human bio notes

• Respiratory system


  A series of organs responsible for taking in oxygen and expelling carbon dioxide
• Respiratory system and circulatory system

  Closely linked - delivers blood with lots of carbon dioxide and little oxygen to the lungs, the oxygen diffuses into the blood via structures in the lungs and carbon dioxide diffuses out of the blood
• Key parts of the respiratory system

  • Nostrils
  • Nasal cavity
  • Pharynx
  • Larynx
  • Epiglottis
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
  • Thoracic cavity
  • Lungs
  • Pleura
  • Ribs
  • Intercostal muscles
  • Diaphragm
• Nostrils


  External opening with coarse hairs, provides a passage of air to pass through and filters large dust particles
• Nasal cavity


  • Bone divided into two chambers, each chamber has 3 shelves called conchae, lined by highly vascular mucous membrane, upper membrane has olfactory receptors, lower membrane has ciliated cells
  • Filters, warms, and moistens air before it enters the lungs
  • Detects smell
  • Resonating chamber which enhances the sounds produced in speech
  • Cilia beat to move mucus, which has dust trapped in it, towards the throat
• Pharynx


  Region from the nasal cavity to the top of the trachea and oesophagus, passageway for food (into oesophagus) and air (into the larynx)
• Larynx


  Made from cartilage and contains vocal folds, which have elastic ligaments to form vocal cords, vocal cords vibrate against each other as air passes through the larynx to produce sound
• Epiglottis


  Flap of cartilage tissue that projects from the rear wall of the larynx, during swallowing it closes off the trachea so food and liquid can't enter the lungs, during inhalation it closes the oesophagus to direct air into the trachea
• Trachea


  • Contains C-shaped cartilage rings and is lined with ciliated, mucous membranes, passage of air, C-shaped cartilage allow for flexibility and support to hold the tube open and to prevent trachea from collapsing, mucus traps dust and debris, with the cilia moving these particles up the pharynx to be swallowed
• Bronchi


  • Trachea divides into two bronchi, tube that contains C-shaped cartilage rings, lined with ciliated mucous membranes, provides air passage to and from each lung, C-shaped cartilage allows for flexibility and holds the bronchi open
• Bronchioles


  • Bronchi divide into very small tubes, with walls of tubes contain smooth muscle and elastin, contains cilia and mucus, provides an air passage to flow to and from each lung to deliver air to alveoli, they expand when body needs more oxygen, cilia and mucus protect lungs from contaminants
• Alveoli


  • Tiny air sacs (occur in clusters) with thin walls (one cell thick) and are surrounded by blood capillaries (highly vascular), large surface area, site for gas exchange: oxygen diffuses from the air into the blood, carbon dioxide diffuses from the blood into the air
• Thoracic cavity


  A region of the body, which is mostly occupied by the lungs, it is bound by the ribcage and the diaphragm, protects the lungs and the heart
• Lungs


  • Divided into two - left and right, contains air passages and air sacs (alveoli), highly vascular, surrounded by outer membrane (pleura), passage of air to flow, allows gas exchange to occur
• Pleura


  • Two layered structures, outer wall attached to inner layer of thoracic cavity, inner wall attached to lungs, holds lungs in position within thoracic cavity
• Pleural fluid


  A thin layer of fluid found between the pleura membranes, holds the lungs against the inside of the chest and allows them to slide along the wall without friction when breathing
• Ribs


  • Form the framework of the chest, protect organs within the thoracic cavity
• Intercostal muscles


  • Skeletal muscle between ribs, move the rib cage upwards and outwards to increase the volume of the chest cavity, and therefore the lungs during inhalation
• Diaphragm


  • Dome-shaped sheet of skeletal muscle that separates the chest (thoracic cavity) from the abdomen, diaphragm contracts by flattening downwards, this increases the volume of the chest cavity and the lungs during inhalation
• Breathing


  The mechanical movement of air in and out of the lungs
• Cellular respiration


  A chemical process that occurs in cells where the energy stored in glucose is released and stored as ATP
• Ventilation


  The process by which air is moved into and out of the lungs
• Inspiration (inhalation)


  The process of taking air into the lungs
• Expiration (exhalation)


  The process of taking air out of the lungs
• Inspiration/inhalation


  External intercostal muscles contract and pull the rib cage upwards and outwards, diaphragm (muscle) contracts and flattens pushing the chest cavity downwards, as the pleura adheres to the internal wall of the chest cavity, the lungs expand with the expanding chest cavity and the volume of the lungs increases, an increase in lung volume decreases air pressure, therefore air moves into the lungs, from an area of high pressure outside to an area of low pressure inside the lungs
• Expiration/exhalation


  External intercostal muscles relax and the rib cage moves downwards and inwards, diaphragm (muscle) relaxes and pushes back up into the thoracic cavity, as the pleura adheres to the internal wall of the chest cavity, the volume of the lungs decreases, a decrease in lung volume increases air pressure, therefore air moves out of the lungs, from an area of high pressure inside the lungs to an area of low pressure outside the body
• Pressure gradient


  The differences in air pressure between the internal thoracic activity (your lungs) and the outside air (atmospheric pressure = 101.3kPa), air flows from places of high pressure to places of low pressure
• Expired air contains less oxygen and more carbon dioxide than inspired air
• Respiration


  The transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction
• Gas exchange between the alveoli and blood capillaries

  1. Oxygen diffuses from the air in the alveoli to the blood because the concentration of oxygen in the air in the alveoli is high compared to the concentration of oxygen in the blood, where the concentration of oxygen is low

  2. Carbon dioxide diffuses from the blood to the air in the alveoli because the concentration of carbon dioxide in the blood is high compared to the concentration of carbon dioxide in air in the alveoli, where the concentration of carbon dioxide is low
• How the lungs and alveoli are well-suited for gas exchange

  • Millions of alveoli provide large internal surface area for efficient gas exchange
  • Each alveolus is well supplied with blood vessels, allowing as much blood as possible close to the air in the alveolus, decreasing the distance gas molecules are diffusing
  • Wall of alveoli are very thin, one cell thick, so the gases don't have far to move into or out of blood
  • Lungs are positioned deep inside body to prevent evaporation of fluid
  • Lung volume can be changed so air can flow into and out of lungs, ensuring constant changing of air and difference in concentrations of oxygen and carbon dioxide in air and blood
• Emphysema


  Alveoli are damaged and lose elasticity and replaced with fibrous tissue, reducing surface area, breathing out no longer occurs passively
• Lung cancer


  Involves the development of a tumour in the walls of the air passages
• Mesothelioma


  Cancerous tumor that develops in the pleura
• Pneumonia


  Infection of the lungs causing inflammation and fluid build up in alveoli
• Tuberculosis


  Infection of the lungs by the bacteria tuberculosis which attacks the lung tissue, can spread to other tissues
• Asthma


  Allergic response to foreign substances that enter the body, during an asthma attack the muscles surrounding the bronchioles spasm, causing a narrowing of the air passage and difficulty of breathing
• Circulatory system


  The link between the cells inside the body, which have certain requirements, and the environment outside the body, which supplies those requirements, involves the carrying of nutrients to the cells and in carrying wastes away from these cells
• Heart


  • The pump that pushes blood around the body, located between two lungs in the mediastinum, behind and slightly to the left of the sternum, conical shape (fist sized), wall of heart is composed of cardiac muscle, pericardium completely encloses the heart, each side of the heart is divided into 2 chambers - atria (thin walled, receive blood from the veins) and ventricles (thick walled, receive blood from the atria and pump the blood around the body), left ventricle wall thicker because it needs more cardiac muscle to pump the blood over a longer distance, around the body
• Circulatory system


  Involves the carrying of nutrients to the cells and in carrying wastes away from these cells