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• Eight human organ systems include skeletal, muscular, circulatory, respiratory, nervous, digestive, reproductive, and immune
• It is important to identify the eight different human organ systems

Circulatory System

• The circulatory system's role is to transport oxygen, nutrients, and hormones to cells while removing waste products such as carbon dioxide
• The three components of the circulatory system are blood, heart, and blood vessels and they work together to carry out a function

Blood Structure and Function

• Blood is primarily composed of plasma, a pale yellow liquid, that contains hormones, salts, blood cells, nutrients, and gases
• Plasma accounts for approximately 55% of blood volume
• Within the blood, red blood cells transport oxygen to cells and remove carbon dioxide for excretion via the lungs
• White blood cells defend the body against pathogens
• Platelets facilitate blood clotting to stop bleeding when damage occurs

Blood Vessels Structure and Function

• Arteries transport blood away from the heart at high pressure and contain thick outer walls with thick layers of muscle and elastic fibers
• Arteries carry oxygenated blood, with the exception of the pulmonary artery
• Veins carry blood toward the heart at low pressure compared to arteries, thus they have thinner walls and thinner muscle and elastic fibers
• Veins contain valves to prevent backflow and carry deoxygenated blood, with the exception of the pulmonary vein
• Capillaries are small, thin-walled blood vessels that connect arteries and veins, this allows for the exchange of oxygen and carbon dioxide, nutrients and waste materials

Heart Structure and Function

• The heart diagram is displayed as if viewed from someone lying on their back
• The left side of the heart has a thicker outer wall because it pumps blood at higher pressure
• The upper chambers of the heart are atria, and the lower chambers are ventricles
• The septum divides the left and right sides of the heart, preventing mixing of oxygenated and deoxygenated blood
• The right side of the heart (ventricle) pumps blood to the lungs for reoxygenation
• The left side of the heart (ventricle) pumps oxygenated blood to the body
• Valves open and close rhythmically to prevent backflow and ensure proper blood direction
• Aorta: the largest artery, carries oxygenated blood from the left ventricle to the body
• Pulmonary artery: carries deoxygenated blood from the heart to the lungs
• Pulmonary vein: carries oxygenated blood from the lungs back to the heart
• Vena cava: returns deoxygenated blood from the body to the heart
• Left atrium: receives oxygenated blood from the pulmonary veins
• Left ventricle: pumps oxygenated blood to the body
• Right atrium: receives deoxygenated blood from the vena cava
• Right ventricle: pumps deoxygenated blood to the lungs
• Septum: prevents mixing of oxygenated and deoxygenated blood

Direction of Blood Flow

• The direction of blood flow through the heart begins with blood entering the vena cava and moving through the right atrium
• Blood then passes through the tricuspid valve and into the right ventricle, followed by the pulmonary valve and pulmonary artery
• Blood proceeds to the lungs for reoxygenation, then returns via the pulmonary veins to the left atrium
• Next, blood flows through the mitral valve into the left ventricle which moves through the aortic valve into the aorta, and then to the rest of the body

Red Blood Cell Adaptations

• Red blood cells contain haemoglobin to bind and transport oxygen and lack a nucleus, which increases space for haemoglobin
• They have a thin outer membrane to shorten the diffusion distance for oxygen
• The biconcave disc shape increases the surface area for oxygen absorption
• The small and flexible shape enables them to squeeze through narrow capillaries

Respiratory System Role

• The respiratory system involves breathing, also known as ventilation, and gas exchange
• Ventilation includes inhalation of oxygen-rich air and exhalation of carbon dioxide-rich air, utilizing respiratory muscles like the diaphragm
• Gas exchange is the swapping of oxygen and carbon dioxide across the alveolar membrane and the bloodstream for transport through the body

Respiratory System Structure and Function

• Nasal cavity: Draws in air and filters and moistens it
• Trachea: Connects the throat with the bronchi
• Rings of Cartilage: Prevents the trachea from collapsing
• Bronchi: Tubes that go to each lung
• Bronchioles: Tubes that take air to the alveoli
• Alveoli: Site for gas exchange (carbon dioxide leaves the blood and oxygen enters the blood)
• Diaphragm: Aids breathing
• Lungs: Organs containing the alveoli and bronchioles
• Ribs: Bones that protect organs including the heart and lungs

Process of Gas Exchange

• Blood low in oxygen and high in carbon dioxide enters the capillary
• Carbon dioxide moves from the blood into the alveoli
• Oxygen moves from the air in the alveoli into the blood
• Oxygen is transported to body tissues by red blood cells

Adaptations of Alveoli

• Millions of alveoli provide a large surface area for gas exchange
• Their round shape increases this surface area
• A moist lining (surfactant) helps oxygen dissolve
• They have thin membranes to reduce the distance for oxygen to move, and are surrounded by capillaries

Respiration vs. Gas Exchange vs. Breathing

• Respiration is the process where cells convert glucose and oxygen into carbon dioxide, water, and energy
• Breathing is the process of inhaling and exhaling air
• Gas exchange is the process of exchanging oxygen and carbon dioxide between the bloodstream and the alveoli

Digestion

• Animals consume food for nutrients to carry out life processes
• The six main types of essential nutrients are protein, carbohydrates, fats, vitamins, minerals, and fluid
• Macronutrients = Protein, carbohydrates, fats
• Micronutrients = Vitamins, minerals
• The body needs nutrients obtained from our diet, to function correctly and maintain overall health

Digestive System Parts

• Mouth
• Oesophagus
• Stomach
• Small intestine
• Large intestine
• Rectum
• Anus

Digestion Process

• Ingestion: Food is taken into the mouth
• Digestion: Large, insoluble nutrients are broken down into small, soluble nutrients
• Absorption: Digested food is taken into the blood
• Egestion: Undigested food is removed
• Mouth - Ingestion and digestion
• Food is chewed
• Food mixes with saliva from salivary glands to form a bolus
• Saliva contains amylase to chemically digest carbohydrates and saliva lubricates the saliva
• Oesophagus
• Bolus moves down via peristalsis which is a wave-like motion
• Stomach - Digestion
• The stomach is an elastic that holds many liters of food
• It is lined with gastric pits which contain the following:
• Hydrochloric acid: corrosive, which creates optimum acidic conditions for enzymes, kills many pathogens
• Pepsin: catalyses the breakdown of proteins into amino acids
• Mucus: forms a protective layer

Small Intestine, Large Intestine, Rectum and Chemical and Mechanical Digestion

• Small intestine – Digestion and Absorption
• Final stages of digestion of lipids, carbohydrates and proteins by enzymes secreted by the pancreas
• Proteins → amino acids
• Carbohydrates → glucose
• Lipids → fatty acids and glycerol
• Products are small and soluble and absorbed into the bloodstream in the small intestine villi, increases the surface area
• Large intestine - Absorption
• Water and ions are absorbed back into the body, and the remaining faeces is left behind
• Rectum and Anus - Egestion
• The rectum is an elastic sack that stores waste until it is ready to be released
• Mechanical and Chemical Digestion
• Digestion is the action of breaking down LARGE INSOLUBLE nutrients into SMALL SOLUBLE nutrients
• Mechanical: Physical action of breaking food down into smaller parts
• Chemical: The breaking down of insoluble food particles into smaller particles, mainly through enzymes that occurs in the mouth, stomach and small intestine

Adaptations of the Small Intestine

• The adaptations of the small intestine that allow digested nutrients to be absorbed into the blood quickly are:
• Long length – the small intestine is around 3-5 metres long
• Villi - One cell thick to reduce diffusion distance across the bloodstream
• Capillary network - Increases the amount of digested food absorbed into the bloodstream
• Microvilli - Increases the surface area of digested nutrients

Respiratory and Circulatory System Work Together

• Respiratory: Oxygen from the air via the respiratory system that involves the trachea / bronchi / bronchioles to the alveoli
• Circulatory: Red blood cells or pulmonary vein carries the oxygenated blood to the heart which then transfers the blood to the rest of the body

Importance of Respiration

• Respiration converts glucose and oxygen into carbon dioxide, water, and energy
• Reproduction benefits from respiration needed for cell division
• All processes require energy in the form of ATP and without ATP the functions won't occur