gas exchange system

Why do single-celled organisms not need exchange surfaces

• Metabolic activity it low so low demand for oxygen for respiration

• Large surface area to volume ratio

Why are exchange surfaces necessary for larger organisms

• High metabolic activity

• Smaller surface area to volume ratio

• Larger distances between cells where oxygen is needed and the supply of oxygen

How does size of organism correlate to SA:V

The bigger the organism, the smaller the SA:V

What are the features of efficient exchange surfaces

• large surface area - provides more surface area for diffusion to take place through (eg root hair cells)

• Thin - short diffusion distance (eg epithelial cells of alveoli)

• Good blood supply - maintains steep concentration gradient (eg dense capillary network around alveoli)

• Good ventilation - maintains steep concentration gradient (eg fish gills)

• Haemoglobin - binds to oxygen

Define gas exchange in mammals

Process whereby oxygen enters the blood capillaries in the alveoli and carbon dioxide leaves

What is the diaphragm and what is its role

A muscular sheet that contracts and relaxes to alter the pressure and helps control inhalation and exhalation

What is the role of the lungs

Contains alveoli for gas exchange

What is the role of cartilage

To keep airways open

What is the pleural membrane and fluid, what is its function

The membrane surrounding the lungs which lubricates the lungs to reduce friction during inhalation and exhalation.

What is the difference between cartilage in the bronchi and in the trachea

The trachea has C shaped rings due to its proximity to the oesophagus where the bronchi have interconnected cartilage plates instead of

What is the structure and function of the trachea

• carry clean, warm air from nose to chest

• Supported by C-shaped rings of cartilage to stop trachea from collapsing but allowing food to move down oesophagus

• Smooth muscle contracts to narrow lumen

• Elastic fibres allow lumen to dilate

• Lined with goblet cells (produce mucus to trap pathogens) and ciliated epithelial cells (move mucus to throat)

What is the structure and function of the bronchi

• leads to left and right lungs

• Supported by smaller rings of cartilage

• Smooth muscle contracts to narrow lumen

• Elastic fibres allow lumen to dilate

• Lined with goblet cells and ciliated epithelial cells

What is structure and function bronchioles

• Narrow tubes with columnar epithelial cells

• Made from smooth muscle and elastic fibres so can contract and relax to control air flow

• No cartilage or goblet cells present

What is the structure and function of the alveoli

• site of gas exchange

• Elastic fibres allow alveoli to stretch and recoil to return to original shape.

• Have squamous epithelial cells, but no smooth muscle, cartilage or goblet cells

How are goblet cells adapted to their function

• microvilli to increase the surface area

• Lots of secretory vesicles to release mucus through exocytosis

• Lots of rough endoplasmic reticulum to produce large quantities of mucin (protein in mucus)

• Golgi to process the mucin

How does the respiratory system deal with external air

• nasal passages are highly vascular so warm any cold air

• Nasal hair traps any larger particles

• Goblet cells secrete protective mucus which traps pathogens so macrophages roaming in mucus can engulf pathogen.

• Ciliated epithelial cells waft mucus up and it is swallowed into stomach acid which kills the pathogens.

Explain the importance of ciliated epithelial cells and goblet cells in the trachea and bronchi

• goblet cells secrete mucus

• Dust particles and bacteria stick to the mucus

• Cilia beat these particles up to the throat where they are swallowed

• Stomach acid kills any pathogens

• Keeps bronchial tree clean and defends against infection

Explain the importance of cartilage in the trachea and bronchi

• Keeps trachea and bronchi open during pressure changes of ventilation

• When food is passing down oesophagus, ring structure enables trachea to be flexible so neck can bend

• Provides attachment for smooth muscles in trachea

• Ring structure allows trachea to lengthen and shorten during ventilation movements.

Explain the importance of smooth muscle in the respiratory system

• muscle contracts to enable trachea/bronchi/bronchioles to dilate or constrict

• Changes diameter of airway, helping regulate airflow

• Gives some elastic recoil after stretching, which helps move air out.

Name and label this structure

Trachea

Describe what happens in the alveoli

• gas exchange

• Oxygen diffuses from air to blood and carbon dioxide from blood to air

• Oxygen binds to haemoglobin in red blood cells

• Volume of alveoli increases during inspiration

• Ventilation ensures concentration gradients of gases maintained

How are the alveoli adapted for gas exchange

• very large surface area so large surface area to volume ratio

• Thin squamous epithelial cells so short diffusion distance

• Most, lined with tissue fluid so gases can dissolve - contains surfactants to lower surface tension and allow lung expansion

• Good blood supply from capillaries and good ventilation maintaining steep concentration gradient.

Define ventilation

Inhalation and exhalation of air between the lungs and the outside

Outline the mechanism of ventilation in the lungs during inhalation

• external intercostal muscles contract moving rib cage up and out

• Diaphragm contracts and becomes flatter

• Increase in volume of thorax

• Decrease in pressure of thorax

• Air flows into lungs as atmospheric pressure is higher than pressure in thorax

Outline the mechanism of ventilation in the lungs during exhalation

• internal intercostal muscles contract so ribs move in and down

• Diaphragm relaxes and becomes domed in shape

• Decrease in thorax volume

• Increase in thorax pressure

• Air moves out until pressure in lungs fall

• Abdominal muscles can be used to make a stronger exhalation

How are the alveolar walls adapted for enabling ventilation movements

• Contains elastic fibres

• Enables dimension changes due to ventilation

• Elastic recoil helps to push air out of alveoli