Organ Systems - Class 5 Notes & Olympiad Questions

Organ Systems

Our bodies are made up of many different parts that work together to keep us alive and healthy. These parts are organised into systems called organ systems.

Some of the main organ systems in our bodies are:

Circulatory System

a) The circulatory system, also known as the cardiovascular system, is responsible for circulating blood throughout our bodies. The heart, blood vessels (arteries, veins, and capillaries), and blood make up this system.
b) The heart pumps the blood, and the blood vessels act as a network of tubes that carry oxygen, nutrients, and other important substances to all parts of the body.

Respiratory System

a) The respiratory system helps us breathe. It includes organs such as the lungs, nose, throat, and diaphragm. When we breathe in, we take in oxygen, and when we breathe out, we release carbon dioxide.
b) The lungs are the main organs in this system, where the exchange of oxygen and carbon dioxide takes place.

Digestive System

a) The digestive system is responsible for breaking down the food we eat into smaller parts and absorbing nutrients to provide energy for our bodies.
b) It includes organs like the mouth, oesophagus, stomach, small intestine, large intestine (also known as the colon), liver, and pancreas. Each organ plays a different role in the digestion and absorption of food.

Excretory System

a) The excretory system is responsible for removing waste and toxins from our bodies.
b) The main organs of the excretory system are the kidneys, bladder, ureters, and urethra.
c) The kidneys filter waste products and excess water from the blood to produce urine. The urine travels through the ureters to the bladder, where it is stored until it is eliminated from the body through the urethra.

Reproductive System

a) The reproductive system is responsible for the creation of new life.
b) It differs between males and females.

Nervous System

a) The nervous system is like the body's control centre. It includes the brain, spinal cord, and nerves.
b) The nervous system is in charge of controlling and regulating all the activities that happen in our body. It manages both internal processes like circulation, digestion, and respiration, as well as the things we do in our daily lives.
c) The brain controls our thoughts, emotions, and movements. The spinal cord carries messages between the brain and the rest of the body. Nerves spread throughout our body and help us feel sensations like touch, temperature, and pain.
d) The brain and the spinal cord work together as a team called the central nervous system.

The Brain

a) The brain is the most important organ in our body and acts as the control centre. It's part of the nervous system, which helps our body function properly.
b) The brain is located in the head and is protected by a bony structure called the cranium. It is made up of three main parts: the cerebrum, cerebellum, and medulla oblongata.

1. Cerebrum

a) The cerebrum is the largest part of the brain, and it's divided into two halves called hemispheres.
b) It controls our senses, like seeing, hearing, and tasting. It's also responsible for thinking, reasoning, and emotions.
c) The left hemisphere controls the right side of our body, while the right hemisphere controls the left side.

2. Cerebellum

a) The cerebellum is found at the back of the brain, just below the cerebrum. It's smaller than the cerebrum but plays an important role.
b) It helps with balance, posture, coordination of muscles, and even speech.

3. Medulla Oblongata

a) The medulla oblongata is also known as the brain stem. It is located below the cerebellum.
b) It works non-stop and controls vital functions like our heartbeat, breathing, and the functioning of many internal organs. It acts as a bridge between the brain and the spinal cord.
c) It's crucial to protect our brain because if the medulla oblongata gets injured, it can lead to the heart and lungs stopping, causing instant death.

The Spinal Cord

a) The spinal cord is a long, thick bundle of nerves that starts from the base of the medulla, a part of the brain and runs through the backbone, which is made up of many bones called vertebrae. It is well protected by the vertebral column.
b) One important function of the spinal cord is controlling reflex actions. Reflex actions are automatic reactions that happen without us thinking about them. For example, when you touch something hot, you automatically pull your hand away. The spinal cord plays a role in these quick reactions because it's where reflex actions take place.
c) The spinal cord also helps the brain communicate with the rest of the body. It does this through nerves. Nerves are made up of tiny cells called neurons. They carry messages from different parts of our body to the brain and spinal cord.
d) Our organs are connected to the brain through nerves. There are three types of nerves: sensory nerves, motor nerves, and mixed nerves.

i) Sensory nerves send information from our sense organs (like our eyes, ears, and skin) to the brain or spinal cord. They help us see, hear, and feel things.
ii) Motor nerves send information from the brain or spinal cord to our muscles and are responsible for making our muscles move.
iii) Mixed nerves carry both sensory and motor messages. They carry information to and from the brain, helping us sense and respond to the world around us.

Skeletal System

a) The skeletal system is our body's framework. It includes all our bones, which support our body and protect vital organs like the brain, heart, and lungs.
b) Bones also produce blood cells and store minerals like calcium.
c) When we are born, we have around 300 bones, but as we grow older, the number decreases, and by the time we reach adulthood, we have 206 bones in our body.
d) The largest bone in our body is called the femur, also known as the thigh bone. It's the bone in our upper leg.
e) The smallest bone in our body is called the stapes. It is located in the middle ear and helps transmit sound vibrations.

Functions of Bones in the Body

Our skeletal system plays important roles in our body:

1. Support and Shape: The skeletal system provides support to our body and gives it a proper shape. It acts like a strong framework that holds everything together.

2. Protection: Some bones have a protective function. For example, the rib cage protects our lungs and heart, while the skull protects our brain. These bones act as a shield, keeping our delicate organs safe.

3. Movement: Bones work together with muscles to enable us to move. Muscles attach to bones, and when they contract, they cause the bones to move. This allows us to walk, run, jump, and perform various activities.

Parts of the Human Skeleton

The human skeleton is made up of different parts:

The Skull

a) The skull, also known as the cranium or brain box, is made up of eight bones. Its main job is to protect the brain, which is the most important organ in our body.
b) The skull also provides protection for the eyes, ears, and nose.
c) The bones in the skull are connected by special joints called sutures. These sutures help to keep the bones in place and provide stability to the skull.

The Ribcage

a) The rib cage, also known as the thoracic cage, is like a cage made up of 12 pairs of curved bones.
b) The first ten pairs are connected to the breastbone in the front and the backbone in the back. The remaining two pairs are only connected to the backbone and are called floating ribs.
c) The rib cage's important job is to protect the lungs and the heart, which are vital organs in our body.

The Vertebral Column

a) The vertebral column, also known as the backbone, is made up of 33 bones called vertebrae. These bones are stacked on top of each other, forming a column.
b) The vertebral column has two main functions: it protects the spinal cord, which is like a messaging highway, and it also supports the head, neck, and body, allowing us to stand upright and move.

Bones of Arms and Legs

a) The bones in our arms and thighs are long and hollow.
b) These long bones help provide structure, strength, and support to our limbs, allowing us to perform various activities like reaching, grabbing, walking, and running.

The Girdles

Our body has two types of girdles: the shoulder girdle and the hip girdle.

a) The shoulder girdle supports the bones of our arms and allows us to move our arms in different directions and perform activities like reaching and throwing.
b) The hip girdle, on the other hand, supports the bones of our legs. It is much stronger than the shoulder girdle because it has to bear the full weight of our body. The bones of the hip girdle connect the spine to the legs and provide stability and support while walking, running, and standing.

Joints

Joints are the places where two bones come together. They play a crucial role in facilitating movement in our bodies. Joints can be categorised into two types: movable joints and immovable joints.

1. Movable Joints

Movable joints allow free movement in our body and are found in limbs where flexibility is important. There are different types of movable joints:

i) Ball and Socket Joint:This joint enables circular movement. For example, the bone in our upper arm fits into the socket of our shoulder, allowing a wide range of movements like rotating, spinning, and swinging. The thigh bone also connects to the hip bone through a ball and socket joint.

ii) Hinge Joint: This joint allows movement in only one direction. We find hinge joints in our knees, elbows, and fingers. They allow bending and straightening movements.

iii) Gliding Joint: The gliding joint permits slight movements. These joints are present between vertebrae in our spine, at the wrist, and at the ankles. They allow small gliding or sliding movements.

iv) Pivot Joint: Pivot joints enable movement in various directions. For example, the joint between the skull and the first two vertebrae allows our head to move from side to side and nod up and down.

2. Immovable Joints

Immovable joints, as the name suggests, do not allow any movement. They are found at the sutures of the skull, where the bones of the skull meet. These joints are firmly interlocked, providing stability and protection to the brain.

Muscular System

a) The muscular system allows us to move. It includes muscles, which are responsible for all our body's movements. Muscles help us walk, run, jump, and even smile.
b) Muscles are special tissues in our body that are made up of fibres. These fibres are connected to the bones with the help of tough, white materials called tendons. We have around 600 muscles in our body, and they are soft and fleshy.

There are two main types of muscles:

1. Voluntary Muscles

a) These muscles are under our control and movement. We can choose to move them or not.
b) For example, the muscles in our hands and legs that we use for activities like running, lifting things, or eating are voluntary muscles. When we move these muscles, it's called voluntary movement.

2. Involuntary Muscles

a) These muscles are not under our control. We cannot directly decide when they should move or stop. They work automatically to perform essential functions in our bodies.
b) For example, the muscles in our heart, lungs, stomach, and intestines are involuntary muscles. They keep working without us consciously thinking about them.
Involuntary muscles are not attached to our bones like voluntary muscles.

Types of Teeth

There are different types of teeth in our mouth that have specialised functions to help us bite, tear, break down, and grind our food depending on our dietary needs.

1. Incisors

a) These teeth are located at the front of each jaw and there are four of them in each jaw.
b) Incisors have a sharp cutting edge, which helps to bite and cut food.
c) Herbivores often have larger incisors to help them tear through tough plant material.

2. Canines

a) Canines are situated next to the incisors.
b) They are sharp and pointed teeth that assist in tearing food.
c) In carnivores, canines are typically the longest teeth and slightly curved.
d) There are two canines in each jaw.

3. Premolars

a) Found at the back and sides of the jaw, premolars work to break down food into smaller pieces before swallowing.
b) They are positioned next to the canines and help in cracking and chewing food.
c) There are four premolars in each jaw.

4. Molars

a) Molars are located at the back and sides of the jaw, following the premolars. These teeth are responsible for grinding food.
b) There are six molars in each jaw. In herbivores and omnivores, both premolars and molars have flat surfaces that aid in chewing.