Skeletal System and Nervous system

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.