited where two or more bones meet. They have 2 functions:
- Mobilize the skeletal
- Protective role in the process
There are 3 types of joints:
1. Fibrous (connective between bones)
- The bones are joined by fibrous tissue, namely dense fibrous connective tissue and
no joint cavity.
- Amount of movement allowed depends on the length of connective tissue fibers
uniting bones
- Most are immovable, although few are slightly movable
o Sutures → occur only between bones of the skull. Junctions are completely
filled by a minimal amount of very short connective tissue fibers. It is
immovable which prevents damage to the brain
o Syndesmoses → bones are exclusively connected by ligaments; movement
depends on length of connecting fibers
▪ Short = little/no movement
▪ Long = large amount of movement
o Gomphoses → a peg-in-pocked fibrous joint. Gompho is Greek for nail.
▪ Hold tooth in socket
2. Cartilaginous (connection of 2 bones on the base of cartilage)
- United by cartilage, like fibrous joint. They are not highly movable. Two types:
o Synchondroses: bar or plate of hyaline cartilage unites the bones at
synchondrosis (junction of cartilage)
, ▪ Epiphyseal plate in long bones of children
▪ Immovable joint between costal cartilage of the first rib
o Symphyses: joint where fibrocartilage unites the bone is a symphysis. Since
fibrocartilage is compressible and resilient, acts as a shock absorber + limited
amount of movement.
▪ Intervertebral joints + pubic symphysis of pelvis
3. Synovial joints
- Articulating bones are separated by a fluid-containing joint cavity. Freedom of
movement. The synovial joint consists of 6 parts:
o Articular cartilage → glassy-smooth hyaline cartilage covers the opposing
bone surfaces as articular cartilage. Thin spongy cushion absorb compression
placed on joint + keep the bone ends from being crushed
o Joint cavity → potential space that contains small amount of synovial fluid
o Articular capsule → two layers articular capsule encloses joint cavity:
▪ External fibrous layer (connective tissue, bones are not pulled apart)
▪ Synovial membrane (loose connective tissue, make synovial fluid)
o Synovial fluid → slippery synovial fluid occupies all free spaces within the
joint capsule. Fluid derived by filtration from blood flowing through
capillaries in membrane.
▪ Weeping lubrication: joint is compressed, and pressure is relieved
o Reinforcing ligaments → synovial joints are reinforced and strengthened by a
number of bandlike ligaments (most are capsular ligaments)
▪ Extracellular ligament
, ▪ Intracapsular ligament
o Nerves and blood vessels → synovial joints are richly supplied with nerve
fibers and blood vessels
Functional classification of synovial Joints: looking at their shapes
- Hinge joints → two movements
o Flexion
o Extension
▪ Elbow
▪ Knee
▪ For example, a door
- Ball-and-socket joint → circle
movement
o Movements in all direction
o Three direction, 3 axes
▪ Hip
▪ shoulder
▪ For example, Joystick →
you can move it to all
directions
- Saddle joints
o Thumbs
- Condyloid joint (ellipsoid)
o Fingers, wrist
- Pivot joint
o Neck
- Plane joint
o Nonaxial, more translations
o Clavicle and scapula
- Rotation joint
o Ulna (rotate in fibers)