Digestive and Respiratory Systems

Digestive System

• Digestion starts as teeth grind food, the saliva in the mouth begins to break it down
• The tongue mixes salvia and food, forming a bolus
• The bolus travels down the pharynx and oesophagus
• The oseophagus pushes the bolus into the stomach via peristalsis
• The liver creates juice called bile that assists in the digestion of fats
• The pancreas produces pancreatic fluid which helps digestion of proteins
• The stomach releases gastric juices which continues to break down food and mixes with the bolus, creating chyme
• Chyme enters the small intestine where food is transformed into nutrients
• These nutrients pass through the walls of the small intestine into the blood
• What is not absorbed by the small intestine continues to the large intestine
• This absorbs water and minerals that then pass into the blood
• Undigested substances form a faecal bolus, and this is expelled through the anus via defecation

Respiratory System

• Breathing occurs via two stages:
• Pulmonary ventilation which is the process of air entering the lungs during inhalation, and exiting during exhalation
• Gas Exchange where oxygen from inhaled air passes into the blood, and carbon dioxide from the blood passes into the lungs and is released
• Air enters the respiratory system via the nostrils, which are on the inside of the nose, and they help heat, moisten and filter the air
• The pharynx connects the larynx, the oesophagus, and the trachea
• The larynx contains vocal cords, which vibrate and make sound
• The trachea, or windpipe, is a solid tube that carries air to the lungs via the bronchi
• The bronchi are two branches of the trachea which further divide into smaller tubes called bronchioles
• The bronchioles carry air to the lungs
• The lungs are two spongy organs which are formed by the pulmonary alveoli, which is where gas exchange happens
• The diaphragm is a muscle that contracts and relaxes so we can breath in and out

Circulatory System

• Blood is made up of plasma and blood cells, it is a red liquid
• The plasma is a liquid that transports nutrients and waste
• The blood cells transport oxygen
• Red blood cells carry oxygen and carbon dioxide, and give blood its colour
• White blood cells protect the body from infection
• Platelets stop the bleeding and seal wounds until a scar can form
• Blood vessels transport blood around the body
• The heart is a muscle located slightly to the left of the chest between the two lungs
• It pumps blood in a rhythmic cycle that involves two phases, systole which is contraction, and diastole which is relaxation
• Atria are the upper chambers connected to the veins, and bring blood back
• There are values between the atria and ventricles, these open and close to stop blood from returning to the atria
• Ventricles are the lower chambers and connect to the arteries, which take blood rich in oyxgen to the body
• Blood flows through a process called double circulation
• Deoxygenated blood enters the right atrium through the vena cavae
• Then it goes to the the right ventricle where it is pumped into the lungs through the pulmonary artery
• Pulmonary or minor circulation then begins and gas exchange occurs in the alveoli, the blood picks up oxygen and releases carbon dioxide
• The pulmonary circuit ends when oxygenated blood returns through the pulmonary veins to the left atrium of the heart
• The blood then flows to the left ventricle
• Systemic or major circulation begins when oxygenated blood is pumped from the left ventricle through the aorta artery to the body's organs
• Blood takes in carbon dioxide from all over the body and systemic circulation ends when deoxygenated blood enters the heart again at the right atrium through the vena cava

Excretory system

• Sweat glands produce sweat
• The kidneys remove waste from the blood and send it back to the circulatory system
• Kidneys make urine with water and waste products, they are bean shaped
• The ureters take urine from the kidneys to the bladder
• Urine leaves the body through the urethra
• The urethra is a tube that connects the bladder to the outside of the body
• The bladder stores urine and when it is full pushes the urine out the body

Summary Points

• Nutrition provides our cells with nutrients and oxygen so they obtain energy
• Cells are the smallest units of life
• There are 4 processes in nutrition, these are, digestion, respiration, circulation and excretion
• Digestion transforms food into nutrients
• Digestion needs the help of organs like the liver and pancreas, and is carried out by the digestive system
• Undigested substances become faeces and are expelled
• Breathing gets oxygen which gives us energy
• Expelling the waste product carbon dioxide occurs when we breath out
• Breathing happens because of the respiratory system, which uses organs like the lungs and alveoli for gas exchange
• Circulation is the process of transporting oxygen and nutrients to all the cells
• It ensures that all waste substances produced by cell activity are collected
• Systole and diastole movements of the heart pump blood
• Human circulation is complete and double, including pulmonary and systemic circulation
• Excretion is the elimination of waste caused by cellular activity
• Systems to carry this out include the respiratory and excretory systems
• The respiratory system expels carbon dioxide, the excretory system gets rid of urine and sweat