Skeletal System and Nervous system
Our body is a wonderful machine . It Has many parts that help it to move , work, drink, etc. These parts are organ. We can see some organ like eyes , nose , and hands . some organs are inside the body like stomach, heart, lungs , etc, and cannot be seen. A group of organs that works together to perform a particular function for the body is called organ system.
Skeletal system
The framework of the bones that gives shape , support and strength to the body is called skeletal system. an adult human skeleton has 206 bones of different shape and sizes . The main parts of human skeleton are skull, back bones or spine , rib cage and two pairs of limbs. These limbs are attached to pair of girdle and hip girdle.
Skull
The skull of adult human contain holes for eyes , ears , nose and the mouth. the upper parts of the skull is made up of 8 flat bones that protects our brain. the Face and the jaw bones contains 14 bones . All bones in the skull are fixed except the bones in the lower jaw that can move . it enables us to eat and speak.
Backbones or spine
The skull is attached to the backbones that forms the main axis of skleton . Our backbones is made up of 33 small bones called vertebrae . The vertebrate join together to form a strong column called vertberal column. It is flexible and protects the delicate spin card . The joints of vertebrates allow slight movement . due to this , we can move or backbone forward and back word . Each vertebra has hole through which thew delicate spinal cards passes.
Ribcage : Ribs are thin, flat and curved bones . They make a cage around our chest. This cage of the bone is called ribcage . It protects or heart and lungs . There are 12 pair of ribs in the ribcage . A long bones at the centre of the chest holds the ribs at front . The ribs are also attached to the backbone . The last two pairs of ribs are called floating ribs because they are free and joined only to the backbone .
Limbs : Arms and legs are called limb. the Upper limb arms) is attached to the shoulders girdles or pectoral girdle . The upper arm has one long bone called the humerus, while the lower arms has two small bones called radius and ulna . The wrist and the fingers have several small bones . The bones of limb is attached to the hip girdle or pelvic girdle . The upper bone of leg is called femur or thigh bone . it is the largest bones in our body. The lowe bones of leg are tibia and fibula . The forlims are used for doing different tasks, such as writing lifting and pulling the objects . The hindlimbs are used for walking and running
Function of skeletal system
1. It gives shape and support to the boy.
2. It protects the delicate internal organs like brain, spinal cards , heart and lungs
3. It helps to move our body with the help of mucles.
Joints
The place where the two bones meet is called a joints . The bones are Joints together by strong tissues s called ligaments that can move freely or immovable that do not allow any movement between the bones ) .All the Joints except skull are movable . movable jointys are of four kinds
Ball and Socket joints : This type of joints is found in the hips and shoulders . This joints is formed when the round end of a bone fits into the holes or sokets of another bones . it allows movement in all directions
Hinge Joints : These joints are like the hinhes in door . They allow movement of the bones in one direction that is either up or down. These joints are found in our elbow , fingers , knees and toe .
Pivot joints : this joints is found in neck. the skull is joined to the backbone through pivot joints . The joints helps us to move our head upwards,downwards and sideways .
Gliding joints :
this joints is found in wrist , ankles and between any two vertebrates of the backbone . It allows the bones to slide against each other .
Muscles : Muscles are made up of tough elastics tissues . THey are attached to the bones by strong fibres called tendenos . There are about 650 muscles in our body. Muscles help to move the bones .
Types of muscles
Our body has three types of muscles
1. Voluntary Muscles : The muscle that are under our control are called voluntary muscles . Muscle s in our arms and legs are example of voluntary muscles .
2.Involuntary or smooth muscles :
The muscles that work but are not under our control are called involuntary muscles . They work automatically. muscles in our stomach and intestine are involuntary muscles .
3. Cadiac muscles : These muscles are a type of involunary muscles found in the wall of hearts . they are also not under our control. Unlike other types of muscles , cardiac muscles work throughout or life and never get tired .
Nervous system
Nervous system controls all other body systems and senses organs . All he activiteies like walking , laughing , thinking and learning are controlled by trhe nervous system. Brain, spianl card and nerves are the main parts of the nervous system.
Brain
Brain is like a master computer . It controls all the activiteis of our body. it is situates at trhe top of the spinal cord . Brain is very delicate . It is surrounded by as box cranium inside the skull . The skull protects it from shocks and jerks . Brain is divided into three parts
Cerebrum , cerebellum and medulla oblongata .
Cerbrum: It is the largest part of the brain. it helps us to remenber thingsd , understand meanings and solve the problem. thus it is called the cetre of intelligence
Cerebellum: It is a small parts and lie below the cerebrum at the back of hte head . It controll our muscles activities and helps us balance ou body during movement
Medulla Oblangata Or brain stem : it is the lower portiopn of hr brain. It join brain to the spinal cord . involuntary action like hertbeat, bretahing and sneezing are controlled by it . It is active even when we are asleep.
Spinal card: It connects the brain with all the body parts . It starts from the back portion of the brain medulla oblongata ) and contuinues down to the lower end of our backbone,it is protected by the vertbral column
Nerve
Our body has network of nerve to carry message between the brain and other parts of the body . There are three types of nerves :
1. Sensory nerves: These nerve carry message from th sense organs to the brtain and the spinal; cards
2. Motor nerve : These nerves carry message from the brain or the spinal cord to the different part of the body.
3. Mixed nerves : These nerves carry message to the brain a well as bring orders from the brain .
Reflex action : a reflex action is a quick and automatic response of the body to stimulus controlled by the spinal cord . The reflux action allows fast reaction. Thses types of action are not controlled by the brain.
when e touch something hot , the sensory nerves in the finger carry a message of pain from the skin to the spinal cord . the Spinal cord sends order to the hand to pull it back through the motor nerves . Some other examples of reflex action are coughing ,sneezing , blinking , watering of mouth on lookinf at some tasty food , etc.
