Topic 2

• Cells → Tissues → Organs → Organ Systems


  how cells communicate and work together to form a complex system and maintain homeostasis.

  
• Cells


  The basic building blocks of all living organisms
• Tissue


  group of similar cells with a similar structure and function
• Organ


  group of tissues that work together to perform specifc functions
• Organ system


  group of organs that work together to form organisms
• Need for exchange surfaces

  high metabolic demand - need lots of O2

  large surface area to volume ratio so diffusion distances are too large to supply oxygen by diffusion alone

  .
• What does the size of their surface define


  Defines how quickly they can absorb substances
• What does the size of their volume define

  Defines how much of the substance is needed
• As multicellular organisms increase in size, they face two problems:

  1) Their surface area does not increase as fast as the volume

  2) Their volume increases Diffusion is not quick enough to move substances to where they're needed in the organism's body
• Adaptations of effective exchange surfaces in all organisms
• the alveoli.


  tiny sacs in the lungs, where gas is exchanged during breathing
• The human lungs provide an exchange surface adapted for:

  -absorbing oxygen - needed for respiration - into the blood from the air

  -transferring carbon dioxide - produced by respiration - from the blood into the lungs then the air
• structure of the respiratory system

  There are 3 major parts of the respiratory system: the airway, the lungs, and the muscles of respiration.
• the lungs


  -enclosed in the thorax

  -protected by 12 pairs of ribs

  -ribs are moved by two sets of intercostal muscles

  -a muscular diaphragm below the lungs

  -lungs are sealed within two airtight pleural membranes (wrap around the lungs and line the rib cage.)
• Capiliaries


  tiny blood vessels that deliver supplies to individual cells and takes away waste materials
• Where does the exchange of gases occur?

  between the alveoli and blood in the capillaries that supply the lungs

  
• How are aveoli adapted for gas exchange?

  Large surface area:

  - many alveoli in the lungs

  - alveoli are highly folded

  - alveoli are lined with water - dissolved gases

  - large network fo capillaries surrounding the aveoli

  
  

  Short diffusion pathway:

  - blood capillary directly outside alveoli

  - alveoli epithelium is only one cell thick

  - capillary walls only one cell thick

  - small capillary diameter

  
  

  Concentration gradient:

  - ventilation is continually happening

  - The blood is continually moving

  - The blood passing next to the aveoli slows down
• Ventalation


  movement of air in and out of the lungs
• diaphragm


  Large, flat muscle at the bottom of the chest cavity that helps with breathing
• intercostal muscles


  Muscles which move the rib cage during breathing
• breathing in (2)


  1) air moves into lungs from the exchange surface of the alevoli

  2)diagrpham and ribcage move to create a low air pressure in the lungs than the air out of the body
• what are the muscles used in breathing (2)

  diaphragm,

  external and internal intercostals
• external and internal intercostals when creating in

  contraction expands and lowers the ribs during breathing
• what's breathing in and out called

  inhaling and exhaling
• gills in fish


  -Water drawn into mouth and out from pharynx across gills

  -Flow of blood in gill capillaries opposite the flow of water across gills

  -Blood always exposed to water having higher oxygen content
• adaptations for gas exchange *(4)

  - a large surface are allows faster diffusion to occur across the surface

  -thin wallets ensure diffusion distance to remain short

  -good ventilation with air= diffusion gradients can be maintained

  -good bloody supply= maintains a high concentration gradient
• by which process does gas exchanges occur

  diffusion
• ribs


  The bones in the chest that protect the heart and lungs.
• intercostal muscles


  Muscles which move the rib cage during breathing
• Diaphragm


  Large, flat muscle at the bottom of the chest cavity that helps with breathing
• Trachea


  windpipe

  Allows air to pass to and from lungs
• bronchus


  one of the two tubes that connect the lungs with the trachea
• bronchioles


  smallest branches of the bronchi
• Alveoli


  tiny sacs of lung tissue specialized for the movement of gases between air and blood
• When we breathe in (inhale)


  diaphragm contracts, flattens and increase the volume of the thorax, which gases a decrease in air pressure inside the lungs to outside the body, drawing air in
• when we breathe out

  diaphragm relaxes moves upwards and back into its domed shape, this decrease the volume of the thorax, which causes an increase in air pressure inside the lungs to outside the body forcing the air out
• external and internal intercostal muscle

  work as antagonistic pairs (work in different directions to each other)
• inhalation the external set of intercostal muscles contract to pull the ribs up and out


  increases the volume of the chest cavity (thorax), decreasing air pressure, drawing air in
• exhalation, the external set of intercostal muscles relax so the ribs dropdown and in


  This decreases the volume of the chest cavity (thorax) increasing air pressure, forcing air out
• forced exhalation