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UNIT 2: BODY SYSTEMS

SKELETAL SYSTEM:

The skeletal system consists of 270 bones at birth, and decreases to 206 by adulthood, due to some bones fusing together.

Types of bones to memorise:

• Cranium - The skull

• Mandible - The jaw bone

• Clavicle - The collarbone

• Pelvis - Near the hip area

• Fibula - The smaller lower leg bone

• Calcaneus - The balls of the feet

• Cervical - The first seven vertebrae of the spinal cord, near the skull

• Scapula - The ‘wing bones’ in the back

• Humerus - The ‘funny bone’, the upper bone of the arm.

• Ulna - The smaller bone in the lower arm

• Femur - The largest bone in the body, located in the upper leg/thigh.

• Tarsals - Bones that form the ankle and heel

• Sacrum - Located above the coccyx (tailbone).

• Coccyx - the tailbone

• Radius - The larger bone of the lower arm.

• Carpals - The wrist bones

• Metacarpals - The bones that form your fingers

• Patella - The kneecap

• Metatarsals - The bones that are after the tarsals

• Lumbar - 5 vertebrae between the rib cage and pelvis.

• Phalanges (for the hands) - the bones that form your fingertips

• Phalanges (for the feet) - bones that form your toes.

• Sternum - The breast bone

• Ribs - A cage that protects your lungs.

• Tibia - The larger lower leg bone

• Thoracic - 12 vertebrae that are after the cervical vertebrae.

Regions of vertebrae:

Cervical - 7 vertebrae

Thoracic = 12 vertebrae

Lumbar - 5 vertebrae

Sacrum - 5 fused

Coccyx - 4 fused (tailbone)

Tips for memorising bones:

Fibula - ‘fine’

Tibia - ‘thick’

Ulna - pinky side

Radius - thumb side

Tarsals - feet

Carpals - hands

Vertebrae:

The vertebrae are the bones that make up the spine. As you move down the body, the size of the vertebrae increases. The spinal cord runs through the hole in the vertebrae, and it relies on vertebrae for protection.

Functions of the skeletal system:

• Allows movement - bones provide surfaces for muscles to attach, and they allow muscles to pull on them to produce more movement.

• Shape and protection - bones give the correct shape to the body and protect organs.

• Mineral storage - they store minerals such as calcium, iron, potassium and phosphorous. These will be released when the body needs them.

• Production of blood cells - bone marrow (inside most bones) produce red and white blood cells.

Red blood cells - carry oxygen to muscles, are red because of a protein called haemoglobin, which contains iron, and the production of red blood cells are abundant during growth years, and decrease with age.

White blood cells - fight infection in the body, part of the immune system.

MUSCULAR SYSTEM:

The muscular system is an organ system that consists of approximately 600 muscles.

Types of muscles:

Trapezius - The muscle near the scapula, in the upper back.

Deltoid - The upper part of your arm, near your shoulders.

Pectoralis major - The chest muscles

Biceps brachii - The muscle below the deltoids

Triceps brachii - The muscle behind the biceps

Wrist flexors - Muscles in your front forearm

Rectus abdominis - The ab muscles

Obliques - The sides of your hips, on either side of the abs

Adductors - The muscles near your pelvic area, in the front.

Quadriceps - The frontal thigh muscles

Gastrocnemius - The muscle below the knee, on the back of the leg

Soleus - Muscles near your ankles

Tibialis anterior - Near your tibia

Erector spinae - The muscle in the middle lower back

Latissimus dorsi - The muscles on either side of the erector spinae

Gluteus maximus - The ‘butt’ muscles

Abductors - Muscles below the pelvic area, on the back side

Hamstrings - Thigh muscles, on the back of the leg

Functions of muscles:

• Create movement - muscles pull on bones to produce movement

• Posture - skeletal muscles are essential to keeping posture, and their flexibility and strength help keep posture

• Heat production - When muscles contract, they create heat.

MUSCULOSKELETAL SYSTEM:

The musculoskeletal system relates to the bones, ligaments, tendons and skeletal muscles. The collaboration between the skeletal and muscular systems allow movement.

Ligaments and tendons:

Ligaments - Strong fibrous bonds that connect bone to bone. They provide stability at the joint where the muscles occur.

Tendons - Strong fibrous bonds that connect muscle to bone. When muscles contract, they pull on tendons, which pull on bones, which allows movement.

Flexion and extension:

Flexion - flexing a muscle

Extension - extending a muscle

Reciprocal inhibition: When muscles work in pairs. The agonist muscle (the one that contracts/shortens) contracts, while the other muscle (the antagonist muscle) relaxes/lengthens.

CARDIOVASCULAR SYSTEM:

The cardiovascular system, also known as the circulatory system, consists of the heart and blood vessels working together to transport gases and nutrients around the body.

Functions of the cardiovascular system:

• Circulates blood around the body

• Transports oxygen and nutrients to the cells

• Transports waste away from the cells

• Maintains stable body temperature

Types of blood vessels:

Arteries - have thick, elastic walls, and is responsible for transporting oxygenated blood to the muscles

Capillaries - have thin, non-elastic walls, and are responsible for the exchange of nutrients and waste between body cells. They transport both oxygenated and de-oxygenated blood.

Veins - have thin, not-so-elastic walls, carry de-oxygenated blood to the heart, and have valves inside, to prevent backflow. They rely on skeletal muscles to pump blood to the heart.

The heart:

The heart is a pump designed to push blood through the cardiovascular system. It is located slightly left to the chest, and is protected by the ribs. The adult heart is around the size of large fist.

In diagrams of the heart, the left and right sides are swapped, because you are looking at the front of it.

Atria are chambers that receive blood, while ventricles are chambers that pump blood.

The septum divides the heart into two halves. The right carries de-oxygenated blood, while the left carries oxygenated blood.

Pathway of blood: The veins first take blood into the right atrium, via the superior and inferior vena cava, and then into the right ventricle, which pumps blood to the lungs via pulmonary arteries. The blood travels via the lungs to alveoli, which are small air sacs at the end of bronchi. The alveoli are connected to capillaries, where gaseous exchange takes place. After that, the capillaries take blood to the heart via the pulmonary veins, to the left atrium, then the left ventricle, then out into the aorta and the rest of the body.

RESPIRATORY SYSTEM:

The respiratory system consists of the nose, mouth, throat, voicebox, windpipe and lungs, and is specialised for gas exchange.

Functions of the respiratory system:

• Brings air from atmosphere to lungs

• Transfers oxygen from air into the blood

• Removes carbon dioxide from blood

• Expels heat in exhaled air

• Allow vocal chords to create speech

The lungs:

The lungs are the major organ in the respiratory system, located behind the ribs in the chest cavity. It allows oxygen inside the blood, and helps get rid of carbon dioxide.

Alveoli:

Alveoli are tiny air sacs in the lungs, and the site where oxygen and carbon dioxide are exchanged.

Diaphragm:

The diaphragm is a muscle in the respiratory system, and it helps us breathe in and out.

Breathing:

Is the process of taking air in and out of the lungs. It is broken into two phases; inspiration and expiration.

Concentration:

Breathing relies on tendency of air particles to move from areas of high concentration (high pressure) to areas of low concentration (low pressure).

Inspiration:

The process of inhalation, or air going into the lungs.

• The diaphragm contracts, moving downwards.

• The muscles between the ribs (intercostal muscles) contract, increasing the size of the chest cavity.

• These steps causes pressure to decrease in the lungs.

• Air is drawn into the lungs as gases move from areas of high concentration to low concentration.

Expiration:

The process of exhalation, or air getting expelled from the lungs.

• The diaphragm relaxes, moving upwards.

• The muscles between the ribs (intercostal muscles) relax, decreasing the size of the chest cavity.

• These steps cause pressure to increase in the lungs.

• Air is drawn out of the lungs as gases move from areas of high concentration to low concentration.

Gaseous exchange:

ALVEOLI AND CAPILLARIES

This happens between the alveoli and capillaries at the lungs. Carbon dioxide moves into the alveoli, and oxygen moves into the capillaries.

CAPILLARIES AROUND SKELETAL MUSCLES AND MUSCLE CELLS

Oxygenated blood becomes deoxygenated, as carbon dioxide moves to the capillaries, and oxygen moves to the muscles.