BODY SYSTEMS
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What is a body system?
The human body is made up of multiple systems that work together to form life. Body systems are an organized group of tissue that forms a particular function. These functions work with other systems in the body.
In total, there are 11 different systems that work together with different parts of our body, allowing it to function. Some of the main systems of the body are the skeletal, circulatory, respiratory, nervous, muscular & digestive. Understanding these systems helps people know how the body functions and why the health of each of them is important for overall quality of life.
The Skeletal System
Axial Skeleton – forms the basic structure by which the rest of the skeleton is supported. Consists of the Skull, Spine, and Thorax or Rib Cage.
Appendicular Skeleton – Consists of the limbs joined together by the girdles of the pelvis and shoulders.
Functions of the Skeletal System
Supports the organs and tissues of the body. Without this support they would collapse under their own weight.
Provides Protection for internal organs. For example, the cranium protects the brain; the thorax protects the heart and lungs.
Provides a base for the attachment of muscles and so allows Movement with the bones acting as levers.
A source of supply of blood cells and a store for minerals required for the body to function. For example, red and white blood cells are produced in the bone marrow, which is found in the middle of bones.
The human skeleton
The human skeleton is made up of 206 bones, including bones of the:
Skull – including the cranium and mandible
Spine – cervical, thoracic and lumbar vertebrae, sacrum and tailbone (coccyx)
Chest – ribs and breastbone (sternum)
Arms – shoulder blade (scapula), collar bone (clavicle), humerus, radius and ulna
Hands – wrist bones (carpals), metacarpals and phalanges (fingers)
Pelvis – hip bones
Legs – thigh bone (femur), kneecap (patella), shin bone (tibia) and fibula
Feet – tarsals, metatarsals and phalanges.
Joints
Joints are where two bones meet. They make the skeleton flexible without them, movement would be impossible.
Joints allow our bodies to move in many ways. Some joints open and close like a hinge (such as knees and elbows), whereas others allow for more complicated movement — a shoulder or hip joint, for example, allows for backward, forward, sideways, and rotating movement.
Classification of joints
Immovable, or fibrous, joints don't move. The dome of the skull, for example, is made of bony plates, which move slightly during birth and then fuse together as the skull finishes growing. Between the edges of these plates are links, or joints, of fibrous tissue. Fibrous joints also hold the teeth in the jawbone.
Partially movable, or cartilaginous move a little. They are linked by cartilage, as in the spine. Each of the vertebrae in the spine moves in relation to the one above and below it, and together these movements give the spine its flexibility.
Freely movable, or synovial move in many directions. The main joints of the body — such as those found at the hips are freely movable. They are filled with synovial fluid, which acts as a lubricant to help the joints move easily.
Types of joints
Hinge joints allow movement in one direction, as seen in the knees and elbows.
Pivot joints allow a rotating or twisting motion, like that of the head moving from side to side.
Ball-and-socket joints allow the greatest freedom of movement. The hips and shoulders have this type of joint, in which the round end of a long bone fits into the hollow of another bone.
What connects joints?
Cartilage is a smooth shiny surface on the bones which allows them to glide across each other freely.
Ligaments are fibrous bands that connect bones to bones. These maintain stability in the joint.
Tendons are tough inelastic cords that attach muscles to bones. These further strengthen the joint and allow the joint to move.
Synovial Fluid is a lubricant that keeps the joints moist and nourishes the cartilage to enable easy movement
Skeletal system movement
Flexion - A decrease in the angle of a joint. For example, moving your wrist up to your shoulder.
Extension - An increase in the angle at a joint, or returning the body part back to the normal anatomical position. For example, standing up straight after crouching down.
Adduction – Movement towards the body’s midline. For example, crossing your left leg over your right.
Abduction – Movement away from the body’s midline. For example lifting your arm up so it’s in line with your shoulder.
Rotation – Movement about an axis. For example, circling your arms.
Circumduction – Moving a limb so that the end of the limb does a circle. For example, circling your wrists.
Pronation - Movement of the forearm so the palm of the hand turns up.
Supination – Movement of the forearm so the palm of the hand faces down.
The Muscular System
The human body is made up of over 600 muscles, and everyone of those muscles has a specific role to play. Muscle tissue makes up half of your total bodyweight.
Voluntary Muscles - Also known as “skeletal muscles” because they are responsible for moving your skeleton around. These muscles are termed “voluntary” because your body is free to move them whenever it chooses. They are under your control.
Involuntary Muscles - These muscles work all the time and you cannot directly control them. An example is your heart.
How do muscles work?
Skeletal muscles always work in pairs when they move bones. The muscle doing the work is called the Agonist, and the muscle that is relaxing is called the Antagonist.
Types of muscle contractions
Concentric Muscles: When the muscle exerts a force and shortens in length
Eccentric Muscles: The opposite of concentric, when the muscles exert a force but lengthen
Isometric: The midway between concentric and eccentric where the muscle is neither lengthening nor shortening
Commonly used Muscles
Deltoid: Located on the shoulder, it helps to move your arms in multiple directions and provides stability to the shoulder joint.
Pectoral: Found on the chest, these muscles are responsible for moving the arms across the body and performing pushing motions.
Biceps: Located on the front of the upper arm, this muscle allows you to bend your elbow and rotate your forearm.
Abdominals: These muscles are in the front of the abdomen, helping with core stability, trunk flexion, and protecting internal organs.
Tibialis Anterior: Found on the front of the lower leg, it allows you to flex your foot upward and control foot movements during walking or running.
Triceps: Located at the back of the upper arm, this muscle helps with straightening the elbow and stabilizing the shoulder.
Latissimus Dorsi: Situated on the back, this muscle assists in pulling movements, such as pulling your arms down or behind you.
Gluteals: Found in the buttocks, these muscles are responsible for hip movement, including extending and rotating the hip.
Quadriceps: Located at the front of the thigh, they are responsible for straightening the knee and aiding in walking, running, and jumping.
Hamstrings: Situated at the back of the thigh, these muscles help in bending the knee and extending the hip.
Gastrocnemius: Found at the back of the lower leg, this calf muscle helps with pushing the foot down and is essential for walking and running.
Types of muscle fibres
The Circulatory System
The circulatory or cardiovascular system is responsible for supplying all parts of your body with adequate blood.
It is the system that provides your organs and muscles with oxygen and nutrients while removing their wastes and carbon dioxide.
The Heart
A muscular pump that moves the blood around the body.
The heart is divided into 4 chambers, the top chambers are called the atriums and the bottom two are called the ventricles.
The two sides of the heart are divided by a muscular wall called the septum; this is because each side of the heart has a specific job to do.
Blood
On average a person has approximately 5 litres of blood.
This only takes about one minute to travel around the human body.
You blood is 55% fluid (plasma) and 45% solid particles (red blood cells, white blood cells, and platelets)
Red & White Blood Cells
Red blood cells are the oxygen carriers of the body. Their job is to carry oxygen from your lungs to your body cells. Red blood cells that are carrying oxygen are a bright red colour, whereas cells that have delivered their oxygen to the body are dark in colour.
White blood cells are larger than red blood cells but fewer in number. White blood cells fight infection and kill bacteria that enter the body.
Arteries and Veins
Three different blood vessels are responsible for circulating blood around the body. These vessels are:
Arteries: Elastic tubes which carry blood away from the heart. They carry blood rich in oxygen and branch out into smaller vessels called arterioles. The pressure in the arteries is higher than in other vessels because they carry blood away from the heart.
Veins: Capillaries then feed into venules (small veins) which lead into veins. Veins carry used blood back to the heart from the body so that it can be sent to the lungs to pick up oxygen again. Veins are low in pressure so they have valves inside them to prevent the backflow of blood.
Capillaries: Capillaries are tiny vessels that work their way through joints, bones, muscles and organs, dropping off oxygen and nutrients, and picking up waste and carbon dioxide.