The Skeleton System
What would happen if humans didn't
have bones? You'd be floppy like a
beanbag. Could you stand up? Forget
it. Could you walk? No way. Without
bones you'd be just a puddle of skin
and guts on the floor.
The human skeleton consists of 206 bones. We are
actually born with more bones (about 300), but many
fuse together as a child grows up. These bones support
your body and allow you to move. Bones contain a lot of
calcium (an element found in milk, broccoli, and other
foods). Bones manufacture blood cells and store
The longest bone in our bodies is the femur (thigh
bone). The smallest bone is the
stirrup bone inside the ear. Each hand has 26 bones in
it. Your nose and ears are not made of bone; they are
made of cartilage, a flexible substance that is not as
hard as bone.
Joints: Bones are connected to other bones at joints.
There are many different types of joints, including: fixed
joints (such as in the skull, which consists of many
bones), hinged joints (such as in the fingers and toes),
and ball-and-socket joints (such as the shoulders and
Differences in males and females: Males and females
have slightly different skeletons, including a different
elbow angle. Males have slightly thicker and longer legs
and arms; females have a wider pelvis and a larger
space within the pelvis, through which babies travel
when they are born.
LOCOMOTION AND SUPPORT
Human and animals need to move from one place to another
1. Find food
4. Avoid predators/dangers
The ability to move in particular direction in its environment is
To allow movement and locomotion , animals need support
System. Support in human and animals is provided by a
Framework called a skeleton.
The skeletel System is composed of
Bones and cartilages. The function of
Skeletal system are:
1. It support and gives a definite shape
of the body.
2. It acts as a lever system , allowing
movement to take place.
3. It protect delicate organs:
i. The cranium protect brain
ii. The vertebral column protect the
iii. The rib cage protects the heart and
4. The bone marrow produces blood cells
5. It stores calcium and phosphorous in
the form of calcium phosphate
The Skeleton is divided into two main parts:
1. The Axial skeleton – The skull
- The vertebral column
- The sternum and the ribs
2. The Appendicular skeleton- The pectoral girdle
- The pelvic girdle
The skull : 22 bones
The cranial bones-protect the
Brain .The facial bones –support
Of digestive system and
Suture is the immovable joints
that held the skull together
Axial skeleton – THE SKULL
Axial Skeleton- STERNUM AND RIBS
Thoracic cage – consists of
12 pairs of ribs and a
-encloses and protect the
Organ in the thoracic cavity
And upper abdominal
A pair of ribs articulates with each vertebra.The tuberculum articulates with
the facet on the tranverse process and the capitulum articulates with the
The vertebral column or backbone/spine.
Composed of a series of bones called
7 cervical vertebrae, 12 thoracic
vertebrae,5 lumbar vertebrae, 5 sacral
vertebrae and 4 caudal vertebrae.
*Functions: Permit movement of the
vertebral column and absorbvertical
Axial skeleton- VERTEBRAL COLUMN
The ATLAS – the first cervical vertebra ( centrum is absent,
neural spine is short, the tranverse process is long, broad and
flat and the present of vertebrarterial canal
(This attachment allows the nodding
Movement of the head.
The AXIS – the second cervical vertebra (The tranverse process
are small, the neural spine is large. The centrum is small and
projects upwards to form the odontoid process which articulates
with the atlas . This allows the head to move from side to side
Pivot joints allow rotation of one bone on another .
Example : The joint between the atlas and the axis
The thoracic Vertebra – has a long, thick neural spine. The
centrum is short and thick. It has a facets for articulate with
The LUMBAR vertebra are larger and stronger than the other
vertebrae. They give support to the abdomen and provide for
attachment of the back muscles.
The appendicular skeleton
consist of pectoral girdle ,
humerus ,ulna , radius , pelvic
girdle , femur , tibia and fibula.
The PELVIC GIRDLE consists of 2 hip bones
that provide strong and stable support for
the vertebral column.The hips bones are
joined to each other at a joint called
THE STRUCTURE OF A JOINT
A JOINT is a place where two or more bones meet.
The bones are held together by though and elastic fibres
Ligaments allow movement of the bones at the joint prevent
dislocation of the joint during movement
Synovial membrane secretes synovial fluid into the synovial cavity
Synovial fluid acts as a lubricant to reduces friction between
the end of the bones.
Cartilage that cover the end surfaces of the bone , cushions the joints,
absorbs shocks and reduces friction . It also protects the bones
from wearing away.
The most flexible joints. The moveable bone has a rounded end which
fits into sockets in a fixed bone. The moveable bone can swivel , or
move in many direction.
The face contains 12
which are attached
to the skin. Any
movement by these
changes in facial
When the biceps contracts, the tendons transmit the pulling force produced by
the contraction to the forearm. At the same time the triceps relaxes,As a result , the
elbow joint flexes or bends and the forearm moves upwards. When the triceps
contracts and the biceps relaxes , the forearm extends or straightens
The flexor muscle in the upper part of a
grasshopper’s leg contracts , the lower
leg is pulled towards the body. This is
sitting position and the hind leg is folded
in Z shape
A grasshopper uses three legs to support the body to
the ground, while the other three legs move together to
make successive steps while walking.
Hydrostatic skeleton in earthworm
When circular muscle contract , the longitudinal muscle relax and the animal
Becomes thinner and longer . During locomotion , the circular and longitudinal
Muscles contract rhythmically to produce peristaltic waves along the body.
SUPPORT IN AQUATIC PLANTS
- natural bouyancy of the water
- the stem have plenty of air sacs to keep them light and
reduce their density.
The tissues are spongy and with large air space known
as aerenchyma tissues.
Cross section of stem to show the air sacs of aerenchyma tissue
Cross section of stem of water hyacinth
Floating plants – have broad leaves , firm but flexible. enough to resist
tearing by wave action . Stem and leaves have aerenchyma tissues.
Submerged plants – Hydrilla sp. Have thin , narrow and
flexible leaves to provide little resistance – the plant can be
tugged at and pulled by water currents without being
damaged. No woody tissue.
Support in terrestrial plants
-woody plants – cellulose wall tissue which have
deposits of lignin for added strength.
Eg: schlerenchyma tissue , xylem vessels and tracheids
-non-woody plants such as herbaceous plant and climbers
depend on the turgidity of their cells and other supportive
tissues for give support.
Parenchyma tissues – store starch , sugar and water
Collenchyma tissues – thickened cellulose wall.
Cross section of
Xylem vessels with different types of thickening by lignin.
pitted spiral annular
Aquatic plants are supported by the :
Buoyancy of water
Air sacs on the stems
Woody plants are supported by the:
Herbaceous plants are supported by
Turgidity of cells
Collenchyma tissues ,parenchyma