Transport In Animals

1. Human heart : 

• consists of 4 chambers : right atrium, right ventricle, left atrium and left ventricle. 
• pump blood to all parts of the body.
• made up of cardiac muscle. 




Front/venrtral  view of heart

 

2. Superior vena cava
    --> carries deoxygenated blood
    --> from the head + arms
    --> into right atrium.

3. Inferior vena cava
    --> carries deoxygenated blood
    --> from the lower body + legs
    --> into right atrium

4. Right atrium
    --> receives deoxygenated blood
    --> from vena cava
    --> to right ventricle. 

5. Tricuspid (antrioventricular) valves
    --> prevent blood (from right ventricle) flowing backwards
    --> to the right atrium.

6. Right ventricle
    --> pumps blood
    --> to lungs
    --> via pulmonary arteries.

7. Semilunar valves
    --> prevent blood (from pulmonary arteries)
    --> from flowing backwards
    --> into right ventricle.

 




Cross-section of heart

  










8.   Pulmonary artery branches
      --> carries deoxygenated blood
      --> from right ventricle 
      --> to lungs.

9.   Pulmonary vein
      --> carrying oxygenated blood
      --> from lungs
      --> to left atrium.

10. Left atrium
      --> receives oxygenated blood
      --> from lungs 
      --> to left ventricle.

11. Bicuspid (atrioventicular) valves
      -- > prevent blood (from left ventricle) flow backwards to left atrium

12. Left ventricle
      --> pumps oxygenated blood
      --> to body tissue (via aorta).

13. Semilunar/aortic valves
      --> prevent blood (from aorta) flowing backwards (into left ventricle).

14. Aorta
      --> carries oxygenated blood
      --> from left ventricle
      --> to the rest of the body.

15. Septum separates the right and left side of the heart.

Simplified version of heart

  

Gaseous Exchange in Mammals

(A) Gaseous exchange in mammals

1. Respiratory tract consists of:  nostril, nasal cavity, pharynx, trachea, bronchi + bronchioles.

2. Gaseous exchange occurs at the ­­­alveoli.
3. Alveolar wall = single layer of squamous epithelium cells.
4. Capillary wall = flattened endothelial cells.
5. Thin layer of alveolar wall + rich network of blood capillaries à enhance gaseous exchange between alveolar sac + blood.

6. Deoxygenated blood - enters the lungs - thrugh pulmonary arteries.
7. Oxygenated blood - leaves the lungs - through pulmonary vein.
8. The rate of O₂ + CO₂ diffusion in the alveolar à depends on partial pressure of the gases in the alveolar air.

   9.   In the lung:

à PO₂ in the alveolar air is higher than blood

à O₂ diffuse rapidly from alveolus

à to blood plasma.

10. In the peripheral tissues:

à PO₂ is lower than blood

à O₂ diffuses out from blood

à to tissues.

11. O₂ +  CO₂ à low solubility in blood plasma
12. CO₂ à mainly transported as hydrogen carbonate ion (HCO₃⁺).
13. In the tissues

à PCO₂ is higher than blood

à  CO₂ diffuses out

à into the capillaries.

(B) Gaseous exchange in mammals

14. Blood carries CO₂ in 3 forms:

·   dissolved gas (8%)

·   HCO₃^- ion in the plasma (73%)

·   carbamino haemoglobin in the red blood cells (19%)

15. A large amount of CO₂

·   combines with H₂O in the red blood cells (RBC)

·   to form carbonic acid (H₂CO₃)

·   then ionizes to form H⁺ +  HCO₃^-

16. HCO₃^- from the red blood cell:

·   diffuse out into the plasma.

·   loss of negatively charge HCO₃^- from the red blood cell

·   balanced by the inward diffusion of -ve chloride ions (Cl^-) = chloride shift.

17. In the lungs.

à PCO₂ is lower than in the blood.

à CO₂ diffuses out

à into alveoli.

18. In the plasma:

1.  dissolved CO₂ diffuses out into the alveolar air.

2.  Carbamino haemoglobin:

à dissociates

à form CO₂ + haemoglobin.

3.  Hydrogen carbonate ions (HCO₃^-):

à diffuse into the red blood cells

à reacts with H⁺

à form carbonic acid (H₂CO₃).

à dissociates

à form H₂O + CO₂

à CO₂ diffuses out into the alveolar air

à exhaled.

(C) Gaseous exchange in mammals

1.  O₂  = transported by the haemoglobin molecule in the red blood cells.

2.  Each haemoglobin molecule à carries 4 mol of O_2.

3.  Each polypeptide chain contains:

·   2 subunits of alpha polypeptides chains

·   2 subunits of beta polypeptides chains.

4.   Haem:

à prosthetic group of haemoglobin.

à as a porphyrin ring with a ferum ion (Fe2+) in the middle.

à each capable of carrying a single O₂ molecule attached to the ferum ion

à porphyrin ring shows strong cooperative O₂ binding to the haemoglobin.

5.   When one mol of O₂ binds to one of the haem group in the haemoglobin

à produces a conformational change in that subunit

à transmitted to the other 3 subunits

à facilitate O₂ binding to the rest of the polypeptide.

à concerted conformational change of the subunits

à increases affinity of haemoglobin for O₂

à resulting in sigmoid shape for the O₂ dissociation curve of the haemoglobin.

     6. The cooperative effect is reversible

à when one subunit of oxyhaemoglobin unloads its O₂,

à other three quickly follow suit

à conformational change

à lowers its affinity for O₂.

     7. Relationship between PO₂ and % saturation of haemoglobin with O₂
         à represented by O₂ dissociation curve = sigmoid.

   8.   The O₂ dissociation curve shows:

à when haemoglobin is exposed to a gradual increase of PO₂,

à it absorbs O₂ rapidly at first

à but more slowly as the PO₂ continues to rise.

     9. The % of O₂ saturation of haemoglobin = 95%

à when blood flows through the lungs (PO₂ = 105 mmHg).

    10. The % of O₂ saturation of haemoglobin = 70%

à when blood flows through a moderately active/resting muscle (PO₂=40 mmHg).

    11. As the blood from the lungs reaches the muscle at rest:

à 25% of the O₂ carried in the heamoglobin is unloaded to the surrounding tissues

à for cellular respiration.

à 70% of the oxygen is still retained by the haemoglobin.

    12. The % of O₂ saturation of haemoglobin is 40%  

à when the blood flows through the active muscle at PO₂ of 20 mmHg.

    13. When the muscle is active:

à haemoglobin readily unloads 55% of the oxygen

à still retains 40%.

    14. During exercise:

à active tissue is in demand for O₂ to produce energy.

à slight drops in PO₂ (between muscle at rest + muscle during exercise.)

à enough to cause a relatively large increase in the amount of O₂ the blood unloads.

    15. The increase of CO₂ conc/decrease in blood pH:

à will induce haemoglobin to unload more O₂.

à affinity of haemoglobin to O₂ is lower.

à O₂ dissociation curve shifts to the right = Bohr effect.

  16. Foetal haemoglobin:

à has a higher affinity for O₂ than the maternal haemoglobin

à therefore, O₂ dissociation curve lies to the left.

   17.  O₂ must easily dissociate from the maternal haemoglobin to the foetal haemoglobin

   à therefore, easily transferred from maternal to foetal blood.

  18. Myoglobin:

   à  higher affinity for O₂ than haemoglobin.

à  Therefore, dissociation curve lies to the left.

Haemoglobin:

à has a lower affinity for O₂ than myoglobin.

19.   In the muscle:

à O₂ dissociates from haemoglobin

à transferred to myoglobin to be stored.

Lung volume

1. Spirometer used to measure lung capacity.

2. Breathing movement is traced in a form of graph = kymograph.

3. Total capacity in human lungs = + 5 dm3 of air.

4. Tidal volume - air exchanged in normal breath = + 0.5 dm3 .

5. Healthy person breaths + 15 to 20 times per minute.

6  Vital capacity - max volume of air exchanged during forced breathing  = raised to 3.5 dm3.
7. Vital capacity - has two components:

   => inspiratory capacity

   => expiratory capacity

8. Residual volume - volume of air that remains in the lungs = + 1.5 dm3.

9. Total lungs capacity =  5.0 dm3.

Breathing process

1. Breathing control centre are:

• located in two major regions (medulla oblongata + pons).
• in medulla - sets the basic rhythm,
• in pons - moderates it smoothing out the transition between inhalation + exhalation.
• send impulses to the diaphragm + external intercostals muscle.

2. The central chemoreceptors (lies near the breathing control centers):

• detet the changes in pH of the cerebospinal fluid (CSF).
• stimulate the breathing centre
• slow down or speed the rhythmic discharge of nerve impulses

3. Carotid bodies are

• found in the carotid artery in the neck.
• chemoreceptor with nerve endings in the wall of carotid artery
• monitors the changes of blood pH in the carotid artery.

4. Aortic bodies are

• found in aorta.
• chemoreceptors that monitor the changes of blood pH.
• nerve endings in the wall of aorta.

5. Aortic and carotid bodies:

• also called peripheral chemoreceptors.
• impulses are relayed to the breathing control centres.
• change of CO2 conc. in the blood triggers a series of chain reactions.
• blood CO2 conc. back to normal,
• negative feedback loop.

6. In the blood plasma:

• CO2 released by cellular respiration 
• reacts with H2O to form carbonic acid (H2CO2)
• dissociates to form hydrogen carbonate ions (HCO3+) and hydrogen ions (H+).
• increase in hydrogen ions (H+) conc.
• increase the acidity of the blood plasma,
• decreasing the pH.

7. In the region of medulla

• CO2 diffuses into CSF from the surrounding capillary.
• then reacts with H2O in the fluid to form carbonic acid (H2CO3).
• dissociates to form hydrogen carbonate (HCO3+) and hydrogen ions (H+).
• The acidity in the CSF increases
• resulting in the decreases in the pH.

8. When blood flows through Peripheral Chemoreceptors (from aortic + carotid bodies) + Central Chemoreceptor

à detect increase in H⁺ conc

à send impulses to breathing control centre (in medulla oblongata)

à sends impulses to diaphragm + external intercostals muscles to contract faster

à breathing rate increases (to expel excess CO2)

à lungs expand (for faster breathing)

à stimulates stretch receptors (in lungs)

à send impulses to the breathing control centre

à sends impulses (via parasympathetic nerve) to the diaphragm + external intercostals muscle

à to slow down the contraction

à breathing rate returns to normal

à negative feedback reaction.