#16 The Respiratory System (English)

The Respiratory System

Respiration

The chemical reactions that break down nutrient molecules in living cells to release energy.

Two types of respiration: 

AEROBIC RESPIRATION

·         The release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen.

·          glucose  + oxygen à carbon dioxide + water + energy

·         C₆H₁₂O₆    +   6O₂         à          6CO₂                 + 6H₂O  + energy

·         The energy released from food in respiration is used by cells for:

-          Muscle contraction (movement)

-          Protein synthesis, cell division (growth/repair)

-          Transmission of nerve impulses

-          Maintaining a constant body temperature

-          Active transport

-          etc.

·         Test for products of aerobic respiration:

-          Carbon dioxide turns limewater cloudy

-          Breathing on a mirror – water in breath condenses

ANAEROBIC RESPIRATION

·         The release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen.

·         glucose    à lactic acid + energy

·         C₆H₁₂O₆    à  2C₃H₆O₃     + energy

·         Lactic acid is toxic and can cause your muscles to become fatigued and to stop doing their job. Because of this, we can only respire anaerobically for a short period of time.

·         The lactic acid diffuses from the muscles into the blood, and is taken to the liver. The liver breaks it down by combining it with oxygen. Therefore, extra oxygen is needed. This oxygen debt is paid off during the recovery period after exercise.

         Anaerobic respiration in yeast:

-          glucose  à    ethanol  + carbon dioxide + energy

-          C₆H₁₂O₆   à  2C₂H₅OH +             2CO₂             + energy

·         Yeast is a single-celled fungus.

·         Anaerobic respiration by yeast is used in brewing. Yeast is added to a mixture of sugar and other substances, and it ferments the sugar to alcohol.

·         Respiration in yeast is also used in bread making. The bubbles of CO₂ make the bread rise.
-          Respiration occurs in the mitochondria of a cell.

 Gas exchange

 The process of gases moving into and out of body tissues.

It has to happen in order for cells to get oxygen and get rid of carbon dioxide in aerobic respiration. Gases move into and out of cells by diffusion.

Air goes into the lungs through the mouth or nose, down the trachea and into the right and left bronchi. The bronchi then branch into smaller tubes called bronchioles, which end as tiny sacs called alveoli. Each lung contains several million alveoli and each alveolus has blood capillaries wrapped closely around it. Deoxygenated blood is brought to these capillaries along the pulmonary artery (from respiring cells/tissues in the body). The concentration of oxygen in the alveolus is greater than that in the red blood cells (in the capillaries), therefore oxygen diffuses into the blood. The blood then flows away inside the pulmonary vein (to the heart).

At the same time that oxygen diffuses from the alveoli into the blood, carbon dioxide is diffusing in the opposite direction.

§  How many cell membranes does oxygen have to go through before it is in the red blood cell?

·         Cell lining of alveolus

·         Cell lining of the capillary

·         Cell membrane of the red blood cell.

§  How are alveoli adapted for gas exchange?

·         A lot of surface area

·         Very thin walls

·         Very moist

·         Lie close to millions of capillaries.

 

 

 

 

Breathing = pushing air into and out of lungs for the purpose of gas exchange; occurs using muscle movements.

 

Functions

 §  The nose: important for breathing.

§  Pharynx: where the nasal cavity and mouth cavity meet, in the back of the throat.

§  Epiglottis: a thick flap of cartilage that closes the breathing passage when you swallow food, so that food doesn’t go down the wrong tube.

§  Trachea: the tube that carries air to the lungs.

§  Rings of cartilage: rings around the trachea that hold it open and protect it.

§  Larynx: the voice box. Air pushed across these cords makes sound by vibrating them.

§  Bronchi: the trachea splints into these two large tubes leading to each lung.

§  Bronchioles: tiny tubes leading from the bronchi all over the lungs.

§  Alveoli: tiny balloons at the ends of the bronchioles. These are the GAS EXCHANGE SURFACES of the lungs.

§  Pleural membrane: these slick membranes surround the lungs and protect them from friction when you breathe.

§  Ribs: bones forming a “cage” in the chest or thorax.

§  Intercostal muscles: muscles between the ribs that hold them together. These are used for breathing.

§  Diaphragm: a flat slab of muscle along the bottom of the thorax used for breathing.

Inhaled vs. Exhaled air

Feature	Inhaling	Exhaling
Diaphragm shape	flattens	springs up
Diaphragm muscle	contracts	relaxes
External Intercostal muscles	contract	relax
Internal Intercostal muscles	relax	contract
Ribs	move up and out	move down and in
Lungs	inflate	deflate

	Inspired air	Expired air
Oxygen %	21	16
Carbon dioxide %	0.04	4
Nitrogen %	78	78
Water vapor	Very variable	Always high

Breathing during exercise

During exercise the muscles work hard, and need to release more energy by respiration. The faster the muscle cells respire, the more carbon dioxide they generate. This carbon dioxide goes into the blood and dissolves in the blood plasma to produce a weak acid, carbonic acid. This lowers the pH of blood. Special cells in the brain detect this change and so they send impulses along the nerves to the intercostal muscles and the diaphragm. This causes these muscles to contract harder and faster to keep up with the demand for oxygen, therefore:

-          Increasing the breathing rate – more breaths per min

-          Increasing the tidal volume – more air per breath

 Smoking and its dangers
 

Substance found in cigarettes	Effect on body
Tar (a black sticky substance)	- Can lead to alveoli breaking down (emphysema). - Can cause cancer to form in the bronchi, bronchioles or lungs. - Can cause the cells to divide uncontrollably forming a lump called a ‘tumor.’ - Can affect the cilia and goblet cells in the trachea making colds and diseases more likely.
Nicotine	- An addictive drug which raises the heart rate and blood pressure. - Affects the brain by making people feel more relaxed. -Increases risk of heart disease.
Hydrogen Cyanide	- It damages cells in the lungs
Carbon monoxide	- Reduces the amount of oxygen carried to the cells in your body. - Affects the cilia and the goblet cells. - Anaesthetizes the cilia so that it stops working.  - Causes infections such as bronchitis. - Causes emphysema.
Smoke particulates	- Make the goblet cells work harder, producing more and more mucus. - Irritate the cells lining the alveoli.

How lungs clean themselves

 

·         There is a lot of dust, germs, pollen and pollution in every breath of air you take.

·         The lungs have a system for getting rid of this.  If they can’t, they fill up with dirt, get infected, get cancer, and break down.

·         The walls of the bronchi and bronchioles have 2 kinds of cells that help keep dust from getting to the alveoli:

1.      Goblet cells: make mucus. Mucus is a clear, sticky liquid found in many places in the body. Mucus traps dust, germs and particles.

2.      Ciliated cells: have little hair-like brushes (“cilia”) on their surface. These hairs sweep the dirty mucus up the bronchi to the back of the throat.

3.      The dirt-filled mucus reaches the pharynx (throat) and is swallowed, where everything is digested.