Page 2 - class-XI-ch.8-Lesson notes

Ribs- 24
Hyoid Bone- 1
Vertebral Column -26(adults)

2. Appendicular Skeleton:
Upper limbs- 64
Lower limbs- 62

Function of Bones:

1. Provide Support
2. Provide Protection
3. Bony System Serves for the Attachment of Muscles
4. Bony System gives Shape to the Body
5. Act as Levers
6. Passive Instruments of Locomotion

Classification of Bones

1. Long bone Elongated bone to which powerful muscles, such as those of the leg and arm, are attached.
2. Short bone shaped somewhat like cubes that facilitate flexibility of the joints; examples include the bones of the
wrist and ankle.
3. Flat bone Thin bones that protect certain organs, including most of the bones of the skull as well as the scapula.
4. Irregular bone of varying shapes and sizes, such as the vertebrae and certain bones of the skull or pelvis.
5. Sesamoid bone Resemble seed of sesame. Found in knee, hand & foot.

Types of Joints

Joint is the place at which 2 or more bones meet in skeleton of the body. Joint may be fixed or moveable. Study of
joint is Arthrology. According to capability of movement, the joints can be classified into 3 categories:
1. Immovable or Synarthroses Joints
2. Slightly Moveable or Ampharthroses Joints
3. Freely Moveable or Diarthroses Joints

1. Immovable or Synarthroses Joints: Called fibrous joints. Found in the bones of skull

2. Slightly Moveable or Ampharthroses Joints: Surfaces of the bones are separated by some intervening substance
.Only slight movement is possible.
Joint includes two types:
(a) Symphysis: a joint where 2 long bony surfaces are connected by a broad, flat disc of fibrocartilage e.g. inter-
vertebral & pubis joint.
(b) Synchondrosis: a temporary form of joint. Cartilage is changed to bone before adulthood. Found between
diaphysis & epiphyses of the long bones.

3. Freely Moveable or Freely Moveable or Synovial joints: Include most of the types of joints of the body. Bones are
covered with the hyaline cartilage & are surrounded by a fibrous articular capsule which is strengthened by
ligaments.
These freely movable joints are further classified into Six categories:

(a)Gliding joints
(b)Hinge joints
(c)Condyloid joints
(d)Saddle joints
(e)Ball & socket joints
(f)Pivot joints