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• Bone – The structure of human body made of hard whitish tissues
• Joints – Place where two bones are connected. They could be movable or fixed
• Ligament – bones are connected by flexible fibrous connective tissues called ligament
• Ball Socket joint – It is the joint in which the rounded part of one bone called Ball fits into cavity of the other bone called socket. This joint allows movement in any direction i.e. in 360° angle . E.g. Shoulder and hip joints.
• Hinge Joint – A joint which allows movement only in one direction is called hinge joint (back and forth in 180 ° ). Other examples are joints in knee, toe, fingers etc.
• Pivotal Joint: It allows rotation of one cylindrical bone in a ring formed by another bone and adjoining ligament. E.g. joints of neck, Joint of radius and ulna
• Gliding Joint: bones can only slide over each other, such type of joint is gliding joint. E.g joints at the ankle and wrist
• Saddle joint: in joints like joint of the thumb, all type of movements are possible but rotation is not possible are saddle joint.
• Ellipsoid Joint: It is like ball and socket joint but the shape of bones forms ellipse.
• Human skeletal system
  • Arrangement of bones results into the formation of body shape
  • Human body has 206 bones
  • All bones along with cartilage form structure of human body called human skeletal system
  • It is consist of 2 parts – axial skeleton and the appendicular skeleton.
  • Axial skeleton is made up of skull, spine and ribcage
  • Appendicular skeleton – two arms two legs joined by many joints. In short – 4 bones in the shoulder, 6 bones in the arm and forearm, 58 bones in the hands, 2 pelvic bones, 8 bones in the legs, and 56 bones in the feet.
• Cartilage – skeleton which is softer than bones but harder than muscles are called Cartilage.
• Muscle
  • Soft, fleshy parts of our body made of fibres
  • Muscles are responsible for movement of body and body parts
  • Voluntary and Involuntary Muscles – muscles that carry involuntary (uncontrolled) actions are called involuntary muscles. Muscles that carry voluntary actions (controlled actions are called as involutary muscles)
  • Skeletal Muscles –
    • These are attached to the bones with the help of tendons.
    • Appears straited, produce powerful contraction, and allows rapid movement and fine contraction
    • Are voluntary muscles
  • Heart and Cardiac Muscles –
    • Found in heart and tips of main blood vessels
    • Carryout rythemic contraction and relaxation of heart wall
    • Are involuntary muscle
  • Smooth Muscles
    • Present in the hollow structures of the body such as blood vessels, stomach, intestine
    • Movements are slow and rythemic
    • Are involuntary muscles
• Skin – Structure and its functions
  • Skin is the largest organ and soft covering of our body
  • It is made up of two layers dermis and epidermis
  • Epidermis –
    • Outermost layer of skin, that creates skin color
    • Doesnot contain blood vessel and restricts the passage of water thorugh it
    • Melanocytes produce a pigment melanin which provides color to skin and protect from heat and ultravoilet rays
    • Nails develop from epidermis
  • Dermis –
    • Layer of connective tissue located below epidermis
    • Gives strength and flexibility to skin, protects skin and body during stress.
    • Contains blood vessels, bottom part of hair follicles, nerves, and sweat glands.
  • Hypodermis (subcutaneous tissue or subcutis) –
    • Present below dermis.
    • Not a part of skin but connects skin to underlying bones and muscles
    • Major location for storing body fats
• Gait of Animals
  • Snake –
    • Long backbone from head to tail
    • Bones ribs and skin are interconnected by muscles
    • Moves smoothly on rough surface with twisting motion but find difficult to move on smooth surface
    • It moves in forward direction in a zigzag line rather than in a straight line
  • Earthworm –
    • Has two types of muscles – circular muscles and longitudinal muscles
    • Bones are absent, but bristles (hair like structures are present)
    • Bristles allow earth to fix its one part on the ground while moving
    • The motion of earth worm is possible due to contraction of circular muscle and elongtion of longitudinal muscles
  • Snail –
    • Slow moving animal, contains shell for protection
    • Tentacles bares eyes
    • Has strong thick muscular organ i.e. foot for movement
    • Foot produces mucus which is sticky in nature
    • Muscular foot produces wave like movements which helps snail to move forward
  • Fish –
    • Lives in water
    • Has gills to get dissolved oxygen from water
    • Have transparent eyelids
    • Have streamlined body which helps them to swim faster
  • Cockroach –
    • Brown black insects that climb, walk and fly
    • Three pairs of legs helps them to walk whereas, two pairs of wings help them to fly
    • Body and legs are covered with exoskeleton
    • Movement of legs and wings is facilitate by muscles near them.
  • Birds –
    • Can walk on ground and fly in air
    • Bones are hollow to make body light weight
    • Forelimbs are modified to wings, which are attached to strong muscles to flight, so that it can move up and down
    • Breastbone is modified to support these muscles, it is called keel bone.
    • Body is streamlined which minimise air resistance during flight
    • Duck have webbed toes for swimming in water