L-7 Skeletal System and

Introduction:

The students will learn about:

• different parts of the human • functions of the Skeletal System • types of movable • parts of the Nervous System • reflex actions and sense organs

Skeletal System

The skeletal system is a framework of that gives support to our body. There are 206 bones in an adult human skeleton. The different parts of the skeletal system are: a. - The skull protects the brain. b. Cage - are thin and curved bones that form a cage in the chest called the . The rib cage protects our and . c. Backbone - The backbone protects the . d. Limbs - We have two pairs of limbs:

Upper limbs: The upper limbs have two parts – the upper and the lower arm.

Lower limbs: The lower limbs also have two parts – the upper leg and the lower leg. e. Girdles - Girdles are ring-like bony structures connecting the skull and to the upper and lower limbs.

Functions of the Skeletal System

➢ The skeleton gives shape and support to our body. ➢ Different parts of the skeleton protect our soft internal organs. ➢ The skeletal system allows the movement of different body parts. ➢ Many bones in our body are hollow. They are filled with marrow. Blood cells are produced in the .

Joints

A is a place where two or more bones meet. Bones are held together at the joint by special tissues called ligaments. A tough, elastic tissue called is also present on the surface of bones, at the joints.

Most joints are movable. There are four types of movable joints:

❖ Ball and socket joint: This type of joint allows movement in many directions. ❖ Hinge joint: This type of joint allows back and forth movement. ❖ Pivot joint: This type of joint allows you to move your head up, down and sideways. ❖ Gliding joint: This type of joint allows the bones to slide against each other in a gliding motion.

Ball and socket joint Hinge joint

Pivot joint Gliding joints

Cartilage

❖ Cartilage holds the bones together at the joints. ❖ It also protects the bones. ❖ Some organs such as the nose and have cartilage too.

Muscles

Muscles are tissues that cover the bones. Muscles help in important processes such as digestion. There are three types of muscles in our body: a. Skeletal muscles: Skeletal muscles help in movement. Muscles in the and legs are examples. b. Cardiac muscles: Muscles in the heart are examples of cardiac muscles. They work automatically. c. Smooth muscles: Muscles in the digestive system are examples of smooth muscles. They work automatically.

Nervous System

The nervous system controls the different organs in our body. The brain, the spinal cord and the form the different parts of our nervous system.

Brain

The brain controls our body movements and helps us to store information in our memory. It has three parts: a. Cerebrum: It is the largest part of the and is responsible for learning, memory and logic. b. Cerebellum: It is responsible for muscle coordination and maintaining the balance of our body. c. Medulla: It controls activities such as heartbeat, breathing, swallowing and sneezing.

Spinal Cord a. The spinal cord is a thick cord of tissue that extends down from the brain stem. b. It is protected by the backbone. c. It is responsible for the transfer of information between the brain and the rest of the body. d. It even controls actions that do not involve the brain.

Nerves

There are mainly three types of nerves: a. Sensory nerves- They carry messages from different parts of the body to the brain or spinal cord. b. Motor nerves- They carry messages from the brain or spinal cord to the different parts of the body. c. Mixed nerves- They carry messages both ways.

Reflex Actions

The automatic response of the body to a particular stimulus is called a reflex action. Most reflex actions take place because of messages sent by the spinal cord, the brain is not involved. These actions are very fast.

Sense Organs

Our body has five sense organs: a. Eyes: Eyes help us to see the world around us. A pair of eyes is present within the eye sockets of the skull. The flap like eyelids cover the eyes and lashes present on the eyes protect it from dirt. b. Ears: Ears help us to hear. Each is divided into three parts: outer ear, middle ear and inner ear. c. Nose: The nose helps us to detect different odours. It also helps in breathing. Nose has two nostrils that are lined with hair and mucus to trap dirt from the air. d. : The tongue helps us to sense different tastes such as sweet, sour, bitter and salty. It has numerous taste buds that detect different tastes. e. Skin: The skin helps us to feel, touch and sense heat, cold, pressure and pain. It forms a continuous layer around our body.